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Dec 1983

Volume 54, Issue 12, pp. 1605-1798

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Laué diffraction hard x‐ray spectrometer for laser fusion diagnostics

W. C. Priedhorsky, D. W. Lier, and R. H. Day

Rev. Sci. Instrum. 54, 1605 (1983); http://dx.doi.org/10.1063/1.1137319 (6 pages) | Cited 5 times

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We show that a crystal spectrometer used in the Laué mode is a useful diagnostic of high‐energy x‐ray emission from laser fusion plasmas. It has good collection efficiency and adequate energy resolution for continuum measurements. The instrument measures time integrated x‐ray spectra with a resolving power E/ΔE≊10 for photon energies between 60 and 300 keV. A strong signal and no detectable background are obtained in laser fusion experiments where ∼15 J of x rays are released in a pulsed (1 ns), hard (kT≊200 keV) spectrum. A Lanex/Tri‐X phosphor/film combination is used as a focal plane detector; we report its relative energy calibration. Because of the imperfection of available crystals, detailed measurements of reflectivity along the crystal are required to achieve absolute calibration.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
07.85.-m X- and γ-ray instruments

Simplified diamagnetic techniques for a field‐reversed theta‐pinch plasma

M. Tuszewski and W. T. Armstrong

Rev. Sci. Instrum. 54, 1611 (1983); http://dx.doi.org/10.1063/1.1137320 (4 pages) | Cited 28 times

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Diamagnetic measurements of a field‐reversed theta‐pinch plasma are performed with a simplified diagnostic consisting of either a single‐flux loop and several magnetic probes or magnetic probes only. Numerical and experimental evidence of the validity of these techniques is presented.
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52.70.Ds Electric and magnetic measurements
52.65.-y Plasma simulation

Characteristics of the neutral beam injectors for the Tandem Mirror Experiment Upgrade

T. J. Orzechowski, M. R. Carter, and R. H. Munger

Rev. Sci. Instrum. 54, 1615 (1983); http://dx.doi.org/10.1063/1.1137321 (8 pages) | Cited 1 time

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Neutral beams are used to fuel and heat the Tandem Mirror Experiment Upgrade (TMX–U) at LLNL. We have studied these beams spectroscopically to determine their species mix (H, H2, H+3) and impurity content (H2O). From the shapes of the spectral lines, we measured the divergences of the various components and compared them with the numerically determined divergence. By measuring the area under the various Doppler‐shifted lines, we determined the species mix and found that the atomic species fraction is lower than expected (30% to 45% rather than 60%). Although there is good agreement between the measured and calculated divergence for the atomic component of the beam, the molecular components have larger divergences, part of which can be accounted for by the dissociation of the molecules.
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52.40.Mj Particle beam interactions in plasmas
52.55.Jd Magnetic mirrors, gas dynamic traps
07.77.-n Atomic, molecular, and charged-particle sources and detectors
37.20.+j Atomic and molecular beam sources and techniques

High repetition tokamak CSTN–II

Kenkichi Ushigusa, Takashi Hayashi, Shuichi Takamura, and Takayoshi Okuda

Rev. Sci. Instrum. 54, 1623 (1983); http://dx.doi.org/10.1063/1.1137201 (3 pages) | Cited 5 times

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By employing a condenser system charging up at high speed with a triac switch, a stable tokamak discharge with a high repetition rate was achieved. A good reproducibility of the tokamak discharge made detailed measurements of spatial distribution of plasma and wave parameters possible, with a sampling technique. Basic studies on waves and particle transport in a tokamak configuration are possible with this system.
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52.55.Fa Tokamaks, spherical tokamaks
52.55.Hc Stellarators, torsatrons, heliacs, bumpy tori, and other toroidal confinement devices
84.30.Jc Power electronics; power supply circuits

Framing camera tube for subnanosecond imaging applications

R. Kalibjian and S. W. Thomas

Rev. Sci. Instrum. 54, 1626 (1983); http://dx.doi.org/10.1063/1.1137202 (3 pages) | Cited 9 times

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A dissector/restorer‐type framing camera tube has been characterized with a Nd:YAG mode‐locked laser. The three‐frame format tube, referenced to the photocathode, has a 5×5‐mm field of view and 0.3‐ns duration frames with better than 5 lp/mm spatial resolution. A scan‐rate matching technique is described that can increase the framing speed into the subpicosecond range for this type of camera tube.
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42.79.Ls Scanners, image intensifiers, and image converters
42.79.Pw Imaging detectors and sensors
07.68.+m Photography, photographic instruments; xerography

Miniature TEA N2 laser with automatically timed UV preionization

H. Houtman and J. Meyer

Rev. Sci. Instrum. 54, 1629 (1983); http://dx.doi.org/10.1063/1.1137203 (2 pages) | Cited 11 times

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A novel modification to the Blumlein circuit excitation method is presented which allows for automatically timed UV preionization of the main‐glow discharge of a miniature 337‐nm N2 TEA laser without the use of time‐delayed circuits commonly used in larger transverse discharge lasers. The laser reliably produces subnanosecond, gain‐switched output pulses of 65 kW at rates up to 50 Hz, with a stability of a few percent, and efficiency of 0.06%.
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42.55.Lt Gas lasers including excimer and metal-vapor lasers
52.80.Hc Glow; corona

Simple, low‐jitter, scanning nanosecond delay generator

P. Benetti, A. Bonelli, and P. G. Gobbi

Rev. Sci. Instrum. 54, 1631 (1983); http://dx.doi.org/10.1063/1.1137204 (4 pages)

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We present a simple and inexpensive TTL variable delay generator with nanosecond time step resolution and subnanosecond jitter. Its application is intended for the synchronization of pulsed multilaser systems to be used in resonant ionization spectroscopy studies.
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84.30.Ng Oscillators, pulse generators, and function generators
42.90.+m Other topics in optics (restricted to new topics in section 42)

Vibrating cross hair: A novel laser beam alignment device

A. Weis

Rev. Sci. Instrum. 54, 1635 (1983); http://dx.doi.org/10.1063/1.1137205 (3 pages) | Cited 4 times

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We describe the construction and performance of a low‐cost, easy‐to‐build laser‐beam alignment device (scanner) which allows the simultaneous display of the transverse x–y intensity distributions of two parallel or antiparallel beams. The novel feature of this scanner is that it can measure the relative positions of the two beams simultaneously. This makes it an excellent alignment tool for two‐photon experiments. The device is also useful for monitoring the transverse mode quality and for measuring the beam diameter. It serves for beam diameters down to 40 μ.
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42.79.-e Optical elements, devices, and systems

Synchronous ECL divider for reduced jitter in laser pulse studies

Dolph Moesle

Rev. Sci. Instrum. 54, 1638 (1983); http://dx.doi.org/10.1063/1.1137301 (5 pages) | Cited 1 time

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A fully synchronous five‐decade ECL counter is described, operable to beyond 75 MHz and producing two distinct TTL‐level outputs separated by presettable N+1 and M+1 input pulses. Intended primarily for laser pulse studies, the counter allows precise Q‐switch–mode‐lock synchronization, yielding greater optical pulse stability than with a‐ or semisynchronous synchronizer designs. In addition, the dual modulo feature allows easy selection of one particular optical pulse in the Q‐switched output train for close study.
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42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.60.Fc Modulation, tuning, and mode locking
07.50.Ek Circuits and circuit components
84.30.Sk Pulse and digital circuits

Apparatus for continuous, fast, and precise measurements of position and velocity of a small spherical particle

T. S. Venkataraman, William W. Eidson, Leonard D. Cohen, James D. Farina, and Charles Acquista

Rev. Sci. Instrum. 54, 1643 (1983); http://dx.doi.org/10.1063/1.1137302 (5 pages)

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The position and velocity of optically levitated glass spheres (radii 10–20 μm) moving in a gas are measured accurately, rapidly, and continuously using a high‐speed rotating polygon mirror. The experimental technique developed here has repeatable position accuracies better than 20 μm. Each measurement takes less than 1 μs and can be repeated every 100 μs. The position of the levitated glass spheres can be manipulated accurately by modulating the laser power with an acoustic optic modulator. The technique provides a fast and accurate method to study general particle dynamics in a fluid.
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42.79.Bh Lenses, prisms and mirrors
45.05.+x General theory of classical mechanics of discrete systems
47.50.-d Non-Newtonian fluid flows

High‐precision, wide‐range, dual‐axis, angle monitoring system

Felix J. Schuda

Rev. Sci. Instrum. 54, 1648 (1983); http://dx.doi.org/10.1063/1.1137303 (5 pages) | Cited 8 times

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A system is described that uses a helium–neon laser and lateral effect photodiodes to monitor the θ and ϕ angles of a test mirror. Accuracies of 0.01 arcsec are achieved short term in a laboratory environment. A bandwidth of 900 Hz allows simultaneous real‐time angle monitoring on both coarse (10 000 arcsec) and fine (300 arcsec) angular ranges.
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42.62.-b Laser applications
42.79.Bh Lenses, prisms and mirrors
42.79.Fm Reflectors, beam splitters, and deflectors
85.60.Gz Photodetectors (including infrared and CCD detectors)

Microcomputer‐controlled system used in time‐resolved EXAFS technique

W. H. Liu, X. F. Wang, T. Y. Teng, and H. W. Huang

Rev. Sci. Instrum. 54, 1653 (1983); http://dx.doi.org/10.1063/1.1137304 (4 pages) | Cited 2 times

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A microcomputer‐controlled system was built to measure 100‐μs‐resolved EXAFS (extended x‐ray absorption fine structure) of dynamic systems. We designed a charge integrator to integrate x‐ray absorption signals and a gate circuit to control the time and interval of integration. Since the x‐ray source is synchrotron radiation pulses, it is important to time the integration interval with the synchrotron radiation pulse clock. An Apple II microcomputer is used for the circuit control as well as the data acquisition. The computer is also interfaced with a CAMAC crate to operate the monochromator and other standard EXAFS instruments in synchrotron radiation laboratories. The electronic design of this system is described in this paper.
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07.85.-m X- and γ-ray instruments
82.80.Dx Analytical methods involving electronic spectroscopy
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
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

Development of a new UV resonance Raman spectrometer for the 217–400‐nm spectral region

Sanford A. Asher, Craig R. Johnson, and James Murtaugh

Rev. Sci. Instrum. 54, 1657 (1983); http://dx.doi.org/10.1063/1.1137305 (6 pages) | Cited 22 times

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The design and construction of a new UV resonance Raman spectrometer continuously tunable between 217–750 nm are described. The excitation source is based on a YAG laser which is frequency doubled or tripled to pump a dye laser. UV light is generated by nonlinear frequency doubling and mixing of the dye laser output or doubled output with the 1.06‐μm YAG fundamental. The detection system utilizes an intensified Reticon multichannel array. Commercially available monochromators are modified to make them useful for UV resonance Raman spectroscopy. Some sampling methodologies important for UV resonance Raman measurements are described. Examples of the sensitivity of UV resonance Raman spectroscopy are illustrated.
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07.60.Rd Visible and ultraviolet spectrometers
82.80.Dx Analytical methods involving electronic spectroscopy
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
42.62.-b Laser applications
33.20.Fb Raman and Rayleigh spectra (including optical scattering)

Inexpensive programmable gating unit for transient waveform recorders for NMR

R. K. Shenoy, H. Peemoeller, and D. W. Kydon

Rev. Sci. Instrum. 54, 1663 (1983); http://dx.doi.org/10.1063/1.1137306 (4 pages)

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In order to use transient waveform recorders to digitize the Meiboom and Gill modified Carr–Purcell pulse sequence response in samples with spin‐spin relaxation times of the order of seconds the memory of the recorders must be used effectively. The programmable gate, described in this paper, permits selective sampling of the spin‐echo envelope. The selective sampling capability of the gate is particularly useful for recording multicomponent signals which are commonly found in heterogeneous biological samples.
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07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques

Tuning and matching the TM010 cavity

L. G. Matus, C. B. Boss, and A. N. Riddle

Rev. Sci. Instrum. 54, 1667 (1983); http://dx.doi.org/10.1063/1.1137307 (7 pages) | Cited 6 times

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The cylindrical resonant cavity operating in the TM010 mode is increasingly being used to generate a microwave‐induced plasma (MIP) for elemental analysis by atomic emission spectrometry. In this study, the concepts of tuning and impedance matching for the Beenakker type TM010 resonant cavity are discussed. Proper placement and penetration depth of an antenna coupling probe appear to be a preferable approach to matching the TM010 microwave resonant cavity to a microwave generator. This approach precludes the use of external matching devices that add complexity to the system. In our system, a long probe penetrating 92% into the cavity well and positioned 14 mm from the center of the cavity allowed operation of a critically coupled argon plasma at 13–15 W as recorded from the generator’s calibrated power meter. Additionally, a detector is described that permits measurement of the electric field inside the cavity. The electric field inside the cavity decreases substantially upon ignition of a burning plasma. Aided with a tesla coil, a minimum electric field of 150 V cm−1 allows ignition of an argon plasma. After ignition, the electric field typically reduces to 30 V cm−1 and is not strongly affected by increases in input power. The effect of impedance matching and the electric field caused by increasing the input power to the cavity is also examined.
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52.70.Gw Radio-frequency and microwave measurements

Measuring the electrical resistance of metals to 40 GPa in the diamond‐anvil cell

Robin L. Reichlin

Rev. Sci. Instrum. 54, 1674 (1983); http://dx.doi.org/10.1063/1.1137308 (4 pages) | Cited 34 times

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A four‐probe technique is described for measuring the electrical resistance of metals in a diamond‐anvil cell at pressures up to 40 GPa. The pressure range for electrical resistance measurements was extended by developing insulating gaskets that provide the necessary support for the diamonds and the electrical leads at the diamond edges. The various gasket materials and construction methods that were tested fall into two categories: (1) gaskets made entirely of insulating materials, and (2) gaskets made of metal coated with insulating materials. Gaskets developed in each category were used successfully in making resistance measurements up to 40 GPa. The most reliable gaskets were composites of sheet mica and MgO powder. This report describes the testing and development of the gaskets and presents electrical resistance data obtained for iron and beryllium to 40 GPa.
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07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
72.15.Eb Electrical and thermal conduction in crystalline metals and alloys

High‐frequency temperature and pressure probe for unsteady compressible flows

W. F. Ng and A. H. Epstein

Rev. Sci. Instrum. 54, 1678 (1983); http://dx.doi.org/10.1063/1.1137309 (6 pages) | Cited 15 times

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A 3‐mm‐diam, dual hot‐wire aspiring probe is described which can simultaneously measure total temperature and total pressure in an unsteady high‐speed gas flow. The probe consists of two coplanar constant temperature hot wires at different overheat ratios operated in a 1.5‐mm‐diam channel with a choked exit. Thus, the constant Mach number flow by the wires is influenced only by free‐stream total temperature and pressure. The probe design is a compromise between the conflicting requirements of spatial resolution, frequency response, and angular sensitivity. The dc temperature accuracy of the probe is about 1% while the resolution is 0.3%. Frequency response of the present design is dc to 20 kHz.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.20.Dt Thermometers
47.80.-v Instrumentation and measurement methods in fluid dynamics
47.40.-x Compressible flows; shock waves

Hydriding system for moderately severe conditions of pressure and temperatures

J. Elton and H. Oesterreicher

Rev. Sci. Instrum. 54, 1684 (1983); http://dx.doi.org/10.1063/1.1137310 (3 pages) | Cited 4 times

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A hydriding system capable of pressures up to 1000 atm and temperatures up to 550 °C is described. A pressure generator in which H is outgassed from a metal hydride is used to produce the highest pressures. With this unit one can rather accurately determine the hydrogen uptake in metal hydrides at elevated temperatures and pressures by employing the virial equation of state out to the fourth virial coefficient.
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82.30.Nr Association, addition, insertion, cluster formation
07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
82.60.Hc Chemical equilibria and equilibrium constants
82.80.-d Chemical analysis and related physical methods of analysis

Triple point of succinonitrile and its use in the calibration of thermistor thermometers

B. W. Mangum

Rev. Sci. Instrum. 54, 1687 (1983); http://dx.doi.org/10.1063/1.1137311 (6 pages) | Cited 4 times

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Results are reported of an investigation of the triple point of succinonitrile as a temperature‐fixed point and of its use in the calibration of thermistor thermometers. The average value of the triple point of several samples of this material was determined to be 58.0805 °C, with an estimated uncertainty of ±0.0015 °C relative to the International Practical Temperature Scale of 1968. Three‐point calibrations of thermistor thermometers, using temperature‐fixed points provided by succinonitrile, gallium, and water were compared with 15‐point comparison calibrations performed with a standard platinum resistance thermometer (SPRT). Equations, solved by simultaneous solution using data obtained at the three calibration points, yield values of temperatures in the range from 0° to 70 °C which agree to within about ±1 mK with those obtained by calibration with a SPRT in a bath.
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07.20.Dt Thermometers
84.32.Ff Conductors, resistors (including thermistors, varistors, and photoresistors)
06.20.F- Units and standards

Temperature control for liquid‐helium cryostats below 4.2 K

M. Escorne and A. Mauger

Rev. Sci. Instrum. 54, 1693 (1983); http://dx.doi.org/10.1063/1.1137312 (4 pages) | Cited 1 time

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We report the operational characteristics of a membrane type of manostat and of a throttle valve system which we have constructed to regulate the pressure P above the liquid‐helium bath. The choice of the manostat rather than the other device depends on the nature of the experiments to be performed: in the membrane type of manostat, the temperature is determined with an accuracy limited by the fluctuations ΔT around the mean value T. With throttle valves, the accuracy is limited by the drift of T in time. The performance of both devices prove to be sufficiently good as they stand, since the departure from T in the course of the experiments is lower than 10−2 K in the whole range 1.4<T<4.2 K, being well inside this limit below 2 K. The need for expensive and complex electronic regulations to improve the temperature control is thus exceptional.
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07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment

Fast cold‐trap desorption spectrometers useful in normal vacua

C. J. Milner

Rev. Sci. Instrum. 54, 1697 (1983); http://dx.doi.org/10.1063/1.1137313 (8 pages) | Cited 1 time

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A cold trap used as a desorption spectrometer is, after a certain cold time, heated, and the pressure adjacent to it is monitored as a function of the increasing trap temperature. The temperature at which a peak pressure is observed is characteristic of the chemical species of the desorbing molecules. In the ultrahigh‐vacuum range, where desorption spectrometry has become established, the temperature at peak usually depends greatly on other factors also, in particular on the substrate surface. This paper: (1) demonstrates that, on the contrary, under lower, ‘‘normal,’’ vacuum conditions, such temperatures at peak are usually within a few kelvins of values predictable from vapor–pressure data, and (2) describes a form of cold‐trap system which displays narrow (15 K) and sharp (to 1–2 K) peaks during temperature rise at 100 K/s. The trap consists of a shallow cup or saucer pressed from a 25‐μm brass sheet, forming part of the vacuum wall. Pouring 0.3 ml of liquid nitrogen into the saucer cools it and keeps it cold for ∼15 s. Sharp, narrow peaks are secured by placing a constriction in the vacuum connection very close to the trap surface. A leak‐detection limit of 50 μl Pa/s (concentration limit 1:100 000) is claimed.
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07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment
07.30.Kf Vacuum chambers, auxiliary apparatus, and materials
07.30.Hd Vacuum testing methods; leak detectors

Positive displacement vacuum‐sweep dispenser for small particles

P. M. Sherman, D. R. Glass, and D. Postman

Rev. Sci. Instrum. 54, 1705 (1983); http://dx.doi.org/10.1063/1.1137300 (3 pages)

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A dispenser was developed for feeding small particles into a laboratory burner at a very constant flow rate. A positive displacement of a continuously replaced volume of particles is employed combined with a sonic ejector. The combination meets the requirements for good chemical measurements. The system also satisfies the requirements for laser‐Doppler anemometry.
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07.20.Hy Furnaces; heaters
07.30.Kf Vacuum chambers, auxiliary apparatus, and materials

Effect of gusts of wind on a thermal detector of radiation

K. D. Stock

Rev. Sci. Instrum. 54, 1708 (1983); http://dx.doi.org/10.1063/1.1137314 (4 pages) | Cited 2 times

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At windy weather air turbulences (gusts of wind) occur close to the ground. These turbulences result in adiabatic air pressure changes (∼10−2 mbar). The incident temperature fluctuations (∼mK) may cause strong disturbances in temperature‐sensitive measuring devices. By the example of a so‐called cavity detector the influence of wind on the measurement signal of a detector for optical radiation is demonstrated. A quantitative estimation of the uncertainty of measurement as a function of the wind velocity is given and confirmed by experiments. In addition, measures to reduce this disturbing influence are discussed.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
07.60.Dq Photometers, radiometers, and colorimeters
07.20.-n Thermal instruments and apparatus
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Generalized response of chemiluminescence analyzers

A. A. Mehrabzadeh, R. J. O’Brien, and T. M. Hard

Rev. Sci. Instrum. 54, 1712 (1983); http://dx.doi.org/10.1063/1.1137315 (7 pages) | Cited 4 times

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The mass flow and chemical kinetic equations for a gaseous chemiluminescence (CL) analyzer are formulated and solved. The resultant equation can be used to predict the absolute response of the analyzer as a function of the sample flow rate, the sample gas pressure, the chamber pressure, the chamber volume, the mass flow rate and mole fraction of the reagent gas, and the rate constants of the relevant chemical processes. Thus, the equation allows optimization of these parameters. It is shown that for varying sample pressure the analyzer can be used to measure either concentration or mole fraction and that interfering reactions can sometimes be discriminated against by chamber pressure variation. The equations apply equally well to a flowing‐liquid‐phase CL analyzer, if the chemical mechanism considered is appropriate.
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78.60.Ps Chemiluminescence
51.70.+f Optical and dielectric properties

Fast‐response dual‐beam UV‐absorption ozone photometer suitable for use on stratospheric balloons

Michael H. Proffitt and Richard J. McLaughlin

Rev. Sci. Instrum. 54, 1719 (1983); http://dx.doi.org/10.1063/1.1137316 (10 pages) | Cited 76 times

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Various types of ozone detectors are currently in use, each with different advantages and compromises in response time, portability, sensitivity, accuracy, need for repeated calibration, and expense. We describe here a new dual‐beam UV‐absorption instrument for balloon‐borne measurements of atmospheric ozone. It has two identical absorption chambers, each alternating between reference mode (ozone free) and sample mode by means of a four‐port valve and ozone scrubber. The ratio of the absorption signals, along with the known lengths and ozone absorption cross section, yield the ozone concentration. The dual‐beam feature cancels the effects of lamp intensity fluctuations, while the mode alternation compensates for mechanical changes and also provides continuous measurements. The absorption measurement requires no calibration and, hence, is independent of gas flow rate. The response time is 1 s and, for this measurement duration, the minimum ozone concentration detectable by this instrument (one standard deviation) is 1.5×1010 molecules/cm3 (0.6 ppbv at STP). The overall uncertainty of a 1‐s measurement at the ozone maximum (22 km) is 3.6%, where 2% of this is the accuracy of the ozone cross section. The size and weight are suitable for launch by small balloons, but the cost of the instrument precludes its use as a disposable unit.
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07.60.Dq Photometers, radiometers, and colorimeters
92.60.H- Atmospheric composition, structure, and properties
93.85.-q Instruments and techniques for geophysical research: Exploration geophysics
82.80.Dx Analytical methods involving electronic spectroscopy
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
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