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Dec 1981

Volume 52, Issue 12, pp. 1795-1923

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Design and calibration of the fast ion diagnostic experiment detector on the poloidal divertor experiment

R. Kaita, R. J. Goldston, D. Meyerhofer, and J. Eridon

Rev. Sci. Instrum. 52, 1795 (1981); http://dx.doi.org/10.1063/1.1136535 (7 pages) | Cited 13 times

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A special purpose charge‐exchange analyzer was constructed to measure the spatial distribution of hot‐plasma ions, as a function of energy and time, in the poloidal divertor experiment (PDX). The fast neutrals produced by charge exchange within the tokamak are reionized as they pass through a helium stripping cell in the detector. The energies of these ions are determined by the trajectories they follow between cylindrical deflection plates which are set at known electrostatic potentials. We describe the technique used to calibrate the response of this system as it depends on the energies and the masses of the particles which are being detected.
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52.55.Fa Tokamaks, spherical tokamaks
52.55.Hc Stellarators, torsatrons, heliacs, bumpy tori, and other toroidal confinement devices
52.70.Nc Particle measurements

Time of flight analysis of metastable products from a gas discharge

K. A. Hardy and J. W. Sheldon

Rev. Sci. Instrum. 52, 1802 (1981); http://dx.doi.org/10.1063/1.1136536 (4 pages) | Cited 16 times

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The performance of a metastable atomic beam TOF machine as a thermal plasma diagnostic apparatus is described. The machine consists of two differentially pumped chambers, one containing a hot‐cathode, low‐voltage discharge and the other a channeltron electron multiplier to detect Auger electrons produced by the metastable atoms. Data acquisition and analysis is by a computer‐based pulse height analyzer. The utility of the machine is demonstrated with a discharge in neon.
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52.70.Nc Particle measurements

Time‐resolving extreme ultraviolet spectrograph for fusion diagnostics

R. E. Bell, M. Finkenthal, and H. W. Moos

Rev. Sci. Instrum. 52, 1806 (1981); http://dx.doi.org/10.1063/1.1136537 (8 pages) | Cited 29 times

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A time‐resolving spectrograph for the simultaneous measurement of emissions at extreme ultraviolet wavelengths (300–2200 Å) is described. The spectrograph is a 400‐mm normal incidence f/30 system with seven gratings. Together two of the gratings cover the entire wavelength range at low resolution. The other five gratings have higher dispersion and cover adjacent intervals of the spectrum. The spectral resolution varies between 0.7–4 Å. The detector consists of a windowless microchannel plate/phosphor screen image intensifier, coupled by fiber optics to a 1024‐element self‐scanning integrated photodiode array. The output from the array is digitized and stored by a small desktop computer which has sufficient memory to record up to 80 spectra during a single plasma discharge.
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07.60.Rd Visible and ultraviolet spectrometers
28.52.-s Fusion reactors

Role of the anode area in the behavior of magnetic multipole discharges

A. J. T. Holmes

Rev. Sci. Instrum. 52, 1814 (1981); http://dx.doi.org/10.1063/1.1136538 (10 pages) | Cited 13 times

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A theoretical model and experimental measurements are presented for a hydrogen discharge in a magnetic multipole (bucket) plasma source where the plasma potential is negative with respect to the anode. This plasma potential depends critically on the anode cusp field, and the measurements show clearly that electrostatic ion confinement is obtained when the anode field is strong (1400 G), which leads to a high electrical efficiency for useful ion production. However, when the anode field is reduced, the plasma potential reverts to its normal positive value with respect to the anode with a consequent reduction in electrical efficiency.
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29.25.Lg Ion sources: polarized
29.25.Ni Ion sources: positive and negative
52.80.-s Electric discharges

Gaseous breakdown studies using a modified image converter streak camera

Siu‐Ping Hong, Yuji Shinoda, and N.H. Schiller

Rev. Sci. Instrum. 52, 1824 (1981); http://dx.doi.org/10.1063/1.1136539 (6 pages) | Cited 1 time

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The temporal and spatial information of gaseous breakdowns occurring from the nanosecond to millisecond time scales are important to the basic understanding and applications of gaseous discharges. A streak camera is an ideal tool for acquiring both time‐ and space‐dependent data simultaneously. However, there are several problems associated with using a conventional streak camera for gaseous breakdown studies. Modifications have been made specifically to solve these problems, while the features of the original streak camera are preserved. A signal overlapping problem has been eliminated by extending the dead time to 70 ms. Streak camera response times have been minimized by adjusting the bias voltages. One streak range has been extended to 7 ms to cover the entire event of a gaseous discharge. The modifications and experimental evaluation of the modified streak camera will be presented.
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52.80.-s Electric discharges

Theoretical analysis of space‐charge effects in photochron streak cameras

H. Niu and W. Sibbett

Rev. Sci. Instrum. 52, 1830 (1981); http://dx.doi.org/10.1063/1.1136540 (7 pages) | Cited 24 times

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The influence of space‐charge effects on the nature and extent of intensity‐dependent temporal broadening in picosecond and subpicosecond streak images has been investigated analytically. The results indicate that the limitations on the dynamic range of electron‐optical streak cameras result primarily from space‐charge effects which are most serious in regions of the streak tubes where the photoelectrons travel with low velocities for relatively long times. The predicted values of dynamic range have been found to be in reasonable agreement with experimental measurements for Photochron I and Photochron II streak cameras. Theoretical estimates of the dynamic range of the Photochron IV streak camera which is currently being developed have also been included.
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06.60.Jn High-speed techniques (microsecond to femtosecond)
07.68.+m Photography, photographic instruments; xerography

Photoelectron spectroscopy of supersonic molecular beams

J. E. Pollard, D. J. Trevor, Y. T. Lee, and D. A. Shirley

Rev. Sci. Instrum. 52, 1837 (1981); http://dx.doi.org/10.1063/1.1136541 (10 pages) | Cited 48 times

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A high‐resolution photoelectron spectrometer which uses molecular beam sampling is described. Photons from a rare‐gas resonance lamp or UV laser are crossed with the beam from a differentially pumped supersonic nozzle source. The resulting photoelectrons are collected by an electrostatic analyzer of a unique design consisting of a 90° spherical sector preanalyzer, a system of lenses, and a 180° hemispherical deflector. A multichannel detection system based on dual microchannel plates with a resistive anode position encoder provides an increase in counting efficiency by a factor of 12 over the equivalent single channel detector. The apparatus has demonstrated an instrumental resolution of better than 10 meV FWHM, limited largely by the photon source linewidth. A quadrupole mass spectrometer is used to characterize the composition of the molecular beam. Extensive differential pumping is provided to protect the critical surfaces of the analyzer and mass spectrometer from contamination. Because of the near elimination of Doppler and rotational broadenings, the practical resolution is the highest yet obtained in molecular PES.
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29.27.-a Beams in particle accelerators
47.40.Ki Supersonic and hypersonic flows

Intensity stabilized pulsed analyzing lamp for ultraviolet transient spectrometry

Jørgen Fenger

Rev. Sci. Instrum. 52, 1847 (1981); http://dx.doi.org/10.1063/1.1136542 (5 pages) | Cited 2 times

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This report describes an apparatus for increasing the light intensity of a Varian VIX‐150 UV xenon lamp. The increase is a factor 100 times greater at 220 nm. The light pulse width can be varied from 1 to 10 ms. The intensity of the light pulse can be controlled in two different modes: (1) the light flux from the lamp is kept constant by means of a parallel close‐loop control on a small fraction, 10%, of the radiated flux from the lamp. The intensity variation of a 10‐ms light pulse detected by a photomultiplier used for detecting the transient absorption signal can be held constant to within 5%. The accuracy is not limited by the lamp intensifier, but by a lack of precision in optical alignment of the absorption spectrometer; (2) the photomultiplier for the transient absorption signal controls the light intensity. During the first period of the light pulse the photomultiplier signal acts to provide feedback for the lamp intensifier and a constant light level is then obtained. In the subsequent period a hold circuit continues to keep the light level constant. Within the hold period the feedback signal from the photomultiplier is switched off and it continues as the detector for the transient absorption signal. In this mode of operation, a useful light pulse of 1 ms is obtained; the intensity variation is within 3%.
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85.60.Jb Light-emitting devices

Fatigue in photomultipliers due to excitation by pulsed light sources

R. J. López and M. A. Rebolledo

Rev. Sci. Instrum. 52, 1852 (1981); http://dx.doi.org/10.1063/1.1136543 (3 pages)

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In this paper the fatigue produced by pulsed light sources on an RCA C31034 photomultiplier connected to a photon‐counting system is studied experimentally. This fatigue is compared to that obtained when utilizing a continuous light source with the same mean intensity value. It is found that the fatigue produced by the pulsed source is of the same order as that produced by the continuous source, even though pulses are very distant between them. This is explained assuming that when fatigue magnitude decreases the relaxation velocity of the fatigue decreases as well.
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85.60.Dw Photodiodes; phototransistors; photoresistors

High‐temperature vacuum ultraviolet reflectometer

J. B. Blum, R. L. Coble, and P. A. Kearney

Rev. Sci. Instrum. 52, 1855 (1981); http://dx.doi.org/10.1063/1.1136526 (2 pages) | Cited 1 time

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A system is described which has been used to measure the near‐normal vacuum ultraviolet reflectivity of Al2O3 up to 450 °C. The system consists of a commercially available lamp and monochromator, and a specially designed reflectometer chamber with an internal electrical furnace and heat shields.
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07.60.Hv Refractometers and reflectometers

High temperature ultrahigh vacuum infrared window seal

T. J. Manuccia, J. R. Peele, and C. E. Geosling

Rev. Sci. Instrum. 52, 1857 (1981); http://dx.doi.org/10.1063/1.1136527 (3 pages) | Cited 6 times

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An alkali halide‐to‐metal high vacuum window sealing method is described which is usable to 275 °C with a combined leak plus outgas rate of <3×10−10 atm‐cm3/s. This seal is usable for static laser photolysis of low pressure, reactive gaseous samples, since the only materials to come into sample contact are stainless steel, lead, and the alkali halide window. This method has also been successfully used to seal stainless steel to stainless steel.
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07.20.Ka High-temperature instrumentation; pyrometers
07.30.Kf Vacuum chambers, auxiliary apparatus, and materials

Single pulse switchout system for a passively mode‐locked Q‐switched Nd:YAG laser

Isao Matsushima, Takeshi Kasai, and Masaaki Yano

Rev. Sci. Instrum. 52, 1860 (1981); http://dx.doi.org/10.1063/1.1136528 (5 pages) | Cited 12 times

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A new optical switchout device for a passively mode‐locked Q‐switched laser is presented. This device can switch out a single pulse with energy at a preset level. The stability of the switched out single‐pulse energy is greater than the input pulse train. This is achieved by means of a high speed comparator and avalanche transitor chains. A single pulse of ±13% energy stability is obtained from the pulse train of our Nd:YAG laser oscillator with a ±25% fluctuation. The maximum repetition frequency of 2 kHz is sufficient not only for this kind of laser but also for other applications. The life of the avalanche transistors used here is more than one million shots. The possibility of further improvements in output stability is also discussed.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Simple, reproducible, acoustically transparent pressure transducer with an 18‐ns rise time

A. Migliori and T. J. Hofler

Rev. Sci. Instrum. 52, 1865 (1981); http://dx.doi.org/10.1063/1.1136529 (3 pages) | Cited 3 times

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We describe an inexpensive, unbacked, solid dielectric capacitance‐like pressure transducer and preamplifier. The device has an adjustable sensitivity of about 0.5 μV/Pa into a 50‐Ω load, a geometry‐determined rise time of about 12 ns, and a flat frequency response from a few kHz to its resonant frequency of about 40 MHz. The geometry and method of construction make it simple to calculate response characteristics and it is usable at pressures from 103 Pa to at least 107 Pa.
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07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells

Design of high speed cylindrical NMR sample spinners

F. David Doty and Paul D. Ellis

Rev. Sci. Instrum. 52, 1868 (1981); http://dx.doi.org/10.1063/1.1136530 (8 pages) | Cited 29 times

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See Also: Erratum

Show Abstract
Simple approximate solutions to compressible fluid flow problems are used to arrive at useful design equations for high‐speed spinning on cylindrical air bearings for NMR studies of solids. The optimum radial clearance is shown to depend on the 1/3 power of the rotor diameter, and is 0.027 mm for a 12‐mm rotor, with a surface speed of one half the speed of sound, c. The required air bearing hole diameter is about 0.3 mm with a square root dependence on the rotor diameter. A few general comments are made concerning turbine design, and a simple combination impulse‐reaction type is described which offers some improvement in drive efficiency. Drive air flow is shown to depend approximately on the square root of the rotor volume for a surface speed 0.5 c. Relevant data for a number of high strength materials including hard ceramics are tabulated, and limiting speeds are calculated. The design equations are verified for 8 and 12 mm rotors made from Al2O3 with wall thicknesses equal to 6% of the diameter.
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07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques
06.60.-c Laboratory procedures

Application of Fourier transform‐NMR spectroscopy to submicrosecond time‐resolved detection in laser flash photolysis experiments

R. J. Miller and G. L. Closs

Rev. Sci. Instrum. 52, 1876 (1981); http://dx.doi.org/10.1063/1.1136531 (10 pages) | Cited 17 times

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The physical principles that are the foundation of the time‐resolved experiment are summarized by means of a general expression for the experimental observable—the free induction decay: the reaction dynamics are treated within the framework of the radical pair theory of chemically induced dynamic nuclear polarization (CIDNP) in a strong magnetic field. The basic instrumentation used consists of a pulsed nitrogen laser and a commercial, high‐resolution Fourier transform‐NMR spectrometer operating at a resonant frequency of 60 MHz. Modifications to the NMR spectrometer are described that provide for kinetic experiments with a time resolution of 1.2×10−7s and a spectral resolution on the order of hertz. Selected results from the flash photolysis of two ketones that react by Norrish type I cleavage are reported and discussed to exemplify the information obtainable with this new technique. The advantages and the limitations of NMR detection in flash photolysis experiments are considered.
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07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques

Heating technique for investigating trace element distribution in grains

J. Sörensen, F. Wegmüller, and U. Krähenbühl

Rev. Sci. Instrum. 52, 1886 (1981); http://dx.doi.org/10.1063/1.1136532 (3 pages)

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A heating technique is described which permits investigation of small samples (10–100 mg) of material originating from natural or technical processes. The distribution of trace elements throughout mineralogical samples was measured. It is demonstrated that mechanisms leading to surface coatings can be studied. This apparatus was developed for the investigation of small lunar samples.
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82.90.+j Other topics in physical chemistry and chemical physics (restricted to new topics in section 82)

A new pressure jump cell for direct microscopic observations

J. Wenzel and G. M. Schneider

Rev. Sci. Instrum. 52, 1889 (1981); http://dx.doi.org/10.1063/1.1136533 (2 pages) | Cited 2 times

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A pressure jump autoclave for direct microscopic investigations is described. In the instrument, the pressure jump principle with rupture diaphragm is realized in a simple manner by use of Swagelok standard parts, which may easily be adapted to other types of autoclaves. Up to now the cell has been used for the investigation of aging processes in liquid–liquid precipitates, but the instrument can also be suited for other purposes.
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07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells

Improved method of phase measurement by using an interferometer having a filamentary spatial filter

Sadahiko Mori

Rev. Sci. Instrum. 52, 1891 (1981); http://dx.doi.org/10.1063/1.1136534 (5 pages)

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The method for phase measurement by an interferometer having a filamentary spatial filter, (IFSF), [reported in Rev. Sci. Instrum. 50, 685 (1979) by the author] is much simplified and combined with the multipass interference method. The same accuracy, 2π/100, as the previous experiment is kept through measurements of multiplied phases up to the fifth order. The advantage in the principle of the improved method in comparison with conventional methods is distinctly discussed.
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07.60.Ly Interferometers
07.60.Hv Refractometers and reflectometers

Laser interferometer for high temperature isothermal length changes over long time periods

W. D. Drotning

Rev. Sci. Instrum. 52, 1896 (1981); http://dx.doi.org/10.1063/1.1136553 (5 pages) | Cited 5 times

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A laser interferometer for high precision isothermal length change measurements over long periods of time at high temperatures is described. An example is presented of the length change of a solid material near 500 K measured over several hours. The operating range of the device is from ambient temperature to 900 K, with an ultimate length change resolution of 10 nm. The critical optical alignment of the interferometer is performed and maintained by a minicomputer using an auto‐alignment control feature. Particular emphasis has been placed on long term system stability (measurement time scales greater than a few minutes) for studies of the high temperature isothermal behavior of solid materials as a function of time. To account for small temperature fluctuations in these measurements, a technique is presented for correction of the results for sample length changes induced by thermal expansion.
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07.60.Ly Interferometers
07.20.Ka High-temperature instrumentation; pyrometers

Optimum dc current resolution for high‐source resistances with a dc transformer matched rf SQUID

S. Q. Xue, P. Gutmann, and V. Kose

Rev. Sci. Instrum. 52, 1901 (1981); http://dx.doi.org/10.1063/1.1136544 (2 pages) | Cited 5 times

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By using a cryogenic current comparator with a ferromagnetic core, optimum matching for high‐source resistances of up to about 400 kΩ for a commercially available rf SQUID is achieved. This extends the use of SQUID instruments considerably, especially for applications where the source resistance exceeds 10−1 Ω.
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85.25.-j Superconducting devices
74.50.+r Tunneling phenomena; Josephson effects

Low‐friction, anhydrous, low‐ to high‐temperature furnace sample assembly for piston‐cylinder apparatus

A. L. Boettcher, K. E. Windom, S. R. Bohlen, and R. W. Luth

Rev. Sci. Instrum. 52, 1903 (1981); http://dx.doi.org/10.1063/1.1136545 (2 pages) | Cited 10 times

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A newly designed furnace assembly for piston‐cylinder, high‐pressure apparatus uses NaCl or KBr rather than hydrous materials such as talc or pyrophyllite. Unlike previous designs, our cell can be used hundreds of degrees above the melting temperatures of the salts. This cell requires little or no pressure correction and provides conditions that are free of H2 and H2O. The electrical power requirements are only about 60% of that for talc furnace assemblies, resulting in cooler operation and longer life for the steel and carbide in the pistons and pressure vessels.
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07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells

Computer‐assisted system for measuring capacitance and conductance of a diode using a phase sensitive technique

L. J. P. Ketelsen and R. A. Serway

Rev. Sci. Instrum. 52, 1905 (1981); http://dx.doi.org/10.1063/1.1136546 (5 pages) | Cited 2 times

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This paper describes a system for making accurate and reliable ac measurements of capacitance as a function of frequency, bias voltage, and temperature. The experimental apparatus consists of the basic capacitance measuring circuit and an information gathering device. The basic circuit includes a constant ac voltage source in series with the cell, a dc source for biasing the cell, an ac current amplifier in series with the cell for monitoring the current, and a lock‐in amplifier to measure the ac current. The capacitance device is interfaced with a microcomputer to facilitate handling large quantities of data in a short time. The computer is also used to increment the bias voltage for C–V measurements. The system has the capability of measuring capacitance to an accuracy of about 5 digits. We have used this system to study deep impurity levels in thin‐film, polycrystalline CdS/CuxS solar cells. The deep traps appear as anomalies in the otherwise linear l/C2 versus V plots. These levels play an important role in determining cell characteristics and may also influence the cell’s efficiency. The advantages of the capacitance–conductance system described in this paper are: (1) simple construction; (2) accurate calibration procedure; (3) ability to take data with 4 1/2 stable digits; (4) the admittance can be measured as a function of bias voltage, frequency, and temperature; (5) automation, i.e., computer controlled, and (6) the ability to accurately provide information on unstable samples.
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07.50.-e Electrical and electronic instruments and components
07.05.Hd Data acquisition: hardware and software
07.05.Kf Data analysis: algorithms and implementation; data management
07.05.Rm Data presentation and visualization: algorithms and implementation

Computer‐assisted magnet shimming

David H. West

Rev. Sci. Instrum. 52, 1910 (1981); http://dx.doi.org/10.1063/1.1136547 (3 pages) | Cited 1 time

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An iron electromagnet with a gap width of 23.5 cm and diameter of 30 cm was shimmed so that the field was uniform within ±4.2 parts in 104 over the central 19 cm of the axis. A description is given of the shim configuration used, and of the algorithm by which the measured field changes (produced by perturbing a shim) are used to predict an improved set of shim dimensions. The method is not limited to any specific geometry of either the shims or the region over which field homogeneity is desired.
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07.55.Db Generation of magnetic fields; magnets
85.70.-w Magnetic devices

Telephone monitoring of an unattended computer‐controlled experiment

Charles E. Cohn

Rev. Sci. Instrum. 52, 1913 (1981); http://dx.doi.org/10.1063/1.1136548 (4 pages)

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See Also: Erratum

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The status of an experiment can be monitored by telephone with the aid of a digital speech synthesizer and a telephone coupler.
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07.05.Hd Data acquisition: hardware and software
07.05.Kf Data analysis: algorithms and implementation; data management
07.05.Rm Data presentation and visualization: algorithms and implementation
07.05.Bx Computer systems: hardware, operating systems, computer languages, and utilities

High performance multihole SQUID sensor

Stefan Zarembiński and Bartłomiej Jarmul

Rev. Sci. Instrum. 52, 1917 (1981); http://dx.doi.org/10.1063/1.1136549 (2 pages) | Cited 3 times

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The design of a mechanically stable, thermal shock resistant, and vacuum‐sealed multihole SQUID sensor is described in detail. The relevant technological process involving diffusion welding is outlined.
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85.25.-j Superconducting devices
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