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  • Electrical Engineering, Measurement and Control Technology  (17,843)
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  • Articles  (17,843)
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  • 1995-1999  (17,160)
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  • 1
    Electronic Resource
    Electronic Resource
    "Millikelvin-stabilized cell" for x-ray diffraction measurements with a function of sensing thermal anomalies (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 3298-3299 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Based on our technique of fine temperature control, we developed a new "millikelvin (mK)-stabilized cell" having a function of sensing thermal anomalies for the detailed x-ray diffraction study of solid phase transitions. It is easily mounted on a commercially available goniometer head. The performance was tested using CsPbCl3 single crystal, in which a phase transition is known to take place at 320 K (47°C) from tetragonal to cubic. An abrupt variation in the distance between some two reciprocal points in the precession pattern was clearly detected in a 0.1 K temperature range centered at 47°C along with two thermal anomalies observed. The "mK-stabilized cell" will be very useful to investigate a mechanism of phase transitions occurring in a narrow temperature range. © 1998 American Institute of Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149114
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  • 2
    Electronic Resource
    Electronic Resource
    Calorimetric apparatus for alternating current loss measurements on high-temperature superconductors (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 3320-3325 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The use of high-temperature superconductors in electric power components requires the knowledge of their alternating current (ac) losses. Methods are therefore needed to characterize the conductors with respect to their ac losses under applicationlike conditions. In this article we describe a calorimetric setup for ac loss measurements on long length high-temperature superconductors carrying ac transport currents in ac external magnetic fields at variable temperatures. The variable temperature is achieved by a thermal connection between the sample and a cooling machine. Current in copper coils generates the magnetic field parallel to the plane of the tape and perpendicular to the transport current. This current can be induced in the coil-formed sample. Two slightly different methods are used to determine the ac losses, one in which the temperature rise of the sample, caused by the ac losses, is compared to the temperature rise caused by a reference heater and another in which the increase in power dissipation of the sample is compensated for by a reduction of the power dissipation in the heater. Typical results of the ac loss measurements are presented. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149096
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  • 3
    Electronic Resource
    Electronic Resource
    Temperature-induced reflectivity changes and activation of hydrogen sensitive optically thin palladium films on silicon oxide (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 3331-3338 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The optical properties of several thin metal film palladium-silicon oxide structures are examined at room temperature before and after annealing to 200 °C and also at 90 °C—in all cases in the presence of hydrogen gas. Multicycling sample activation is shown to occur in the presence of hydrogen at room temperature with an increase in reflectivity on exposure to hydrogen, in contrast to thicker 80 Å films. The reflectivity change increases with increasing film thickness (1–10 Å). The surface activation at room temperature, before and after annealing to 200 °C, is compared with the performance at 90 °C, where it is shown that heat treatment strongly influences the behavior of the metal film.© 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149116
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  • 4
    Electronic Resource
    Electronic Resource
    Optical fiber velocimetry: A technique for measuring velocity in two-dimensional flows (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 3215-3222 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In this article we describe a new technique, optical fiber velocimetry (OFV), to instantaneously measure two components of velocity at a point in freely suspended flowing liquid films. The technique relies on the measurement of displacements of an optical fiber tip which is coupled to the flowing film. The deflection of the fiber tip is proportional to the velocity and it behaves as a simple harmonic oscillator. Thus the low frequency response of the fiber gives direct measurements of the flow velocity. A statistical test using data acquired simultaneously by the fiber and by a laser Doppler velocimeter shows good agreement between the two techniques. Velocity power spectra measured in the wake of a von Karman street and in two-dimensional (2D) grid turbulence using the OFV also compare favorably with the laser Doppler velocimeter. The OFV technique is simple and robust, allowing it to be used in a wide variety of flows that have strong 2D characteristics. New prospects of using multiple fibers to measure circulation and velocity correlations at several separated spatial points are discussed. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149086
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  • 5
    Electronic Resource
    Electronic Resource
    A multipurpose scanning near-field optical microscope: Reflectivity and photocurrent on semiconductor and biological samples (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 3240-3244 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A multipurpose scanning near field optical microscope (SNOM) operating at ambient pressure is described with the aim of characterizing the inner parts of biological molecules and any semiconductor or metal microstructure. Therefore, in addition to the requirements of reliability and mechanical stability we have carefully considered analyzing a sample with all available geometries for input/output of photons, in order to get as much information as possible. The SNOM unit consists of two separable cylindrical supports; the lower one contains the sample holder mounted on top of a piezoelectric scanner which is contained in a motor controlled x-y-z stage. A piezo-modulated stretched optical fiber with a few tens of nanometer pinhole and a shear-force apparatus mounted inside the top cylinder allow for topography measurements. The reflectivity of the sample can be measured by applying different methods: the sample can be illuminated on top by an external source, as well as by the optical fiber used for the detection of the reflectivity signal. An aperture in the lower cylinder allows for illumination of the sample on the back: in this case the fiber collects the evanescent wave induced at the top of the sample. Another aperture in the lower cylinder allows measurement of the reflected light which includes a contribution due to the interaction with the fiber. Also photocurrent experiments can be easily performed by illuminating the sample with the fiber and detecting the transmitted signal using a current–voltage converter mounted inside the top cylinder. A video-camera that can reach 170 enlargements is mounted on the top cylinder for positioning the fiber on particular regions of the sample. Reflectivity and photocurrent measurements have been performed on uncoated neurons, CsI compound, Au/GaAs, and PtSi/Si systems, reaching a resolution well below the diffraction limit. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149089
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  • 6
    Electronic Resource
    Electronic Resource
    A peristaltic injection nozzle for collinear laser and molecular beams (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2888-2891 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A novel gas nozzle design that allows for collinear laser and molecular beams is described. Unlike conventional nozzles that open and close to limit the gas flow into a vacuum chamber, this nozzle opens to release a small volume of gas into the chamber. Gas pulses of 300 μs duration and 65±5 μs opening times have been obtained. When room-temperature H2 is used as the source gas, the rotational temperature was found to be 175±12 K, whereas when room-temperature D2 was used, the rotational temperature was found to be 104±7 K. The collinear optical and molecular beam path provided in this design may be useful in photodissociation experiments, the study of atomic and molecular collisions, Rydberg state lifetime measurements, and vacuum ultraviolet generation by nonlinear mixing in gases. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149029
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  • 7
    Electronic Resource
    Electronic Resource
    Saturation of multiplication mechanism in silicon avalanche photodiodes used for single electron detection (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2898-2901 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have examined the multiplication factor of silicon avalanche photodiodes designed for fast timing detection of monoenergetic electrons. The multiplication mechanism was found to be saturated. The highly concentrated space charge generated by a primary electron causes the saturation. This was confirmed by a Monte Carlo simulation of electron trajectories in silicon and an experiment exploiting a subpicosecond laser pulse with a variable illuminating spot size to simulate an electron bombardment. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149030
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  • 8
    Electronic Resource
    Electronic Resource
    Gas-coupled laser acoustic detection at ultrasonic and audio frequencies (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2912-2917 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Airborne acoustic waves have been detected by a laser-beam deflection technique in both the ultrasonic and audio frequency ranges. For ultrasonic applications, a probe beam is directed parallel to the surface of a sample. Ultrasonic waves in the solid are detected when an acoustic wave is radiated from the surface into the ambient air, where the density variations cause a beam deflection. Gas-coupled laser acoustic detection (GCLAD) has been used to record well-resolved through-transmission and surface-acoustic wave forms in various materials. GCLAD has also been incorporated into a C-scanning system where it has been used to image subsurface flaws in graphite/polymer composite panels. Because the laser beam is not reflected from the sample surface, the technique is not dependent upon the surface optical properties of the material under investigation. It is particularly useful for testing graphite/polymer composites and other materials with rough surfaces. The beam-deflection technique has been tested quantitatively in the kHz frequency range by passing a probe beam through a cylindrical resonator. The acoustic spectrum of the resonator was measured from 4 to 13.5 kHz by scanning the frequency of a source and recording the acoustic field with both a microphone and the beam-deflection system. The acoustic fields of the lower-frequency modes are well known and enable both qualitative and quantitative tests of the beam-deflection technique. Measurements on the lowest-frequency plane-wave mode were used for absolute calibration of the microphone. The noise level of the beam-deflection measurements at 4.3 kHz was found to be 0.05 nrad (rms), corresponding to an acoustic pressure of 0.005 Pa (rms). © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149033
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  • 9
    Electronic Resource
    Electronic Resource
    Integrated mass spectrometer–microreactor system for the in situ investigation of oxide semiconductor sensors (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 3314-3319 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This work describes the construction of an experimental setup — a mass spectrometer coupled microreactor — which makes possible the simultaneous monitoring of the electric resistance of a solid sensor sample and the composition of the near surface gas atmosphere. The information obtained from the constant voltage resistance measurement is complemented by the information about of the near-sensor gas composition. The evaluation of both sets of results offers insight into the mechanism of the sensing process. As an example, the results obtained on an undoped, oven-heated CeO2 sensor sample is presented, in a CO and oxygen containing atmosphere between 25 and 900 °C. It was found that between 200 and 300 °C the decrease in the sensor resistance is mainly due to the CO chemisorption. In this temperature range the oxidation of CO is negligible. The CO sensitivity decreases with the temperature in the whole interval examined. However, its value is the highest in this temperature range due to the relatively high surface coverage. In the 300–400 °C range the most important process is the gas phase oxidation of the CO; about 85% of it is transformed. The transformation of CO leads to a smaller surface coverage, and so to a decreasing — but still high enough — sensitivity. A further temperature rise hinders the CO chemisorption and the lack of chemisorption results in no CO sensitivity. It is noted that even the catalytic effect of the CeO2 sample is important in the studied system; its effect on the near-sensor gas composition is easily detectable. The maximum catalytic activity of CeO2 in the CO oxidation was found to be around 400 °C. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149115
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  • 10
    Electronic Resource
    Electronic Resource
    Lubricant film thickness mapping using a capacitance technique on magnetic thin-film rigid disks (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 3339-3349 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe a novel capacitance measurement technique which is used to determine lubricant film thickness on magnetic thin-film rigid disks. Using this technique, variations in lubricant thickness as small as 0.1 nm can be measured quickly and nondestructively. Film thickness measurements made with an ellipsometer are found to be comparable to the capacitance measurements. We compare the uniformity in film thickness of disks lubricated with a dip-coating process with that of disks lubricated with a drain-coating process and find that the drain coated disks have better film uniformity than those that are dip coated. Also, wear tracks in fully bonded and partially bonded perfluoropolyether lubricants are profiled. We find that lubricant depletion occurs more rapidly in fully bonded lubricant than in partially bonded lubricant and that some recovery of the partially bonded lubricant occurs while none is observed in fully bonded lubricant. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149098
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  • 11
    Electronic Resource
    Electronic Resource
    A versatile pulsed X-band ENDOR spectrometer (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 3357-3364 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A versatile high power X-band (8.5–9.5 GHz) pulsed EPR/ENDOR (electron-nuclear double resonance) spectrometer which can generate hundreds of microwave (MW) and rf pulses is described. The pulse programmer is constructed from a word generator with 32 channels and 4 ns resolution, coupled to five digital delay generators which can produce a total of ten pulses with a resolution better than 1 ns. The spectrometer contains two MW and two rf channels that allow independent variation of the frequency, amplitude, and phase of the MW and rf pulses. The ENDOR probe head is based on a bridged loop gap (BLG) resonator, coupling is achieved via a coupling loop connected to a waveguide, and the rf coil serves as a MW shield as well. The adjustment of the coupling is done by an up/down motion of the of the resonator assembly with respect to the fixed coupling loop. A flexible and user friendly data acquisition program written in C++ (Borland version 4.5), which uses the Windows-95 Multiple Document Interface (MDI) programming model, was developed to run the spectrometer. This program allows easy programming of any pulse sequence with sophisticated phase cycling. The performance of the spectrometer is demonstrated by two experiments. The first is the triple resonance hyperfine-selective (HS) ENDOR experiment carried out on a frozen solution of the copper protein laccase. The second is the two-dimensional hyperfine-ENDOR (HYEND) correlation experiment performed on a single crystal of γ-irradiated malonic acid. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149101
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  • 12
    Electronic Resource
    Electronic Resource
    Thermal parameters of dental materials determined by photoacoustic phase lag measurements (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 3392-3397 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A method of measuring the phase lag of the photoacoustic signal obtained by rear surface excitation is employed for the determination of the thermal properties of insulating dental materials such as calcium hydroxide cement, a cavitary varnish and photopolymerized restoration resins. Disk shaped dental materials were glued to the front surface of the thin metal foil window of the photoacoustic cell and illuminated by pulsed light. A three layer model was developed to fit the measurements of the phase angle as a function of the frequency of excitation. The thermal diffusivity and conductivity of the dental material were determined to good precision. The instrumentation employed in the present work is simple and easily obtainable by any laboratory. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149105
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  • 13
    Electronic Resource
    Electronic Resource
    A white-light Michelson interferometer in the visible and near infrared regions (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2854-2858 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A white-light Michelson interferometer in the visible and near infrared regions is described which can obtain the cross-correlation interferogram between the incident light and the transmitted light through samples or optical components. By comparing the autocorrelation interferogram of the incident white light with the cross-correlation interferogram between the incident light and the transmitted light, we can obtain linear response functions of samples or optical components with femtosecond time resolution. Fourier analysis of the interferograms gives also the complex optical constants of the samples without relying on the Kramers–Kronig relation. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149024
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  • 14
    Electronic Resource
    Electronic Resource
    Measurement system for optical Kerr effect induced by continuous wave laser (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2871-2874 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An experimental technique was developed for studying the optical Kerr effect induced by a cw Ar+ laser with 500 mW output. A Pockels cell was used for modulating the pump laser so that the polarization changed periodically between the vertical and horizontal plane. The dielectric anisotropy thus induced in a sample liquid was probed in the ellipsometry with a He–Ne laser. The system was applied to nitrobenzene and p-n-hexyl p′-cyanobiphenyl (6CB), a nematogen in the isotropic phase. The observed birefringence showed a linear dependence on the pump laser intensity and the gradient yielded the Kerr constant: B=5.75×10−14 V−2 m at 30 °C in nitrobenzene and B=6.72×10−12(T−T*)−1 V−2 m in 6CB, T* being the virtual transition temperature to the nematic phase. This technique can be used for investigating the relaxation of molecular orientation in frequency domain. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149027
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  • 15
    Electronic Resource
    Electronic Resource
    Advances in the transient dc photocurrent technique for excited state dipole moment measurements (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2875-2887 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Recent advances in the transient dc photocurrent technique for measuring excited state dipole moments, developed in our group, are discussed. A variety of approaches with detailed analyses of their advantages and disadvantages including cell design, circuit construction tricks, the data acquisition procedure, calibration, and the theoretical treatment of different conditions, are presented. Sensitivity, time resolution limitations, and newly developed features, such as the signal's dependence on light polarization as well as charge separation at interfaces are outlined. Dipole moments of a few molecules (diphenylcyclopropenone, bianthryl, dimethylaminonitrostilbene, Coumarin 153, and fluoroprobe) suitable for calibration purpose are reported—some of them for the first time. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149028
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  • 16
    Electronic Resource
    Electronic Resource
    Instrumentation for time-resolved electron diffraction spanning the time domain from microseconds to picoseconds (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2633-2643 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Recent instrumental improvements which successfully extend the time resolution of pulsed beam electron diffraction to the picosecond regime are described. Based on modifications of an existing nanosecond apparatus, a new sample inlet system, electron pulse generation laser, and amplified detector have been incorporated into the design such that significant improvements in both the signal level and ultimate time resolution are achieved; an upper estimate of the electron pulse width is ∼20 ps. Enhancements are such that, for operation in the nanosecond time domain, an entire diffraction pattern over a useful range of scattering angles may be collected from a gas-phase sample in a single electron pulse. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148991
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  • 17
    Electronic Resource
    Electronic Resource
    Fast pulsed hollow cathode capillary discharge device (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 3118-3122 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A fast pulsed capillary discharge device has been developed and implemented. The device combines the features of a transient hollow cathode discharge with the inherent characteristics of the capillary discharge, to obtain VUV to XUV radiation with ns rise time. The discharge operates in a 0.8 mm inner diameter alumina capillary, at 10–30 kV applied voltage. On axis discharge initiation is assisted by electron beams, which are characteristic of the hollow cathode effect. A short, 5 ns full width at half maximum XUV pulse is produced in association with a ∼1 kA, 5 ns current pulse. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149069
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  • 18
    Electronic Resource
    Electronic Resource
    A simple high pressure flow cell for on-line absorption, Raman, and time resolved laser induced fluorescence spectroscopy in supercritical fluids (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 3127-3131 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A versatile spectroscopic flow cell for high pressure liquids and supercritical fluid solutions is described. The cell is capable of being coupled to either standard or fiber optic spectrometers. There are two perpendicular optical paths that are adjustable in length and aperture diameter. The cell has shown it can be used for absorption, emission, or scattering spectroscopy. The design is simple, inexpensive, serviceable, uses conventional materials, and is self aligning. With apertures of 5.7 mm the cell has been tested to pressures up to 500 atm and temperatures up to 90 °C. However, the cell would allow usage at higher temperatures and pressures if desired. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149071
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  • 19
    Electronic Resource
    Electronic Resource
    An intense atomic hydrogen source with a movable nozzle output (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 3132-3135 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The fabrication and operation of a stable and intense source of atomic hydrogen from an easily movable nozzle is described in detail. The source uses a well-known air-cooled, extended cavity microwave source using molecular hydrogen, but conducts the dissociated atoms to the experimental interaction region via inert Teflon "spaghetti" tubing. A resulting collimated beam with a dissociation fraction exceeding 0.8 and with an average number density of atomic hydrogen of 6×1012 cm−3 at a distance of 2 mm from the exit of the source is obtained. This source of H is attractive, because it is movable and easily interfaced into beam–beam type experiments. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149072
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  • 20
    Electronic Resource
    Electronic Resource
    An improved method of generating analog waveforms from digital data (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2569-2571 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: As normally used, the digital-to-analog converter generates a series of constant amplitude signals that, taken together, approximate the desired analog equivalent of the initial digital signal. Hence, many samples are required to generate a reasonably smooth approximation. Even so, it is usually necessary to filter the resulting approximation to remove the sharp corners of the constant amplitude signals and blend them together. This requirement is particularly troublesome in the case of generating very low frequency analog signals, e.g., a 1 Hz sine wave. In this article we propose an inexpensive improvement in the commercial digital-to-analog converter cards. This improvement results in a waveform with much better quality than that produced by the usual methods. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148960
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  • 21
    Electronic Resource
    Electronic Resource
    Modeling of tunnel diode oscillators and their use for some low temperature investigations (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2550-2560 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The simple method of modeling of tunnel diode (TD) oscillators' work is described, and may be applied also to the other types of negative-differential conductance oscillators. In particular, the calculation of the harmonic oscillation amplitude is performed by the energy balance method, based on TD measured the current–voltage characteristic' (I–V curve), using only one fitting parameter—the tunnel diode's measured bias at which oscillations are quenched by means of which the oscillator's effective total losses are determined also. The formula for calculation of the TD generator's frequency is derived; it agrees with experiment and permits determination of its dependence on the radiotechnical scheme's elements and TD I–V curve's shape. The results of the calculation in comparison with the experiment are reported for the oscillators of various constructions operating at different conditions. For this, more attention is given to the constructive solutions applied in the low temperature experiments. Examples of the TD oscillators' use in cryogenic techniques as well as in the superconducting detectors of particles and radiation are presented. The oscillators described generate, under the certain conditions, low-amplitude (〈40 mV) sinusoidal signals with a highly stable frequency (not worse than ΔF/F=10−9/min at liquid-helium temperatures) and low intensity of higher harmonics in the soft mode. The power released is less than 10 μW and the measuring rf magnetic field's amplitude at a sample, placed inside or near the oscillator coil, is less than 1 mOe. Using designed facilities we have already detected normal-to-superconducting phase transitions of tin grains with diameters of about 2 μm and phase transitions in micrometer thick and 20 μm2 high-Tc superconducting films. © 1998 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1148957
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    Detection of shear wave in ultrasonic range by using a laser Doppler vibrometer (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2572-2573 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A laser Doppler vibrometer is used to measure shear waves propagating through solids in the ultrasonic frequency range. The laser Doppler vibrometer detects translational motion of small spherical lenses mounted on a solid surface. Stacking of wave-form signals increases the signal-to-noise ratio. Wave motion on a solid surface can be obtained from the surface vibrations measured at different incident angles of a laser beam. The observed longitudinal and shear wave amplitudes from a thickness-dilation-mode transducer agreed fairly well with the calculated amplitudes modeled by a piston force source. © 1998 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1148961
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    Erratum: "A modification of Ångström's method that employs photothermal radiometry to measure thermal diffusivity: Application to chemical vapor deposited diamond" [Rev. Sci. Instrum. 69, 237 (1998)] (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2576-2576 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148977
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    Pinhole camera imaging of x rays and energetic neutral atoms for hot plasma diagnostics (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2574-2575 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A compact pinhole camera is found to be useful for observation of a spatial distribution of hot ions by imaging energetic charge-exchange neutral atoms. One can obtain images of neutral atoms and of x rays in the same geometry only by selecting filtering foils at the pinhole opening of a single camera. Easy comparison between the images associated with distributions of ions and electrons is quite beneficial for physical analyses of plasmas. The imaging technique is expected also to be useful to determine space–time-resolved energy spectra of hot ions. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148962
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    Time-gated photon counting method for two-photon spectroscopy using synchrotron radiation and laser (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1931-1933 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new measurement system has been developed for two-photon spectroscopy in solids with a combination of synchrotron radiation and laser. This system is based on a time-gated photon counting technique to observe luminescence signals induced by two-photon excitation. It is demonstrated that this technique enables us to achieve a high sensitivity and a good signal-to-noise ratio because it is a kind of zero method. © 1998 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1148874
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    A digital control system for the iodine stabilized He–Ne laser (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1934-1937 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A digital control system has been developed for the iodine stabilized He–Ne laser. The system is based on a digital signal processor and a general purpose microprocessor. The hardware is briefly described. The algorithms used for laser frequency locking are presented and new methods which are made possible by this system are discussed. An improved way of locking the laser to the fifth or seventh harmonic of the modulation frequency has been implemented digitally. © 1998 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1148875
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    Development of an array calorimeter detector and measurement of KrF laser intensity (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1938-1942 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new array calorimeter detector has been developed and was used to measure the spatial profile of a KrF laser with 300 J energy and a 267 mm diameter in near field. The detector contains 441 (21×21) calorimeters. A tantalum foil is used as the absorber. The boiling of liquid nitrogen is used as the reference temperature of the thermocouples, as it is both insulating and stable. Thus, it is the basis of the physical measurement in the sub-μV–mV level with a multithermocouple detector. The response of the tantalum foil is linear in the range of fluence from 30 mJ/cm2 to 1.1 J/cm2. The experimental results show that the spatial profile of the KrF laser pumped by two side electron beams is saddle shaped with a valley at the center and one peak at each side of the center on the coaxial line of electron beams in the near field. With a decrease of the laser's gas pressure, the distribution become more even rather than flat. © 1998 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1148876
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    Absolute calibration of a flat field spectrometer in the wavelength range 10–70 Å (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1949-1954 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We characterize an x-ray spectrometer in the wavelength range 10–70 Å. The instrument has been designed for the study of the soft x-ray emission from plasmas generated with intense sub-ps laser pulses. It uses a flat field reflection grating with 2400 lines per mm as dispersing element and an x-ray charged coupled device (CCD) as detector. The sensitivity of the spectrometer and CCD detector has been absolutely calibrated by means of a ns-laser generated gold plasma of well known x-ray conversion efficiency. The calibration procedure is explained in detail. Finally, we present examples of spectra emitted by a sub-ps laser plasma. From the spectra follows a resolving power of 150–350 and a low conversion efficiency into the second diffraction order of the flat field grating of only a few %. The measured frequency averaged total conversion of laser energy into x-ray energy emitted into 2π is in the range of 2.4×10−4 up to 6.2×10−3 depending on the material of the solid targets. © 1998 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1148878
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    Time and frequency-resolved photoluminescence up conversion using broadly tuneable picosecond infrared pulses (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1943-1948 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A simultaneous time and frequency-resolved photoluminescence setup based upon the concept of sum-frequency generation has been developed using the parallel collection capabilities of a liquid nitrogen cooled, high quantum efficiency charge coupled device (CCD) detector. This up conversion system can provide excellent time resolution (down to ∼100 fs), when the detector is used in the single channel mode, with large dynamic range. When the CCD detector is used in its full capacity (1024 channels), wide spectral range as well as temporal information are obtained simultaneously from the up-converted signal, thus providing important information on the dynamics of various emission peaks which can occur simultaneously. Together with this, an efficient method for generation of high repetition rate, low energy infrared light between 1.44 and 1.62 μm is described. The technique uses difference frequency mixing of the fundamental wavelength of a mode-locked Nd:yttrium aluminum garnet laser and the output of a synchronously pumped Rhodamine 640 dye laser in a 10 mm long lithium triborate crystal. This source was then used to performed cw and time-resolved up-conversion photoluminescence measurements on a 1.54 μm emitting InGaAsP epitaxial layer. © 1998 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1148877
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    High pressure fiber optic light scattering spectrometer (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1955-1960 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A high-pressure fiber-optic light-scattering spectrometer has been constructed for in situ observation of molecular dissolution/association as well as the polymerization process in supercritical fluids. Single (or multiple) fiber-optic probes, each comprised of a single optical fiber (or multiple optical fibers) and a graded index microlens, are used to transmit the incident laser beam and to receive the scattered light as well as the transmitted light from the high pressure cell. The direct immersion in the scattering medium of the fiber-optic probes makes the spectrometer more compact and more flexible with an easier alignment process. With the miniaturization and flexibility, our high-pressure light-scattering cell can be transported and adapted in combination with other physical techniques, such as synchrotron small angle x-ray scattering which requires a different set of windows (e.g., made of diamond) suitable for x-ray transmissions. This spectrometer has been successfully used for the in situ study of the molecular association behavior of a diblock copolymer of 1,1-dihydroperfluorooctylacrylate and vinyl acetate in supercritical carbon dioxide under pressures up to 552 bar. © 1998 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1148879
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    Novel hybrid interferometer stabilization scheme used in wavelength shift measurement for Bragg grating sensors (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1961-1965 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A novel hybrid interferometer stabilization scheme used for wavelength shift measurement, such as for in-fiber Bragg grating-based sensors, is described. This scheme combines the advantages of the long term optical imbalance stability offered by the locking system used and a comparative insensitivity to vibration-induced noise at frequencies up to 200 Hz, achieved with the use of a so-called "detection-and-compensation" scheme. By including an additional reference beam and the hybrid interferometer stabilization scheme, the vibration-induced fluctuation in the signal can be reduced by about 20 dB, and the value of the phase variation can be reduced by a factor of 20. © 1998 American Institute of Physics.
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    Methods for the analysis and design of a solid state nuclear magnetic resonance probe (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 3384-3391 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Methods for the analysis and design of solid state nuclear magnetic resonance (NMR) probes are presented. These techniques have been applied to a 200 MHz (1H Larmor frequency) 1H–19F–13C cross polarization magic angle spinning probe. Transmission lines have been used throughout the design enabling the production of a highly power efficient probe (1H-22%, 19F-17%, and 13C-33%) capable of detecting 19F NMR signals while applying proton decoupling fields of 250 kHz. These techniques have proven very useful in designing the probe discussed within the text but are not confined to such a triple resonant design. In fact the techniques are sufficiently general to be useful to all radio frequency design efforts including deuterium wide-line probes and multiresonant high resolution NMR probes. A series of simple but useful design concepts are presented which are used to predict the efficiencies of the design presented. © 1998 American Institute of Physics.
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    Formula for the asymmetric diffraction peak profiles based on double Soller slit geometry (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2268-2272 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The asymmetric diffraction peak profiles and peak shift of conventional powder diffractometry systems caused by the angular divergence along the vertical axis are reproduced by asymmetrized peak profile functions. The asymmetrization is achieved by convoluting the angular dispersions of both incident and scattered beams along the vertical axis. A general method for mapping vertical window functions to the horizontal direction is proposed, and the formulas of two types of horizontal window functions mapped from symmetric double vertical Bartlett (triangular) and Gaussian window functions are presented. Both formulas incorporate a single asymmetry parameter connected with the open width of the Soller slits along the vertical direction. When experimental diffraction peak profiles are fitted by asymmetrized pseudo-Voigt functions, the asymmetry parameter gives good coincidence with the Soller slit angle, which is clearly specified in a given diffractometer. © 1998 American Institute of Physics.
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    A fast atomic oxygen beam facility with in situ testing/analysis capabilities (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2273-2277 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A fast atomic oxygen beam facility consisting of a beam source, a mass spectrometer, an Auger electron spectroscope, a scanning tunneling microscope, and a friction tester has been developed to investigate interaction of energetic atomic oxygen with solid surfaces. The fast atomic oxygen beam has been characterized by time of flight distribution, quadrupole mass spectrometry, and quartz crystal microbalance. The time of flight distribution of the beam has shown that the average translational energy of the atomic oxygen beam reaches 4.7 eV and that the full width at half-maximum is 5.5 eV. A flux of the atomic oxygen is calculated from the frequency shift of the quartz crystal microbalance with silver electrodes, and typical flux of the atomic oxygen beam being 4.0×1012 atoms/cm2 s. The flux of atomic oxygen of this source is fairly low, but is corresponding to that in the altitude of 500 km in low Earth orbit. The surface sensitive analysis methods equipped with the facility, such as Auger electron spectroscopy and scanning tunneling microscopy, have provided changes in the surface composition and morphology caused by the atomic oxygen exposure, without receiving any effect of ambient air. The ultrahigh vacuum friction tester especially designed for this facility is used to measure tribological properties of solid lubricants under the atomic oxygen exposures. Such in situ testing capability of this facility enables fundamental research for understanding the reaction scheme of atomic oxygen as well as engineering-oriented research for obtaining high reliability of the space systems. © 1998 American Institute of Physics.
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    Mass analysis of negative ions in etching plasma (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 3437-3438 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Negative ions in etching plasma were extracted from a plasma chamber and mass spectra were measured. For the extraction of the negative ions, the plasma sheath was broken by a cone-shaped extractor electrode which had an orifice on the tip. To avoid disturbing the plasma, the tip of the extractor electrode was slightly stuck out of an electrically earthed wall. To remove electrons from the extracted negative charged flux, a magnetic field was applied to the flux. By using the extractor electrode and the magnetic field for the removal of the electrons, the negative ions could be extracted efficiently and the mass spectra could be measured with low noise. © 1998 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1149119
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    In situ calibration of a flat-field grazing incidence spectrograph with an x-ray charge-coupled device camera using a transmission grating and a laser-produced plasma for x-ray laser research (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2849-2853 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An in situ calibration experiment of a soft x-ray spectrograph for x-ray laser research has been performed. The calibrated spectrograph was a flat-field grazing incidence spectrometer with an x-ray charge-coupled device camera. The absolute sensitivity of the spectrograph was obtained for the wavelength range from 2.6 to 4.0 nm using a transmission grating spectrograph as a reference spectrograph set along the axial direction of a line-focused laser-produced plasma. The absolute sensitivity determined in this work shows nearly the same value as that deduced from the calibration experiment using synchrotron radiation. © 1998 American Institute of Physics.
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    Imaging spectrometer based on an acousto-optic tunable filter (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2859-2867 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This article describes an imaging spectrometer developed for remote sensing applications. The instrument consists of an acousto-optic tunable filter (AOTF), a high sensitive charged coupled device camera and optic lens. The selected AOTF was designed to have a large entrance aperture and to diffract light between 600 and 900 nm with a high spectral resolution. The signal was digitized by the camera and acquired with a developed WINDOWS executable software which drives the instrument. The spectrometer has been operated in a classical mode and in an imaging mode for its evaluation. In the imaging mode, images including different types of targets were acquired in reflection and transmission mode and were used to investigate image homogeneity, spatial resolution, chromatic and geometric aberrations, sensitivity and reliability. Spectra have been extracted from images and were successfully compared with spectra from the same sample area obtained with classical nonimaging spectrometers. This confirms the ability of this instrument to clear up many problems in surface analysis, particularly in the case of laboratory and field measurements used in remote sensing studies. © 1998 American Institute of Physics.
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    Experimental methods in radioactive ion-beam target/ion source development and characterization (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2892-2897 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have developed off-line experimental techniques and apparatuses that permit direct measurement of effusive-flow delay times and ionization efficiencies for nearly any chemically reactive element in high-temperature target/ion sources (TIS) commonly used for on-line radioactive ion-beam (RIB) generation. The apparatuses include a hot Ta valve for effusive-flow delay-time measurements, a cooled molecular injection system for determination of ionization efficiencies, and a gas flow measurement/control system for introducing very low, well-defined molecular flows into the TIS. Measurements are performed on a test stand using molecular feed compounds containing stable complements of the radioactive nuclei of interest delivered to the TIS at flow rates commensurate with on-line RIB generation. In this article, the general techniques are described and effusive-flow delay times and ionization efficiency measurements are reported for fluorine in an electron-beam plasma target/ion source developed for RIB generation and operated in both positive- and negative-ion extraction modes. © 1998 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1149225
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    An external electronic feedback system applied to a cryogenic μ-calorimeter (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2017-2023 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In order to improve the maximum counting rate of cryogenic μ-calorimeters used as particle detectors, the application of an external electronic feedback (EEF) system is under development in Genoa, Italy. A description of the experimental setup of such a system and a model which describes the properties of the EEF applied to a current biased μ-calorimeter is reported. The model shows the maximum performance obtainable with such a system, which in principle allows one to improve the detector speed by some orders of magnitude. The model includes also a theoretical noise analysis and the calculation of the intrinsic energy resolution obtained using this kind of system, showing that the EEF does not worsen the energy resolution. The theoretical calculations have been compared with the experimental results obtained in Genoa. The comparison shows a good agreement between theoretical predictions and experimental results. In particular it has been possible to reduce the pulse length, considered as equal to five time constant, from more than 110 ms to less than 4 ms, gaining about a factor of 30 in the detector speed. The corresponding energy resolution with the feedback system is 1.75 times worse than without the feedback system. © 1998 American Institute of Physics.
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    An optical probe for local measurements of fast plasma ion dynamics (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2024-2026 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A novel insertable probe for local measurements of equilibrium and fluctuating plasma ion flow velocity and temperature via Doppler spectroscopy is described. Optical radiation is collected by two fused silica fiber optic bundles with perpendicular viewlines. Spatial resolution of about 5 cm is achieved by terminating each view with an optical dump. The collected light is transported by the fiber bundles to a high-resolution spectrometer. Two components of the velocity are measured simultaneously—the radial along the insertion of the probe and a perpendicular component (which can be varied by simply rotating the probe by 90°). The accuracy of the velocity measurements is better than 1 km/s. The probe is armored by a boron nitride enclosure and is inserted into a high temperature plasma to obtain radial profiles of the equilibrium and fluctuating plasma velocity. Initial measurements have been done in Madison Symmetric Torus reversed field pinch. © 1998 American Institute of Physics.
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    Real-time phase-selective data acquisition system for measurement of wave phenomena in pulsed plasma discharges (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2027-2031 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A novel data acquisition system and methodology have been developed for the study of wave phenomena in pulsed plasma discharges. The method effectively reduces experimental uncertainty due to shot-to-shot fluctuations in high repetition rate experiments. Real-time analysis of each wave form allows classification of discharges by wave amplitude, phase, or other features. Measurements can then be constructed from subsets of discharges having similar wave properties. The method clarifies the trade-offs between experimental uncertainty reduction and increased demand for data storage capacity and acquisition time. Finally, this data acquisition system is simple to implement and requires relatively little equipment: only a wave form digitizer and a moderately fast computer. © 1998 American Institute of Physics.
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    A sensitive broadband high-frequency electron spin resonance/electron nuclear double resonance spectrometer operating at 5–7.5 mm wavelength (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1817-1822 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A novel high-frequency electron spin resonance (ESR) spectrometer is described. The features are high sensitivity, a continuously tunable operating frequency of 40–60 GHz, a cylindrical cavity with a novel coupling scheme, and simultaneous detection of absorption and dispersion. A radio frequency coil can be integrated into the cavity for electron nuclear double resonance (ENDOR) experiments. ESR and ENDOR spectra of a test sample are presented in order to demonstrate in particular the scientific potential of a variable-frequency spectrometer. © 1998 American Institute of Physics.
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    A high-pressure cell for optical microscopy and measurements on the phase diagram of poly(diethylsiloxane) (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1823-1827 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new high-pressure cell as useful equipment for a polarizing microscope is described. Measurements in a temperature range between −40 and +270 °C under hydrostatic pressures up to 300 MPa allow for example the observation of polymer morphology and phase transitions. In addition to a documentation on video and photograph, respectively, the computer-controlled light intensity measurement offers the possibility of a quantitative analysis. Investigations on the phase diagram of poly(diethylsiloxane) have been carried out and show, that the transition temperature from mesophase to isotropic melt decreases with increasing pressure for pressures above 160 MPa. © 1998 American Institute of Physics.
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    A new design for study on reactivity of clusters (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1837-1839 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This article reports on a new apparatus, called the laser double ablation reactor, for studies on the reactivity of clusters. Structure and operative principle of the apparatus were presented. With this apparatus reactions between manganese/carbon clusters and sulfur clusters, and between silver and sulfur clusters were studied. The experiments indicate that manganese/carbon clusters appear inert when they react with sulfur clusters, while for reactions between silver and sulfur clusters, the products [AgS4]+, [AgS8]+, [AgS12]+, and [AgS16]+, mainly are obtained. In comparison to the results obtained by Fourier transform ion cyclotron resonance, it shows that the new apparatus is very efficient for study on reactions between clusters. © 1998 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1148851
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    A new sputtering device of radio-frequency magnetron discharge using a rectangular hollow-shaped electrode (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1833-1836 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new sputtering device using a radio-frequency magnetron discharge with a rectangular hollow-shaped electrode has been developed for a low-pressure discharge (∼ a few mTorr). The spatial structures of the electron density, the etching rate of the target material (copper), and the deposition rate were measured in uniform and convex profiles of the externally applied magnetic field. The device realized the uniform use of the target material under the arrangement of the magnetic-field configuration. The resistivity of the deposited copper thin film was also obtained, which was found to be similar to that of conventional copper (∼10−8 Ω m). © 1998 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1148850
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    Electrochemical cell for in situ x-ray diffraction under ultrapure conditions (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1840-1843 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An electrochemical cell has been developed for in situ x-ray diffraction from a working electrode under clean conditions equivalent to ultrahigh vacuum conditions of 5×10−10 mbar. The substrate crystals can be prepared ex situ and transferred into the cell under protection of ultrapure water within a few seconds. The oxygen level in the electrolyte is reduced by continuous N2 flow to less than 0.2% compared to that of a fresh electrolyte. This can be done while rotating the cell by 360° about the surface normal. The electrode potential is accurately measured at the position of the crystal using a Luggin capillary and a standard reference electrode. We demonstrate the performance of our cell by in situ synchrotron x-ray diffraction measurements on ultrathin Co layers electrodeposited on Cu(001) in an aqueous H2SO4/CoSO4 solution. © 1998 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1148852
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    Aspects of the suspension system for GEO 600 (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 3055-3061 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The GEO 600 gravitational wave detector is currently under construction in Germany. To ensure that the detector sensitivity is not limited by seismic noise above 50 Hz a significant degree of seismic isolation has to be provided for each test mass. To achieve this level of isolation each test mass, which will be made from fused silica (mass ∼14 kg), will be suspended as the final stage of a triple pendulum from an isolation stack consisting of layers of stainless steel masses and graphite loaded silicone rubber. Extending from the stack will be three cantilever springs supporting an upper mass from which a double pendulum stage will be suspended. This double pendulum will incorporate cantilever springs in the upper stage in order to enhance the vertical isolation, and will use fused silica fibers in the lower pendulum stage in order to minimize thermal noise from the pendulum modes. The expected performance from this arrangement of stacks, vertical spring stages, and double pendulums should achieve our goals for seismic isolation. © 1998 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1149054
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    Transfer function analysis of the constant voltage anemometer (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2385-2391 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The transfer function for the constant voltage anemometer (CVA) circuit has been derived in terms of circuit and hot-wire parameters and the expressions for the natural frequency and damping ratio have been obtained. Bandwidth in each case was determined from the plot of the normalized transfer function. The theoretical bandwidth behavior calculated from the transfer function plots for the prototype agrees with independent tests of the prototype using laser radiation heating of the hot wire in an air jet. The near constant value of the bandwidth of the CVA with the variation in the hot-wire overheat and its Reynolds number that were observed with the laser tests have been substantiated with the theoretical values from the transfer function. Bandwidth testing with sine wave injection, in situ time constant measurement for proper compensation setting, method to optimize the design to have nearly a constant bandwidth even with different compensation time constants and the operational advantages of CVA are also discussed. © 1998 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1148964
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    Ion flux measurements with the improved collector probe system at the TEXTOR-94 tokamak (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2671-2674 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A collector probe system at the TEXTOR-94 tokamak has been upgraded becoming a versatile tool in studies of erosion and deposition processes under plasma discharges. The reconstruction dealt with the distinct modification of the computer aided probe steering system and the collector probe head. The new operation system, based on a LabView environment, allows unlimited number of preprogrammed linear and angular probe movements and is applied for either integrated or time-resolved measurements of ion fluxes in the scrape-off plasma. Particular advantage is related to the possibility of such measurements during a selected part of a tokamak discharge, for instance the flat top, neutral beam injection phase, neon injection for plasma cooling, etc. The upgraded system and the results from some of the experiments, where the new possibilities have been beneficial, are presented in the article. © 1998 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1148996
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    High-speed multishot pellet injector prototype for the Frascati Tokamak Upgrade (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2675-2680 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The Frascati Tokamak Upgrade (FTU) may require multiple high-speed pellet injection in order to achieve quasi-steady-state conditions. A research and development program was thus being pursued at ENEA Frascati, aimed at developing a multishot two-stage pellet injector (MPI), featuring eight "pipe gun" barrels and eight small two-stage pneumatic guns. According to FTU requirements, the final goal is to simultaneously produce up to eight D2 pellets, and then deliver them during a plasma pulse (1 s) with any time schedule, at speeds in the 1–2.5 km/s range. A prototype was constructed and tested to demonstrate the feasibility of the concept, and optimize pellet formation and firing sequences. This laboratory facility was automatically operated by means of a programmable logic controller (PLC), and had a full eight-shot capability. However, it was equipped as a first approach with only four two-stage guns. In this article we will describe in detail the guidelines of the MPI prototype design, which were strongly influenced by some external constraints. We will also report on the results of the experimental campaign, during which the feasibility of such a two-stage MPI was demonstrated. Sequences of four intact D2 pellets in the 1.2–1.6 mm size range, fired at time intervals of a few tens up to a few hundreds of ms, were routinely delivered in a laboratory experiment at injection speeds above 2.5 km/s, with good reproducibility and satisfactory aiming dispersion. Some preliminary effort to address the problem of propellant gas handling, based on an innovative approach, gave encouraging results, and work is in progress to carry out an experiment to definitely test the feasibility of this concept. © 1998 American Institute of Physics.
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    Plasma measurements with triple and single probes in an asymmetrical parallel plate rf plasma reactor (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2681-2684 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In an asymmetrical parallel plate reactor measurements of Ar radio-frequency (rf) plasmas are done with both single and triple probes. All measurements are carried out with the same probe construction and the probe systems are realized by changing probe circuit connections. Ar plasmas are generated with a frequency of 13.56 MHz at a pressure of 50 mTorr and a power of 20 W. In order to remove the alternative component the compensation circuits are connected to the probe system. It is found that there is a fairly good agreement between two probe characteristics obtained with the single and the triple probes. Influences of a time variation of the plasma potential on the results are reduced, but cannot be completely removed. The reason why the measurement results obtained with the single and the triple probes suffer from the same effect of the alternative component is explained using the equivalent circuits of the probe systems. © 1998 American Institute of Physics.
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    Design, operation, and housing of an ultrastable, low temperature, ultrahigh vacuum scanning tunneling microscope (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2691-2695 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have designed and constructed a low temperature, ultrahigh vacuum scanning tunneling microscope (STM), taking extreme measures to isolate the microscope from acoustic, vibrational, and electronic noise. We combined a 4 K STM with line-of-sight dosing to enable one to position the crystal surface in front of an impinging molecular beam as in scattering experiments. Due to the mechanical stability of the instrument and the minimal thermal drift associated with working at 4 K we are able to locate and to image repeatedly isolated adsorbates and atomic-scale structures, such as step edges, for extended periods days. The instrument has been designed for the topographic and spectroscopic characterization of atoms and molecules on metal and semiconductor surfaces, for the investigation of the mechanism by which the STM images adsorbates on surfaces, and for inelastic electron tunneling spectroscopy of single molecules. © 1998 American Institute of Physics.
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    A compact fluorescence and polarization near-field scanning optical microscope (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2685-2690 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We present a transmission, fluorescence, and polarization near-field scanning optical microscope with shear-force feedback control that is small in size and simple to operate. This microscope features an ultrafine mechanical tip/sample approach with continuous manual submicron control over a range of several millimeters. The piezo-driven 12 μm x-y scan range is complimented by a 4 mm coarse mechanical translation range in each direction. The construction materials used in the mechanical feedback loop have been carefully chosen for thermal compatibility in order to reduce differential expansion and contraction between the tip and sample. A unique pressure-fit sample mount allows for quick and reliable sample exchange. Shear-force feedback light is delivered to the scan head via an optical fiber so that a remote laser of any type may be used as a source. This dither light is collimated and refocused onto the tip, delivering a consistently small spot which is collected by a high numerical aperture objective. This new scan head incorporates an optical system which will permit the linearization of scan piezo response similar to a scheme used successfully with atomic force microscopy. This is designed to both overcome the piezo's inherent hysteresis and to eliminate drift during long duration spatial scans or spectroscopic measurements at a single location. The scan head design offers added flexibility due to the use of optical fibers to deliver the dither and scan linearization light, and functions in any orientation for use in conjunction with upright or inverted optical microscopes. © 1998 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1148999
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    One and two dimensional space scannings of x-ray beams by diffraction on surface acoustic waves: Application to x-ray imaging (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2704-2707 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: X-ray diffraction on surface acoustic waves with tunable wavelength provides a way to perform beam scannings. 1D and 2D space scannings of x-ray beams by this method are presented. The feasibility of a purely optical method to perform scanning x-ray imaging without any mechanical movement is discussed. © 1998 American Institute of Physics.
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    New and versatile ultrahigh vacuum scanning tunneling microscope for film growth experiments (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2696-2703 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: With the increasing popularity of the scanning tunneling microscope (STM) in surface science, many ideas for additional and new technical features have been proposed. The work herein contributes to this evolution with a special STM design. The STM described is part of an experimental apparatus for thin film growth investigations in ultrahigh vacuum. Besides the STM, the apparatus includes facilities for thermal desorption spectroscopy and Auger electron spectroscopy and a Kelvin probe for measuring dynamic work function changes. The Kelvin probe is optimized for gas adsorption experiments as well as for in situ film growth investigations during metal deposition. These added features combined with the STM and easy sample transfer yield a new powerful tool for in situ controlled preparation and extensive characterization of thin films. In the present work we describe the novel features of this STM and we demonstrate the efficiency of the whole system by giving a few representative results. © 1998 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1149001
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    A programmable prescaler for minimizing counting errors with PC-based data acquisition cards (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1909-1913 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Many commonly used PC-based data acquisition counter boards are specified to count regularly occurring events at rates up to 7 MHz. Boards with this frequency limit begin to systematically and significantly underestimate the rate of randomly occurring events occurring at average frequencies much lower than the specified 7 MHz rate due to the dead time of the counter. This report highlights the origin of this error and describes an easily constructed prescaler circuit that permits accurate event counting at rates up to, and even exceeding, the nominal speed of the counter. © 1998 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1148863
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    Simple device for monitoring secondary electron emission of materials in the pulse mode (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1916-1917 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A simple device for simultaneously measuring the secondary electron emission coefficient σ and the primary current in the pulse mode has been built. It allows convenient monitoring of these parameters for either conductive or insulating materials.
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    URL: http://dx.doi.org/10.1063/1.1149170
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    Effect of laser beam deflection on the accuracy of interferometer measurements (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1584-1586 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The laser interferometry is a frequently used diagnostics for plasma density measurements. The measurements in plasmas with no density gradients allow direct correspondence of the fringe shift and plasma density along the laser line of sight. The change of the interferometer contrast due to scene beam deflection in plasmas with density gradients reduces the fidelity of interferometer measurements due to the change in the contrast of the fringe. The analytic expression for the maximum acceptable deflection angle is derived, analyzed, and compared to the experiment. Ways to improve the accuracy of interferometer measurements are proposed. © 1998 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1148868
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    High resolution reflectivity diffractometer on Station 2.3 (Daresbury Laboratory) (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1224-1229 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A high resolution reflectivity diffractometer (HRRD) has been recently commissioned on Station 2.3 at the SRS, Daresbury Laboratory. Using the instrument which is x-ray wavelength tunable, the characterization of the interface structure in an ion-assisted deposited Co/Cu multilayer has been carried out. In order to improve the electron density contrast of the sample, we have used an x-ray energy near the Cu K edge of 8.989 keV. By scanning the normal (specular), near normal (off specular), and parallel axes (transverse) of the surface, we have obtained useful reflectivity intensity data. By applying simulations to the data, we have determined a total roughness (rms) of 6.0±0.5 Å with a significant contribution from correlated interfacial roughness (4.2±0.2 Å). Other detailed structural information obtained has successfully demonstrated that the commissioned instrument is a viable tool for reflectivity studies. © 1998 American Institute of Physics.
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    A simple extended-cavity diode laser (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1236-1239 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Operating a laser diode in an extended cavity which provides frequency-selective feedback is a very effective method of reducing the laser's linewidth and improving its tunability. We have developed an extremely simple laser of this type, built from inexpensive commercial components with only a few minor modifications. A 780 nm laser built to this design has an output power of 80 mW, a linewidth of 350 kHz, and it has been continuously locked to a Doppler-free rubidium transition for several days. © 1998 American Institute of Physics.
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    Solubility of solids in supercritical fluids from the measurements of the dielectric constant: Application to CO2–naphthalene (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2732-2737 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new method for the measurement of solid solubilities in supercritical fluids is described in detail. The method is based on the measurement of the dielectric constant of the saturated supercritical solution solvent–solute and that of the supercritical solvent as a function of pressure along different isotherms. Our method is simple, absolute, easy to use, and permits precise measurement of the solubility of solids in supercritical fluids. Solubilities of naphthalene in supercritical CO2 in the pressure range 12–30 MPa are reported along the isotherms 313.15, 318.15, and 323.15 K. © 1998 American Institute of Physics.
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    Optical interferometric signal generator based on electrical phase-locked loop technique (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1246-1252 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: To simulate a phase-modulated interferometer, a novel electrical signal generator has been demonstrated. There are two phase-locked loop (PLL) circuits used in our system to process the phase signal. The first PLL is adopted as a voltage-controlled phase shifter, and the second PLL is used to amplify the phase signal to get a phase shift with a dynamic range over ±16π rad. This system can be further modulated with sinusoidal, sawtooth, and triangular wave forms for interferometric signal detection. © 1998 American Institute of Physics.
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    Double-modulation electro-optic sampling for pump-and-probe ultrafast correlation measurements (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1257-1260 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe a novel electro-optic double-modulation (DM) sampling technique for ultrafast transient spectroscopy, which is characterized by a superior signal-to-noise ratio compared to that of a regular single-modulation technique. DM is achieved by a combined effect of a radio-frequency modulation, which eliminates most of the low-frequency noise, and an audio-frequency modulation, which makes use of a high-performance, low-frequency lock-in amplifier. The DM sensitivity is comparable to that of the more sophisticated schemes involving electrical mixing and the A–B noise reduction method. We show that the DM technique offers superior performance in two-beam transient pump-and-probe correlation measurements compared to the regular single frequency modulation technique and is an ideal scheme for three-beam picosecond correlation measurements. © 1998 American Institute of Physics.
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    Photoreflectance spectroscopy with white light pump beam (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1261-1266 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Using a dual chopping scheme where both the pump beam and the probe beam are chopped, we show that it is possible to perform photoreflectance spectroscopy with a broadband white light source as the pump beam instead of a laser source. We show that although the signal strength is reduced by a factor of 1/π in the dual chopping scheme, it nevertheless has several advantages. A white light pump beam provides a wide range of excitation energy values, enabling one to characterize semiconductors of different band gaps spread over a wide energy range with a single modulation source. In the case of semiconductor heterostructures, simultaneous as well as selective excitation of different interfaces can be achieved easily. This technique is not plagued by the problem of background due to luminescence often encountered in low-temperature photoreflectance measurements. In this article, we present the details of this technique and demonstrate its usefulness by applying it to selected semiconductor heterostructure samples. © 1998 American Institute of Physics.
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    Cluster formation and uranium photoionization in the afterglow of a pulsed hollow cathode lamp (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1270-1274 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Uranium photoionization was observed in the afterglow of pulsed hollow cathode lamps illuminated by a dye laser tuned near the electronic transition around 591.5 nm (5L60−16 900 cm−1 7M7). The photoionization signal was used to monitor the time evolution of the ground state uranium vapor density in the cathode hole. Lifetimes over 1 ms were measured for the uranium vapor; that makes this device attractive for multistep photoionization spectroscopy. The obtained results lead to the conclusion that these long times are due to cluster formation in the afterglow. © 1998 American Institute of Physics.
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    Measurements of dead time and characterization of ion counting systems for mass spectrometry (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1282-1288 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A method for characterization of electron multiplier-based pulse counting systems is presented. Specific attention is paid to measurement of the counting system dead time. The systems discussed here are typically used to measure the abundance of ions passing through a mass spectrometer. A method for the determination of dead time by measurement of at least two isotopic ratios of an element with at least three isotopes is given. This method differs from the "text book" method typically used to measure the dead time. The theoretical basis for the measurements is given and an example of measurements of Ti isotopes by secondary ion mass spectrometry (SIMS) is shown. Dead time measurements on SIMS instruments can be performed in a few hours of machine time. A brief description of the pulse detection and counting circuit and its operation is also given. Guidelines for the proper measurement of pulse shapes and the determination of reasonable settings for electron multiplier gain, preamplifier gain, and discriminator threshold are also discussed.
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    A novel distributed system for plasma immersion ion implanter control and automation (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1495-1498 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The high voltage and electromagnetic field environment poses a big challenge to a control system for plasma immersion ion implantation (PIII). The automation process must be immune to electric field interference produced by the high voltage power supply, modulator, radio-frequency or microwave plasma generator, MEVVA plasma sources, and so on. We have recently designed and installed a distributed control system, PIIIDCS, to automate the operation of our PIII facility. Programmable logic controllers are used as the field control stations because of their good anti-interference ability and good real time response. A DH-485 network is used as the communication link between the field controllers and the management station in order to improve the robustness and reliability of the system. The newly developed interface is designed to work in a graphic mode in Microsoft Windows 95. Test runs have shown that the system is reliable, flexible, and easy to operate. The development of this novel control system will expedite the development of commercial PIII instrumentation. © 1998 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1148785
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    High-pressure light scattering apparatus to study pressure-induced phase separation in polymer solutions (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1463-1471 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new high-pressure time- and angle-resolved light scattering apparatus has been developed to study the kinetics of phase separation in polymer solutions and other fluid mixtures under pressure at near- and supercritical conditions. The system consists of a high-pressure polymer loading chamber, a solvent charge line, a variable-volume scattering cell (with a built-in movable piston connected to a pressure generator, and an expansion rod driven by an air-actuated diaphragm), and a recirculation pump which are all housed in a temperature-controlled oven. The system is operable at pressures up to 70 MPa, and temperatures up to 473 K. The scattering cell is a short path-length cell made of two flat sapphire windows that are separated by 250 μm. It is designed to permit measurements of transmitted and scattered light intensities over an angle range from 0° to 30°. A linear image sensor with 256 elements is used to monitor the time evolution of the scattered light intensities at different angles. With this sensor, the angle range from 2° to 13° is scanned at a sampling rate of 3.2 ms/scan. The pressure quenches are achieved by movement of the air-actuated movable expansion rod, or by the movement of the piston with the aid of the pressure generator to bring about either rapid (at rates approaching 2000 MPa/s) or slow pressure changes in the system. Quench depth is also adjustable, and very deep (70 MPa) or very shallow (as low as 0.1 MPa) pressure quenches are readily achievable. The temperature and the pressure of the solution in the scattering cell, and the transmitted and scattered light intensities at different angles are recorded in real time through a computerized data acquisition system before and during phase separation. The experimental system is especially suited to follow the kinetics of phase separation in polymer solutions and to assess the metastable and unstable regions where phase separation proceeds by the nucleation and growth, and the spinodal decomposition mechanisms, respectively. The capability of the instrument is demonstrated for polystyrene/methylcyclohexane solutions. © 1998 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1148782
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    Multidimensional fluorescence spectroscopy using a streak camera based pulse fluorometer (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1512-1518 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Modern streak camera based pulse fluorometers readily allow data collection in two-dimensions. We have developed a modular instrument that is easily adapted for recording time-resolved emission spectra, fluorescence depolarization data, and time series of time-resolved fluorescence decays. The instrument is based on a synchroscan streak camera and a passively mode-locked Ti:Sapphire laser using second harmonic generation and third harmonic generation to extend the excitation wavelength range to the visible and ultraviolet. The performance of the instrument was tested using standard biological samples. The dynamic range is typically 600:1, and the detection limit is less than 1 fW. With respect to the fluorescence decay kinetic (first time axis), the temporal resolution is better than 10 ps, and rotational correlation times of 50 ps are measured routinely. For the second time axis, the maximum time resolution is approximately 2 ms. © 1998 American Institute of Physics.
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    Photomodulated thermoreflectance detection of hydrogen gas using optically thin palladium film on silicon oxide (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1505-1511 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The sensitivity of various thicknesses of optically thin film palladium layers evaporated onto silicon oxide substrate is investigated in the presence of a hydrogen/air atmosphere at room temperature. The magnitude of the resulting reflectivity change is measured using an excite-probe technique, through laser excited photothermal modulation of a probe beam. This allows for the recovery of information from both the amplitude and phase channels of the hydrogen sensor output. Data indicates that concentrations of 0.1% hydrogen in the presence of a balanced air mixture and at room temperature may be measured with an 8 nm palladium film. The presence of inhomogeneities in the palladium layers leads to anomalous behavior. © 1998 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1148787
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    A high resolution dual mass gate for ion separation in laser desorption/ionization time of flight mass spectrometry (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1661-1664 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A dual mass gate is described which allows for high resolution separation of ions under realistic laser desorption/ionization and matrix assisted laser desorption/ionization time of flight mass spectrometry conditions at 10 kV kinetic energy. The device consists of two interleaved comb units sequentially positioned in the ion beam path. This allows significant improvement in resolution relative to one unit by separation of "low pass" and "high pass" functions. Principal limits as given by mechanical dimensions of the device and electrical properties of the switches are also discussed. © 1998 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1148823
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    A pseudorandom pink noise for the computer-based measurements of linear responses (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2796-2801 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We propose a nonbinary pseudorandom sequence for the measurement of linear responses. Compared with a maximal length shift register sequence (m sequence), this sequence is more suitable for digital processing based on computers; with the use of discrete Fourier transforms, the response functions are reproduced without approximations from digitally sampled data because the input power spectrum is pink, i.e., completely flat in a given frequency range and 0 otherwise. In practice, the new sequence is simply the sum of harmonics with arbitrary phases and is produced readily with digital wave form generators. For reducing the peak power of this sequence, the amplitude distribution is better to be bimodal rather than Gaussian. For demonstrating its feasibility with common digital hardware, the magnetic resonance of Rb atoms in a sub-MHz region was measured successfully. With the use of the fast Fourier transform algorithm, our software task was only 0.4% of that for the cross-correlational calculation based on an m sequence. © 1998 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1148980
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    Improved two-dimensional product imaging: The real-time ion-counting method (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1665-1670 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A novel ion-counting method for significantly improving the spatial resolution and detection sensitivity of two-dimensional product imaging in molecular beam experiments is presented. The method makes use of real-time digital image processing to retrieve, threshold, and determine the local maximum of each ion hitting a microchannel plate assembly. The current version can process data at rates up to 3.07 Mbyte/s, and methods for accelerating this rate are proposed. © 1998 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1148824
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    A new toroidal electrostatic analyzer and application to surface analysis (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1671-1675 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new toroidal electrostatic analyzer (ESA) configuration for medium energy ion scattering has been designed and fabricated for structural analysis of surfaces. The present analyzer has a wide interelectrode distance of 16 mm and an energy range of 10% of the pass energy at a constant applied voltage. The analyzer is mounted horizontally on a turntable and accepts ions scattered within a well defined angular range. To get a good energy resolution, we employed a photon-counting image acquisition system (PIAS: Hamamatsu Photonics) with spatial resolution of 40–50 μm, combined with a three-stage microchannel plate. The electric fields of the toroidal ESA including the fringing fields were calculated by a finite element method. Ion trajectories through the analyzer were calculated using a Monte Carlo method. In this way, the optimum conditions of the geometry and size of the entrance and exit slits were determined. Our toroidal analyzer resolved three surface peaks from the Si isotopes (28Si, 29Si, and 30Si) clearly in the aligned spectra from H-terminated Si(001) and Si(111) and the energy resolution (ΔE/E) was estimated to be about 1×10−3. We describe the notable features of the new setup of the toroidal analyzer and show direct detection of H on Si(001) and Si(111) as a typical application. © 1998 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1148825
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    Transportation of intensive ion beams (invited) : Proceedings of the 7th international conference on ion sources (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1359-1366 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This proceeding considers excitation of ion and electron oscillations in a plasma formed by the beam of fast positive ions. Linear and nonlinear stages of the oscillations developing, and the influence of these oscillations on the beam transportation properties are described. Also briefly described are some techniques for the stabilization of instabilities of electron and ion oscillations in compensated ion beams. © 1998 American Institute of Physics.
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    A microbeam Cs ion source for accelerator mass spectrometry : Proceedings of the 7th international conference on ion sources (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1353-1358 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A negative ion sputter source incorporating a microbeam Cs+ source intended for application in accelerator mass spectrometry (AMS) has been developed from a General Ionex HICONEX 834™ source. (HICONEX is a trade mark of High Voltage Engineering Europa.) The source is part of a microbeam AMS system, designed for in situ microanalysis of geological samples known as AUSTRALIS (AMS for UltraSensitive TRAce eLement and Isotopic Studies) recently developed at the Heavy Ion Analytical Facility laboratory. With requirements of precise beam positioning on mineralogical samples, a high magnification sample viewing system is a vital part of the source, enabling live observation of the sputtering process and visual tuning of the primary beam. Microbeam of Cs+ of 30 μm in diameter can be produced routinely with adequate intensity for a number of applications. The "screen" electrode in the secondary ion extraction system facilitates steering of the primary beam affected by the extraction field, back into the geometric center of the sample. The injector system includes high resolution electric and magnetic analyzers, improving the background suppression before injection into the accelerator. © 1998 American Institute of Physics.
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    Thermo-optical and dielectric constants of laser dye solvents (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1243-1245 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The present work is devoted to the experimental measurements and calculations of thermo-optical and dielectric constants of four commonly used dielectric polar and nonpolar laser dye solvents; toluene, chloroform, carbon disulphide, and benzene. Using a modified high precision laser Mach–Zehnder interferometric technique the refractive index n and its thermal coefficient dn/dT were measured at two different laser wavelengths (514.5 and 632.8 nm). The measured experimental data of n and dn/dT were used in determining about 16 important physical constants and related parameters. On the other hand, the density and molar refraction as a function of temperature for the four solvents are calculated. © 1998 American Institute of Physics.
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    Soft x-ray fluorescence spectrometer using a multilayer interferential transmission plate (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1267-1269 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We give the principle of a soft x-ray fluorescence spectrometer based on a multilayer interferential transmission plate. When using photographic films or charge coupled device arrays, the apparatus does not require mechanical displacement. We illustrate the method with the Kα emission line of silicon and aluminum samples. © 1998 American Institute of Physics.
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    A new optical oscilloscope (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1253-1256 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new optical oscilloscope has been developed on the basis of the image-converter tube camera technology. Optical or electrical pulses in single or repetitive mode can be tested. When single pulse without time dependence on the sweep circuit is tested, an optical-fiber delay unit is adopted to ensure the pulse is captured. The optical oscilloscope works at a fixed frequency while repetitive pulses of any frequency less than 20 GHz were tested. A newly designed photocathode optical oscilloscope tube, control circuits, and a linear charge-coupled device readout system have been incorporated into the optical oscilloscope. Experimental results show that the temporal resolution of the optical oscilloscope is better than 5 ps, the spectral response range is 380–850 nm, and the single pulse can be captured with the probability of 100%. © 1998 American Institute of Physics.
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    Design and performance of an electrospray ion source for magnetic-sector mass spectrometers (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1275-1281 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An electrospray ion (ESI) source capable of operating at accelerating potentials of up to 11 kV has been designed and fabricated. The ESI source has been shown to deliver ion beams with a total current up to 20 pA and an emittance of 2–3 mm mrad in analysis of the peptide gramicidin S (molecular mass 1140.7 Da) and the protein bovine insulin B chain (molecular mass 3495.9 Da). Coupled to a two-sector tandem mass spectrometer, the ESI source produced efficiently the multiply charged ions of proteins, such as bovine ubiquitin (molecular mass 8564.8 Da) and cytochrome c (molecular mass 12327 Da). The high ion currents and high kinetic energies of the electrospray ions (up to 200 keV) characterize this ESI source as a powerful tool to be used in structural analysis of macromolecules by collision-induced dissociation. © 1998 American Institute of Physics.
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    A simple design of sextupole magnets with optimized circular pole faces (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1293-1294 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A circular pole face for a sextupole magnet makes the mechanical design simple to fabricate. We have optimized the radius of the circular face to minimize the field error. We have obtained a thumb rule that the optimized radius for a sextupole should be 0.56 times the half-aperture of the magnet. © 1998 American Institute of Physics.
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    Time-resolving, position-sensitive detection system for scattering and recoiling imaging spectrometry (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1289-1292 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A time-resolving, position-sensitive, single particle detector has been developed for scattering and recoiling imaging spectrometry. A custom designed multiple stop time-to-digital converter is integrated with a commercially available position sensitive detector system utilizing microchannel plates and a resistive anode encoder. The detector system successfully captures images of scattered and recoiled ions and fast neutrals from surfaces in time frames as short as 10 ns. © 1998 American Institute of Physics.
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    A 3.9 MeV photoinjector and delay system for Wakefield measurements (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1295-1297 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We report on the characterization of the 3.9 MeV electron beam from a rf photoinjector at the Argonne Wakefield Accelerator. This beam is used to diagnose wakefields produced by the 15 MeV beam from a second rf photoinjector. We measured the emittance with the usual quadrupole scan method but used a fitting algorithm that includes space-charge forces. This photocathode gun has produced a beam charge per pulse ranging from 10 pC to 4 nC, but is normally operated at 100 pC with a measured normalized emittance of 3.4 π mm mrad and bunch length of 8 ps full width at half maximum. © 1998 American Institute of Physics.
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    URL: http://dx.doi.org/10.1063/1.1148793
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    Time-resolved study of the negative ion density in a volume H− ion source by photodetachment (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1298-1301 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Time-resolved measurements of the negative ion density and of other plasma parameters in a pure hydrogen Tandem source have been effected using the laser photodetachment technique. The study was made for hydrogen filling pressures in the range 7–11 mTorr and an arc current of 120 A. We found a strong time variation in negative ion density was present during the discharge pulse (0.5 s). The maximum negative ion density was observed at the beginning of the pulse, at the lowest filling pressure studied, followed by a rapid decrease. An improvement of the current distribution during the pulse was obtained by increasing the filling pressure. The electron density is highest at 7 mTorr and stays almost constant during the pulse. The increase in filling pressure leads to electron density values lower by a factor of 4 which are constant during the discharge pulse. The highest relative negative ion density during the pulse is obtained at 9 mTorr. The time variation of the negative ion density does not follow that of the electron density at the same discharge conditions. This indicates that the negative ion density is affected not only by the electron density, but also by the neutral particle density, as assumed by the mechanism of volume production of H− ions in a plasma. We attribute the time variation of the negative ion density during the discharge pulse to the ion pumping of hydrogen. © 1998 American Institute of Physics.
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    An instrument for investigating high electric field phenomena at small electrode separations (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2067-2071 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An instrument with the tip positioning capability of a scanning tunneling microscope and the imaging capability of a field emission electron microscope has been developed. This instrument provides the ability to investigate the current-voltage characteristics of field emitter tips in the metal-vacuum, transition, and metal-vacuum-metal tunneling regimes. It also allows a field emitter tip to be imaged before and after these "close approach" measurements are made. Nonreproducible tunneling characteristics observed in the transition region have been associated with large changes in the apex of the field emitter tip. © 1998 American Institute of Physics.
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    Design and performance of a programmable-temperature scanning tunneling microscope (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2072-2080 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In this article we introduce a novel scanning tunneling microscope (STM), which operates in a sample temperature range from 60 to at least 850 K. The most important new feature of this STM is that, while one selected part of the surface is kept within the microscope's field of view, the sample temperature can be varied over a wide range of several hundreds of degrees during actual imaging. The extremely low drift of the scanner and sample was achieved by the combination of a thermal-drift compensated piezoelectric scanner design with a newly developed sample stage. The design of the sample stage defines a fixed center from which thermal expansions, in all three directions, are forced outwards. The performance of the microscope is demonstrated for several surfaces including Au(110), on which we follow one particular surface region over a temperature range of more than 270 K. © 1998 American Institute of Physics.
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    A thermal microprobe fabricated with wafer-stage processing (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2081-2084 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A thermal microprobe has been designed and built for high resolution temperature sensing. The thermal sensor is a thin-film thermocouple junction at the tip of an atomic force microprobe (AFM) silicon probe needle. Only wafer-stage processing steps are used for the fabrication. For high resolution temperature sensing it is essential that the junction be confined to a short distance at the AFM tip. This confinement is achieved by a controlled photoresist coating process. Experiment prototypes have been made with an Au/Pd junction confined to within 0.5 μm of the tip, with the two metals separated elsewhere by a thin insulating oxide layer. Processing begins with double-polished, n-type, 4 in. diameter, 300-μm-thick silicon wafers. Atomically sharp probe tips are formed by a combination of dry and wet chemical etching, and oxidation sharpening. The metal layers are sputtering deposited and the cantilevers are released by a combination of KOH and dry etching. A resistively heated calibration device was made for temperature calibration of the thermal microprobe over the temperature range 25–110 °C. Over this range the thermal outputs of two microprobes are 4.5 and 5.6 μV/K and is linear. Thermal and topographical images are also obtained from a heated tungsten thin film fuse. © 1998 American Institute of Physics.
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    A resonance shear force rheometer modeled as simple oscillating circuit (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2095-2104 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A novel resonance method for studying the viscoelasticity of very thin liquid films and elastic materials is developed using a shear force apparatus. The shear stress created by an oscillating piezo unit attached to leaf springs is recorded as the lateral displacement by capacitance probe. The oscillation frequency is varied around the resonance frequency of the mechanical system in order to trace the amplitude and the phase of the resonance peak. Two reference states are obtained: the resonance of free oscillations in air and one under constrain introduced by the cantilever spring in contact with the shear mechanical unit. The presence of a liquid film changes these resonance states depending on the film thickness and the cantilever load. A simple mechanical model is proposed entrapping the contribution of different parts in effective spring, mass, and damping constants. The model separates the effect of the liquid film from the background oscillation of the mechanical parts. The method is applied here to investigate the elastic contact between two solid surfaces. © 1998 American Institute of Physics.
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    Thermal expansion measurements of liquid metallic samples measured under microgravity conditions (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2110-2113 
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    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We report the method and first examples of thermal expansion measurements of liquid metallic samples measured under μg conditions. The experiments were performed in an electromagnetic levitation facility (TEMPUS facility) on board the space orbiter Columbia (mission MSL-1). The sample was imaged by a high-resolution CCD camera with on-board recording. After the mission the video tapes were analyzed by digital image processing. First measurements were made with a molten Pd78Cu6Si16 sample in the temperature range of about 800 to 1150 °C. The measured value of the coefficient of volume expansion is 8.9×10−5/°C in this temperature range. © 1998 American Institute of Physics.
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    Electrically induced thermal transient experiments for thermal diffusivity measurements on chemical vapor deposited diamond films (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2105-2109 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: To investigate the in plane thermal diffusivity of chemical vapor deposited diamond layers, two new techniques were developed based on electrically induced converging and linear thermal waves. With these methods, free-standing, laser-cut diamond samples, 100 μm or larger in thickness can be analyzed. Laser cutting leaves a graphitic surface layer along the cutting edge. Therefore, a short high voltage pulse, applied at the graphitic rim resistor, is used to generate a thermal transient. The propagation of the wave is measured optically either in the center of the circular disk or at one side of a bar shaped sample. Both techniques require only very little sample preparation. They are shown to be simple, accurate, and independent of sample thickness and induced energy. In order to analyze the experimental data we present both an analytical model and a numerical simulation. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148905
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    Raman spectroscopy combined with small angle x-ray scattering and wide angle x-ray scattering as a tool for the study of phase transitions in polymers (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2114-2117 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A novel combination of simultaneous experimental techniques has been developed as a tool for the study of phase transitions in polymers. Based upon a small angle x-ray scattering (SAXS) synchrotron radiation beamline it has been shown to be feasible to collect, in addition to the time-resolved SAXS data, wide angle x-ray scattering and Raman spectroscopy data with a time resolution of a few seconds. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148907
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    Local mechanical spectroscopy with nanometer-scale lateral resolution (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2085-2094 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new technique has been developed to probe the viscoelastic and anelastic properties of submicron phases of inhomogeneous materials. The measurement gives information related to the internal friction and to the variations of the dynamic modulus of nanometer-sized volumes. It is then the nanoscale equivalent to mechanical spectroscopy, a well-known macroscopic technique for materials studies, also sometimes called dynamic mechanical (thermal) analysis. The technique is based on a scanning force microscope, using the principle of scanning local-acceleration microscopy (SLAM), and allows the sample temperature to be changed. It is called variable-temperature SLAM, abbreviated T-SLAM. According to a recent proposition to systematize names of scanning probe microscope based methods, this technique should be included in the family of "mechanothermal analysis with scanning microscopy." It is suited for studying defect dynamics in nanomaterials and composites by locating the dissipative mechanisms in submicron phases. The primary and secondary relaxations, as well as the viscoplasticity, were observed in bulk PVC. The wide range of phenomena demonstrate the versatility of the technique. A still unexplained increase of the stiffness with increasing temperature was observed just below the glass transition. All of these observations, although their interpretation in terms of physical events is still tentative, are in agreement with global studies. This technique also permits one to image the variations of the local elasticity or of the local damping at a fixed temperature. This enables the study of, for instance, the homogeneity of phase transitions in multiphased materials, or of the interface morphologies and properties. As an illustration, the homogeneity of the glass transition temperature of PVC in a 50/50 wt % PVC/PB polymer blend has been demonstrated. Due to the small size of the probed volume, T-SLAM gives information on the mechanical properties of the near-surface, which may differ from bulk properties.© 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148903
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    Micro-machining workstation for a diode pumped Nd:YAG high-brightness laser system (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2118-2119 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A Nd:YAG micro-machining workstation that allows cutting on a scale of a few microns has been developed and operated. The system incorporates a telescope viewing system that allows control during the work and a software interface to translate AutoCad files. Some examples of the performance are given. With this setup we demonstrate the possibility of machining within a few microns with a Nd:YAG laser. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148908
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  • 94
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    A low-energy ion implanter for surface and materials science (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2120-2126 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A low-energy ion-beam facility for surface and materials science has been built which allows ion beam treatments of solid surfaces via single-ion impacts up to high-fluence implantations. The system offers mass-separated ion beams of 0.5–10 keV by a normal acceleration, and of 5–2000 eV by an acceleration/deceleration lens combination. Its energy spread is estimated to be as small as 2 eV in the whole range. Ion current densities are available in the range between 0.1 nA/cm2 and up to 50 μA/cm2, corresponding to a particle flux of 109–1014 ions/cm2 s. Homogeneous implantation profiles are achieved using an electrostatic x-y deflection system. First applications for ion induced defect production on highly oriented pyrolytic graphite surfaces detected via scanning tunneling microscopy are presented. Hillock shaped defect formations were detected and attributed to protusions of the atomic surface structure, which were induced by interstitials and interstitial clusters between the first atomic planes originated from recoil atoms of the collision cascade. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148909
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    A sample cell and low-temperature accessory design for fluorescence-mode x-ray absorption spectroscopy of air-sensitive and corrosive compounds (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2127-2129 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A sample cell and low-temperature cooling unit design suitable for x-ray absorption spectroscopy (XAS) of oxygen and/or water sensitive compounds is presented. The cell is a simplified and optimized modification of a previously suggested design. The low-temperature accessory is specifically designed for good thermal isolation and equilibration at liquid nitrogen temperatures, eliminating the need for a more expensive commercial cryostat. The entire construction can be directly attached to an ion chamber and either a standard Lytle detector or energy-discriminating germanium-element solid-state detector via helium gas-purged adaptor flanges. The apparatus was tested at liquid nitrogen temperatures and gave good temperature stability within ±0.1 K. The XAS signal from an air-sensitive potassium/pyrene complex at 100 K taken at the X-6B beam line at the National Synchrotron Light Source facility at Brookhaven National Laboratory is presented. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148910
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    Ion source development at GSI : Proceedings of the 7th international conference on ion sources (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1079-1081 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Different ion sources are used at GSI to match the requirements for specific tasks at the accelerator. At the standard injector a Penning ionization gauge ion source is used (design ion U10+, m/q〈24, 1 emA). Further development of this source is mainly aiming at an increase of the extractable currents and an increase of the lifetime of the source. The new injector produces the beam by means of an electron cyclotron resonance source (Caprice-type). Here the design ion is U28+, m/q〈8.5, 5 eμA. Clearly, the oven technology is our main development goal. In addition we are trying to improve the extraction flexibility by a moveable accel–decel system. For our high current project ion sources are required which are capable to deliver a beam of several mA even for heavy ions. Design ion here is U4+, m/q〈65, 15 emA. For that application two different types of ion source are used: the multicusp ion sources "cold or hot reflex discharge ion source" and "multicusp ion source" for gaseous ions and the MEVVA source for metal beams. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148638
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    Transportation of intensive ion beams (invited) : Proceedings of the 7th international conference on ion sources (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1088-1088 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This proceeding considers excitation of ion and electron oscillations in a plasma formed by the beam of fast positive ions. Linear and nonlinear stages of the oscillations developing, and the influence of these oscillations on the beam transportation properties are described. Also briefly described are some techniques for the stabilization of instabilities of electron and ion oscillations in compensated ion beams. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148748
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  • 98
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    Toward a realistic and tractable model for negative-ion extraction from volume sources : Proceedings of the 7th international conference on ion sources (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1103-1105 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A negative-ion source extraction model has been formulated and implemented that explicitly considers the motion of positive ions and the volume generation of negative ions. It is found that (1) for high-beam currents, the beam current is limited by a transverse space-charge limit, meaning that an increase in negative-ion density at the extraction sheath will result in a lower-beam current (this result is universally observed at high-beam current); (2) there is a saddle point with a potential barrier preventing most volume-produced negative ions from being extracted [the combination of (1) and (2) indicates that most of the negative ions being created do not find their way into the beam]; (3) the introduction of cesium may cause an increase in the transverse space-charge limit; (4) cesium also results in an increase in the fraction of volume-produced negative ions that are extracted; (5) cesium may also result in reduction of extracted electrons by producing a less negative bias on the plasma electrode with respect to the plasma, thus allowing the transverse space-charge limit budget to be taken up virtually totally by the ions. [The combination of (3)–(5) represents the way an actual increase in the beam current can be achieved]; (6) a strong ion time scale sheath instability due to violation of the Bohm criteria produces an anomalous ion temperature, which increases with the beam current, as routinely seen in measurements; and (7) the introduction of cesium may result in a reduction in this instability. These insights may lead to improvements in volume negative-ion sources.
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    URL: http://dx.doi.org/10.1063/1.1148749
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    The virtual cathode: Key to the numerical simulation of negative ion extraction : Proceedings of the 7th international conference on ion sources (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1107-1109 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The simulation of volume produced negative ions from a plasma is by far more complicated than the extraction of positive ions, while in experiments the only difficulty seemes to be connected with the power of the electrons, which are extracted at the same time. The reason for this complication in simple minded simulations is the infinite space charge, which builds up in the turning point of the positive ions in the extraction aperture for the negative ions. Smearing out the energy of the positive ions seems to help, however, this is mostly not justified by experiments, showing a low ion energy, especially in the region between the magnetic filter and the extraction hole. This difficulty may be overcome by using experience from virtual cathode formation in magnetically focused, decelerated electron beams. The decelerated electrons behave similarly to the reflected positive ions and are forming a virtual cathode in the reflection zone. From the analysis of the electron deceleration experiment, a simple power law is deduced to describe the decreasing electron current by the local potential. In turn, this power law may also be applied to the positive ion current, resulting in simulations without space charge singularity, even in the case of monoenergetic ions. As a first step towards the numerical simulation of negative ion extraction, a linear model has been made, using this power law. The transition from a Boltzmann distribution for the plasma electrons to a truncated one for the extracted beam electrons is considered as well, parallel to Langmuir's treatment of a thermal diode for electrons. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148713
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  • 100
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    Simulation of 10 A electron-beam formation and collection for a high current electron-beam ion source : Proceedings of the 7th international conference on ion sources (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1120-1122 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Presented is a report on the development of an electron-beam ion source (EBIS) for the relativistic heavy ion collider at Brookhaven National Laboratory (BNL) which requires operating with a 10 A electron beam. This is approximately an order of magnitude higher current than in any existing EBIS device. A test stand is presently being designed and constructed where EBIS components will be tested. It will be reported in a separate paper at this conference. The design of the 10 A electron gun, drift tubes, and electron collector requires extensive computer simulations. Calculations have been performed at Novosibirsk and BNL using two different programs, SAM and EGUN. Results of these simulations will be presented. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148714
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