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  • Articles  (13,676)
  • American Association for the Advancement of Science  (8,091)
  • Wiley  (4,717)
  • American Institute of Physics (AIP)  (868)
  • 2020-2024
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  • Electrical Engineering, Measurement and Control Technology  (868)
  • Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics  (119)
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  • Articles  (13,676)
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Publisher
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  • 2020-2024
  • 2000-2004
  • 1995-1999  (9,003)
  • 1955-1959  (2,401)
  • 1935-1939  (2,272)
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  • 101
    Electronic Resource
    Electronic Resource
    Stand-alone microprocessor controlled fast sweep Langmuir probe driver (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 3405-3411 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This article describes a power supply and data logger for a Langmuir probe interfaced to a personal computer. The system provides a voltage sweep range from −125 to +100 V in 100 steps in a time ∼0.15 s. Restricted sweep ranges and single point operation are also possible. Probe current measurements are in the range from −1.0 to +100 mA with a precision of 5 μA on the most sensitive range, while the voltage may be set with a precision of 56 mV. Novel features of the system include: the use of integrate-and-dump techniques to implement the process of analog-to-digital conversion and to provide effective noise suppression; a solution to the problem of floating the power supply on top of the potential developed across the grounded current sensing resistor based on the power supply rejection ratio characteristics of a high voltage operational amplifier; and the development of an interface and control board employing the GPIB protocol to communicate with a host computer. Successful operation of the system has been demonstrated in the electrically noisy environment of a helicon plasma source. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148301
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  • 102
    Electronic Resource
    Electronic Resource
    Large-field high-resolution x-ray microscope for studying laser plasmas (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 3412-3420 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In 1948, P. Kirkpatrick and A. V. Baez developed an x-ray microscope (energy range about 100 eV–10 keV) composed of two concave spherical mirrors working at grazing incidence. That device, named KB microscope, presents a 3–5 μm resolution within a field having a radius about 100 μm; outside that field, its resolution lowers rapidly when the object point recedes from the center. The adjunction of two similar mirrors can notably increase the useful field (typically, the resolution can be better than 10 μm within a 2-mm-diam field of view), which is necessary for studying laser plasmas. Its main advantage with respect to more simple optics, as the pinhole, is that it can be located far enough from the plasma to avoid any destruction during the shot. We describe such a microscope that we call KBA microscope and present some images of fine metallic grids. Those grids were backlighted by x-ray sources, either a cw one or a series of laser plasmas from the Octal–Héliotrope facility. Examining the films in detail shows that the experimental results are very close to the theoretical characteristics; hence the interest of this device for the x-ray diagnostics on the future powerful laser facilities. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148302
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  • 103
    Electronic Resource
    Electronic Resource
    In situ calibration of microchannel-plate-based x-ray pinhole camera for observation of magnetically trapped plasma (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 3421-3425 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The electronic amplification gain of a microchannel plate (MCP), as employed for detector and image amplifier of an x-ray pinhole camera, tends to decrease as the output current increases, posing problems both in quantitative analyses and in construction of a three-dimensional emissivity distribution. We report that the output-current dependent MCP gain is described in a simple empirical formula that is determined by an in situ calibration experiment using a steady-state low-temperature discharge plasma. We examine the validity of the formula affirmatively in correcting raw data of x-ray images of magnetically trapped hot plasma. It is also demonstrated that the correction leads to a three-dimensional distribution of soft x-ray emissivity in a quadrupole-mirror-trapped hot plasma that is consistent with other indirect measurements. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148303
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  • 104
    Electronic Resource
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    Spectroscopic imaging system for quantitative analysis of the divertor plasma of the Tokamak de Varennes (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 3426-3435 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A toroidally viewing spectroscopic imaging system has been developed for the Tokamak de Varennes providing measurements of the poloidal distribution of the absolute radiated power of deuterium and impurity species in the upper divertor region. Real time digitization is achieved using a low cost PC based digital imaging system. This system is used to obtain measurements of the divertor strike point as well as the shape of the flux surfaces in the divertor. The diagnostic's excellent spatial resolution and toroidal view provides an opportunity to quantitatively compare the measured two dimensional (2D) radiated power distribution to that calculated from 2D Monte Carlo transport codes. These 2D images provide unique and valuable information on the physics of local plasma interactions with divertor components and particle transport in a closed divertor. Additionally, by using two cameras simultaneously, the line ratio technique can be applied to the images to estimate plasma parameters in the divertor. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148304
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  • 105
    Electronic Resource
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    A fully automated precise measurement system for sound velocity and internal friction in solids down to liquid helium temperatures using the vibrating reed technique (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 3436-3441 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The design and fabrication of a fully automated, computer controlled, precise measurement system for sound velocity and internal friction using the vibrating reed technique is described in detail. Relative variation of sound velocity and internal friction has been measured using automatic frequency locking. A detailed description of the apparatus is given. The associated electronics that took care of quite a few problems in getting a good lock-in condition have been highlighted. With a bath cryostat and sample insert, measurements were made down to liquid helium temperatures with a temperature control accuracy better than 10 mK. The resonance frequency and the peak amplitude were recorded as a function of temperature which in turn provided temperature variation of sound velocity and internal friction with a relative accuracy better than 1 part in 104 and 1.5%, respectively. Precise nature of the results obtained using this setup is highlighted for a specimen of an amorphous alloy near it's Curie temperature. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148305
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  • 106
    Electronic Resource
    Electronic Resource
    Temperature dependence of the fluorescence lifetime in Pr3+:ZBLAN glass for fiber optic thermometry (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 3447-3451 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An analysis of the fluorescence decay behavior of Pr 3+ in ZBLAN glass, at different concentrations, has been undertaken, for applications of the material to fiber optic thermometry. The study has shown that with the temperature increase, the measured lifetimes of the fluorescence emission from the Pr 3+ doped glass are also seen to increase slowly. The results obtained are found not to support a simple two-level model based on the thermalization of the states involved but a new three-level model that has been introduced can explain the observed results in a very satisfactory way. The application of the work in optical thermometry is discussed and comparisons with other systems are made. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148307
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  • 107
    Electronic Resource
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    Analysis of the double exponential behavior in alexandrite for optical temperature sensing applications (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 3442-3446 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An analysis of the fluorescence decay behavior of alexandrite emission, at higher dopant concentrations, has been undertaken for optical sensor application purposes. A double exponential decay behavior of the fluorescence emission has been observed, which differs from the single exponential behavior of alexandrite at lower concentrations of the active Cr 3+ ion. The origin of the phenomenon has been investigated both experimentally and theoretically and found to be produced by the joint contribution from the Cr3+ dopant in both the mirror, as well as in the inversion sites of that ion. The two lifetimes resulting, each having a different temperature dependence, both can be represented through the use of the configurational coordinate model which considers the effect of thermal quenching. The intensity ratio of these two aspects is seen to change regularly with the temperature within the important region for sensing of 273–773 K, and thus provides an alternative means to produce a calibrated fluorescence-based sensor. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148306
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  • 108
    Electronic Resource
    Electronic Resource
    Vacuum near-field scanning optical microscope for variable cryogenic temperatures (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 3458-3463 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe the design of a novel near-field scanning optical microscope for cryogenic temperatures and operation in vacuum. A helium flow cryostat is used for active temperature control of the sample in the range between 8 and 330 K, while all components of the near-field microscope are kept at room temperature. This design greatly simplifies near-field microscopy at variable sample temperatures and permits large piezoelectric scan ranges of up to 100×100×10 μm 3, the implementation of hardware-linearized piezoelectric scan stages, as well as flexible coarse positioning. First experiments with single GaAs quantum wires demonstrate the excellent performance of this new instrument. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148308
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  • 109
    Electronic Resource
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    Self-illumination calibration technique for luminescent paint measurements (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 3452-3457 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In a recent article [W. M. Ruyten, Appl. Opt. 36, 3079 (1997)] a theoretical model is presented which accounts for the effects of self-illumination and spectral leakage of a diffusely reflecting test article in luminescent paint measurements. It is shown in the present work how measurements on two, square, painted samples at a range of included angles can be used to check the applicability of the above model for a particular paint, and to determine the spatially averaged reflection coefficient of the paint, Rred, at the emission wavelength. The technique is demonstrated for the pressure-sensitive paint FIB7, yielding Rred=0.79±0.15, where the uncertainty indicates the degree to which the reflection characteristics of the paint deviate from those of a diffuse reflector. The proposed technique constitutes a complete calibration for the correction algorithm developed in the above-referenced article in the case that spectral leakage can be neglected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148332
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  • 110
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    A transmission x-ray microscope based on secondary-electron imaging (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 3464-3476 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A design for a transmission x-ray microscope with 20 nm transverse spatial resolution is presented. The microscope, which is based on the electron-optical imaging of the photoemitted electrons from an x-ray shadowgraph, consists of a transmission x-ray photocathode coupled to a photoelectron emission microscope (PEEM—also called a PEM for photoelectron microscope). Unlike the conventional PEEM, which produces a surface map of photoelectron yield, this microscope can provide information on the subsurface properties of thin samples. The analysis of the microscope's electron-optical performance is based on the evaluation of Gaussian focusing properties and third-order aberration coefficients computed using several complementary methods. The electron optical properties of the microscope are examined with an emphasis on issues affecting overall performance and achieving the best possible resolution. Preliminary experimental results using a cesium iodide photocathode are shown. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148309
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  • 111
    Electronic Resource
    Electronic Resource
    Spectroscopic diagnosis of foam z-pinch plasmas on SATURN : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 1083-1086 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Solid and annular silicon aerogel and agar foams were imploded on the SATURN accelerator to study plasma initiation, acceleration, and stagnation. SATURN delivers 7 MA with a 50 ns rise time to these foam loads. We fielded several spectroscopic diagnostics to measure plasma parameters throughout the z-pinch discharge. A spatially resolved single frame time-gated extreme ultraviolet spectrometer measured the extent of plasma ablation off the surface of the foam. A time integrated crystal spectrometer showed that characteristic K shell radiation of silicon in the aerogel and of sulfur and sodium impurities in the agar were attenuated when the foam loads were coated with a conductive layer of gold. A time-resolved pinhole camera showed that in general the quality of the pinch implosions was poor but improved with increasing efforts to improve current continuity such as prepulse and conductive coatings. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147740
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  • 112
    Electronic Resource
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    X-ray imaging of targets irradiated by the Nike KrF laser : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 1099-1102 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Foil targets irradiated by the Naval Research Laboratory Nike KrF laser were imaged in the x-ray region with two-dimensional spatial resolution in the 2–10 μm range. The images revealed the smoothness of the emission from target and backlighter foils, the acceleration of the target foils, and the growth of Rayleigh–Taylor instabilities that were seeded by patterns on the irradiated sides of CH foils.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147796
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  • 113
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    A combined apparatus of scanning reflection electron microscope and scanning tunneling microscope (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 116-119 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A scanning reflection electron microscope (SREM) combined with a scanning tunneling microscope (STM) has been developed for the purpose of nanoscale structure fabrication under ultrahigh vacuum conditions. A STM unit consists of a piezoelectric tube scanner and an inch runner for coarse and fine approach of a STM tip. A sample holder and the STM unit have six drive axes relative to an electron gun for simultaneous observation by SREM and STM. Energy-dispersive x-ray spectroscopy equipment is also installed for surface sensitive elemental analysis. It has been demonstrated that on a Si(111)7×7 surface atomic steps and 7×7 unit, cells can be observed in the SREM and STM images, respectively, and that surface elements with less than 1 ML thickness are detectable. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147750
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  • 114
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    High precision mechanical approach mechanism for a low temperature scanning tunneling microscope (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 129-132 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A novel mechanical micropositioner has been developed for producing exact linear displacements in the nm range. Incorporated in a low temperature scanning tunneling microscope (STM), it is used as a coarse approach mechanism for the tunneling tip. The advantage of the design is the high accuracy of the linear motion and the absence of backlash. The design principle is discussed and its positioning accuracy and stability for STM imaging are demonstrated. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147846
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  • 115
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    A tri-arc system for growing high-purity crystals of metallic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 3504-3511 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A tri-arc Czochralski crystal growth system, for preparing high-purity crystals of metallic materials, is described. To improve the environmental cleanliness within the chamber beyond that found in conventional tri-arc systems, the equipment is built to ultra-high-vacuum standards (although actual operation in vacuum is not possible) so that leaks into the system and degassing of contaminating gases from the chamber walls during growth are minimized. Crystal growths of the intermetallic compounds TiAl and HoCo 2 are illustrated. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148314
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  • 116
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    Zone-averaged method to minimize polarizer and analyzer imperfections in a phase-modulated spectroscopic ellipsometer (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 3519-3522 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have theoretically investigated the effects of polarizer and analyzer imperfections in a phase-modulated spectroscopic ellipsometer adopting a photoelastic modulator. Jones matrices having off-diagonal elements have been introduced to represent the imperfections of the polarizer and analyzer, and the effects of the imperfections were analytically derived to the first-order approximation. It was found that the effects of the imperfections could be completely eliminated by the zone average. Also, the effects of an incorrect setting of the modulation amplitude were found to be largely reduced by the zone average. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148316
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  • 117
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    Piston–cylinder apparatus for high-pressure impedance spectroscopy (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 193-196 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A simple piston–cylinder apparatus was developed for impedance spectroscopy at pressures up to 3 GPa and temperatures up to 500 °C. The apparatus is of the compound cylinder type, with the innermost cylinder made of a commercially available low-cost alumina-based ceramic, with pistons of hard metal that allow electric connections. Cell electrical resistance was higher than 1 MΩ at T〈300 °C and higher than 100 kΩ at 400 °C. The inductivity in the wires and pistons was about 2 μH. The sample was enclosed in a h-BN capsule, which insured a good hydrostaticity without disturbing the measurement. The equipment proved to be very useful in determining the activation volume of the conduction process in several ionic conductors.© 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147808
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  • 118
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    An endoscopic fluorescence imaging system for simultaneous visual examination and photodetection of cancers (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 203-212 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe the design and performance tested during six years of clinical trials of a fluorescence endoscope for the detection and delineation of cancers in several hollow organs. The apparatus is based on the imaging of the laser-induced fluorescence that differs between a tumor and its surrounding normal tissue. The tests are carried out in the upper aerodigestive tract, the tracheobronchial tree, the esophagus, and the colon. In the three former cases an exogenous dye is used (Photofrin II), whereas in the latter case fluorescein molecules conjugated with monoclonal antibodies directed against carcinoembryonic antigen are injected. The decrease of native tissue autofluorescence observed in early cancers is also used for detecting lesions in the tracheobronchial tree. The fluorescence contrast between the tumor and surrounding normal tissue is enhanced by real time image processing. This is done by simultaneously recording the fluorescence image in two spectral domains, after which these two images are digitized and manipulated with a mathematical operator (look-up table) at video frequency. Moreover, the device that is described below allows for an immediate observation of the endoscopic area under white light illumination during fluorescence detection in order to localize the origin of the "positive" fluorescence signals. Typical results obtained in the tracheobronchial tree and in the colon are presented and the sources of false positives and false negatives are evaluated in terms of the fluorescent dye, tissue optical properties, and illumination optics. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147811
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  • 119
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    Bandwidth and detection limit of a crossing–sampling spectrum analyzer (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 240-242 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We report the performance of a spectrum analyzer that determines the Fourier spectrum of an analog input sa(t) using only as data the time locations {ti} where sa(t) intersects with a reference sinusoid r(t)=A cos(2πWt). If A≤|sa(t)| within the sampling period T, then one crossing exists within each interval Δ=1/2W. The spectrum is computed directly from {ti}, which consists of 2M=T/Δ crossing locations. The theoretical bandwidth and frequency resolution of the analyzer is given by 2W and 1/T, respectively. However, electronic circuits have a finite temporal response and the crossings can only be located with finite accuracy. A trade off, therefore, is expected between the measurement bandwidth and the detection limit in a real crossing-based analyzer. In our design, the accuracy can be varied to increase the bandwidth, through the use of a versatile field programable gate array. The relation between the detection limit, dynamic range, and bandwidth of our device is experimentally studied and analyzed. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147816
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  • 120
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    Optically isolated current-to-voltage converter for an electron optics system (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 250-251 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A simple, inexpensive, optically isolated current-to-voltage converter circuit has been developed for the measurement of bipolar currents in the range of 10 pA–1 μA on the biased elements of an electron optics system at voltages up to 3.5 kV. The design takes advantage of low-leakage, low-power complementary metal–oxide semiconductor operational amplifiers as well as linear optocouplers to create a low-noise battery-powered front end with an expected battery life of three years using a single 9 V lithium battery.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147738
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  • 121
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    Measurements of nonthermal confined alpha particles in Tokamak Fusion Test Reactor D–T plasmas (invited) : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 269-274 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Experience with the α charge exchange recombination spectroscopy and pellet charge exchange confined, nonthermal alpha particle diagnostics over the first two years of Tokamak test fusion reactor (TFTR) D–T operation is summarized. A brief summary of the concept, instrumentation, and analysis techniques for each diagnostic is given, followed by examples of alpha physics results. Issues important to further development of these diagnostic techniques for TFTR and ITER are discussed. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1148053
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  • 122
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    Diagnostic neutral beam and active spectroscopy requirements for the Alcator C-Mod tokamak (invited) : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 265-268 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Considerations are presented on the application of a diagnostic neutral beam to the Alcator C-Mod tokamak for active profile measurements of ion temperature, poloidal and toroidal rotation, impurity and minority species densities, and internal magnetic field. Calculations indicate that, for a typical 50 keV, 0.13 MW hydrogen beam, charge exchange recombination measurements for plasmas with line average densities up to 2.5×1020 m−3 will yield, with good signal-to-noise ratio and ∼1 cm spatial resolution, measurements of helium and low Z impurity density profiles with better than 1 ms time resolution, and ion temperature and rotation profiles with ∼1 ms time resolution. Motional Stark effect (MSE) measurements appear feasible over most of the operating density range of the device (at least up to 5×1020 m−3), also with ms time resolution. Spatial resolution of the MSE measurements will depend on the toroidal width of the beam and the angle of the view with respect to the beam; for a 5 cm wide beam with a 60° viewing angle, 2.5 cm spatial resolution is expected. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147821
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    Optimization of the extracted current density from the high energy diagnostic neutral beam injector of TdeV : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 289-291 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Development of a high energy (40 kV, 1 A) neutral beam injector for diagnostic applications on TdeV is in progress. The injector operates with its source at ground potential and the neutralizer canal at ≤−40 kV. The electrons in the neutralizer canal are retained by an electrostatic trap. The residual ions are collected near ground potential. Several diagnostics, including calorimetry, spectroscopy and a scanning multipin open probe array, are used to study the beam characteristics on its test stand. Hall probes and voltage dividers coupled with fiber optic links are used to optimize the efficiency of the extraction system, the electron trap, and the residual ion collection units. In its first stage of development, the injector has been optimized for operation with a single hydrogen beamlet. A beamlet divergence of less than 0.5 degrees was obtained. Up to 75 mA of ion current at 35 kV was extracted. The addition of another six extraction holes boosted the total extracted current to more than 600 mA at 36 kV. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147739
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    E(parallel)B energy-mass spectrograph for measurement of ions and neutral atoms : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 292-295 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Real-time measurement of plasma composition and energy is an important diagnostic in fusion experiments. The Thomson parabola spectrograph described here utilizes an electric field parallel to a magnetic field (E(parallel)B) and a two-dimensional imaging detector to uniquely identify the energy-per-charge and mass-per-charge distributions of plasma ions. An ultrathin foil can be inserted in front of the E(parallel)B filter to convert neutral atoms to ions, which are subsequently analyzed using the E(parallel)B filter. Since helium exiting an ultrathin foil does not form a negative ion and hydrogen isotopes do, this spectrograph allows unique identification of tritium ions and neutrals even in the presence of a large background of 3He. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147824
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    Calibration of the heavy ion beam probe parallel plate analyzer using the gas target and reference beam : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 308-311 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The most important and difficult problem in heavy ion beam probe diagnostics is the absolute measurement of the plasma potential. The analyzer that measures the energy of the secondary ions must be perfectly calibrated. The accuracy necessary should be at least 10−4. We used two methods of calibration: in situ using the gas target, and in vitro using the reference beam. Calibration allows one to obtain the gain G and dynamic coefficient F of the analyzer. We developed a procedure of fast calibration that uses the dynamic curve Ub/Ua(δi), where Ub and Ua correspond to the accelerating voltage of the beam and the voltage on the analyzer, and δi is a normalized difference of currents on the plates. The analyzer used on the T-10 tokamak was calibrated by both methods. Results of both calibrations are in a reasonable agreement at the moderate values of the entrance angle. The nonideal effects caused by ionization of the gas target and asymmetric secondary electron exchange are considered. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147856
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    Development and characterization of semiconductor ion detectors for plasma diagnostics in the range over 0.3 keV : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 324-327 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: For the purpose of plasma-ion-energy analyses in a wide-energy range from a few hundred eV to hundreds of keV, upgraded semiconductor detectors are newly fabricated and characterized using a test-ion-beam line from 0.3 to 12 keV. In particular, the detectable lowest-ion energy is drastically improved at least down to 0.3 keV; this energy is one to two orders-of-magnitude better than those for commercially available Si-surface-barrier diodes employed for previous plasma-ion diagnostics. A signal-to-noise ratio of two to three orders-of-magnitude better than that for usual metal-collector detectors is demonstrated for the compact-sized semiconductor along with the availability of the use under conditions of a good vacuum and a strong-magnetic field. Such characteristics are achieved due to the improving methods of the optimization of the thicknesses of a Si dead layer and a SiO2 layer, as well as the nitrogen-doping technique near the depletion layer along with minimizing impurity concentrations in Si. Such an upgraded capability of an extremely low-energy-ion detection with the low-noise characteristics enlarges research regimes of plasma-ion behavior using semiconductor detectors not only in the divertor regions of tokamaks but in wider spectra of open-field plasma devices including tandem mirrors. An application of the semiconductor ion detector for plasma-ion diagnostics is demonstrated in a specially designed ion-spectrometer structure. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147923
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    Radio frequency-driven energetic tritium ion tail measurements in the Tokamak Fusion Test Reactor using the pellet charge exchange diagnostic : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 340-343 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Charge exchange interactions of ions with the ablation cloud of an injected low-Z impurity pellet can be used to measure the energy spectrum and radial profile of confined fast ions in a fusion plasma. On the Tokamak Fusion Test Reactor we use this technique to directly measure energetic alphas from D–T reactions, tritons from D–D reactions, and radio frequency (rf)-driven minority tail ions (e.g., H, 3He, T). We describe the status of the pellet charge exchange (PCX) diagnostic including a brief description of the measurement technique and discussion of operational experience. PCX measurements of the energy spectrum, radial density distribution, and heating deposition profile of rf-driven tritium ions during 2ΩT heating of L-mode plasmas are presented. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1148060
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    Investigation of nonthermal particle effects on ionization dynamics in high current density ion beam transport experiments : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 350-353 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Light ion inertial fusion experiments require the presence of a moderate density background gas in the transport region to provide charge and current neutralization for a high current density ion beam. In this article, we investigate the effects of nonthermal particles such as beam ions or non-Maxwellian electron distributions on the ionization dynamics of the background gas. In particular, we focus on the case of Li beams being transported in an argon gas. Nonthermal particles as well as thermal electrons are included in time-dependent collisional-radiative calculations to determine time-dependent atomic level populations and charge state distributions in a beam-produced plasma. We also briefly discuss the effects of beam ions and energetic electrons on the visible and vacuum ultraviolet (VUV) spectral regions. It is found that the mean charge state of the gas, and hence the electron density, is significantly increased by collisions with energetic particles. This higher ionization significantly impacts the VUV spectral region, where numerous resonance lines occur. On the other hand, the visible spectrum tends to be less affected because the closely spaced excited states are populated by lower energy thermal electrons. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147827
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    Automatic fast fitting of single Langmuir probe characteristics on RFX : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 365-368 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An array of single Langmuir probes is routinely used in the RFX reversed field pinch for time-resolved measurements of edge electron density and temperature. In order to allow an automatic analysis of the large number of current–voltage characteristics, three different methods have been developed, which consider restricted subsets of data with voltage lower than an upper cutoff value. The first one determines this limiting voltage by a neural network based technique, combined with criteria for the rejection of too noisy characteristics. In the second one a standard fitting routine is applied repeatedly to the data while varying the upper cutoff voltage. The third one consists of a numerical technique, where the best fit is obtained by minimizing a properly defined cost function. An error index is also calculated, which allows the reliability of the results to be easily estimated. The best results have been achieved using the last two methods.© 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147831
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    Design and performance of a belt-type high pressure, high temperature apparatus (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 189-192 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A modified belt-type high pressure, high temperature apparatus without tungsten carbide has been designed and constructed based on the theory of multilayered pressure vessels. The calculated interferences seem to give adequate support for reaching a high pressure of 10 GPa and simultaneously temperatures up to 1400 °C. We estimate the highest pressure reached in our experiment to be ∼17 GPa in the sample region, based on the load versus pressure curve calibrated in bismuth, tin, and lead. Talc gaskets were used along with a tubular graphite furnace for high temperatures. This represents a relatively simple and inexpensive device for material synthesis and phase transformation studies. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147807
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    Passive frequency and intensity stabilization of extended-cavity diode lasers (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 1-7 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Studies are reported on frequency drifts in extended-cavity diode lasers caused by external effects, such as changes in temperature and air pressure. A laser system operating at 780 nm has been constructed utilizing low expansion materials and such mechanical structures that compensate for the external effects. By placing the laser system in a pressure-proof and temperature-controlled housing, a relative frequency stability of better than 10−10 (40 kHz) is obtained for integration times of 10 μs to 10 s. The drift of the laser frequency caused by spectral aging of the diode laser is about 3 MHz/h. As a consequence of high passive stability, the variations of the laser intensity are also greatly reduced to a relative drift value of 4×10−5/h. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147810
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    Improved multistage wide band laser frequency stabilization (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 223-229 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Suppression of laser frequency fluctuations is an essential technology for planned interferometric detectors for astrophysical gravitational waves. Because of the low degree of residual frequency noise which is ultimately required, control topologies comprising two or more cascaded loops are favored. One such topology, used in the Laser Interferometer Gravitational-Wave Observatory 40 m interferometer, relied on electro-optic Pockels cell phase correction as a fast actuator for the final stage. This actuation method proved susceptible to spurious amplitude modulation effects, which provided an unintended parasitic feedback path. An alternate arrangement, which achieves comparably effective frequency stabilization without using a phase correcting Pockels cell, was introduced and successfully tested. © 1997 American Institute of Physics.
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    A high-frequency modulated tunable diode laser absorption spectrometer for measurements of CO2, CH4, N2O, and CO in air samples of a few cm3 (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 230-239 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Investigations of the relationship between changes in climate and the variation of composition of the atmosphere can be performed most directly and with the highest resolution possible by analyzing the air sampled and preserved in the polar ice sheets for hundreds of thousands of years by nature itself. For the determination of CO2, CH4, N2O, and CO in air samples of 1–3 cm3 extracted from ice cores, a high-frequency modulated tunable diode laser absorption spectrometer has been developed. The instrument can measure CO2, CH4, N2O, and CO at ambient mixing ratios of 300 ppmv (1 ppmv=10−6 volume mixing ratio), 1700, 300, and 100 ppbv (1 ppbv=10−9 volume mixing ratio), respectively, with a precision of 1%–2%. The measurement of high CO2 mixing ratios is not constrained by the detection limit. For other gases mixing ratios of 20 ppbv of CH4, 0.9 ppbv of N2O, and 1.6 ppbv of CO are detectable with the instrument in 2 cm3 standard temperature and pressure. These detection limits and the measurement precision are sufficient for the determination of past changes in atmospheric composition. The technique is also suitable for other applications in which several infrared active trace gases have to be determined in the low ppbv and possibly even in the upper pptv range in air samples of a few cm3 or small samples of other matrices. The sensitivity or the reproducibility of the instrument can be improved by another order of magnitude by using more powerful lasers and by averaging over longer periods. Such improvement could result in a capability to detect sub-ppbv mixing ratios in samples of the present size or ppbv measurements in even smaller air samples. The higher reproducibility would also make the technique interesting for measurements of isotope ratios. © 1997 American Institute of Physics.
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    Implementation of a SELFOC lens for the light collection element for single molecule spectroscopy at cryogenic temperatures (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 254-255 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We introduce the use of a SELFOC gradient index lens as a micro-optical element for collection and focusing of luminescence of single molecules in solid matrices. We demonstrate its performance by measuring single molecule spectra of terrylene in n-alkanes and compare its signal-to-noise ratio and collection efficiency with that of a microscope objective. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147819
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    A practical fiber optic air-ratio sensor operating by flame color detection (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 197-202 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This article discusses the development of a simple fiber-optic sensor used to detect the air-ratio in a premix type gas boiler, by monitoring and appraising the color of the flame emission, including the effect of radical emissions. Such boilers with a multi-port plate burner show an improved thermal efficiency, with the environmentally friendly effect of a reduction in both NOx and CO in the exhaust gas. The sensor is used to monitor and maintain the air-ratio in order to enable effective feedback control, and a low-cost, durable and small sensor solution is presented. Tests carried out show the potential of the sensor for use outside the laboratory and image processing techniques are used to analyze the spectral features of the emissions seen to confirm the spectral regions of use of the fiber-optic sensor. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147809
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    Continuous highly charged ion beams from the National Institute of Standards and Technology electron-beam ion trap (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 1998-2002 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe our newly modified beam line and present its performance in conjunction with the National Institute of Standards and Technology electron-beam ion trap. We find that, contrary to previously reported results from similar ion sources, the highest intensity time-averaged ion fluxes are achieved by letting the ions boil out of the trap in a continuous stream rather than periodically dumping the trap to produce a pulsed beam. We produced continuous beams of 3.0(6)×106 Xe44+ ions per second and lower flux beams of charge states up to Xe49+. Also, in pulsed mode, we created beams with very high peak flux, over 1010 Xe44+ ions per second.
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    Novel bandpass electrostatic analyzer (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 2023-2026 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A novel electrostatic analyzer for energetic charged particles has been developed that has a simple geometry and has demonstrated a wide field of view (90°×4° in the prototype device). The bandpass of the device can be adjusted by changing the size of the entrance and exit apertures, and the design intrinsically retains information about the spatial distribution of the incoming particles. Comparisons between numerical simulations of the device and laboratory tests are presented.
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    URL: http://dx.doi.org/10.1063/1.1148091
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    First results from the small tight aspect ratio tokamak multifrequency pulse radar reflectometer (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 2040-2045 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A multifrequency pulse radar reflectometer (PRR) has been designed, commissioned, and is operating successfully on the small tight aspect ratio tokamak (START). The data obtained with this technique allow the study of the density profile evolution during the shot, revealing aspects of the plasma behavior during such events as the internal reconnection. A simple and effective profile-reconstruction algorithm using the stepwise profile approximation permits the monitoring of the plasma density profile immediately after each shot. Cross checks between the START hydrogen cyanide (HCN) interferometer and the line integral density determined by integrating the PRR generated data shows good agreement. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1148075
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    Monolithic crystalline fiber optic temperature sensor (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 2068-2070 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A fiber optic temperature sensor of the fluorescence decay type using a novel construction has been demonstrated. In this new design, both the fiber and the sensing element are made of crystals, and the two are fused together to produce a monolithic probe. As the entire probe is crystalline, it can potentially be used to measure extremely high temperatures. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1148098
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    ac-mode atomic force microscope imaging in air and solutions with a thermally driven bimetallic cantilever probe (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 2082-2090 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An ac imaging mode for atomic force microscopy (AFM) has been developed that employs a thermally driven bimetallic cantilever to sense surface topography. Oscillations are induced in a composite cantilever, comprising a Si3N4 layer and Au overcoat, by local heating with a resistive wire heater placed in close proximity to the cantilever. Cantilever bending occurs upon heating due to the difference in thermal expansion coefficients of the Si3N4 and Au layers. The magnitude of this bending is a function of the heat input, the cantilever geometry, the frequency of the excitation, and the thermal properties of the surrounding medium. A commercially available contact mode AFM has been modified to perform ac mode imaging by driving the cantilever with a peak-to-peak amplitude of 5–15 nm using resistive heating. The heating frequency was typically fixed near the cantilever's resonance frequency, which was in the range of 15–50 kHz in the air and 2–15 kHz in solution for the cantilevers used here. Simultaneous cantilever deflection and amplitude measurements during sample approach indicate that the cantilever free amplitude is damped upon surface contact. While imaging, a fixed damping of the cantilever oscillation is used as a feedback signal to maintain a constant tip-sample separation. Images with this ac imaging mode were obtained in both air and liquid environments. Results show an improvement in image quality in the ac mode over the corresponding contact images, which is the result of a decrease in lateral forces with an oscillating tip. This provides a simple and robust method for ac-mode AFM imaging in air and solutions that can be achieved with only slight modification to a commercially available contact-mode microscope. © 1997 American Institute of Physics.
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    Differential isothermal capacitance transient spectroscopy for the studies of deep levels in semiconductors (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 2116-2120 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Differential isothermal capacitance transient spectroscopy (DICTS) and normalized isothermal capacitance transient spectroscopy (NICTS) were proposed to improve the resolution of the conventional isothermal capacitance transient spectroscopy (ICTS) which could characterize the deep levels in semiconductors isothermally. The resolution of the methods was studied for the closely spaced energy levels by the numerical simulation. Though the resolvable emission rate ratio R (R=λ2/λ1, where λ1 and λ2 are each thermal emission rate for two levels) of ICTS was around 5, R of DICTS was around 4. Moreover, R of NICTS reached 3.5 which is less than that of any other conventional methods. The error ratio of the estimation is almost the same as ICTS. The new method was applied to study the deep levels in a Si:Au system as an example and found two closely spaced energy levels explicitly. © 1997 American Institute of Physics.
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    Versatile 4 K nuclear magnetic resonance probe and cryogenic system for small-bore high-field Bitter magnets (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 2132-2137 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A complete design for a versatile nuclear magnetic resonance cryostat/probe system specifically adapted for small 32 mm bore bitter magnets is described. The probe solves two main problems associated with constrained environments (1) high voltage arcing across cold tuned circuits in helium atmosphere and (2) loss of temperature control due to helium bubbles in a long Dewar tail at high fields. The probe implements a variable cold-tuned system with an evacuated space for tuning capacitors to avoid high voltage breakdown. The cryostat makes use of a unique counterflow design. The simple construction and disassembly ensures reliability and allows quick repair and replacement of parts. © 1997 American Institute of Physics.
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    Fiber optic sensors for use in monitoring flow front in vacuum resin transfer molding processes (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 2156-2157 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A distributed fiber optic sensor array developed for use in vacuum resin transfer molding systems is described. The sensor is placed in the mold and can be used to monitor resin infiltration even in complicated parts because of its small size and flexibility. The sensor components themselves are low cost and become incorporated in the part during the molding process. Careful design of the sensor elements is necessary to avoid sensitivity to mechanical stresses associated with the resin infiltration process. © 1997 American Institute of Physics.
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    Instrumental improvements in optical waveguide light mode spectroscopy for the study of biomolecule adsorption (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 2172-2176 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Optical waveguide light mode spectroscopy (OWLS) is a new technique that is particularly well suited to the in situ study of biomolecule adsorption kinetics on surfaces. Here we describe improvements to a commercial OWLS instrument in order to allow for easy combination with other ex situ surface-characterization methods, such as x-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry, and atomic force microscopy. Further, the problem of contamination of the waveguide surface arising from the use of silicone in the flow-through cuvette with which biomolecules are brought into contact with the adsorbing surface had to be resolved, as it greatly altered the wetting and adsorption properties of the waveguide. Finally, through physical vapor deposition of thin, nanosized layers of titanium oxide onto the waveguide layer, it is possible to simulate the surface properties of oxide-covered titanium implant surfaces. However, scanning angle constraints set by the mechanics of the commercial instrument must be borne in mind. © 1997 American Institute of Physics.
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    Optical and mechanical design of the Antarctic Submillimeter Telescope and Remote Observatory (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 2200-2213 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Antarctic Submillimeter Telescope and Remote Observatory (AST/RO), a 1.7 m diameter telescope for astronomy and aeronomy studies at wavelengths between 200 and 3000 μm, was installed at the South Pole during the 1994–95 Austral summer. The optical design is Gregorian, offset in both azimuth and elevation, with the exit pupil at the chopping tertiary mirror: this arrangement provides for consistent illumination of the primary mirror even when the beam is thrown one degree or more on the sky. Aberrations are minimized by the choice of secondary mirror offset angle. Alignment is accomplished by mechanical means. There is a Coudé focus in a warm, spacious receiver room and also a Nasmyth focus. Both the elevation and azimuth axes are driven by two pinion gears with opposed torques to eliminate backlash. The encoders are unusually robust but have high friction, necessitating a stiff coupling. The azimuth limit switch scheme permits 1.5 rotations, but the switches will operate under extreme conditions with no single point of failure. The instrument is now operational with four heterodyne receivers and three acousto-optical spectrometers. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1148071
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    Measurements of the neutron source strength at DIII-D : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 536-539 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A set of neutron counters and a pair of scintillators measure the 2.5 MeV neutron emission produced by the DIII-D tokamak. The neutron counter set provides a large dynamic range (∼7 orders of magnitude) while the scintillators provide the very fast resolution needed for studying transient events. The counters are absolutely calibrated in situ with a 252Cf source and the scintillators are cross calibrated to the counters. The historic variations in the emission measured by the various detectors have been compared and are consistent within the estimated accuracy of the absolute calibration (15%). In the discharges with the highest emission levels (2.4×1016 n/s), the signals from the neutron counters and the scintillators agree well. Comparisons with other diagnostics also corroborate the neutron measurements.© 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147646
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    TFTR natural diamond detectors based D–T neutron spectrometry system : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 553-556 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Three natural diamond detectors (NDD) based spectrometry systems have been developed and used on TFTR to perform D–T neutron spectrum and flux measurements. DT neutrons interact with the NDD through the 12C(n, alpha)9Be reaction to produce a narrow peak in the pulse height distribution which has 2%–3% energy resolution and is well isolated from other reactions by ∼2 MeV in energy. The NDD detector is also highly radiation resistant (5×1014 n/cm2) and compact in size (diameter ∼4 mm, thickness ∼0.2 mm). Three detectors have been installed near TFTR. One, installed in a central sight line of the neutron collimator views perpendicularly from below. Two other detectors placed inside radiation shields in the TFTR test cell have tangential and perpendicular cones of view. These three spectrometers provide spectrometry of D–T neutrons escaping the tokamak with angles with respect to plasma current in the ranges close to 90°, 110°–180°, and 60°–120° correspondingly. The fastest standard electronics have been used to reduce the influence of pulse pileup during spectrometry measurements at count rates up to 3×105 counts/s. Results of the first D–T neutron spectra and flux dynamics measurements made with the three NDD based spectrometers during TFTR high power neutral beam injection are presented. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147651
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    Neutron diagnostics for ITER : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 569-572 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Neutron diagnostics will play a prominent role in the control and evaluation of thermonuclear plasmas in ignition device to test engineering concepts (ITER). As in present D-T experiments, measurements of neutron yield and of fusion power and power density are essential. In addition, the spectral width of the 14.1-MeV t(d,n)α neutron emission should be a reliable indicator of ion temperature in an ignited plasma. More detailed measurements of the neutron spectrum may allow determination of the densities of tritium, deuterium, and confined alpha particles. Although the central fusion power density in ITER will be comparable to the maximum values obtainable in TFTR and JET, neutron flux on the first wall will be ten times higher, and the neutron yield per discharge will be about five orders of magnitude greater than previously experienced. The thermal and radiation shielding necessary to protect the ITER superconducting coils from the intense flux at the first wall will restrict diagnostic access for neutron cameras and spectrometers, complicate the design of material activation systems, and limit the applicability of conventional calibration techniques for neutron source strength monitors. These considerations, together with unprecedented reliability requirements and the need for full remote handling of many components, pose demanding challenges for the design of the ITER neutron diagnostic systems. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147906
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    Design of an electronic charged particle spectrometer to measure 〈ρR〉 on inertial fusion experiments : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 589-592 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The design and fabrication of a new diagnostic that measures the energy spectra of charged particles from targets on the Omega Upgrade are actively underway. Using seven 512×512 charge coupled devices (CCDs) and a 7.5 kG permanent magnet, this instrument will uniquely determine particle identities and measure particle energies from 1 MeV up to the maximum charged particle energies of interest for ρR measurements (10.6 MeV knock-on tritons, 12.5 MeV knock-on deuterons and 30.8 MeV tertiary protons). The resolution of the diagnostic will be better than 5%. We have tested the response of SITe back-illuminated CCDs to 1.2–13.6 MeV protons from our Cockcroft–Walton accelerator and to alpha particles from an Am241 source, and the results agree extremely well with predictions. With its high density picture elements, each CCD has 105 single-hit detectors. In the case of a low DT yield of 109 neutrons, about 100 knock-on charged particles will be detected when the spectrometer aperture is 60 cm from the implosion. Measurements of ρR up to 150 mg/cm2 can be obtained from knock-on D and T spectra, and values up to 300 mg/cm2 can be determined from secondary proton spectra. The sensitivity of the CCDs to 14 and 2.5 MeV neutrons has been experimentally determined using our Cockcroft–Walton accelerator source and indicates that by incorporating neutron shielding, the signal to neutron noise ratio at a yield of 1011 will be better than 100:1. In the development phases of this program, we plan to utilize CR-39 track detectors concurrently with the CCDs. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147660
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    Design and simulation of a broadband, high speed quasioptical beam switch array for moderate pulse reflectometry : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 470-472 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: High speed, high on-off contrast ratio switches utilizing beam control grid array technology are under development for use in moderate pulse reflectometry. This approach, which utilizes arrays consisting of hundreds of Shottky varactor diodes embedded within an overmoded wave guide, is expected to generate switching times in the 100–500 ps range with high power handling capabilities. The switches are designed for initial wideband operation in V band (50–75 GHz) operation although they can be operated both at lower and higher frequencies, and are intended for use in a moderate pulse reflectometry system such as used on the RTP tokamak. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147608
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    Control of a multidegree of freedom standing wave ultrasonic motor driven precise positioning system (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 1779-1786 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A newly developed positioning system incorporating a multidegree of freedom standing wave ultrasonic motor (SWUM) is presented and its advantageous features, operating principles, and some experimental results are described. The principle of motorization is based on the conversion, through frictional contact, of a stationary bending vibration sustained in a slotted metallic resonator, into rigid body displacements. A small autonomous multidegree of freedom nanopositioner using a SWUM motor is presented for fine positioning in scanning tunneling microscopy. The positioning system is achieved via the simultaneous operation of two identical pulse width modulation servo-control systems, each having a laser vibrometer position feedback loop. The closed loop position schemes are theoretically considered and their results are demonstrated and evaluated in practice. Evaluations of experimental tests indicate that a positioning resolution less than 100 nm are successfully achieved for an unlimited X−Y travel range with linear speeds between 1 mm s−1 and few cm s−1. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147966
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    An apparatus for the characterization of the static and dynamic wettability of complex interfaces (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 1801-1808 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The apparatus described in this work is a novel tool which improves the capabilities of studying the static and dynamic features of wetting. It is composed, on the one hand, of an operational part which includes the mechanical setup for the precise deposition of drops and their correct viewing once they start evolving on a substrate. On the other hand, a specific vision system completes the instrument and is made up of different cameras and focusing optics, capable of acquiring images at variable rates (up to 200 Hz) and of a data-processing card designed to provide parameters such as contact angles, interfacial tensions, and spreading kinetics. Numerous examples of the use of this apparatus are provided in order to illustrate its merits within a wide range of static and dynamic situations related to the basic properties of interfaces. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147996
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    Magnetic resonance force detection and spectroscopy of electron spins in phosphorus-doped silicon (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 1823-1826 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Electron spin resonance (ESR) of phosphorus-doped silicon was detected using a low temperature magnetic resonance force microscope (MRFM). Force-detected ESR spectra were obtained using an amplitude or frequency modulated microwave field to cyclically saturate the spin magnetization. For a sample containing 4×1018 phosphorus atoms/cm3, a single strong ESR line was observed. For a sample containing 8×1016 phosphorus atoms/cm3, a pair of lines split by the 42 G 31P hyperfine interaction was observed. This result demonstrates the possibility of using MRFM techniques for spectroscopic purposes. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147967
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    Simple probe for variable pressure deuterium nuclear magnetic resonance studies of soft materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 1827-1830 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A deuterium nuclear magnetic resonance probe in which samples can be studied at pressures up to 3 kbar is described. Characteristics of this device include simple design involving a beryllium copper pressure vessel, a modular coil assembly, and containment of the sample in a sealed polyethylene tube. The probe has been designed for operation at a deuterium frequency of 23 MHz in a 100 mm bore superconducting magnet at temperatures ranging from −20 to 100 °C. The probe has been used in isobaric and isothermal studies of phospholipid bilayer headgroup orientation, phase behavior, and molecular dynamics. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1148000
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    He〈sup LOCATION="PRE"〉3 immersion cell for ultralow temperature study of amorphous solids (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 1831-1834 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have constructed a 3He immersion cell for dielectric measurements of insulating amorphous solids in a nuclear demagnetization cryostat at temperatures between 500 μK and 150 mK. The samples are directly immersed in 3He with two heat exchangers per electrode which are thermally isolated from each other and have a very low capacitance to ground. The cell incorporates a 195Pt pulsed NMR thermometer with a novel superconducting magnet and a3He viscometer for calibration. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1148055
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    Ultrahigh speed imaging system for the measurement of solidification velocity via direct observation of rapid solidification (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 1846-1852 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An ultrahigh speed imaging system has been developed and built to image rapid solidification of materials. The system collects data from a 10 by 10 array of parallel tapped photodiodes. Up to 8192, frames of data are digitized with 8-bit flash converters at frame rates ranging from 500 to 1 000 000 frames per second. The system has been used to image solidification of a gamma titanium aluminum (γ-TiAl) alloy, with composition Ti-60a/o Al, over a range of undercoolings. The data collected includes the first images of solidification from multiple solidification fronts, images of solidification of a disordered phase followed by the alloy ordering, and quantitative measurement of solidification velocity as a function of undercooling in a γ-TiAl alloy. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147956
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    Multipass/multipulse Thomson scattering on CDX-U (abstract) : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 689-689 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A multipass/multipulse Thomson scattering system has been implemented on CDX-U in collaboration with the Ioffe Institute, St. Petersburg. The system consists of a low energy (1.5– 2.5 J), passively Q-switched ruby laser, and a multipass optical cavity enclosing the plasma. Multiple reflections of the beam within the cavity increase by about an order of magnitude the number of scattered photons, allowing temperature density to be measured with good accuracy even at very low plasma density. By feeding the returned beam back into the laser, the system can deliver several pulses over a 1 ms period. However, the experiments on CDX-U show that a mechanical shock wave reaching the multipass system affects the feedback and laser output per pulse drops significantly. Therefore we operate the system by fine tuning the laser cavity, so that output is practically independent of feedback from multipass cavity. Also, by optimizing the transmission of the passive Q-switch and the pumping power, we obtain that laser output is concentrated in single large pulse of 2–2.5 J energy. We achieve circulating energy in the plasma in excess of 12 J per pulse, while minimizing at the same time stray light. As shown by results from CDX-U, this enables in some cases better than 10% accuracy, despite relatively low plasma density conditions. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147674
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    Thomson scattering stray light reduction techniques using a CCD camera : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 704-707 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The DIII–D Thomson scattering system has been expanded to measure divertor plasma temperatures from 1 to 500 eV and densities from 0.05 to 8×1020 m−3. To complete this system, a difficult stray light problem was overcome to allow for an accurate Rayleigh scattering density calibration. The initial stray light levels were over 500 times higher than the expected Rayleigh scattered signal. Using a charge-coupled device (CCD) camera, various portions of the vessel interior were examined while the laser was fired through the vessel in air at atmospheric pressure. Image relaying, exit window tilting, entrance and exit baffle modifications, and a beam polarizer were then used to reduce the stray light to acceptable levels. The CCD camera gave prompt feedback on the effectiveness of each modification, without the need to reestablish vacuum conditions required when using the normal avalanche photodiode detectors (APD). Once the stray light was sufficiently reduced, the APD detectors provided the signal time history to more accurately identify the source location. We have also found that certain types of high reflectance dielectric coatings produce 10–15 times more scatter than other types of more conventional coatings. By using low-scatter mirror coatings and these new stray light reduction techniques, we now have more flexibility in the design of complex Thomson scattering configurations required to probe the central core and the new radiative divertor regions of the DIII–D vessel. © 1997 American Institute of Physics.
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    A prototype imaging second harmonic interferometer : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 709-712 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have built a prototype imaging second harmonic interferometer, which is intended to test critical elements of a design for a tangential array interferometer on C-Mod6. The prototype uses a pulsed, 35 mJ, 10 Hz multimode, Nd:YAG laser, LiB3O5 doublers, a fan beam created by a cylindrical lens, four retroreflector elements, and a CCD camera as a detector. The prototype also uses a polarization scheme in which the interference information is eventually carried by two second harmonic beams with crossed polarization. These are vector summed and differenced, and separated, by a Wollaston prism, to give two spots on the CCD. There is a pair of these spots for each retroreflector used. The phase information is directly available as the ratio of the difference to sum the intensities of the two spots. We have tested a single channel configuration of this prototype, varying the phase by changing the pressure in an air cell, and we have obtained a 5:1 light to dark ratio, and a clear sinusoidal variation of the ratio as a function of pressure change. © 1997 American Institute of Physics.
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    A self-calibration technique for a Thomson scattering system : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 725-727 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A self-calibration technique, based on the use of two lasers of different wavelengths is described. Such a scheme is essential in the presence of inaccessible optical components, as found on large present day machines. In these devices spectral characteristics may change with time, posing a problem for the calibration of a Thomson scattering diagnostic. From a combination of the scattered spectra generated by the two lasers on the same plasma, the temperature and the unknown, slowly varying spectral transmission of the different channels can be determined. A visible wavelength scattering system on a high-temperature plasma is assumed with laser wavelengths of 800 and 530 nm. Details of the analysis procedure and the results of fitting for the unknown spectral calibrations are presented. A statistical analysis of the error in the fitted calibration curve is included. A practical solution, with reference to ITER, is proposed. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147686
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    High-luminosity monochromatic x-ray backlighting using an incoherent plasma source to study extremely dense plasmas (invited) : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 740-744 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new diagnostic method for dense plasmas, monochromatic x-ray backlighting, is described. In this method, shadow images of a bright, dense plasma can be obtained with high spatial resolution using monochromatic radiation from a separate plasma, permitting a major reduction in the required backlighting source power. The object plasma is imaged utilizing spherically bent mica crystals as x-ray optical elements. Experimental results, namely images of test objects obtained using x-ray radiation having different photon energies, are presented. Shadow images of exploding Al wire plasmas in the 1s2–1s2p line radiation of He-like Al XII are also shown. Spatial resolution as fine as 4 μm is demonstrated. The scheme described here is useful for backlighting extended high density plasmas, and could be a less costly alternative to using x-ray lasers for such purposes. © 1997 American Institute of Physics.
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    Tomography by the maximum entropy method for the W7-AS and W7-X multichannel bolometer systems : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 762-765 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A maximum entropy approach has been applied to the tomographic inversion of the line integrated measurements of radiation power flux by a multichannel bolometer system. This method was applied to an H-mode discharge in the W7-AS stellarator, with increasing radiation from the plasma core after the transition being observed. Also, a neutral beam injection discharge was investigated, and the time evolution of a marfe was documented. This method has also been applied to the preliminary design of a multicamera system for full tomographic reconstruction in the W7-X stellarator. In addition, measurements with wire mesh shielded metal foil bolometers have been carried out and the shielding of these bolometers from microwaves produced by the 140 GHz gyrotrons used for electron cyclotron heating has been demonstrated. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147912
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    Fielding and calibration issues for diamond photoconducting detectors : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 782-785 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Diamond photoconducting detectors (PCDs) are routinely fielded as soft x-ray diagnostics on Sandia's Saturn facility. We have developed an improved detector mount that provides a 200 ps time response, is easily cleanable, and is very rugged. In addition, we have developed a new, fast insertion unit to apply bias voltage to the detectors. Absolute calibration of the PCDs is carried out either at the Brookhaven National Synchrotron Light Source or on Sandia's laser calibration facility. We are now fielding diamond elements that have the dimensions 1×3×0.5 mm and 1×1×0.5 mm. We are neutron damaging some of the 1×1×0.5 mm detectors to reduce their sensitivity. We can tailor PCD sensitivity by adjusting element size and neutron damage level. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147914
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    Characterization of new semiconductor detectors for x-ray tomography in the ASDEX Upgrade Tokamak and its generalized physics interpretations : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 774-777 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The energy response of a new semiconductor detector in the ASDEX Upgrade Tokamak for plasma x-ray tomography studies is characterized using synchrotron radiation from a 2.5 GeV positron storage ring at the National Institute for High Energy Physics in Japan. This international collaborating research clarifies a fairly good agreement between the x-ray energy response data and our recently proposed theoretical predictions for such a semiconductor x-ray-detector response. The x-ray response for several positions on the active area of the detector unit is studied; a good uniformity observed guarantees that the detector can employ any sized and shaped collimator for the x-ray tomography regardless of any correction factor coming from the response nonuniformity on the detector active area. Operational conditions of the detector for the ASDEX Upgrade plasma diagnostics are optimized using its capacitance measurements as a function of an applied bias as well as the numerical evaluations of the detector response; these are also directly verified by the synchrotron-radiation experiments. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147913
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    Spatial resolution of gated x-ray pinhole cameras : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 792-795 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have conducted an investigation of the spatial resolution of a new gated x-ray pinhole camera (FXI). The spatial resolution, or its Fourier transform the modulation transfer function (MTF), is critical for quantitative interpretation of recent hydrodynamic instability data taken on the Nova laser. We have taken data corresponding to backlit straight edges, pinholes, and grids, both on the bench and in situ on Nova. For both the pinhole and edge data, the MTF at all wavelengths of interest can be deduced from a single image. Grids are of more limited usefulness, giving the value of the MTF only at the spatial period of the grid. These different techniques for characterizing the MTF of gated x-ray pinhole cameras will be discussed, with results specific to the FXI presented. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147743
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    Point projection radiography with the flexible x-ray imager : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 796-798 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Radiography techniques utilizing large-area x-ray sources (typically ≤7 keV) and pinhole-imaging gated x-ray diagnostics have long been used at the Nova laser facility. However, for targets requiring higher-energy x-ray backlighters (〉9 keV), low conversion efficiencies and pinhole losses combine to make this scheme unworkable. The technique of point projection radiography has been improved upon to make imaging at high x-ray energies feasible. In this scheme a "point" source of x-rays, usually a small diameter (≤25 μm) fiber, is illuminated with a single, 100-ps pulse from the Nova laser. A gated x-ray imager with a 500-ps electronic gate width is used to record the projected image. [K. S. Budil et al., Rev. Sci. Instrum. 67, 485 (1996).] The experimental challenges this technique presents and experimental results will be discussed. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147744
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    Extreme ultraviolet probing of laser imprint in a thin foil using an x-ray laser backlighter : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 802-805 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: For direct drive inertial confinement fusion, a capsule is imploded by directly illuminating the surface with laser light. Beam smoothing and uniformity of illumination affect the seeding of instabilities at the ablation front. We have developed a technique for studying the imprint of a laser beam on a thin foil using an x-ray laser as an extreme ultraviolet (XUV) backlighter. We use multilayer XUV optics to relay the x-ray laser onto the directly driven foil, and then to image the foil modulation onto a charged coupled device camera. This technique allows us to measure small fractional variations in the foil thickness. We have measured the modulation due to imprint from a low intensity 0.35 μm drive beam incident on a 3 μm Si foil using an yttrium x-ray laser on Nova. We present results from a similar technique to measure the imprinted modulation due to a low intensity 0.53 μm drive beam incident on a 2 μm Al foil using a germanium x-ray laser at the Vulcan facility. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147747
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    Use of Langmuir probes in a weakly ionized, steady-state plasma with strong magnetic field (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 4043-4050 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This article describes the use of Langmuir probes to measure plasma parameters in low density, low temperature plasmas with a strong applied magnetic field. The experiment has been performed at the Physics Department of Milan's University on the steady-state toroidal machine "Thorello." Results have been analyzed by taking into account instrumental and ionic sheath effects. Finally, experimental results have been compared with direct measurements of the electron distribution function in Thorello. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1148346
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    Determination of TFTR far-field neutron detector efficiencies by local neutron flux spectrum measurement : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 540-543 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Neutron detectors have often been located on the tokamak fusion test reactor (TFTR) test cell floor 3 m or more from the vacuum vessel for ease of detector access, to reduce radiation damage, minimize count saturation problems, and to avoid high magnetic fields. These detectors include Si surface-barrier diodes, fission chambers, natural diamond detectors, and T2 production in a moderated 3He cell. To evaluate the performance of these detectors during deuterium–tritium (D–T) operation, we determined the neutron flux spectrum incident on the principal detector enclosure using nuclide sample sets containing Al, Ti, Fe, Co, Cu, Zn, Ni, Zr, Nb, In, and Au activation foils. Foils were installed and then removed after ample exposure to TFTR D–T neutrons. High efficiency, high purity Ge detectors were used for gamma spectroscopy of the irradiated foils. The incident neutron fluence and spectral distribution were unfolded from the measured results, and used to derive absolute detector efficiencies. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147647
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    Current initiation in low-density foam z-pinch plasmas : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 848-851 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Low density agar and aerogel foams were tested as z-pinch loads on the Saturn accelerator to study current flow initiation. In these first experiments, we studied the initial plasma conditions by measuring the visible emission at early times with a framing camera and a streaked one-dimensional imaging system. Later, near the stagnation when the plasma is hotter, x-ray imaging and spectral diagnostics were used to characterize the plasma. Filamentation and arcing at the current contacts were observed. Bright implosion features were also observed. Increasing the early time conductivity, by coating the target with a high-z layer and by providing a low-current prepulse, is the most important factor in obtaining good coupling to the machine. None of the pinches were uniform along the z axis. The prime causes of these problems are believed to be the electrode contacts and the current return configuration. Solutions are discussed. © 1997 American Institute of Physics.
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    An overview of ITER diagnostics (invited) (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 862-867 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The requirements for plasma measurements for operating and controlling the ITER device have now been determined. Initial criteria for the measurement quality have been set, and the diagnostics that might be expected to achieve these criteria have been chosen. The design of the first set of diagnostics to achieve these goals is now well under way. The design effort is concentrating on the components that interact most strongly with the other ITER systems, particularly the vacuum vessel, blankets, divertor modules, cryostat, and shield wall. The relevant details of the ITER device and facility design and specific examples of diagnostic design to provide the necessary measurements are described. These designs have to take account of the issues associated with very high 14 MeV neutron fluxes and fluences, nuclear heating, high heat loads, and high mechanical forces that can arise during disruptions. The design work is supported by an extensive research and development program, which to date has concentrated on the effects these levels of radiation might cause on diagnostic components. A brief outline of the organization of the diagnostic development program is given. © 1997 American Institute of Physics.
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    Diagnostics for plasma processing (etching plasmas) (invited) : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 880-885 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Plasma processing diagnostics play two different roles—characterization and control. The goal of plasma characterization is to establish connections of data with external parameters and to verify models. The goal of control diagnostics is to make noninvasive in situ measurements of relevant processing parameters. Diagnostics used in semiconductor etching are considered. These include Langmuir probes, laser induced fluorescence, optical emission spectroscopy, infrared and Fourier transform infrared absorption spectroscopy, mass spectrometry, microwave interferometry, and radio frequency diagnostics. An example is given of the use of many diagnostics in characterizing SiO2 and Si etching by fluorocarbons. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147752
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    A study of CR-39 track response to charged particles from NOVA implosions : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 596-598 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have exposed CR-39 track recording material to a number of NOVA implosions. Radiation from the implosion passed through an array of ranging filters, which aided identification of the incident particles and their energies. The etching procedure was calibrated by including a piece of track exposed to DD protons from a small accelerator. For the same shots, we quantitatively compare the DD neutron yield with the DD proton yield determined from the track. In DT implosions, tracks produced by neutron interactions prevent observation of charged-particle tracks that are produced by the processes of knock on, secondary, or tertiary fusion. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147662
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    Interpretation of neutron time-of-flight signals from current-mode detectors : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 610-613 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Neutron time-of-flight (nToF) signals from current-mode neutron detectors are often used to determine burn-averaged ion temperature from ICF targets because the spread of the neutron energy distribution is a function of the temperature of the reacting ions. The measured signal will, however, be a convolution of the actual neutron signal, the detector response, and the response of the recording system. In addition, scattered neutrons will arrive at the detector later than unscattered neutrons, further broadening the signal. The ion temperature derived from nToF data depends strongly on the functions used to fit the data or the methods utilized to unfold the neutron energy spectrum. A functional form based on known and measured properties of the detectors is used to fit the integral of the time-of-flight signal, allowing ion temperature derivations from targets with lower neutron yield than previously possible.
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    Proton recoil detector of fusion neutrons using natural diamond : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 624-627 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Diamond, with its high radiation damage resistance, is an attractive alternative to silicon for neutron measurements in next step fusion experiments. A 200-μm-thick type IIa natural diamond with Ti/Au contacts was tested at the LAMPF-WNR facility by time-of-flight neutron energy identification. The crystal, having a carrier lifetime of up to 1 ns, was arranged in a low-energy-resolution, high-sensitivity proton recoil telescope consisting of a polyethylene radiator and a low-energy-proton Teflon filter. This arrangement is similar to the triton burnup monitor of Croft et al. [Rev. Sci. Instrum. 64, 1418 (1993)], where a silicon photodiode was used as a recoil proton detector. The observed sensitivity for 14 MeV neutrons (DT) is (1.25±0.15)×10−3 counts/neutron. However, a high contribution of neutron-induced events in the diamond, mainly carbon (A=12) recoils, was observed. A one-dimensional calculation for the detector response to carbon recoil and proton deposition is compared to the measurements. Poor energy resolution of the diamond detector precludes pulse height discrimination between direct 2.5 MeV neutrons events and proton events corresponding to 14 MeV neutrons. Therefore, an overall DT/DD neutron sensitivity ratio of only ∼6.5 is achieved. This value is much lower than the ratio of 540 reported by Croft et al. in their silicon (A=28) monitor.
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    Thomson scattering from two-species laser-produced plasmas (invited) : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 641-646 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We report on recent Thomson scattering measurements from two ion species laser-produced plasmas. A flat disk coated with multiple alternate thin layers of gold and beryllium was irradiated with one laser beam of the Nova laser facility and the resulting two ion species plasma was probed with a second laser beam at a distance of 500 μm with time-resolved spectroscopy of the Thomson scattered light. A controlled variation of the Au fraction of the plasma was achieved by changing the relative thicknesses of the individual multilayers of the target. Two ion acoustic waves belonging to the Au and Be species were clearly observed. Besides their usual application to deduce electron temperatures, the relative damping of both waves provides an accurate measurement of the ion temperature of the plasma. In addition, the relative ion densities can be measured with high accuracy from the relative phase velocities of both waves if the ion charge state is known independently or vice versa. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147908
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    Development of a visible framing camera diagnostic for the study of current initiation in z-pinch plasmas : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 656-659 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We assembled and tested a visible framing camera system to take 5 ns FWHM images of the early time emission from a z-pinch plasma. This diagnostic was used in conjunction with a visible streak camera allowing early time emissions measurements to diagnose current initiation. Individual frames from gated image intensifiers were proximity coupled to charge injection device cameras and read out at video rate and 8-bit resolution. A mirror was used to view the pinch from a 90° angle. We observed the destruction of the mirror surface, due to the high surface heating, and the subsequent reduction in signal reflected from the mirror. Images were obtained that showed early time ejecta and a non-uniform emission from the target. This initial test of the equipment highlighted problems with this measurement. We observed nonuniformities in early time emission. This is believed to be due to either spatially varying current density or heating of the foam. Images were obtained that showed early time ejecta from the target. The results and suggestions for improvement are discussed in the text. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147592
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    First results from the phase contrast imaging system on TEXT-U : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 676-679 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A phase contrast imaging (PCI) diagnostic with a vertical beam covering the central third of the plasma was successfully operated to study density fluctuations in the TEXT-U tokamak. The diagnostic had a wave number range of 0.5–12 cm−1, a bandwidth of 500 kHz and a sensitivity of about 1010 cm−3. We present the optical design of the system and discuss three calibration techniques. We compare density fluctuation spectra obtained with spectra from Langmuir probes at the edge and the heavy ion beam probe diagnostic in the core of the plasma. This provides evidence that the PCI diagnostic is sensitive to both edge and core turbulence. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147717
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    Design of luminescent detectors for the TJ-II device : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 680-682 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We outline designs for several rare-earth-based phosphor powder detector systems for monitoring the broadband VUV plasma radiation in the TJ-II torsatron device. These include a global radiation detector, a detector with temporal and spectral resolution, and a third with radial scanning capabilities. We describe the selection of a phosphor powder for this application having good response from the soft x ray to the VUV, a fast response time, and the capability of operation at high temperatures. In addition, we give details of a method developed in-house for depositing thin uniform layers of powder on glass substrates for use as phosphor screens. Finally, we present some detector test results obtained in the plasma of the TJ-I U torsatron. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147718
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    Full aperture backscatter station imager diagnostics system for far-field imaging of laser plasma instabilities on Nova : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 672-675 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In ICF, the understanding of laser plasma scattering processes is essential for laser target coupling and for controlling the symmetry of indirect drive implosions. The existing Nova full aperture backscatter station has been useful in understanding laser plasma instabilities occurring in hohlraums by measuring the quantity, spectral distribution, and near-field spatial distributions of Brillouin and more recently Raman backscatter. Equally important is an understanding of the far-field spatial intensity distribution which could help in understanding filamentation, threshold and saturation processes. This article describes a broadband, color-corrected far-field imager and associated diagnostics capable of imaging the source of scattered light to better than 25 μm resolution. Brillouin and Raman backscatter can be imaged through the Nova beam-7 focusing lens or the imager can be used like a microscope to image side scatter from other beams. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147716
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    A feasibility study of an infrared tangential viewing polarimeter for measurement of the electron density profile in ITER (abstract) : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 698-698 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Preliminary results of a feasibility study of a CO2 laser tangential viewing polarimeter for measuring electron density profiles in ITER are reported. For ITER plasma parameters and a polarimeter wavelength of 10.6 μm, a Faraday rotation of up to 26° is predicted. An electro-optic polarization modulation technique has been developed at ORNL. Laboratory tests of this polarimeter demonstrated a sensitivity of ≤0.01°. Because of the similarity in the expected Faraday rotation in ITER and Alcator C-Mod, a collaboration between ORNL and the MIT Plasma Fusion Center has been undertaken to test this polarimeter system on Alcator C-Mod. A 10.6 μm polarimeter has been constructed and integrated into the existing C-Mod multichannel two-color interferometer. Detailed analyses and the preliminary results of the C-Mod measurements will be shown.© 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147909
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    Electrodynamic trapping and manipulation of particle clouds (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 70-78 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Apparatus and techniques were developed to electrodynamically trap and manipulate groups of microparticles. The equipment consists of a vibrating orifice aerosol generator, an inductive particle charger, a plenum chamber, and a double-ring electrodynamic balance. Salt particles (NaNO3) of controllable and measurable mass and charge were produced and introduced into the balance in nitrogen at flow rates up to 25 cm3/min. Ordered arrays of any number of particles up to 26 were assembled and manipulated. Methods for compressing the arrays are presented, and controlled ejection of single particles from a trapped array is demonstrated. Particles of opposite polarity were successfully levitated and kept apart, and aggregation of these particles was then induced by changing the electric field. Raman spectra were recorded for multiple salt particles, each having a diameter of 3.5 μm, by aligning them in a laser beam. The enhanced Raman signal is compared with that from a single particle isolated from the array. From the results, a detection limit of 0.4 pg per particle was estimated. © 1997 American Institute of Physics.
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    Thomson scattering measurements in the RFX reversed field pinch : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 718-720 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The first systematic measurements of the electron temperature (Te) spatial profile have been obtained in the reversed field pinch experiment RFX with a single pulse Thomson scattering (TS) diagnostic. Scattered light from a ruby laser pulse (E≤15 J, Δt=30 ns) is collected through three objectives from 10 positions along a diameter in the plasma equatorial plane, with a spatial resolution of 2.5 cm. Plasma discharges with current in the range 700–900 kA have been investigated finding evidence of a quite flat Te profile. Data dispersion significantly greater than experimental uncertainties provides an indication of remarkable plasma fluctuations. Results are in good agreement with Te measurements from other single chord spectroscopic diagnostics (SiLi detector and SXR double filter), showing a reliable operation down to an electron density ne=3×1019 m−3. Integration of this apparatus with a ND:YLF laser system for multipulse Thomson scattering measurements, sharing the same input optics, is under way. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147762
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    A framed monochromatic x-ray microscope for ICF (invited) : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 735-739 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The Laser Fusion Experiments Groups from the Laboratory for Laser Energetics (LLE) and the Los Alamos National Laboratory (LANL) have jointly developed an instrument capable of simultaneously space-, time-, and spectrally resolving x-ray emission from inertial confinement fusion (ICF) targets. Uses of the instrument include framed imaging of line emission from fuel or shell dopants and monochromatic backlighting. The x-ray imaging is accomplished with a Kirkpatrick-Baez (KB)-type four-image microscope, which has a best spatial resolution of ∼5 μm and a sensitive energy range of ∼2–8 keV. Time-resolved x-ray images are obtained with a pair of custom framing cameras, each of which records two of the four images in two independent 80-ps time intervals. In addition, the energy range of the images can be restricted to a narrow (monochromatic) spectral range (∼10–100 eV) by the introduction of diffracting crystals. This technique has been demonstrated with an e-beam-generated dc x-ray source, and at the LANL Trident laser facility and the LLE OMEGA laser facility with x-rays from laser-produced plasmas. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147688
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    An evaluation of multilayer mirrors for the soft x ray and extreme ultraviolet wavelength range that were irradiated with neutrons : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 757-760 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The Plasma Spectroscopy Group at the Johns Hopkins University develops high photon throughput multilayer mirror (MLM) based soft x ray and extreme ultraviolet (XUV 10 Å〈λ〈304 Å) spectroscopic diagnostics for magnetically confined fusion plasmas. The D-T reactions in large fusion reactor type devices such as the International Thermonuclear Experimental Reactor will produce neutrons at a rate as high as 5×1019 n s−1. The MLMs, which are used as dispersive and focusing optics, will not be shielded from these neutrons. In an effort to assess the potential radiation damage, four MLMs (No. 1: Mo/Si, d=87.8 Å, Zerodur substrate with 50 cm concave spherical curvature; No. 2: W/B4C, d=22.75 Å, Si wafer substrate; No. 3: W/C, d=25.3 Å, Si wafer substrate; and No. 4: Mo/Si, d=186.6 Å, Si wafer substrate) were irradiated with fast neutrons at the Los Alamos Spallation Radiation Effects Facility (LASREF). The neutron beam at LASREF has an energy distribution that peaks at 1–2 MeV with a tail that extends out to 100 MeV. The MLMs were irradiated to a fast neutron fluence of 1.1×1019 n cm−2 at 270–300 °C. A comparison between the dispersive and reflective characteristics of the irradiated MLMs and the corresponding qualities of control samples will be given. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1148449
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    New optical methods for short wavelength hot plasma diagnostics : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 770-773 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have developed new types of experimental methods for high-temperature plasma diagnostics based on both glass capillary converters (GCCs) and multilayer mirrors (MLMs), where the optical GCC device provides guiding, focusing, and polarization analysis of short wavelength radiation with a large bandwidth, and the MLM elements are used for dispersing, focusing, and polarization sensitive studies of radiation within a narrow bandwidth. In particular, we report here for the first time, to the best of our knowledge, the development and testing of such new optical diagnostic devices for: (i) pinhole chamber with GCC, (ii) GCC converter for time-resolved x-ray measurements, (iii) polarimeters–spectrometers with GCC and MLM for measurements of polarization and spectral characteristics of short wavelength radiation, and (iv) high sensitivity extreme ultraviolet spectrometers. © 1997 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1147694
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    Los Alamos pinhole camera (LAPC): A new flexible x-ray pinhole camera : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 786-788 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have recently designed, built, and fielded a versatile, multichannel x-ray pinhole camera. The Los Alamos pinhole camera was designed to fit into any 6 in. manipulator (SIM) which is a standardized target chamber diagnostic tube. There are currently compatible SIMs available at the Trident, Omega, and NOVA laser systems. The camera uses nine pinholes in a 3×3 array to produce images at the film plane. The film housing is designed to hold multiple sheets of stacked x-ray film which also uses a dark slide to protect the film before exposure. Magnifications of 12, 8, 4, and 2X are selected by slip-on nose cones, which support pinholes, collimators, and blast shields. Individual channel filtering is provided by a 3×3 filter pack containing nine separate filter sub packs. Spatial resolution is limited by the pinhole diffraction limit and field of view is dependent on magnification and filter pack diameter. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147741
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    Dual microchannel plate module for a gated monochromatic x-ray imager : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 789-791 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Development and testing of a dual microchannel plate (MCP) module to be used in the national inertial confinement fusion (ICF) program has recently been completed. The MCP module is a key component of a new monochromatic x-ray imaging diagnostic which is designed around a four channel Kirkpatrick–Baez microscope and diffraction crystals and is located at the University of Rochester's Omega laser system. The MCP module has two separate MCP regions with centers spaced 53 mm apart. Each region contains a 25 mm MCP proximity focused to a P-11 phosphor coated fiberoptic faceplate. The two L/D=40, MCPs have a 10.2 mm wide, 8 ohm stripline constructed of 500 nm copper overcoated with 100 nm gold. A 4 kV, 150 ps electrical pulse provides an optical gatewidth of 80 ps and spatial resolution has been measured at 20 lp/mm. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147742
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    Development of surface-wave ion source using coaxial-type cavity (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 79-82 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A compact 2.45 GHz surface-wave ion source has been developed for the production of stable beams from gaseous feed materials. The source has been operated with two different geometries of surface wave generation, that is, a dielectric disk on ground plane structure and a dielectric disk between the parallel plate structure with a holey top plate. The designer can control the intensity of the emitted microwave simply by varying the thickness of the dielectric plate. The sources have been operated with three different thicknesses of the dielectric plate: td=10, 15, and 20 mm. td=10 mm is the optimum coupling condition. Moreover, the ion beam current of the holey-plate structure is 1.5 times as high as that of the dielectric disk structure. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147746
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    Diagnostics for studies of absorption and energy transfer process features in low-density porous targets irradiated with powerful laser pulses : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 810-813 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A diagnostic methodology for studies of powerful laser pulse interaction with a porous material of low average density in conditions of interest for advanced inertial confinement fusion targets is discussed. These diagnostics were used in experiments with a powerful 1 μm Nd:laser beam incident upon "agar-agar" targets (C14H18O7)n of different average density from 1×10−3 to 5×10−3 g/cm3 and thickness from 100 to 1000 μm with and without thin aluminium layers (0.5–6 μm) on the front and rear surfaces. Intensity at the focal spot area 100 μm in diameter ranged from 1013 to 1014 W/cm2. It is shown that it is possible to estimate the longitudinal and transverse dimensions of the laser–plasma interaction region and to obtain the plasma dynamics data by recording: the visible and IR radiation at the rear side of illuminated targets with streak camera; x-ray images with filtered pin holes; and multiframe shlieren- and shadowgraphy snapshots (0.3 ns laser pulses at 0.53 μm wavelength have been used). © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147915
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    One- and two-dimensional fast x-ray imaging of laser-driven implosion dynamics with x-ray streak cameras : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 828-830 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: One- (1D) and two-dimensional (2D) x-ray imaging techniques with x-ray streak cameras have been developed and utilized for investigating implosion dynamics of laser fusion targets. Conventional streaked 1D images of the shell motion of the imploding target was recorded together with the time-resolved 2D multi-imaging x-ray streak images of the core shapes on the same x-ray streak camera. Precise comparison of the core dynamics between the experimental and simulation results was performed with an accuracy of 30 ps by fitting the trajectories of the x-ray emission from the imploding shell. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147700
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    X-ray diagnostics of hohlraum plasma flow : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 831-833 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In this study we use spectroscopy and x-ray imaging to investigate the macroscopic plasma flow in mm-sized laser-produced hohlraum plasmas. By using multiple diagnostics to triangulate the emission on a single experiment, we can pinpoint the position of dopants placed inside the hohlraum. X-ray emission from the foil has been used in the past to measure electron temperature. Here we analyze the spatial movement of dopant plasmas for comparison to hydrodynamic calculations. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147701
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  • 193
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    Measurement of H/D ratio and ion temperature on a HT-6M Tokamak (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 83-84 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: By combining optical fibers with piezoelectric scanning Fabry–Perot interferometer, the profiles of Hα and Dα have been determined simultaneously in a single Tokamak discharge. Consequently, the ratio of hydrogen to deuterium and ion temperature are obtained. Not only is the uncertainty of shot-to-shot avoided, the results of the experiment indicate that this instrumentation has the advantage of rapid wavelength scanning, large dispersion, high resolution, and good adaptability of working in adverse circumstances such as at a Tokamak site. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147704
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  • 194
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    Experimental investigation of the interaction of 100 TW laser with solid targets (abstract) : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 847-847 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We report on the first plasma experiments with the 100 TW laser at LLNL. We have experimentally investigated the interaction of 1 μm, 40 J, 400 fs, 5×1019 W/cm2 laser pulses with multilayer solid targets. Various diagnostics were used to characterize this interaction. An x-ray pinhole camera monitored laser spot size and plasma location on target. Part of the laser beam was split off to probe the density scale length of the preformed plasma. An optical system for Schlieren photography was designed to record the images of plasma with electron density gradients as low as 1021 cm−4 with characteristic scale length of 10 μm. The range of electron densities was 1018–2020 cm−3. CR-39 plastic track detectors were employed to measure the fast ion blowoff from the plasma. Using a foil-filter technique the proton energy spectrum up to 6 MeV was measured. It was found that the high energy tail usually had a narrow (FWHM ∼10°) cone of expansion. Energy conversion to the fast ions (above 0.5 MeV) was estimated to be ∼0.3%–1% of laser energy. In addition, charge-coupled devices were used for detecting characteristic K α emission caused by fast (〉1 MeV) electrons. (See article by K. Wharton for further discussion of the fast electron measurements.) Estimated fast electron yield ∼3%.© 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148452
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    Investigation of the response of superconducting quantum interference devices to temperature variation (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 85-88 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have measured the temperature dependent change ∂Φ/∂T in the flux signal of a superconducting quantum interference device (SQUID) operating in a flux locked loop. Thin film niobium dc SQUIDs were used for these investigations. One and the same device could be operated either as dc or rf SQUID allowing one to compare the effect of temperature variation in both modes of operation. We have found that relaxation of trapped flux appears to be the dominant result of temperature variation. The asymmetry of the two critical junction currents in dc SQUID operation could be seen, as well as an influence of an external magnetic field on ∂Φ/∂T. This influence was an order of magnitude smaller when the device was operated as an rf SQUID, compared to dc SQUID operation. By the use of a high frequency demagnetization process, ∂Φ/∂T could be reduced from typical values of about 0.3 Φ0/K to less than 0.05Φ0/K in certain cases. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147709
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    Recent results from tokamak divertor plasma measurements (invited) (abstract) : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 886-886 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: New diagnostics have been developed to address key divertor physics questions, including: target plate heat flux reduction by radiation, basic edge transport issues, and plasma wall interactions (PWIs) such as erosion. A system of diagnostics measures the target plate heat flux (imaging ir thermography) and particle flux (probes, pressure and Penning gauges, and visible emission arrays). Recently, Te, ne, and Pe (electron pressure) have been measured in two-dimensions (2D) with divertor Thomson Scattering. During radiative divertor operation Te is less than 2 eV, indicating that new atomic processes are important. Langmuir probes measure higher Te in some cases. In addition, the measured Pe near the separatrix at the target plate is lower than the midplane pressure, implying radial momentum transport. Bolometer arrays, inverted with reconstruction algorithms, provide the two-dimensional core and divertor radiation profiles. Spectroscopic measurements identify the radiating species and provide information on impurity transport; both absolute chordal measurements and tomographic reconstructions of images are used. Either intrinsic carbon or an inert species (e.g., injected Ne) are usually observed, and absolute particle inventories are obtained. Computer codes are both benchmarked with the experimental data and provide important consistency checks. Several techniques are used to measure fundamental plasma transport and fluctuations, including probes and reflectometry. PWI issues are studied with in situ coupons and insertable samples (DiMES). Representative divertor results from DIII-D with references to results on other tokamaks will be presented. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147711
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    Verification of unfold error estimates in the unfold operator code : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 890-893 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Spectral unfolding is an inverse mathematical operation that attempts to obtain spectral source information from a set of response functions and data measurements. Several unfold algorithms have appeared over the past 30 years; among them is the unfold operator (UFO) code written at Sandia National Laboratories. In addition to an unfolded spectrum, the UFO code also estimates the unfold uncertainty (error) induced by estimated random uncertainties in the data. In UFO the unfold uncertainty is obtained from the error matrix. This built-in estimate has now been compared to error estimates obtained by running the code in a Monte Carlo fashion with prescribed data distributions (Gaussian deviates). In the test problem studied, data were simulated from an arbitrarily chosen blackbody spectrum (10 keV) and a set of overlapping response functions. The data were assumed to have an imprecision of 5% (standard deviation). One hundred random data sets were generated. The built-in estimate of unfold uncertainty agreed with the Monte Carlo estimate to within the statistical resolution of this relatively small sample size (95% confidence level). A possible 10% bias between the two methods was unresolved. The Monte Carlo technique is also useful in underdetermined problems, for which the error matrix method does not apply. UFO has been applied to the diagnosis of low energy x rays emitted by Z-pinch and ion-beam driven hohlraums. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147713
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    Generation of 1 ns excimer laser output pulse by direct wave clipping (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 8-13 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In this article, a 1 ns excimer laser pulse was obtained successfully from an ultraviolet preionized XeCl laser using a direct wave-clipping technique with some improvements over the conventional scheme in consideration of obtaining more suitable discharge and steeper front edge of original light pulse. The effects of laser operation stability and optical setup of the experiment scheme on output characteristics are discussed. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147753
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    A noise-rejecting current amplifier for surface atmospheric ion flux measurements (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 3563-3565 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Large area electrodes are required to determine atmospheric charge fluxes at the earth's surface. These also act as antennas for power line hum, swamping the small atmospheric electric signals. A battery-powered head-amplifier resolving 0.025 pA is described here, which uses active compensation to substantially cancel the interference, allowing the atmospheric charge fluxes to be resolved in the presence of the interference. The overall response is nominally −100 mV/pA, with 30 dB of 50 Hz rejection. The head amplifier can drive a low impedance line. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148323
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    Development of infrared focal plane arrays for space (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 3566-3578 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Space astronomy requires large-area cryogenic infrared focal plane arrays (FPAs) with high quantum efficiency, extremely low dark current, low power dissipation, and background limited noise performance. To meet these requirements, especially at temperatures of 5–15 K, Santa Barbara Research Center designed and fabricated a new multiplexer, CRC-744. The FPAs made by bonding InSb detector arrays to CRC-744 multiplexers were evaluated at the University of Rochester. The best array achieved the read noise of 5 e − with 12 s integration and 7 e − with 200 s integration with Fowler-64 sampling at 15 K, the average dark current of 〈0.2 e−/ s at both 15 and 29 K, and the average quantum efficiency of 87% at both 15 and 29 K. The 10%–90% rise time was 4 μs driving a 600 pF external load. The power dissipation was 0.3–0.4 mW when running flat-out (100% duty cycle). The full well capacity was 105 e− (230 mV) with 400 mV of applied bias. The above test results demonstrate that the FPAs meet background-limited space experiment requirements. The CRC-744 multiplexer works well down to at least 5 K (the lowest temperature of our tests). © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148324
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