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  • Articles  (125,912)
  • 1990-1994  (125,912)
  • Computer Science  (53,046)
  • Geography  (37,123)
  • Electrical Engineering, Measurement and Control Technology  (35,743)
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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2785-2791 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A modular polarization spectrometry system for the measurement of the degree of polarization (linear or circular) of luminescence intensity is described. It is based on polarization modulation with a photoelastic modulator and two lock-in amplifiers for signal recovery. Interfaced to the spectrometer is a microcomputer configured with CRT monitor, disk drive, and digital printer to provide system control and to permit digital data storage and data manipulations such as multiple scan averaging and averaged background subtraction. The system described is capable of measuring linearly polarized emission, linearly polarized excitation luminescence, and circularly polarized emission spectra. The modular design also allows the spectrometer to be rapidly and easily modified for the measurement of circular dichroism, magnetic circular dichroism, or magnetic circularly polarized emission. The system performance is demonstrated.
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2808-2818 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Development of initial versions of hardware and software for a Hewlett-Packard HP-5971A mass selective detector (MSD) was performed in order to improve its capabilities for monitoring gaseous waste streams. The development allowed for initial evaluation of the feasibility of the conversion of the MSD from an integrated gas chromatography/mass spectrometry (GC-MS) detector to a stand-alone, on-line, real-time mass spectrometry (SOR-MS) detector. Chemical compound quantitation is accomplished via mass spectrometric step heights, rather than gas chromatographic peak areas or heights. Contributions of more than one chemical compound to a single M/Z ratio are accounted for by nonlinear deconvolution of the mass spectrum, provided a calibration can be obtained for all contributing chemical compounds. The enhanced MSD was tested by a number of calibration and monitoring experiments in order to evaluate the potential and limitations of the conversion. With sufficient care and awareness of the potential and limitations, it appears to be possible to convert the GC-MS detector to a SOR-MS detector. In particular, this conversion could allow for simple monitoring of reactive chemical compounds.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2855-2859 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A scanning tunneling microscope (STM) operable from room temperature to 1.5 K with an integrated sample preparation chamber has been constructed and successfully tested. Both the sample and the tunneling tip can be cleaned and/or modified in a UHV processing chamber which is connected at the top of a liquid-helium flow cryostat. The STM is mounted to a threaded rod inside the cryostat so that it can be translated vertically. This allows a newly prepared sample/tip to be transferred onto the STM and lowered into a cryogenic environment without breaking vacuum, minimizing surface contamination which causes significant tunneling problems at cryogenic temperatures.
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2874-2881 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The accuracy of measurement of the thickness of uniform thin films on solid substrates by null ellipsometry is severely limited when the substrate is rough. It is impossible to separate these two effects experimentally with the null ellipsometer, and there is no theoretical basis or generally used model available to separate these effects. Thus, a dual rotating-compensator Mueller matrix ellipsometer has been constructed to carry out film thickness measurements on rough substrates. Measurements were made on a set of specially prepared specimens of 8630 steel, roughened by grit blasting with aluminum oxide. Grit sizes and blasting pressures were varied to produce 11 different roughness values ranging from 0.01 to 1.295 μm Ra, as measured with a stylus tracer device. Upon each of the 11 roughness groups, films of magnesium fluoride were overlaid to thicknesses of 89, 180, 254, and 315 nm. One set of specimens was left uncoated. Experimental results for film thickness measurements on rough surfaces matched the ideal (for smooth surfaces) form well for roughnesses up to 0.13 μm Ra, at most angles of incidence. For rougher specimens, significant deviations in results were observed for all but the largest angles of incidence. The nonideal data were attributed to the cross-polarization effects of surface geometry, and apparent depolarization. The resolution of thickness measurements was 1 nm for polished specimens, and decreased continuously to 10 nm for the roughest specimens examined.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2894-2895 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new characterization method of materials processed by ion beams or laser beams using a two-color interferometer with two frequency-doubling optical crystals is described, based on the dispersion property of the materials. Resolution of measurement is improved to an optical phase of 1° (subnanometers) by use of a heterodyne technique with acousto-optic modulators.
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  • 6
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    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2939-2940 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A simple coincidence circuit has been built and attached to conventional pulse counters to obtain the energy distribution of the coincident ion pair arising from the three-body polar dissociation process H+3+He→H++H++H−. The coincidence circuit is based on TTL components and a solid-state delay line. A method to derive the true coincidence H+–H− energy distribution is described, from which properties such as the inelastic energy loss and angle of proton ejection can be obtained.
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  • 7
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2968-2974 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The ability to produce high quality films in an electron cyclotron resonance reactor is dependent on the gas distribution system. In an effort to understand gas distribution effects, a variety of gas ring injection systems were implemented during silicon nitride growth. Film refractive index, uniformity, and stress were used to gauge each gas distribution system. As a result, we have demonstrated that evenly distributed gas injection systems are the most desirable producing uniform films. Film thickness uniformity was significantly influenced by the design of the gas ring as well as the gas flow. Theoretical models supported the observed results and identified desirable properties for gas ring distribution systems.
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  • 8
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    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2996-2999 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A set of experiments was carried out with TEXTOR neutral beams inside the torus to obtain detailed knowledge about the beam for later use in experiments such as charge exchange recombination spectroscopy and for energy deposition calculations. A segmented graphite plate and an infrared camera were used to gain information about the total beam power profile for different beams (H, D, He) and particle energies. Spatially resolved measurements of Doppler-shifted Hα line intensities were used to calculate the relative widths and fractional powers of the three beam species (for H and D) at different energies (this report mainly deals with this method). By these measurements the beams are fully characterized so that charge exchange spectroscopy could be employed to yield impurity concentration profiles in spite of an extended beam and lines of sight not tangential to the plasma surfaces. The results for a 50 keV hydrogen beam are also taking into account the calorimetric measurements inside the injector box. The beamlets are composed of two Gaussian profiles. The broader profile (divergence of 3° and a power fraction of 30%) is mainly scraped off in the injector itself. The composition of the smaller profile, which almost exclusively determines the power to TEXTOR, is calculated from the measured results. The power fractions for the three species (E, E/2, E/3) are 50%, 37.6% and 12.4% respectively. The divergences horizontally are 0.87, 0.92, 0.95 degrees and vertically 0.91, 0.98, 1.02 degrees respectively. The exact position of the beam inside TEXTOR and its direction are determined as well.
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  • 9
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 3005-3011 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A picovoltmeter working at 4.2 K and based on a direct current superconducting quantum interference device (dc SQUID) with additional passive positive feedback for investigating the properties of superconducting thin films, Josephson junctions, and SQUIDs has been developed. It has a large small-signal bandwidth fm(approximately-equal-to)800 kHz, a slew rate of (approximately-equal-to)38 mV/s, a dynamic range of 146 dB, and a voltage resolution of 5 pV/Hz1/2 for a signal source impedance Rs=0 Ω. The noise temperature is (approximately-equal-to)0.6 K for Rs=1 Ω. In this article the dynamics and noise properties of the instrument are discussed.
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  • 10
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2675-2679 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An interfacial rheometer to measure the dynamic response of a liquid–liquid interface subjected to a small amplitude oscillatory shear stress is described. Experiments are conducted in a deep channel rheometer fitted with an oscillatory floor. This instrument is used to examine the rheological behavior of interfaces in the presence of surfactants. Rheological parameters are calculated from a hydrodynamic analysis incorporating interfacial rheological models. It is demonstrated here that an adsorbed layer of macromolecular surfactants at an oil–water interface is viscoelastic even though the adjacent phases are Newtonian.
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  • 11
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    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2568-2573 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have developed a new fabrication method for Wolter-type x-ray focusing mirrors. In this method, a slight gap between the master mandrel and the glass replica produced by vacuum replication was filled with epoxy resin to decrease the roughness and the figure displacement of the mirror surface. The mirror was evaluated both by taking x-ray microphotographs of No. 1000 and No. 2000 copper meshes with Al Kα and C Kα x rays, and by focusing x rays with several wavelengths using synchrotron radiation. No apparent degradation was found in the micrographs even when we changed the irradiating x rays from the C Kα to the Al Kα. The focused beam profile remained unchanged even at the wavelength of 1.24 nm. The beam size in the meridional plane also decreased to 50% of the beam size focused by a mirror fabricated only by vacuum replication. These results indicate that the present method successfully decreases the surface roughness to less than 6.2 nm (peak-to-valley) and improves the figure accuracy of the mirror surface.
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  • 12
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2585-2586 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Gated imagers used to record x-ray emission in the 1–5 keV range in laser-plasma interaction experiments have suffered from resistive gain degradation between voltage drive pulse input and output ends of a microchannel-plate stripline. The reduction in gain as the pulse travels down the strip results in a lower signal-to-background ratio in the last image on a strip than in the first image. Compensation for this gain nonuniformity using a tapered stripline in place of the normally straight striplines is discussed.
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  • 13
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2599-2606 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A Mach probe is used to measure poloidal and toroidal flows induced by a biased electrode in IMS. Mach probe theories are reviewed and classified as either magnetized or unmagnetized. A simple geometric model of the IMS Mach probe shows that the variation of the effective probe area as a function of the probe orientation with respect to the magnetic field is 20%–25%, predicting the probe to be only slightly magnetized. Measurements of the variation in the total ion saturation current collected by the probe, as the angle with respect to the magnetic field is varied, demonstrate this level of magnetization only at low neutral pressure at large minor radius, while in other cases the variation in the total collected current is negligible. Based on this result an unmagnetized model [M. Hudis and L. M. Lidsky, J. Appl. Phys. 41, 5011 (1970)] is chosen to analyze the IMS Mach probe data. Comparison of Mach probe poloidal flow measurements as a function of minor radius to calculations of the E×B drift velocity and the ion diamagnetic drift velocity from radial profiles of floating potential and ion saturation current, respectively, shows agreement to within 15%.
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  • 14
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2527-2531 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: For a V-shaped atomic force microscopy cantilever beam, the spring constants in the three principal directions are given in terms of the beam geometry and material properties. For the lateral stiffness, a closed-formed expression is presented. Also, the normal and the longitudinal stiffness are obtained from a few simple equations. The results are compared with a finite element study and found to be very accurate. All spring constants depend strongly on the cantilever thickness, which is difficult to measure. In addition, the lateral and longitudinal stiffness are sensitive to the location and the height of the attached pyramid.
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  • 15
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2672-2674 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An experimental technique for the accurate measurement of the conductivity in liquid mixtures at a constant temperture is described. The equipment is fully computerized, the conductimeter and the burette being controlled through the IEEE-488 and the RS-232C interfaces, respectively. The automatic procedure provides the measurement of the experimental parameters for each concentration as a statistical average of 2400 data. It permits an increase in the accuracy of the results, optimizing the time and avoiding human mistakes along the set of measurements.
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  • 16
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2680-2692 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Mass analyzed low-energy ion beams delivered into a UHV growth chamber have enormous potential for novel materials studies. However, there are significant practical problems in the production of useful ion fluxes at energies down to a few electron volts. Many of these problems have been investigated during the testing of a unique new instrument. This instrument consists of a dual source, mass analyzed, low-energy, ion beam system attached to an ultrahigh-vacuum (UHV) deposition chamber which houses equipment for in situ Auger electron spectroscopy and reflection high-energy electron diffraction analysis of the deposited material. A second UHV chamber, connected to the deposition chamber by means of a vacuum lock and sample transfer device, houses equipment for in situ low-energy electron diffraction and time-of-flight scattering and recoiling spectrometry. The instrument is briefly described herein and data are presented to illustrate the effects of various parameters on the performance of the ion beam. The parameters considered are beam line pressure, field penetration, electromagnetic fringing fields, retarding lens configuration, and ion arrival energy at the target (from 5 eV to 10 keV). The effects of these parameters on the energy spread and profile of the beam, ion-beam flux on target for various species, high-energy neutral atom content and electron content of the beam, and target chamber pressure are discussed. Examples showing the utilization of the instrument for (1) synthesis of the metastable binary compound carbon nitride, (2) deposition of ultrathin Al/Si multilayers, and (3) studying the growth mechanism of Si thin films, are presented. The prospects for materials research, film deposition, surface modification, and ion/surface chemistry studies using such an instrument are assessed.
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  • 17
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2726-2730 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We propose an application for the NTC (negative temperature coefficient) thermistor miniature bead as a sensor to measure the volume flowing through a microporous membrane over a 0–15 cm3/min range. Only one thermistor is used and small temperature changes that can occur during the experiment can be ignored. No compensation or linearity circuitry is used [C. Yang, M. Kümmel, and H. Soeberg, Sensors and Actuators 15, 51 (1988)]. Assembly is easy and it can be adapted to automatic control, for example, to control the flow of a peristaltic pump by connection to an A/D D/A board and computer. When the experimental data was fitted to a potential type curve (y=axb), a sensitivity between 5% and 8% and a correlation coefficient of 0.99 were obtained. The response of the sensor when the flow changes is immediate, although the time taken for the measurement to stabilize is dependent on the size of the variation (between 4 and 7 s). The fitting curve is used to determine the volume flow that is caused by a pressure gradient applied to the membrane placed between two bulks with the same fluid.
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  • 18
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2737-2738 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Microfabricated tips, usually used for atomic force microscopy (AFM), can be modified and used in a scanning nearfield optical microscope. Initial images show a resolution of about 80 nm (λ/8) demonstrating the quality and usefulness of these tips. They are mechanically stable, potentially commercially available, and have high light transmissibility. Furthermore, they can be easily combined with an atomic force microscope to give simultaneous nearfield optical and AFM images.
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  • 19
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2412-2413 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An ultrahigh vacuum leak valve is described, which can be baked up to 450 °C. The throughput can be adjusted between 1×10−10 and 5×10−6 Pa m3 s−1. The actuator is a piezoelectric stack which can be easily removed and set back. The baking temperature with the actuator in place is limited by the thermal specifications of the piezoelectric material. The inner surfaces, which are solely stainless-steel and gold, allow an almost unlimited choice of working gases.
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  • 20
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2417-2418 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In the cited article, an x-ray source developed for extended x-ray absorption fine structure measurements is described. After the publication, the authors have further improved the performance by employing a compact rotating anode and by optimizing an electron gun. This new x-ray generator provides high tube current of 1100 mA at 18 kV with the narrow focal spot of about 0.1 mm in width. Extremely intense monochromatic x rays, which are completely free from higher order reflections, are now available in a laboratory, and the measurement time required for a practical sample has been shortened to less than 2 h.
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  • 21
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The design of a novel electrode structure for electric-field ionization of Rydberg atoms in a fast atomic beam is described. It allows the resolution of the ion signal from Rydberg atoms with adjacent effective principal quantum numbers n* in the range of 14≤n*≤40 and minimizes the volume where field ionization takes place. These features drastically reduce the number of background events arising from collisions of fast atoms with residual gas molecules and thus are essential for trace analysis applications of the technique of resonance ionization spectroscopy in collinear geometry.
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  • 22
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2139-2140 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Using resonant ultrasound spectroscopy (RUS) we have determined the crystallographic orientation of a tantalum single crystal from a measurement of its mechanical resonance spectrum. This accomplishment is significant not only because it reduces the sample requirements for RUS but also because it is the simplest method for simultaneous determination of a crystal's elastic constants and microscopic crystallographic orientation.
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  • 23
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2147-2148 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The maximum transmitted intensity through a (n,−n) double-crystal x-ray monochromator with sagittally (cylindrically) bent second crystal takes place when the virtual source lies on the surface of the cylinder. In this case all beams diffracted from the first flat crystal are also diffracted from the second cylindrically bent crystal. The magnification in this case is exactly 1/3 independently of Bragg angle.
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  • 24
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2155-2156 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A photoacoustic cell was designed for routine studies (e.g., samples adsorbed on filter paper). Teflon disks that are easily cleaned and removed are used as the sample holders. The cell was characterized by recording the photoacoustic waveform with a digital oscilloscope.
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  • 25
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1502-1505 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe a complete diode laser system stabilized at 852 nm on the D2 line of Cs with a linewidth narrower than 100 kHz. This system is intended to be employed for optical pumping, cooling, and detection of Cs atoms in atomic frequency standards. The square root of the Allan variance, evaluated by measuring the beat-note of two similar systems, is better than 1×10−12 for τ up to 1000 s. A month of continuous locked operation has been observed.
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  • 26
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1964-1967 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have developed a self-healing mercury-wetted target as a practical source of soft x-ray radiation for photoexciting extreme ultraviolet lasers. A threaded rod, rotating in a pool of mercury, demonstrates a soft x-ray conversion efficiency similar to that of expendable gold-coated targets in synchronous photopumping of a photoionization Xe2+ laser at 109 nm. Surfaces self-heal or are continuously regenerated by rewetting, while mercury debris is removed by evaporation from the target chamber walls and optics. Long target lifetime and self-cleaning performance of the new target system are attractive features in future high-repetition-rate, high-throughput applications for photopumping of extreme ultraviolet or soft x-ray lasers, and more generally as incoherent sources for soft x-ray lithography and spectroscopy.
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  • 27
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1988-1992 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new technique to suppress the unwanted, spurious signals often encountered in photoreflectance spectra from semiconductors and semiconductor microstructures is described here. This approach utilizes a properly phase-shifted signal from the reference source that is applied to the lock-in amplifier's differential input. This paper demonstrates that this new approach is superior to existing methods of background minimization and is simpler to implement. It is particularly effective when the spurious signal is much larger than the underlying desired trace.
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  • 28
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2028-2033 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have measured atomic hydrogen velocity distributions in an effusive beam coming out of a rf discharge dissociator by using a magnetic deflection technique. Dissociator pressures varied between 0.028 and 0.340 Torr. At low dissociator pressures the measured atomic velocity distributions were narrower than the expected beam Maxwellians; at higher pressures they were indistinguishable from beam Maxwellians at the dissociator wall temperature, indicating full thermalization of the atoms prior to exiting the dissociator. Monte Carlo simulations of the thermalization process within the dissociator reproduce these results, and point out the important role of vibrational excitation of the background hydrogen molecules as an energy loss mechanism. Our results are significant when designing magnetic state selectors for spin- or hyperfine-polarized atomic hydrogen beams.
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  • 29
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1575-1579 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Medium energy (100–300 keV) time-of-flight spectrometry for surface analysis uses the correlated detection of an energetic ion and the secondary electrons emitted as it passes through a carbon foil. When microchannel plates are employed in this detection scheme, a typical mean efficiency of detection of less than 30% is achieved. When instead a surface barrier detector is used to detect the ion, providing simultaneous acquisition of velocity and energy information, certain advantages are realized over the two microchannel plate configuration in the characterization of low level constituents of surfaces. Specifically, energy-discriminated gating of the start pulse was observed to nearly eliminate count rate dependent background in a time-of-flight spectrum. Further reduction in background was obtained by the selective elimination of forward recoil species or backscatters from the substrate. Replacement of the stop microchannel plate by a surface barrier detector has resulted in improved detection efficiency for He, as well as provided a means for further study of the processes which affect time-of-flight spectrometer response, including multiple scattering and secondary electron emission in the start foil. In this publication, we describe the application of this particle telescope to the backscattering analysis of gold on silicon and the forward scattering measurement of hydrogen in a self-supporting carbon film.
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  • 30
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1590-1593 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An electron cyclotron resonance (ECR) plasma is produced at pressures up to 10 mTorr with a circular TE01 mode microwave. The plasma density is almost radially uniform even at 10 mTorr. SiC films are formed on silicon wafers by introducing methane gas into the ECR plasma. It is shown that a circular TE01 mode microwave is useful for the ECR plasma chemical vapor deposition (CVD).
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  • 31
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1613-1615 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: At the tokamak ASDEX upgrade, an extensive cooling water calorimetry system was installed. This system has measured the toroidal and poloidal distributions of the energy deposition by monitoring the temperature rise of the cooling water in 80 separate cooling units in the divertor plates and the central heat shield.
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  • 32
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1636-1643 
    ISSN: 1089-7623
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new type of neutron spectrometer, which is called COTETRA (counter telescope with thick radiator), has been developed for diagnosing DT fusion plasma. It is based on the recoil proton measurement and has such advantages as: (1) direct measurement of the neutron energy without the unfolding procedure, (2) sufficiently fine energy resolution and high detection efficiency for 14 MeV neutrons, (3) wide dynamic range of counting rate, and (4) good n–γ discrimination. A prototype of COTETRA was constructed and tested using a DT neutron accelerator. The energy resolution of 5.3%±0.9% was obtained for 14 MeV neutron with the detection efficiency of 1.3×10−4 [counts/(n/cm2)]. A Monte Carlo simulation code was developed and the performances of COTETRA were examined. The calculation agrees with the results of the experiment within its margin of error and suggests that energy resolution up to 3% with a detection efficiency of 10−5 [counts/(n/cm2)] could be achieved if the condition of the radiator could be successfully adjusted.
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  • 33
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1657-1662 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Electric and magnetic characteristics of a Co-Fe-Si-B-based amorphous thin wire with a diameter of 120 μm were investigated at low temperatures from an applicative point of view. The electric resistivity decreases with the decrease of temperature and has the minimum point at about 30 K. The maximum decrease of the resistivity is, however, only 2.7% as compared with that at room temperature. The magnetic characteristics in term of the coercive force, the saturation induction, and the maximum permeability are all increased with the decrease of temperature. The coercive force shows the increase of 25% at 4.4 K as compared with that at room temperature; and the saturation induction and the maximum permeability about 15%. The very slight decrease of electric resistivity and the increase of the coercive force with the decrease of temperature promise a high-frequency application of the wire at low temperature. These results led to the fabrication of a multivibrator-type magnetometer being able to work at low temperature below 77 K. The magnetometer has a sensitivity of about 1 mV/mG at room temperature in a magnetic field range between +1 and −1 Oe. The sensitivity change is less than 0.5% even at low temperature of 6 K, as compared with that at room temperature.
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  • 34
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1675-1678 
    ISSN: 1089-7623
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new enclosed injector system for low temperature kinetic studies is described. This system offers a number of advantages over more conventional designs of moveable inlet injectors. The enclosed injector prevents the introduction of contaminants into the flow reactor. In conventional designs, ambient contaminants adsorbed onto the outside of the injector could be transported into the flow reactor. The enclosed injector exposes the reactant gas to the same length of inlet tubing at a uniform temperature regardless of the injector position. In addition, the enclosed injector minimizes temperature gradients in the flow reactor caused by heat transfer along the injector. This is a particular problem when the flow reactor is operated near atmospheric pressure at reduced temperatures. Finally, this design is significantly more compact than conventional injector designs. This system has been successfully employed in studies of the heterogeneous reaction of N2O5 with sulfuric acid aerosols over the temperature range 225–293 K.
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  • 35
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1711-1713 
    ISSN: 1089-7623
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An examination of the results of the accuracy measurements of a bench top audio-frequency selective voltmeter, based on the superheterodyne principle, showed that an accuracy of the order of only 10% of measured values could be achieved if no internal error correction procedure in the measurements had been used. The temperature variations of the parameters of the quartz band-pass filter have been identified as the main source of the measurement error. An application of the internal reference signal from a relatively simple and inexpensive source improved the overall accuracy up to the order of 3%. Finally, it was shown that by combining the wide band and selective measurements of the signals from the built-in tracking generator further improved the overall accuracy to better than 1% and eliminated altogether the need for using any separate source of internal reference signals.
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  • 36
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1728-1731 
    ISSN: 1089-7623
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The use of ion sources in induction linacs for heavy ion fusion is fundamentally different from their use in the rf linac-storage rings approach. Induction linacs require very high current, short pulse extraction usually with large apertures which are dictated by the injector design. One is faced with the problem of extracting beams in a pulsed fashion while maintaining high beam quality during the pulse (low emittance). Four types of sources have been studied for this application. The vacuum arc and the rf cusp field source are the plasma-types and the porous plug and hot alumino–silicate surface source are the thermal types. The hot alumino–silicate potassium source has proved to be the best candidate for the next generation of scaled experiments. The porous plug for potassium is somewhat more difficult to use. The vacuum arc suffers from noise and lifetime problems and the rf cusp field source is difficult to use with very short pulses. Operational experience with all of these types of sources is presented.
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  • 37
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1749-1752 
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A compact 5-cm-diam multipolar electron cyclotron resonance (ECR) ion source is characterized. The source is experimentally studied with no grids using argon gas with 50–250 W of 2.45-GHz microwave input power. Using a microcoaxial probe it was confirmed that the exciting electromagnetic fields within the resonant cavity were indeed TE111, as expected from the critical cavity dimensions. Double Langmuir probe measurements indicate high densities of about (4–5)×1011/cm3 near the source, and 5 cm downstream from the source output the densities become very uniform with a value of about 5×1010/cm3 over a 10-cm diameter. Electron energy distribution functions (EEDF) were measured using a single Langmuir probe. Average electron energies were seen to be about 8–10 eV with an energy distribution function falling between a Maxwellian and a Druyvesteyn distribution. Ion energy distribution functions (IEDF) were measured with a multigrid energy analyzer. It was seen that the distribution functions were narrow and peaked [with a full width half maximum (FWHM) of about 5 eV] except under certain conditions. Above 200-W input power, and also below about 0.5 mTorr there is significant broadening of the ion distribution function. It is speculated that the former may be caused by gas heating, and the latter may be caused by the presence of Ar+2 ions. With its high current densities ((approximately-greater-than)10 mA/cm2) and low average ion energies (〈40 eV), it is expected that this ion/plasma source will be very useful in many etching and deposition applications.
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  • 38
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1603-1605 
    ISSN: 1089-7623
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The Ashby–Jephcott interferometer is used to measure the temporal variations in electron densities in plasmas. A double-ended HeNe laser is used as part of an interferometer to make these measurements. In the present work, the experimental setup of the original method has been modified to prevent the drift in the temporal fringe patterns that are observed. This allows for more precise measurements of electron densities in plasmas. Further, the modification allows for commercially available HeNe lasers to be used to measure electron densities. The fringe patterns observed in a Z-pinch discharge using the original Ashby–Jephcott method and the modified method are shown. The differences in the temporal variation of the electron density measurements using the two methods are discussed.
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  • 39
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1002-1005 
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A technique to distinguish between materials that can and cannot shield microwaves in liquid nitrogen was developed. The samples are placed in a modified X-band waveguide, which operates by the same "insertion loss'' principle as a coaxial device used to measure shielding effectiveness from 300 to 1000 MHz. Verification of the waveguide fixture was accomplished by measuring the shielding effectiveness of a good conductor, coppper; a nonconductor, Teflon; and two intermediate conductors, steel and a carbon-filled elastomer. After verification, the waveguide fixture was used at liquid nitrogen temperatures to compare the shielding effectiveness of YBa2Cu3O7−x, a high temperature superconductor, with copper, a known shielding material.
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  • 40
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    Review of Scientific Instruments 65 (1994), S. 1012-1014 
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    Notes: An autocollimator based optical system has been developed which allows the relative angular positions of separate reflecting targets to be measured with high accuracy over a relatively large area. Misalignments suffered by the autocollimator head during translation between different measuring points are accounted for by utilizing a large plane reference mirror. Accuracies better than ±2 arcsec have been obtained over a 0.5 m diameter circular exploring area.
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  • 41
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    Review of Scientific Instruments 65 (1994), S. 1021-1022 
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new miniature interferometer has recently been developed for monitoring the changes of film thickness and refractive index, wherein a semiconductor laser and a photodiode detector are integrated to form a laser/detector hybrid. The laser light is collimated by a lens. When the laser light hits a film, it is reflected twice by the two interfaces between the film and the surrounding mediums. The two reflected light beams are interfered at the detector by the same lens. Due to the interference, the detected intensity is a function of the film thickness. The swelling of thin gelatin gel film has been used to demonstrate the use of this novel sensor. The sensor is ready to be used in many applications, such as inside a vacuum chamber, on a robot arm, and in a small reaction container, wherever a conventional interferometric setup cannot be easily implemented because of its size.
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  • 42
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    Review of Scientific Instruments 65 (1994), S. 1045-1050 
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: At the Workshop, the operation of various new and existing ECR ion sources was reported, with most of the emphasis on new methods to improve the performance and extend the variety of species. Much attention was paid to theoretical aspects, in particular to the basic question of electron heating; a complete investigation is still considered to be a long term project. A number of measurements of diagnostic character were presented. The strong radial component of the field in the magnetic trap turns out to play a crucial role in the confinement of hot electrons and hence in the production of very high charge state ion beams. A donor for cold electrons in any form—like a biased probe, plasma cathode, or electron gun—contributes strongly to increased output and stability of operation of the ECR ion source.
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  • 43
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    Notes: We would like to present the initial results and description of the superconducting electron cyclotron resonance ion source (SCECR) operating in the high-B mode—a new high magnetic field, low-frequency mode of operation. First, we describe the operating characteristics of this mode, which include very high mirror confinement in all directions, yet having a minimum field low enough for electron cyclotron resonance heating of 6.4 GHz. The source performance for oxygen, neon, argon, krypton, and xenon is presented and comparisons are made with several existing high-performance ECR sources. In this high-B mode the SCECR matches or exceeds the performance of all existing ECR sources. These results perhaps invalidate the classical frequency squared source performance scaling law, and suggest the new possibility of high-performance, low-frequency (and hence low cost) sources as will be discussed.
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  • 44
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    Review of Scientific Instruments 65 (1994), S. 1063-1065 
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The space-charge compensation of electron beams by hot ions with a Boltzmann energy distribution has been investigated by solving Poisson's equation. A unique relation is obtained between the degree of central compensation and the ion temperature: At high temperatures (as compared to the potential depression inside the beam) the compensation is low and the ions stay inside the electron beam only to a minor part, while at low ion temperatures, the beam is almost fully compensated. The potential difference between the beam axis and the surrounding tube is reduced by compensation, but when measured in terms of the temperature of compensating ions, it increases. This shall better confine the ions to the electron beam, the more complete the compensation. Increasing with the square of their charge state, trapped ions are heated by the ionizing beam electrons through small angle Coulomb collisions. For different ions with different charge states, the almost compensated electron beam acts as an energy filter, where the hotter ions are lost radially or axially. Therefore highly charged ions, which became "hot'' by waiting for stepwise ionization, can be cooled by lower charged ones, which still are "cold.'' This phenomenon has been called "evaporative cooling'' in electron beam ion sources (EBIS) and traps (EBIT) and space-charge compensation of the electron beam is the driving physic for it.
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  • 45
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    Review of Scientific Instruments 65 (1994), S. 1078-1080 
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Synchrotrons like the heavy-ion synchrotron SIS at GSI need an efficient low duty cycle injector (typical 1-pulse/s and 200-μs pulse length). To improve the peak current, an electron cyclotron resonance (ECR) ion source has been designed using a pulsed magnetic field (PuMa) to force ion extraction. We replaced the hexapole of a 10-GHz Minimafios ECR ion source by a vacuum chamber containing a water-cooled bilayered solenoid coil and a decapole permanent magnetic structure. A pulse line feeds the solenoid with a 250-μs pulse which increases the magnetic field in the minimum B region by 0.3 T. This process opens the magnetic bottle along the beam axis resulting in an extracted ion pulse. First tests of the PuMa ECR configuration in cw and pulsed operation are presented and analyzed.
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  • 46
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    Notes: The Quadrumafios electron cyclotron resonance ion source (ECRIS) has been especially designed to permit physical studies of the plasma; this paper describes the source itself (which has been operated at 10 GHz in a first step), its preliminary performances, and the different diagnostics involved, which mainly concern the electron population [electron cyclotron emission (ECE), x rays, diamagnetism, microwave interferometer, and electron analyzer]. The results are presented and discussed: There is of course a close relationship between the parameters of the plasma and the performances of the source; this point will be discussed in the article.
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  • 47
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    Review of Scientific Instruments 65 (1994), S. 1097-1099 
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    Notes: A new electron cyclotron resonance (ECR) ion source has been developed in the laboratory. The ECR condition at 2.45 GHz is obtained in a multicusp arrangement using a set of four parallelepiped-shaped SmCo magnets regularly spaced around a cylindrical ionization chamber 50 mm in diameter and 50 mm in height. The electromagnetic cavity is made of a shielded quarter-wavelength Lecher line resonator coaxially coupled to the microwave generator through an excitation loop antenna and a SMA-type connector. The extracted argon ion beam current density has been measured for different excitation modes fixed by the loop antenna orientation. A current density of 1 mA/cm2 has been reached with an incident microwave power of 110 W and a chamber pressure of 9×10−3 mbar. The small dimensions of this ion source and its performance allow to use it not only in applications such as ion beam processing and cleaning or surface treatments in advanced microelectronics, but also as a neutralizer for ion deposition applications.
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  • 48
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    Review of Scientific Instruments 65 (1994), S. 1101-1103 
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In our argon, oxygen, or nitrogen broad beam ion source, 80 mm in diameter, which is either an electrostatic reflex ion source, or a magnetic and electrostatic reflex ion source, the hot filament has been replaced by a carefully optimized microwave plasma (MP) cathode under the electron cyclotron resonance condition. Different geometries of antennae in which the microwave transverse electric field is more or less favored have been tested. A major improvement was obtained when a dc polarization of these antennae was superimposed onto the microwave field, allowing a fine tuning via the sheath thickness adjustment. Registered cathode currents under various conditions of pressure of neutrals, microwave power, and polarization voltage have shown a gain of a factor of 3 relative to the previous case where the single disk antenna was at a floating potential. Best results with argon gas at a pressure of 3×10−2 mbar were obtained with a spear-head shaped antenna fed at a microwave power of 50 W and polarized at 26 V. Extracted ion beam current densities as high as 5 mA/cm2 resulted from these different MP cathode improvements. Moreover, we have shown that the internal electronic tuning of the source can advantageously replace the traditional external tuning.
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    Review of Scientific Instruments 65 (1994), S. 1110-1112 
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A microwave discharge ion source has been designed in order to obtain high efficiencies for positive ionization of the recoils to be produced at the exotics at the cyclotron Tandem facility. After a charge exchange process the negative ions will be injected into the 15-MV Tandem, already working at the Laboratorio Nazionale del Sud. The short ionization time and the fast wall recycling make this source very well suited for the purpose of high efficiency ionization of the recoils. The operational principle and the design are described in the following.
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    Review of Scientific Instruments 65 (1994), S. 1122-1124 
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The particular microwave off-axis injection into the electron cyclotron resonance (ECR) ion source Alice, the reflected power and the occasionally observed waveguide arcs, required a careful study both of the waveguide termination and the microwave transmission line. The high-voltage microwave window was redesigned, improving the choke flange and showing the opportunity of treating the teflon insulator to obtain a surface resistivity in the range of 107 Ω. A simple plasma model, unidimensional and based on the Krook model for electron motion, is here considered for the ECR plasma; effects of rapid spatial variation of the external magnetic field are naturally included. Profiles of the waves in the ECR cavity are given, as well as an expression for the impedance of the plasma; no substantial reflections are evidenced for a typical plasma case (ωpl/ω=0.7).
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    Review of Scientific Instruments 65 (1994), S. 1125-1126 
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The studies and the experimental work for constructing an electron cyclotron resonance ion source (ECRIS) for the new tritium linear accelerator (TRILAC) at the Institute of Atomic Physics are presented. The absence of consumable parts, the low neutral pressure, and the high ionization efficiency with light elements make ECRIS very attractive for this accelerator. Some special configurations for the microwave system and for the plasma chamber are presented. A suitable modified structure of a power helix-type traveling wave tube (glass envelope with helix) in conjunction with its corresponding lateral rectangular waveguide tapers is presented. Application of an iris-loaded circular waveguide (traveling wave structure of a linear accelerator) as a slow wave structure is also under study. Problems like unstable tuning and arcing, which are encountered in the known structures, could be avoided by using slow wave structures of traveling wave type.
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  • 52
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    Notes: The design of "KRION-C'' with an energy of up to 80 keV and preliminary results on the ionization of sulfur and argon ions are presented. The cryogenic electron beam ionizer "KRION-C'' was used as an ion source for the first run with sulfur relativistic nuclei at the accelerating facility of the Laboratory of High Energies (LHE) in Dubna.
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    Review of Scientific Instruments 65 (1994), S. 1148-1150 
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    Notes: A small, compact negative heavy ion source based on plasma sputtering has been developed at KEK. This ion source was successfully used for a secondary-ion mass spectrometry (SIMS) system and a beam current density of about 3 mA/cm2 was obtained at the sample position of the SIMS system with a Au− ion beam.
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    Review of Scientific Instruments 65 (1994), S. 1162-1164 
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    Notes: To meet the requirement of fusion research for neutral beam injection, Southwestern Institute of Physics began the development of high current ion sources in the late seventies. A 7 cm duoPIGatron ion source, a 7×35 cm multifilament field free ion source, and an 8.5 cm multicusp ion source have successively been designed, built, and tested. The 7 cm duoPIGatron ion source was developed to study physical and technological aspects relevant to the high current ion source. The 8.5 cm multicusp ion source was developed to provide neutral beam injection for a mirror device MM-2U. It produces a 9 A, 25 keV, 50 ms hydrogen ion beam. In addition, a lithium ion source for plasma diagnostics has been developed.
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    Review of Scientific Instruments 65 (1994), S. 1165-1169 
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    Notes: During the last decade, different types of multicusp ion sources, such as high current, high concentration H+, H+2, or N+ ion sources, negative ion sources, radio-frequency-driven sources, and high charge state ion sources have been developed at the Lawrence Berkeley Laboratory. This article reviews the history of the research and development of these ion sources and their applications.
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    Review of Scientific Instruments 65 (1994), S. 1182-1184 
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Recent studies on the Munich laser ion source were aimed at the understanding and optimization of the production mechanism of negative ions. The possibility of extremely high, pulsed negative ion currents is due to the outstanding features of the laser produced plasma: a high electron density in conjunction with a low electron temperature. The intensity of the laser beam is restricted to a relatively small range from 5×107 up to 1×109 W/cm2. More than 20 different ions have been produced from pure element targets and from a number of salts. The yields achieved are in good agreement with a model including Saha equilibrium distributions. The comparison between pure elemental targets and alloys or salt shows a strong influence of ions with a low ionization potential on the negative ion production.
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  • 57
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    Review of Scientific Instruments 65 (1994), S. 1189-1191 
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    Notes: Several H−/D− dc sources employing multicusp confinement and magnetic filtering to enhance H−/D− production have been designed, built, and tested. Source performance in terms of beam output, emittance merit as functions of arc current, confinement magnetic strength, plasma volume, beam exit diameter, and extraction lens configuration have been studied in detail. At present, up to 9 mA H− and 3 mA D− beams with a normalized emittance of 0.44 mm mrad for H− beam have been extracted. A number of sources are tailored to fit the requirements of individual projects. In this article, a general description of source structure, power and biasing algorithms, and extraction geometries of these cusp sources will be given.
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    Review of Scientific Instruments 65 (1994), S. 1198-1200 
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A large vacuum-immersed negative-ion source has been investigated for the development of the neutral beam injection system in a large helical device. The structure of the vacuum-immersed source is compact and light because it is free from atmospheric pressure. Therefore, this is very advantageous for a large-scaled ion source. Moreover, since the grids of the accelerator are supported by post insulators, enhanced pumping of gaps between grids is expected, leading to a reduction of stripping loss of negative ions. The gas pressure distribution between grids was calculated and the stripping loss of H− ions was estimated and the effectiveness of the vacuum-immersed source structure was confirmed. The gas temperature effect of the gas pressure distribution is also considered by using a Monte Carlo code.
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    Review of Scientific Instruments 65 (1994), S. 1210-1212 
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: To investigate electron energy dependence of pure H− volume production, we have recently designed a double-plasma-type negative ion source. In this source, both energy and density of fast electrons are well controlled. With the use of this source, the effect of fast electrons on H− production, i.e., the so-called two-step process of H− production, is discussed.
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  • 60
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1170-1172 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This article is a suggestion for the development of a microwave driven volume source. A high electron temperature plasma is to be generated by coupling microwaves at the electron cyclotron resonance into a closed field line magnetic field configuration to form the discharge chamber of a volume source. As an example, a toroidal magnetic field configuration is examined. Numerous advantages of this scheme are cited, most important of which is the possibility of having a tandem volume source with a very steep plasma temperature gradient.
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  • 61
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1179-1181 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Two types of the surface-plasma sources of negative hydrogen ions developed at Budker Institute of Nuclear Physics are discussed. The source characteristics and the mechanism of negative ion production are presented. It is shown that several channels of plasma particle surface conversion and desorption are responsible for an intense negative ion production in these sources. The results of a detailed study of the quasistationary honeycomb and its comparison with the data for hollow-cathode Penning sources are presented.
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  • 62
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1266-1268 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Research results of the metal vapor vacuum arc (MEVVA) ion source are reported in this paper. As cathode materials, for example, Al, Ti, Fe, and Cu are used, respectively. A triggering pulse with a pulse height of 12 kV, pulse length of 90 μs, and repetition rate of 1–5 pulses/s is applied between the trigger electrode and the cathode. The pulse duration of the extracted ion beam is 800 μs. When the extraction voltage is 28 kV, the extracted beam current intensity for Al, Ti, Fe, and Cu is 255, 290, 240, and 300 mA, respectively.
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  • 63
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    Notes: The article presents results of experimental investigation of iodine laser interaction with Al, Cu, and Ta targets, obtained on the laser system PERUN (λ=1.315 μm, E〈50 J, γ∼350 ps) by means of corpuscular diagnostics. Ion energy distributions, average charge, and percent composition of the expanding plasma were determined. The plasma electron temperature was estimated to be Te∼550±100 eV. The maximum velocity (energy) of Al ions was estimated to be V∼9×107 cm/s (∼110 keV), Cu ions V∼6×107 cm/s (∼107 keV), and Ta ions V∼3×107 cm/s (∼110 keV); the maximum measured charge state was z=13 for Al ions (time-of-flight base L=196 cm), z=22 for Cu ions (L=116 cm), and z=9 for Ta ions (L=116 cm).
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  • 64
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    Notes: The characteristics of a large negative-ion source with external filter is investigated for the neutral-beam injection system in a large helical device. The magnetic cusp field is set up at almost the same strength as that in our well optimized 1/3 ion source with rod-type magnetic filter. An H− ion current of 5.2 A is extracted from the ion source with Cs seeding. The H− current corresponds to 19.7 mA/cm2, and the value is comparable to the current density obtained using the 1/3 scaled ion source with a rod-type magnetic filter at the same extraction voltage. In low operating pressure, the ion source with the external filter has a better performance on the extraction of H− ions.
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  • 65
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1295-1297 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Several versions of Mevva ion sources have been developed in our institute since 1988. It operates in a pulsed mode with a pulse length of 1.2 ms and a repetition rate of up to 50 pps. A time-averaged beam current of 10 or 50 mA has been extracted at 30–80 kV from Mevva IIA-H and Mevva IIB, respectively. In order to develop surface modification of materials by ion implantation we have constructed three kinds of Mevva ion source implantation systems. High dose (3–5×1017 cm−2) implantation with Ti, Ce, Y, and Ti+C, etc. has been carried out for improving the lifetime of metal cutting tools, relay contacts, dies, and some sophisticated components.
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  • 66
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1186-1188 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A compact, 2.5 cm diam rf-driven multicusp ion source has been developed and tested for H+ ion production in pulse mode operation. The source is optimized for atomic hydrogen ion species and extractable current. It is found that hydrogen ion beam current densities in excess of 650 mA/cm2 can be achieved with H+ species above 80%. The geometry and position of the porcelain-coated copper antenna were found to be of great significance in relation to the efficiency of the ion source.
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  • 67
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1223-1225 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A plasma sputter type of negative and positive ion source with electron cyclotron resonance (ECR) discharge has been developed at KEK. The ECR discharge was produced by a 2.45 GHz microwave source. In this ion source, negative heavy ions are produced at the surface of the metal which is placed in a Xe gas plasma confined in a cusp magnetic field. Positive ions are generated by ionizing of sputtered neutral atoms in the ECR discharge. The microwave is introduced into the source through a sputter target using a waveguide type of microwave transformer.
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  • 68
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    Notes: A simple and small ion source (∼1 cm3) was developed to produce negative ions of even those elements having electron affinity less than ∼1 eV. A powdery sample (∼10 mg) deposited on a gauze (G, ∼0.1 cm2) was bombarded with electrons (up to ∼3 mA and ∼300 eV) emitted from a filament (F). The ions desorbed from G were easily extracted because F was mounted beneath G. Those ions of H−, D−, Li−, Cl−, Na−, F−, and Ag− were readily produced from various samples such as alkali hydrides and halides. The total ion current, its density and the ion yield (ion to electron current ratio) of H− from NaH, for example, were as large as ∼0.1 mA, ∼1 mA cm−2 and ∼1%, respectively, although the electric power to heat F was only ∼5 W. Similarly, H+ was readily produced. Introduction of H2 had little effect upon the yield of H±.
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  • 69
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    Review of Scientific Instruments 65 (1994), S. 1325-1326 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A high current O+ ion source is desirable for applications to SIMOX and materials modification. To meet the requirements of this field, a new type of nonfilament high current O+ ion source has been developed successfully in our institute. Using O2 as discharge material, the typical extraction characteristics are as follows: The total oxygen ions current is 100 mA, of which the content of O+ is 80%, beam current density is larger than 200 mA/cm2 when the power consumption is 100 W; therefore the economic property is 1 mA/W. Feeding N2, the total extraction beam current is 100 mA of which 70% is N+ while the power consumption is 135 W.
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  • 70
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    Notes: The improvement of the properties and working life of the Freeman source is described. The experimental results show that the magnetic mirror field caused by a pair of mild steel circular plates, 15 mm in diameter and 2 mm thick, placed outside the discharge chamber can increase the ionized efficency of the gas feed. The atom–ion ratio of nitrogen was increased from 66% to 81%, and the heating filament current was decreased about 30 A, from 130 A down to 100 A for a new filament of 2 mm in diameter at the same arc voltage, arc current, and external magnetic field condition. Additionally, a Mo shield cylinder 14 mm in diameter put behind the reflect cathode surrounding the BN insulator prevented the metallization of the BN insulators, and resulted in increasing the stability of the arc discharge until the end of the filament working life of the Freeman source. The improvement occurred because it restricted the deposition of the sputtered W and Mo atoms coming from the hot filament and reflect cathodes onto the BN insulator, hence maintaining a high resistance of 70 MΩ between the anode and cathode. The new design with a combination of the cathode shield cylinder and magnetic mirror field improved the running property of the Freeman source, the mass spectrum of nitrogen, and the working life of the Freeman source, to about 40 h.
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  • 71
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1337-1339 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In this article, we describe four kinds of pocket PIG ion sources with a permanent magnet. They are a side extraction PIG source and three end extraction PIG sources. The beam intensity of the sources is about 1–2 mA for gas ions, and the power consumption is less than 100 W, and the power consumption of a PIG ion source with a ring permanent magnet made of CeCoCu magnetic material for gas ions is less than 4 W for an extracted 0.5 mA ion beam sometimes at the high voltage and small arc current discharge mode. The sources also can be used for metal ions; for this purpose one can get tens μA of Be, Al, Fe, Ti, Zr, Hf, Ta, and W in the sputtering discharge mode. Now the sources have been used for research in semiconductor and material science.
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  • 72
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    Review of Scientific Instruments 65 (1994), S. 1354-1354 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The results of calculations of the liquid metal subsurface layer atom binding energy and temperature under operating conditions of a Ga liquid metal ion source (LMIS) are given. The concepts developed in this article can help to explain the presence of excited neutral atoms of the LMIS substance in the desorption flux.
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  • 73
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1262-1262 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The presence of background gas in the discharge chamber of the MEVVA source influences the extracted beam. A strong influence of the background gas pressure in the arc region on the total extracted beam current and on the charge state distribution of the metallic ions have been observed. Different gases have been investigated together with different cathode materials. Up to 90% of the total beam current can be gaseous ions, depending on the arc and gas injection conditions.
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  • 74
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    Notes: Improvements have been made in a metal ion source, which made it possible to produce high density metal vapor plasma for extracting high current metal ion beams. Experiments of chromium ion beam extraction were performed. The ion beam current reached 250 mA at the extraction voltage of 36 kV. Furthermore, stable operation was achieved at the extracted current of 117 mA. The temporal drift of ion beam current was within ±1% for 1 h.
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1278-1280 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Experimental results of comparative tests of a spark ion source (closed geometry) with a MEVVA ion source (open geometry) are presented in this paper. Carbon (graphite) and some pure metals (such as Al, Cu, Ta) have been used as the working substances. It was discovered that the vapor ionization degree in the spark depended on the discharge gap shape that changed in time and became self-sustaining during the tests. It is supposed that this dependence had been determined both by the considerably increased value of power density released in the discharge, accompanied by the intense working substance transfer, and by a voltage drop growth in the spark ion source which led to deeper ionization of the vapors by fast electrons. Prolonged tests of the closed shape ion source (22 000 pulses, f=0.3 Hz) have been carried out. Spectra have been obtained for different times from the beginning of the test. Results are discussed.
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  • 76
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1310-1310 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A compact 5-cm-diam multipolar electron cyclotron resonance (ECR) ion source is characterized. The source is experimentally studied with no grids using argon gas with 50–250 W of 2.45-GHz microwave input power. Using a microcoaxial probe it was confirmed that the exciting electromagnetic fields within the resonant cavity were indeed TE111, as expected from the critical cavity dimensions. Double Langmuir probe measurements indicate high densities of about (4–5)×1011/cm3 near the source, and 5 cm downstream from the source output the densities become very uniform with a value of about 5×1010/cm3 over a 10-cm diameter. Electron energy distribution functions (EEDFs) were measured using a single Langmuir probe. Average electron energies were seen to be about 8–10 eV with an energy distribution function falling between a Maxwellian and a Druyvesteyn distribution. Ion energy distribution functions (IEDF) were measured with a multigrid energy analyzer. It was seen that the distribution functions were narrow and peaked [with a full width half maximum (FWHM) of about 5 eV] except under certain conditions. Above 200-W input power, and also below about 0.5 mTorr there is significant broadening of the ion distribution function. It is speculated that the former may be caused by gas heating, and the latter may be caused by the presence of Ar+2 ions. With its high current densities ((approximately-greater-than)10 mA/cm2) and low average ion energies (〈40 eV), it is expected that this ion/plasma source will be very useful in many etching and deposition applications.
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    Review of Scientific Instruments 65 (1994), S. 1312-1312 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An ECR ion source was excited by microwaves (2.45 GHz). The discharge chamber diameter of the ECR ion source into which microwaves were introduced by a waveguide and a vacuum window, is smaller than the cut off for TE or TM modes. The magnetic structure is built with an NdFeB permanent magnet where the magnetization M is perpendicular to the source axis. This cusp structure enables us to produce an N+ ion current of 1.1 mA (ion current density of 16 mA/cm2) at an extraction voltage of 8 kV with an aperture of 3 mm diameter by a two grid system; ion beam diameter is 0.2 mm by focusing. This ion source is used for bio-organic mutation.
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  • 78
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    Notes: An inherent feature of the vacuum arc discharge is that small droplets of micrometer size (macroparticles) are produced along with the plasma in the cathode spots. Droplet contamination of the substrate can occur when implanting metal ions using a vacuum arc ion source. The contamination can be significant for some cathode materials such as lead and other low melting point metals, which for some ion implantation applications such as for semiconductor doping and metallic corrosion inhibition can be a detriment. We have developed a vacuum arc ion source in which the plasma is filtered before the ions are extracted. By guiding the arc-produced plasma through a 60° bent magnetic duct, macroparticles are completely removed from the plasma. No additional power supply for the guiding magnetic field is required since the pulsed arc current itself is used to drive the magnetic solenoid. Tests have shown that macroparticle-free metal ion implantation can be done while maintaining the high ion beam current typical of vacuum arc ion sources.
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    Review of Scientific Instruments 65 (1994), S. 1334-1336 
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This article gives the physical thinking and technical design for studying a new-type full-ion source. An optimum configuration of the source, the optimum distribution of electric field and magnetic field in the discharge chamber, and the operation parameters are given by theoretical calculations. The source has features as follows: It has a microwave plasma cathode; in principle, it may produce the ions of all elements in the periodic table and provide high current ion beams; the sputtering mechanism for the production of metal ions has been adopted; the configuration of the source and the distribution of the electric field and magnetic field in the discharge chamber contribute more to producing high-concentrated plasma; ions of multiple charge state may be obtained.
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    Review of Scientific Instruments 65 (1994), S. 1340-1341 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe some details of the production of 57Fe and C60 ions by the Nielsen source. Some application results are also given.
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    Review of Scientific Instruments 65 (1994), S. 1345-1347 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Pulsed intense ion diodes were investigated as the device made a unique processing of material surface. For the ion implantation, the intense metal ion beams were obtained from the annular magnetically insulated ion diodes. The metal ions of Cu, Al, Pb, Mo, and Ta, of the energy of ∼100 keV, the total current of ∼1 kA, and the pulse width of ∼0.5 μs were produced. For the pulsed intense heat or momentum, a cylindrically focusing pulse intense light ion beams of the ion current density ∼1 kA/cm2 were generated from a cylindrical magnetically insulated ion diode. By an ion diode of a conical PED, the high density ion beam was focused nearby the source.
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    Review of Scientific Instruments 65 (1994), S. 1355-1355 
    ISSN: 1089-7623
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Considerable interest has been shown in the electrohydrodynamic liquid field emission ion source, from which positive ions emitted under the action of high electric fields, and high brightness sources are being developed with a variety of applications in mind. The basic principles of such sources are discussed. The threshold voltage Vth, the ion current (I) versus extraction voltage (V) relationships under various operating temperatures To, I versus To relationship, the angular current intensity and brightness, energy spread, as well as the current changes slowly with time under a definite voltage, are presented and discussed. The experiments show that the present performance of the ion source is as follows: The threshold voltage is about 5.4 kV, the brightness equal to 1×108A/cm2 sr, and energy spread of 26 eV.
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    Review of Scientific Instruments 65 (1994), S. 1365-1367 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A large volume cylindrical radio frequency (rf)-plasma source with a magnetic line-cusp field has been developed for large scale plasma processing. In this type of plasma source, a capacity-coupled 13.56 MHz rf plasma is produced in the presence of a magnetic line-cusp field. Two versions of the plasma source have been made and tested. The first version has peripheral rf electrodes placed on the outside of the ionization chamber, and is suitable for preparing a large volume uniform plasma. This plasma source can attain a useful area of uniform plasma over a 30-cm-diam region within 10% nonuniformity. The second version is featured by parallel doughnut-plate electrodes which forms part of the chamber wall and serves as a high current source. The electron density in such a version is proportional to the rf power, being equal to 4×1010 cm−3 at 400 W. The measured electron energy distribution function showed the Maxwellian-like distribution from a drift motion in the magnetic line-cusp field.
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    Review of Scientific Instruments 65 (1994), S. 882-886 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new high-pressure NMR probehead designed for a 400 MHz widebore NMR spectrometer is described. For the first time, the electrical leads of the rf circuit, the tubes for the thermostating liquid and the high-pressure fluid, as well as the wires of the Pt-100 resistor for temperature control, are all fitted at the bottom of the high-pressure vessel. The sample can easily be removed through a top plug, which allows a relatively fast exchange of the sample. A rather simple design leads to a low-cost construction. The high-pressure vessel and the rf circuit are placed inside a standard probehead jacket, such that the high-pressure probehead can be fitted into the superconducting magnet in the same way as a commercial probehead.
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    Review of Scientific Instruments 65 (1994), S. 943-945 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The fabrication and behavior of an all-carbon cathode for the growth of diamond films by dc discharge plasma chemical vapor deposition is presented. A graphite rod with a diameter of 2.5 mm was passivated in a methane dc plasma. During this process, the graphite was coated with pyrolytic carbon. Simultaneously, a thorn shaped protuberance (hereafter referred to simply as the thorn) of the same material grew from the end face of the rod towards the anode. The pyrolytic carbon prevented excessive sputtering of the cathode during diamond film synthesis in the hydrogen–methane plasma and the thorn presented a pointlike electron emitter providing a stable discharge. Using such cathodes, polycrystalline diamond films with well faceted crystallites have been grown at rates of approximately 5 μm/h. Nucleation and growth of individual, well faceted diamond crystallites even occurred on the cathode. When producing diamond films at methane concentrations above 1 vol %, a tubular form grows on the end of the cathode thorn.
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    Review of Scientific Instruments 65 (1994), S. 966-970 
    ISSN: 1089-7623
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new ac calorimetry for dielectric solids was developed. A long and thin metal strip directly evaporated onto the surface of the sample is used as a heater and thermometer. Temperature oscillation of the heater is measured from the third harmonic voltage at the heater. Both the heat capacity and thermal conductivity of the sample are obtained by the frequency dependent phase and amplitude of the third harmonic voltage. Since heat capacity addenda and heat leaks in the measurement are extremely small, prior calibration is not required. The calorimeter is fully automated and has been tested on two ferroelectrics, KH2PO4 and triglycine sulfate, at temperatures above 77 K. The optimal frequency region for the calorimetry is also discussed.
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    Review of Scientific Instruments 65 (1994), S. 1322-1324 
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Unlike widely published sources MEVVA, since 1984 we have constructed vacuum arc ion sources of any hard electroconductive materials (like metal or composites type—TiC, TiSiC, NiCrAlY, MoS, TiMoSi, WAlB, TiBNi) for modification of materials. The principle of Technological Accelerator of Metal ion and Electron Kit—source TAMEK, provides realization of regimes mentioned in the title in each (or in any series) of a sequence of f=50 Hz pulses: t=300 μs, Ii〈1 A, Ei〈200 keV, dDi=1016 ion/cm2/min for implantation and t=1000 μs, Iarc〈2000 A, dh=50–200 nm/min for deposition and so realized, if you wish, ion implantation, deposition, mixing, ion-beam-assisted deposition of the same ions without switching off the source. The experimental data demonstrate the possibility of obtaining mutual mixed (10×90 at %) alloyed layers up to 3 μm for time in t=15 min at T=100 °C temperature surface, with structure improving (microhardness) inner layer up to 50 μm in depth and possibility of further coating growth on the surface. This report presents a brief review of TAMEK principle design and its application for modification of constructed materials.
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    Review of Scientific Instruments 65 (1994), S. 1331-1333 
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A study of a small unbalanced magnetron source with a multipole cusp magnetic field anode is described. The coaxial magnetron principle was extended to the small unbalanced planar magnetron source. In the radial arrangement of magnets, the S pole of the magnet is directed toward the center of the permanent magnet annulus, and the core of the magnetized mild steel was only 5 mm in diameter. Such a construction of the unbalanced magnet arrangment makes the magnetron sputtering target as small as 34 mm in diameter, and increases the sputtering area of the target to 60%. The multipole magnetic field put in the anode can make the unbalanced magnetron source run in a higher discharge current at a lower arc voltage condition after beginning the arc discharge at a higher beginning arc voltage.
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    Review of Scientific Instruments 65 (1994), S. 608-611 
    ISSN: 1089-7623
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: New cassettes for 201 mm×252 mm (8‘×10‘) and 201 mm×400 mm (8‘×15.75‘) storage phosphor plates have been developed at the Synchrotron Resource of the Howard Hughes Medical Institute. The purpose for this work was mainly twofold. Firstly, to diminish the number of manual operations when putting the storage phosphor plate into the cassette or when extracting it from the cassette. Secondly, to render such a cassette much lighter than the former metal cassette previously in use. These two goals were achieved by making new cassettes that are operated as one piece instead of two or three independent parts as with the former systems. The cassettes have been extensively tested and found to be very useful.
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    Review of Scientific Instruments 65 (1994), S. 1348-1350 
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    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A variety of intense pulsed ion beams has been generated by the multiplate pseudospark chamber with an axially symmetric, high voltage gas discharge at low pressure of about 10 Pa. The fundamentals of this new type of ion source have been discussed in this paper. The field escalation effect has been proposed to explain the discharge mechanism. The filamentation instability of the ion beam with high current densities has been studied.
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  • 91
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new type of impregnated-electrode-type liquid-metal ion source, which eliminated the heating problem in the previous source, has been developed with multiple tip and reservoirs (TAR's). In the present ion source, the TAR's are connected electrically in series by modifying the TAR holding system. In order to achieve uniform heating of the TAR's, the materials of the knife-edged electrodes, which introduce the heating current to the TAR's, were examined. Tantalum electrodes exhibited better results as compared with the conventional Mo electrodes. Both of the two TAR's could be heated up to 700 °C with a heating power of 200 W. The maximum indium ion current of 9.1 mA was obtained from the four-TAR source with 40 emission points. Since the present ion current was limited by the current capacity of the extraction power supply, an ion current of more than 10 mA will be expected with a larger power supply. The results indicated that an ion current approximately proportional to the number of the emission points was obtained. This kind of ion source could be used as a general ion source in materials science.
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  • 92
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1356-1358 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: For thin film fabrication and surface modification, ion sources with high current, low energy, and broad beam are required. The source should be simple and reliable to operate, mechanically rugged, and highly productive for commercial use. To meet these requirements, a Hall effect plasma accelerator has been manufactured and tested. A beam energy of 200–300 eV and a beam current density of up to 10 mA/cm2 have been obtained with the source. Operational characteristics and possibility for industrial application are presented.
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  • 93
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1368-1370 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The results of theoretical and experimental investigations of dense plasma source resonantly excited by helicon wave are presented. Driven by a single-loop low-voltage ((approximately-equal-to)300 V) antenna, a source generates a plasma of density up to 5×1011 cm−3 at gas pressures 0.5–20 mTorr, operates at magnetic fields 〈100 Gs, and produces low-energy ion fluxes (〈60 eV) with current densities up to 7 mA/cm2 and 3.5% nonuniformity within a diameter 10 cm. A high-efficiency helicon source originates in a special kind of "resonance'' wave discharge, where a sharp increase of plasma resistance occurs near the helicon wave dispersion branches.
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  • 94
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1378-1382 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Experiments involving polarized beams and/or internal polarized targets are performed or proposed at many laboratories equipped with various type of accelerators and storage rings. Currently, the most powerful sources of polarized atoms and ions base on the atomic beam and the optical pumping methods. The present status of the polarized hydrogen source is discussed, with emphasis on the most recent improvements of the basic techniques allowing for the production of highly polarized, intense, dc or pulsed, positive or negative ion beams.
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  • 95
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1383-1387 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The progress of ion source research in China, including the main achievements, present status, suggestions, and problems are reviewed.
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  • 96
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1392-1394 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The ion beams are produced by a cylindrical thermal contact-ionization plasma source with an electrostatic lens system. The source plasma is produced at the inside surface of a 5-mm-diam 20-mm-long Re foil cylinder protected with a W cylinder. The surface is heated up to 3000 K by electron bombardment. The material to be ionized is fed to the surface through a guide pipe from a reservoir. Generation of all alkaline metal ions have been tested and a beam current of hundreds of μA is obtained. The efficiency for Li+ production is 30%, while that for Cs+ is nearly 100%. Alkaline earth ion beams, except Mg, are generated. A current of Ba+ up to 200 μA is obtained, while a Tl+ beam of over 200 μA is achieved. Halogen negative ion beams, except F−, of the order of 10 μA are also obtained when alkali halides are used. Attempts to extract Li− from the source are also being made.
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  • 97
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In easily attainable high vacua (Pr≈20–0.2 μTorr), the efficiency (β+) for producing ions (M+) from diatomic molecules (MX) incident on a polycrystalline surface of W, Mo, or Re was measured as a function of surface temperature (T≈800–2300 K). Theoretical analysis of β+ elucidated the temperature dependence of the effective work function (φ+) for the ionization. Namely, (1) above ∼2000 K, each surface is kept virtually clean, having φ+≈5.2, 4.9, and 5.4 eV for W, Mo, and Re, respectively. (2) At ∼1400–1200 K, the range of which depends upon Pr, φ+ is increased up to ∼7 eV by adsorption of residual gas molecules (RGM), thereby yielding β+=1 for even Tl and the current density of ∼10 μA cm−2 for the flux of 1014 molecules cm−2 s−1. (3) Below ∼1200 K, however, φ+ is much decreased by coadsorption of MX and RGM. A theoretical diagram of T vs φ+ is devised to predict the best condition for β+=1. The best condition (φ+, T, and Pr) to make β+ as large as possible may readily be selected according to the diagram and the present data on φ+.
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  • 98
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This project developed an automated controller based on an artificial neural network and evaluated its applicability in a real-time environment. This capability was developed within the context of a small angle negative ion source on the Discharge Test Stand at Los Alamos. The controller processes information obtained from the beam current wave form, developing a figure of merit (fom) to determine the ion source operating conditions. The fom is composed of the magnitude of the beam current, the stability of operation, and the quietness of the beam. Using no knowledge of operating conditions, the controller begins by making of rough scan of the four-dimensional operating surface. This surface uses as independent variables the anode and cathode temperatures, the hydrogen flow rate, and the arc voltage. The dependent variable is the fom described above. Once the rough approximation of the surface has been determined, the network formulates a model from which it determines the best operating point. The controller takes the ion source to that operating point for a reality check. As real data is fed in, the model of the operating surface is updated until the neural network's model agrees with reality. The controller then uses a gradient ascent method to optimize the operation of the ion source. Initial tests of the controller indicate that it is remarkably capable. It has optimized the operation of the ion source on six different occasions bringing the beam to excellent quality and stability.
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  • 99
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The characteristics of a 30 mA, 35 kV H− beam from a volume source have been determined using emittance measurements. A low energy-beam transport (LEBT) system consisting of six electrostatic quadrupole lenses and a short (about 5 cm long) single-stage einzel lens is designed with the aim of transporting the beam over a distance of about 30 cm and focusing a clean, matched beam into a radio-frequency quadrupole accelerator of the Superconducting Super Collider. The system parameters are chosen on the basis of simulation of beam dynamics. The emittance growth in the LEBT section is within a factor of about 1.5 and this satisfies the requirement of the emittance budget. The LEBT system is designed to be mechanically rugged.
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  • 100
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1438-1440 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A two dimensional electrostatic particle simulation was done to study the extraction of positive (negative) ions from a volume plasma source. The simulation model is a rectangular system which consists of an extraction grid (left wall), a plasma grid, and a grounded wall (right wall). Upper and lower boundaries are connected by the periodic boundary condition. Full dynamics of charged particles are followed. Positive (negative) ions are extracted from the plasma region through a slit in the plasma grid to the extraction grid. Electrons are reflected by the magnetic filter and confined in the region to the right of the magnetic filter. Simulation results are compared with the Child–Langumuir law where the extracted ion current is proportional to the three-halves power of the potential of the extraction grid. In the case of the positive ion extraction, simulation results agree quite well with the Child–Langumuir law. Whereas, in the case of the negative ion extraction, simulation results agree with the law only for the lower value of extraction grid potential.
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