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Feb 1982

Volume 53, Issue 2, pp. 131-263

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New method for focusing x rays and gamma rays

R. K. Smither

Rev. Sci. Instrum. 53, 131 (1982); http://dx.doi.org/10.1063/1.1136941 (11 pages) | Cited 14 times

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A new method for focusing x rays and gamma rays is described that can focus monochromatic radiation from a point source or parallel beam down to a line image. If two focusing elements are used or if a single element bent in two directions is used, the radiation can be focused to a point image. Conversely, radiation from a point source can be converted into a parallel beam. The method makes use of bent diffraction crystals in which the intercrystalline‐plane spacing is varied as a function of position in the crystal. The Bragg angle for diffraction of monochromatic radiation will now vary as a function of position in the crystal, and this new degree of freedom can be used to obtain focusing of the diffracted beam. A number of ways to achieve this variation in crystal‐plane spacing is discussed, including the use of thermal gradients and the variation of the elemental composition of the crystal. The applications of this new focusing system to a gamma‐ray telescope and to the production of a real image of a strong x‐ray source are considered.
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07.85.-m X- and γ-ray instruments

Point focusing x‐ray camera and the study of total external reflection

Hisashi Kurata

Rev. Sci. Instrum. 53, 142 (1982); http://dx.doi.org/10.1063/1.1136942 (6 pages) | Cited 4 times

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The total external reflection coefficients of a glass and gold reflector for CuK radiation were determined experimentally, with results in good agreement with the theoretical calculation. Partial monochromatization of the reflected beam by the glass reflector was also verified experimentally. Based on this study, a point focusing x‐ray camera with two bent (horizontal and vertical) reflectors was designed and made. The horizontal reflector uses a glass mirror, and the vertical reflector uses either a glass mirror or a monochromator. This camera can thus be used in either a mirror–mirror (Franks optics) or a mirror–monochromator configuration (Huxley–Holmes optics). By changing the vertical reflector, the configuration can be simply exchanged and the best use of the characteristics of the two available optics can be made. The choice of optics depends mainly upon the irradiated size of the specimen: the mirror–mirror optics gives narrow beams (3′–6′), and the mirror–monochromator optics gives convergent beams (1°–1.2°) and much greater intensity. Small‐and wide‐angle diffraction patterns are detected with variations of specimen to film distance. For diffraction angles smaller than about 1°, both cases require a fine focus source smaller than about 0.1×0.1 mm in projection to prevent the production of Kα1–Kα2 doubled diffraction pattern by the monochromator and a reduction of resolution due to the extent of the focusing point by the glass reflector.
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07.85.-m X- and γ-ray instruments

Mechanical filter for the suspension of gravitational wave antennas

Eugenio Coccia

Rev. Sci. Instrum. 53, 148 (1982); http://dx.doi.org/10.1063/1.1136943 (6 pages) | Cited 14 times

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We discuss here the design of a new suspension for Weber‐type gravitational wave antennas. The suspension consists of cantilever beams and operates as a mechanical filter for the external mechanical noise. The attenuation of the filter and the stresses applied on the antenna are computed and verified experimentally. When the filter is optimized, the attenuation depends on the value of an angular frequency, ωc, characteristic of the material of the beams. Attenuation of the order of 10−6–10−7 can be obtained at 1 KHz for a 1000‐kg antenna using materials with good anelastic behavior such as Al 5056 and Ti 64.
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04.30.-w Gravitational waves
04.80.-y Experimental studies of gravity

Sciopticon array analysis of ORNL ion sources

P. M. Ryan, J. H. Whealton, and R. R. Feezell

Rev. Sci. Instrum. 53, 154 (1982); http://dx.doi.org/10.1063/1.1136944 (5 pages) | Cited 1 time

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The neutral beam sciopticon (pinhole camera) has been expanded to an array of pinhole apertures in order to simplify the process of distinguishing between beam imperfections caused by extraction nonuniformities and those caused by beamlet missteering. An analysis scheme is presented whereby the power transmission loss due to beamlet missteering may be estimated if the average beamlet divergence anlge is known. For a well‐focused ion source, the sciopticon array can also give the approximate beam focal length and average beamlet divergence angle. Results from testing five ORNL ion sources indicate that the principal mechanism for differences in power transmission is beamlet missteering.
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29.25.Lg Ion sources: polarized
29.25.Ni Ion sources: positive and negative
41.75.Ak Positive-ion beams
41.75.Cn Negative-ion beams

Cesium supersonic jet for D− production by double electron capture

M. Bacal, H. J. Doucet, G. Labaune, H. Lamain, C. Jacquot, and S. Verney

Rev. Sci. Instrum. 53, 159 (1982); http://dx.doi.org/10.1063/1.1136945 (9 pages) | Cited 4 times

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A steady‐state, supersonic cesium jet generator has been developed for use in an intense negative deuterium ion source, based on double electron capture. The cesium target thickness is 2.5×1015 atoms/cm2 for an oven temperature of 600°C, with an average geometrical thickness of 3.0 cm. The cesium flux, determined from calorimetric measurements, is found to be in agreement with a simple calculation of supersonic flow through a slit.
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47.40.Ki Supersonic and hypersonic flows
52.50.-b Plasma production and heating
34.70.+e Charge transfer

Fast response Faraday cup for low‐energy, nanosecond‐pulse ion beams

Toshiyuki Iida, Ryoichi Taniguchi, Toshiaki Fujimoto, and Kenji Sumita

Rev. Sci. Instrum. 53, 168 (1982); http://dx.doi.org/10.1063/1.1136946 (3 pages) | Cited 2 times

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A fast response Faraday cup has been developed for measuring low‐energy, nanosecond‐pulse ion beams. It is made of a coaxial Faraday cup before which a thin gold foil has been set, and it measures the waveform of low‐energy, nanosecond‐pulse ion beams by using the secondary electrons emitted in the forward direction from the foil.
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29.40.-n Radiation detectors

Multichannel CO2‐laser interferometer using a PbSnTe detector array

C. A. J. Hugenholtz and B. J. H. Meddens

Rev. Sci. Instrum. 53, 171 (1982); http://dx.doi.org/10.1063/1.1136947 (4 pages) | Cited 18 times

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A multichannel CO2‐laser interferometer has been built to measure electron line‐density profiles of plasmas. In the work path a sheet‐like beam is transmitted over the total extension of the plasma, to be refocused onto a detector array, where interference with the reference beam occurs. In this way a ’’phase image’’ of the plasma is produced on the detector elements. With the data acquisition system used, it is possible to follow the development in time of the profiles.
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07.60.Ly Interferometers
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
42.55.Lt Gas lasers including excimer and metal-vapor lasers

Detection efficiency of a heavy ion time‐of‐flight spectrometer with thin carbon foils in the start detector

W. Stüdemann and B. Wilken

Rev. Sci. Instrum. 53, 175 (1982); http://dx.doi.org/10.1063/1.1136948 (6 pages) | Cited 3 times

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We report measurements of the effect of heavy‐ion scattering due to the passage through carbon foils with thicknesses of 4.5, 6.7, and 16.9 μg/cm2 in a wide energy range. For comparison of the results with theoretical predictions the actual foil thicknesses were determined by scaling energy loss measurements with tabulated stopping powers. Using these thicknesses the measurements in general agree well with theory. However, particularly for the 4.5 μg/cm2 foil, significant deviations from the specified thickness have been found very likely due to additional cover layers. The results are used to determine the loss in detection efficiency for low‐energy heavy ions in instruments based on the time‐of‐flight method with thin carbon foils acting as converters for secondary electrons.
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07.75.+h Mass spectrometers

Simple powerful tunable single‐mode and mode‐locked TEA CO2 laser

R. A. Dougal, M. A. Gundersen, and P. F. Williams

Rev. Sci. Instrum. 53, 181 (1982); http://dx.doi.org/10.1063/1.1136922 (3 pages) | Cited 1 time

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A simple method for constructing a single longitudinal‐mode CO2 laser that is tunable within individual rotational transitions is presented. Useful power levels, typically 0.3 J per pulse in a single‐mode beam, are obtained from a single‐stage device. Mode‐locked output can also be obtained from the laser. In addition, design and construction of a local oscillator for making absolute in situ frequency measurements is described.
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42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.62.-b Laser applications

Discharge energy loading characteristics of a UV‐preionized TEA CO2 laser

Shun‐ichi Suzuki, Yuko Ishibashi, Minoru Obara, and Tomoo Fujioka

Rev. Sci. Instrum. 53, 184 (1982); http://dx.doi.org/10.1063/1.1136923 (3 pages) | Cited 8 times

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The effects of ultraviolet (UV) preionization energy and initial electron number density on discharge loading are experimentally clarified in a UV preionized TEA CO2 laser. Dependence of the laser output energy on the spatial uniformity of the preionization has also been examined. In order to produce the laser output energy efficiently, the input energy for the UV preionizer is required to be in excess of 2% of the input energy for the main discharge. With the sufficient initial electron number density, the laser energy was little dependent on the spatial nonuniformity of preionization in the discharge volume at low‐energy loadings (≲ 100 J/l). At higher energy loadings, the laser output energy was found to depend not only on the initial electron number density but also on the spatial uniformity of the preionization.
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42.55.Lt Gas lasers including excimer and metal-vapor lasers

Far infrared laser system for the measurement of collision‐induced absorption spectra

I. R. Dagg, L. A. A. Read, and J. Vanderkooy

Rev. Sci. Instrum. 53, 187 (1982); http://dx.doi.org/10.1063/1.1136924 (7 pages) | Cited 4 times

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A system for the measurement of collision‐induced absorption using a CO2 optically pumped FIR laser is described. The report emphasizes the laser stabilization systems that have been developed, the design of the absorption cell, and the detection methods employed to obtain the required data. Also included are some typical results at 15.1 cm−1 for nitrogen, ethylene, carbon dioxide, and ethane gases.
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42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.62.-b Laser applications

New spectrometer and sample technique for deuterium analysis of enriched water samples

J. Dumke, E.‐G. Niemann, H.‐W. Brandt, and K. Heilig

Rev. Sci. Instrum. 53, 194 (1982); http://dx.doi.org/10.1063/1.1136925 (3 pages) | Cited 1 time

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The intensities of the atomic lines Hα and Dα produced in a high‐frequency discharge in water vapor are measured to determine the deuterium content. A special spectrometer uses an interference filter and a Fabry–Perot interferometer for simultaneous recording of both intensities. Electronic calculation gives an observed intensity ratio which can be corrected via a calibration curve, thus yielding the deuterium content in percent. The relative accuracy of the method depends on the enrichment: above 1% deuterium the relaltive limit of error is about ±1%, down to 0.3% deuterium it is better than ±5%. A deuterium concentration of 0.03% can just be distinguished from normal water.
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07.60.Rd Visible and ultraviolet spectrometers
32.10.Bi Atomic masses, mass spectra, abundances, and isotopes

Measurement set for optical fiber loss spectra

J. Stone, H. E. Earl, and R. M. Derosier

Rev. Sci. Instrum. 53, 197 (1982); http://dx.doi.org/10.1063/1.1136926 (5 pages) | Cited 1 time

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A set for measuring optical‐fiber loss spectra is described. The set consists of a tungsten halogen lamp, a monochromator, a Si or InGaAs detector, and novel data processing instrumentation. Fully resolved spectra are obtained from the visible to 1.7 μm with an accuracy of 0.1 dB for both single‐mode and multimode fibers.
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42.81.-i Fiber optics
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Interferometric refractometer for measuring the relative refractive index of two liquids

K. D. Singer, M. S. Merlin, S. J. Lalama, and A. F. Garito

Rev. Sci. Instrum. 53, 202 (1982); http://dx.doi.org/10.1063/1.1136927 (3 pages) | Cited 5 times

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An interferometric technique for directly measuring small differences in refractive index between two liquids of similar refractive index is described. The method is based on measuring the phase change on translation normal to the beam propagation in one arm of a Michelson interferometer of a compensating double wedge filled with the two liquids. Details of the sample cell, interferometer construction, signal detection, and experimental procedure are described. Resolution in refractive index difference of 10−6 has been obtained.
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07.60.Hv Refractometers and reflectometers
07.60.Ly Interferometers

New digital photoelectric correlator

S. Friberg, J. Andersen, and L. Mandel

Rev. Sci. Instrum. 53, 205 (1982); http://dx.doi.org/10.1063/1.1136954 (5 pages) | Cited 20 times

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A simple electronic correlator for two‐time photoelectric correlation measurements has been developed. It functions by registering the distribution of time intervals between pairs of photoelectric pulses. Its basic elements are a clock that is started by the first pulse and is used to digitize the time intervals, a pair of fast counters for counting subsequent pulses, and a set of data registers. The pulses are directed to one or the other counter alternately at regular clock intervals. The operation of the correlator is described and tested by measurements of a randomly modulated light source.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors

External generation of gate delays in a boxcar integrator—Application to deep level transient spectroscopy

K. Kosai

Rev. Sci. Instrum. 53, 210 (1982); http://dx.doi.org/10.1063/1.1136928 (4 pages) | Cited 2 times

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A simple and easily installed modification is described which upon application of external pulses causes the undelayed opening of the gates in the signal processing modules of a Princeton Applied Research Model 162 boxcar integrator. This allows the timing for the aperture delays to be done externally with digital circuitry, thus simplifying the setting of time parameters in deep level transient spectroscopy (DLTS) measurements, as well as giving increased time accuracy, stability, and easier interfacing to a computer. A second circuit is also described which, when used with a modified 162, permits double correlation DLTS to be performed with one, instead of two, instruments.
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07.50.Ek Circuits and circuit components

Microwave sputtering system for the fabrication of thin solid films

I. Kato, H. C. Card, K. C. Kao, S. R. Mejia, and L. Chow

Rev. Sci. Instrum. 53, 214 (1982); http://dx.doi.org/10.1063/1.1136929 (3 pages) | Cited 1 time

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A new microwave‐plasma sputtering method has been developed for the fabrication of thin solid films. One advantage of this method is that the substrate is not exposed to the plasma which can be made very uniform and confined in a predetermined region. It is, therefore, possible to fabricate uniform solid films over a large area and for a wide range of film thicknesses on low melting‐point substrates. Amorphous selenium films fabricated on a glass substrate or a polyethlene sheet are found to be very uniform in thickness, structure, and optical constants over a large deposition area.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
06.90.+v Other topics in metrology, measurements, and laboratory procedures (restricted to new topics in section 06)
52.75.-d Plasma devices
52.70.-m Plasma diagnostic techniques and instrumentation

Typing a semiconductor with point contacts

S. Dhar and B. R. Nag

Rev. Sci. Instrum. 53, 217 (1982); http://dx.doi.org/10.1063/1.1136930 (4 pages) | Cited 1 time

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The results of typing measurements of semiconductor samples using a metal‐semiconductor point contact technique, under different experimental conditions, are presented. The information obtained from these experiments has been verified for correctness by using standard techniques. A circuit arrangement is described which can be attached to a conventional four‐probe resistivity jig in order to extend the applicability of the latter for determination of the type of a sample along with its resistivity measurements.
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85.30.Hi Surface barrier, boundary, and point contact devices
85.30.De Semiconductor-device characterization, design, and modeling

Fast computer‐controlled mirror system for intensity measurements in low‐energy electron diffraction

W. Berndt

Rev. Sci. Instrum. 53, 221 (1982); http://dx.doi.org/10.1063/1.1136931 (4 pages) | Cited 4 times

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A plane mirror rotatable about two orthogonal axes has been developed for imaging low‐energy electron diffraction (LEED) spots into a photometer tube. The mirror is driven by stepping motors and controlled by a PDP 11 computer. Using a sequence of primary‐beam energy values in steps of 2 eV the acquistion time for the normalized intensity data from one diffraction beam between 30–200 eV takes approximately 10 s.
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61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
07.50.-e Electrical and electronic instruments and components

Low‐voltage, high‐current electron gun

Peter W. Erdman and Edward C. Zipf

Rev. Sci. Instrum. 53, 225 (1982); http://dx.doi.org/10.1063/1.1136932 (3 pages) | Cited 87 times

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A simple, high‐performance, electrostatically focused electron gun, which is useful over an energy range extending from a few electron volts to at least 500 eV, is described. The current is delivered in a beam ∼1 mm in diameter, with <50 mrad angular divergence and typically has a current over 1 mA at 100 eV. The design is small, compact, and rugged. This electron gun has been used successfully in both laboratory and sounding rocket experiments.
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29.25.Bx Electron sources
41.75.Fr Electron and positron beams

Mathematical treatment of heat flow in differential scanning calorimetry and differential thermal analysis instruments

Stephen C. Mraw

Rev. Sci. Instrum. 53, 228 (1982); http://dx.doi.org/10.1063/1.1136933 (4 pages) | Cited 27 times

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A general mathematical treatment is given which relates the techniques of classical differential thermal analysis, power‐compensated differential scanning calorimetry, and heat‐flux differential scanning calorimetry. An idealized system, representative of almost any type of differential thermal instrument, is presented, which, unlike those of previous treatments, incorporates two separate thermal resistances. This modification allows the heat‐flux d.s.c. instrument to be considered in a unified analysis with the other techniques. General aspects of the idealized system are presented, and the equations governing heat flow within the system are developed. For each separate technique, the components of the idealized system are identified with the actual components of the physical instrument, and the specific equations which describe the measuring principles of that technique are derived. It is shown that a similar type of thermal resistance governs sample‐temperature lag in both the power‐compensated and heat‐flux d.s.c. cases, and the method of estimating the value of this resistance from the slope of a fusion peak is discussed.
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07.20.Fw Calorimeters
44.90.+c Other topics in heat transfer (restricted to new topics in section 44)

Robinson‐type nuclear quadrupole resonance spectrometer adapted to field‐effect transistors

Jongmin Lee and Sung Ho Choh

Rev. Sci. Instrum. 53, 232 (1982); http://dx.doi.org/10.1063/1.1136934 (4 pages) | Cited 5 times

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A nuclear quadrupole resonance spectrometer, the Robinson circuit adapted with field‐effect transistors, has operated satisfactorily up to 30 MHz with rf levels ranging from 40 mV to 2.6 V peak to peak across the sample coil. The S/N ratio of 14N in hexamethylenetetramin is 85 at room temperature and 150 at 77 K, with a sample volume of 6 cm3 and a time constant of 10 s. The spectrometer is also capable of measuring the spin‐lattice relaxation time by the saturation method.
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07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques

Construction and performance of a simple multishielded Dewar

Li‐He Lin and Francis M. Gasparini

Rev. Sci. Instrum. 53, 236 (1982); http://dx.doi.org/10.1063/1.1136935 (3 pages)

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We have constructed a multishielded Dewar which we have tested at nitrogen and helium temperatures. The Dewar is of extremely simple design, requires no special insulating materials, and attains excellent performance. With an arrangement of 20 shields we have obtained evaporation rates of 5.6 and 3.0 liquid cm3 per hour for liquid helium and nitrogen, respectively. We report measurements of temperature distributions and evaporation rate as a function of the number of shields.
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07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment

New technique for measuring wind velocity

Govind S. Khandelwal and Jag J. Singh

Rev. Sci. Instrum. 53, 239 (1982); http://dx.doi.org/10.1063/1.1136936 (6 pages)

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A new technique for measuring wind velocities of meteorological interest is described. It is based on inverse square law variation of the counting rates as the radioactive source‐to‐counter distance is changed by the movement of the source caused by the wind velocity. The technique is usable anywhere, for all noncorrosive media, except in places with no local gravitational force. Measurements reported herein indicate that the proposed technique may be quite suitable for measuring wind speeds in the range of 5–100 m/s, that are either steady, or, whose rates of fluctuation are less than 1 kHz.
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92.60.Gn Winds and their effects
93.85.-q Instruments and techniques for geophysical research: Exploration geophysics

Optical technique for determining rarefaction wave velocities at very high pressures

R. G. McQueen, J. W. Hopson, and J. N. Fritz

Rev. Sci. Instrum. 53, 245 (1982); http://dx.doi.org/10.1063/1.1136937 (6 pages) | Cited 41 times

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An optical technique to determine rarefaction wave velocities is described. The technique utilizes the property that many transparent materials emit copious radiation when shocked to high pressures. The usual method of producing a rarefaction wave by impacting a target plate with a thinner rapidly moving driver plate is employed. The target plate is made in the form of a step wedge which is covered by the transparent material (or analyzer). When the shock reaches the analyzer it radiates steadily until the rarefaction from the backside of the driver plate overtakes the shock front causing the radiation to decrease. The time between these events is a decreasing linear function of the target thickness and when extrapolated to zero determines the thickness where the rarefaction would have overtaken the shock wave at the surface of the target. Light pipes are used to transmit the radiation to photomultipliers whose response is measured by high‐speed oscilloscopes.
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07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
62.50.-p High-pressure effects in solids and liquids
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