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Feb 1985

Volume 56, Issue 2, pp. 183-333

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Photomultiplier characteristics and practice relevant to photon counting

B. H. Candy

Rev. Sci. Instrum. 56, 183 (1985); http://dx.doi.org/10.1063/1.1138327 (11 pages) | Cited 19 times

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Certain nonideal photomultiplier characteristics are particularly relevant to the practice of photon counting. The literature on some of these characteristics can be rather confusing in the description of the mechanisms involved, such as those associated with single electron response distortion, ringing in anode pulse shapes, etc. This review paper critically studies these areas and in so doing attempts to resolve them. Other relevant but well established areas are reviewed briefly and key papers referenced. The effects of photomultiplier characteristics on photon counting performance are discussed together with associated recommendations for optimum conditions, with due regard to electronic instrumentation.
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85.60.Ha Photomultipliers; phototubes and photocathodes
84.30.Sk Pulse and digital circuits
29.40.Mc Scintillation detectors

Photon counting circuits

B. H. Candy

Rev. Sci. Instrum. 56, 194 (1985); http://dx.doi.org/10.1063/1.1138328 (7 pages) | Cited 4 times

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Two photon counters with variable dead times are described, one of simple design which is suited for low count rates and the other for system dead times down to 2 ns. Cheap, well‐known components are used and the counters were designed by computer aid with a criterion that circuit performance be relatively insensitive to component values. An example of PCB layout is presented.
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07.50.Ek Circuits and circuit components

Efficient and compact discharge XeCl laser with automatic UV preionization

Kenzo Miyazaki, Yuzo Toda, Toshifumi Hasama, and Takuzo Sato

Rev. Sci. Instrum. 56, 201 (1985); http://dx.doi.org/10.1063/1.1138329 (4 pages) | Cited 10 times

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Considerable improvements in overall efficiency of a compact UV‐preionized discharge XeCl laser have been achieved by possible operation at relatively low charging voltages V for high pressure P HCl/Xe/Ne mixtures. A peak overall efficiency of 2.9% has been obtained with the output energy of 280 mJ at V=18 kV and P=4 atm. A maximum output energy of 680 mJ has been extracted with the overall efficiency of 1.8% in 20‐ns (FWHM) pulses at P=6 atm and V=36 kV, corresponding to an energy density of 5.8 J/1. The efficient performance and simple design of the discharge XeCl laser with automatic preionization are described.
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42.55.Lt Gas lasers including excimer and metal-vapor lasers

High repetition rate operation of a closed‐cycle rare‐gas halide laser

Manlio Matera, Roberto Buffa, Pio Burlamacchi, Lorenzo Fini, and Renzo Salimbeni

Rev. Sci. Instrum. 56, 205 (1985); http://dx.doi.org/10.1063/1.1138330 (3 pages) | Cited 3 times

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A rare‐gas halide system operating at a pulse repetition rate up to 103 pps in a burst mode is described. A novel command charging high‐voltage pulse generator has been used for the laser pumping. The transverse gas flow velocity required in the discharge region for stable operation is provided by a closed‐cycle gas circulation system. The operating characteristics of the laser and the preliminary results of an investigation on the high pulse repetition rate limitations are reported.
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42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.60.By Design of specific laser systems

Small acousto‐optic modulation for active mode locking in the iodine photodissociation laser and the effect of supplementary saturable absorber

Yeong Sik Kim and Sang Soo Lee

Rev. Sci. Instrum. 56, 208 (1985); http://dx.doi.org/10.1063/1.1138331 (3 pages) | Cited 2 times

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Active, passive, and active–passive mode locking of the iodine photodissociation laser are investigated. The peak‐to‐background ratio (PBR) of the acousto‐optically mode‐locked pulse is 85% for rf power of 5 W. Passive mode locking using BDN dye gives PBR of 75% and has inferior reproducibility. The active–passive mode locking using the two methods simultaneously is useful for the pressure broadened iodine laser line and gives a PBR of 91%. In this case the rf power required for complete mode locking is calculated to be 7 W which is much less than the required power of 11 W in using active mode locking alone.
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42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.60.By Design of specific laser systems
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Vacuum‐operated digital wavelength meter

Agneta Bränberg and Per Nylén

Rev. Sci. Instrum. 56, 211 (1985); http://dx.doi.org/10.1063/1.1138332 (3 pages) | Cited 3 times

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A vacuum‐operated digital wavelength meter for measurement of laser light has been designed, built, and tested. Special considerations have been paid to the mechanical stability and ease of use. The rigid design, small dimensions, and small weight of the instrument makes it possible to move it between different experimental setups without troublesome realignment. The operation in vacuum also eliminates the need for the air‐to‐vacuum correction.
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07.50.-e Electrical and electronic instruments and components
07.55.-w Magnetic instruments and components
07.60.Ly Interferometers
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)

High‐performance double‐focusing mass spectrometer

A. O. Nier and D. J. Schlutter

Rev. Sci. Instrum. 56, 214 (1985); http://dx.doi.org/10.1063/1.1138333 (6 pages) | Cited 12 times

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A small size double‐focusing mass spectrometer employing the Mattauch–Herzog geometry is described. Although developed primarily for helium isotope analyses, the design is such that it can be modified for a wide range of problems. The maximum radius of curvature of ions in the magnetic analyzer is 9.53 cm. With reasonably wide slits 3He can be separated from the HD+H3 combination usually present as an impurity while making analyses of helium in a static mode. At xenon the overlap at adjacent mass numbers is less than 1/10 000. In static operation the sensitivity approaches that of some of the large high sensitivity instruments employing special ion sources. The response is linear over a large pressure range. Since a conventional electron bombardment ion source is employed, ionizing electron energies may be varied, eliminating doubly charged ions such as 40Ar2+ which may interfere with 20Ne analyses. Because of the compact and rugged construction as well as low power consumption, the design lends itself to portable use in field operations.
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07.75.+h Mass spectrometers

Operation of a microchannel plate counting system in a mass spectrometer

Daniel M. Murphy and Konrad Mauersberger

Rev. Sci. Instrum. 56, 220 (1985); http://dx.doi.org/10.1063/1.1138334 (7 pages) | Cited 4 times

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A multiplier detector system has been developed as part of a mass spectrometer in an ion counting mode. During its operation ions striking a microchannel plate release pulses of electrons which are accelerated to a phosphor layer. The resulting flash of light is carried by a fiber‐optic bundle to a photodiode array. The detector simultaneously counts ions throughout a mass spectrum covering more than 30 amu. It extends the mass spectrometer’s operation toward low count rates for trace gas analysis. Each mass peak can be independently measured at count rates between 0.1 and 1000 counts/s. Higher rates on a few peaks do not blind the entire detector. The detector’s capabilities have been demonstrated by measuring Kr and Xe isotopes in air at natural abundances. The mass spectrometer, detector, and readout electronics are sufficiently compact to permit use in a balloon‐borne experiment.
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07.75.+h Mass spectrometers
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

Optimum angle of deflection electrodes of a cylindrical electrostatic analyzer

C. Oshima, R. Souda, M. Aono, and Y. Ishizawa

Rev. Sci. Instrum. 56, 227 (1985); http://dx.doi.org/10.1063/1.1138335 (4 pages) | Cited 18 times

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The optimum deflection angle of the electrodes in a cylindrical electrostatic analyzer with real slits has been discussed on the basis of numerically calculated electron trajectories. The effect of fringing fields has been included exactly in this calculation. The optimum angle is 126.5°, being independent of the gap between the inner and outer electrodes. By this optimization, the first‐order angle aberration can be eliminated completely.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
41.75.Fr Electron and positron beams

Quantitative data processing of parallel recorded electron energy‐loss spectra with low signal to background

Henry Shuman and Pieter Kruit

Rev. Sci. Instrum. 56, 231 (1985); http://dx.doi.org/10.1063/1.1138336 (9 pages) | Cited 63 times

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The performance of a multielement array detector for measuring small spectral features superimposed on a large background has been examined. In order to have the sensitivity of detection limited only by counting statistics, two factors have to be critically considered: the nonuniform spatial response of the array detector, and the possible addition of noise by the collection system. For the special case discussed here, energy‐loss spectroscopy of 100‐keV electrons, the added noise was small. The detective quantum efficiency (DQE) was measured to be DQE=0.87. Several techniques reducing the effect of the nonuniform response were tested: normalizing the spectra with an experimentally measured response curve, electronic differentiation to reduce the background, dynamic gain correction, and two methods of experimentally averaging the spatial response by measuring a sequence of repositioned spectra. Preservation of the statistical information present in a representative energy‐loss spectrum is shown to be feasible.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
41.75.Fr Electron and positron beams

Ultrahigh‐vacuum double‐axis goniometer for angle‐resolved spectroscopies

K. M. Martini

Rev. Sci. Instrum. 56, 240 (1985); http://dx.doi.org/10.1063/1.1138337 (2 pages) | Cited 2 times

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Described here is a double‐axis goniometer currently used in angle‐resolved neutral atom beam scattering. A special feature is the decoupling of the two rotation axes. An additional design concept is flexibility; the device can be adapted to almost all existing UHV systems, independent of port position and size, and of chamber diameter.
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06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
07.30.Kf Vacuum chambers, auxiliary apparatus, and materials
07.77.-n Atomic, molecular, and charged-particle sources and detectors
37.20.+j Atomic and molecular beam sources and techniques

Quasi‐steady‐state multimegawatt ion source for neutral beam injection

M. M. Menon, C. C. Tsai, J. H. Whealton, D. E. Schechter, G. C. Barber, S. K. Combs, W. K. Dagenhart, W. L. Gardner, H. H. Haselton, N. S. Ponte, P. M. Ryan, W. L. Stirling, and R. E. Wright

Rev. Sci. Instrum. 56, 242 (1985); http://dx.doi.org/10.1063/1.1138338 (8 pages) | Cited 14 times

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A quasi‐steady‐state (pulse duration of 30 s) ion source of the duoPIGatron type has been developed for fusion applications. It was designed to deliver an 80‐keV hydrogen ion beam of low beamlet divergence (Θrms= 0.26°) at a current density of 0.19 A cm−2. Hydrogen ion beams of 40 to 48 A were extracted at beam energies of 77 to 80 keV for 30‐s‐long pulses. The reliability and stability of the ion source operation were demonstrated by extracting about 600 beam pulses at full power and full pulse length. The ion source was also operated with deuterium as the working gas, and the optimum current at 80 keV was found to be about 33 A, in agreement with the expected inverse square‐root scaling of current density with atomic mass.
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29.25.Lg Ion sources: polarized
29.25.Ni Ion sources: positive and negative
52.50.Gj Plasma heating by particle beams
07.77.-n Atomic, molecular, and charged-particle sources and detectors

Electron temperature measurements from induced toroidal current in ELMO Bumpy Torus‐Scale

Taner Uckan

Rev. Sci. Instrum. 56, 250 (1985); http://dx.doi.org/10.1063/1.1138339 (5 pages)

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We have carried out measurements on ELMO Bumpy Torus Scale (EBT‐S) to estimate the electron temperature of the toroidal plasma by inducing a small (∼2 A) fluctuating (5 Hz) ac toroidal current. The modulating frequency used is low enough to minimize the effects of cavity skin time (∼100 ms) and plasma inductance. We have calculated the temperature from the measured values of the current obtained by use of the Rogowsky loop at various fill pressures at 100 kW with 28‐GHz operation. The electron temperature has been estimated to be around 80–90 eV with an error of about 10%–25% in the low T mode, which is in good agreement with the Thomson scattering measurements.
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52.55.Jd Magnetic mirrors, gas dynamic traps
52.25.Kn Thermodynamics of plasmas

Diamond‐anvil high‐pressure cell for optical spectroscopy at low temperature

Toshihiko Kobayashi

Rev. Sci. Instrum. 56, 255 (1985); http://dx.doi.org/10.1063/1.1138340 (5 pages) | Cited 17 times

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A diamond‐anvil high‐pressure cell is described which allows optical studies at low temperatures and variable pressure to 260 kbar and higher. A bellows assembly has been designed to drive diamond anvils and connected helium gas pressure source. The sample pressure can be changed remotely while the sample is maintained at operating temperature. Examples of the application to the optical absorption in InP under high pressure are shown. Tests using different pressure transmitting fluids are reported.
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07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
07.60.Rd Visible and ultraviolet spectrometers
62.50.-p High-pressure effects in solids and liquids
78.40.Fy Semiconductors

Electrical‐transport measurements on fragile single crystals to 7.5 GPa in the diamond anvil cell

S. W. Tozer and H. E. King

Rev. Sci. Instrum. 56, 260 (1985); http://dx.doi.org/10.1063/1.1138341 (4 pages) | Cited 21 times

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A four‐probe method is presented for the study of electrical‐transport properties of materials ranging from insulators to metals. Development of several experimental procedures and apparatuses and the fabrication of a composite gasket has permitted quasihydrostatic electrical resistivity measurements of fragile single crystals. Using a fluid to transmit pressure to the sample, the integrity of the crystal is assured. Pressures to 7.5 GPa have been obtained using the diamond anvil cell.
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07.50.-e Electrical and electronic instruments and components
81.40.Rs Electrical and magnetic properties related to treatment conditions
72.15.Eb Electrical and thermal conduction in crystalline metals and alloys
72.80.-r Conductivity of specific materials

Improved flow visualization technique for quantitative velocity measurement in small test volumes

G. R. Johnson, E. Marschall, and J. H. Esdorn

Rev. Sci. Instrum. 56, 264 (1985); http://dx.doi.org/10.1063/1.1138527 (4 pages) | Cited 5 times

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A flow visualization technique which utilized a photochromic dye in solution was introduced by Popovich and Hummel in 1967. The dye was activated along narrow trace lines by passing sharply focused beams from an ultraviolet light source through the solution. The movement of the dye traces were recorded by high‐speed cinematography and velocities were found from analysis of the resulting pictures. Two variations to this basic method are described. These permit more accurate velocity measurements to be made in certain liquid systems where test volumes are small or near physical barriers, and where the flow is two dimensional or is time dependent. Manufacture of a suitable dye and construction of an inexpensive pulse laser which may be used as an ultraviolet light source are discussed.
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47.80.-v Instrumentation and measurement methods in fluid dynamics

Automatic topographic examination of semiconductors using modulated reflectance

J. L. Aubel, G. Pidick, U. K. Reddy, and S. Sundaram

Rev. Sci. Instrum. 56, 268 (1985); http://dx.doi.org/10.1063/1.1138342 (5 pages) | Cited 8 times

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A modified cell design for studies of electrolyte electroreflectance of solids is reported. A new type of electrolyte cell design for ensuring easy and proper contacts with the surface of the sample wafer is described. The modified system is shown to be suitable for fast and convenient acquisition and display of spectra, or the variation of composition or carrier concentration as a function of position on the sample. Typical results for GaAs:Si and MBE‐grown Ga1−xAlxAs/GaAs samples are shown.
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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
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
78.20.Jq Electro-optical effects
07.05.Bx Computer systems: hardware, operating systems, computer languages, and utilities

Analysis of the lumped τ2 effect in relaxation calorimetry

John P. Shepherd

Rev. Sci. Instrum. 56, 273 (1985); http://dx.doi.org/10.1063/1.1138343 (5 pages) | Cited 26 times

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In thermal relaxation calorimetry, the heat capacity can be calculated from the time constant τ1=Cp/Kb of the exponential decay of the cooling curve. If the thermal bond between the sample and sample holder is poor, the cooling curve is described by T−T0=A1 exp(−t/τ1)+A2 exp(−t/τ2). Analysis shows that the heat capacity of the sample plus addenda is Cp=Kb (A1τ1+A2τ2)/(A1+A2). For most cases, a good approximation is given by Cp=Kb (A1τ1/ΔT), which does not require the measurement of A2 or τ2. An expression is presented for calculating the conductance of the thermal bond of the sample to the substrate.
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07.20.Fw Calorimeters
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment
05.70.-a Thermodynamics
65.40.Ba Heat capacity

Instrument to measure the polarization state of waves

John V. Olson and R. Domke

Rev. Sci. Instrum. 56, 278 (1985); http://dx.doi.org/10.1063/1.1138344 (5 pages) | Cited 3 times

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We report here on the design and implementation of analog circuitry which allows the processing of the components of vector waveforms to obtain polarization information. The waveforms are the voltages derived from orthogonal sensors such as magnetometers or seismometers which provide information on the time variation of vector processes. The circuits take the voltages from the individual sensors and process them to produce estimates of the spectral matrix at a particular frequency. From the components of the spectral matrix one may determine the wave polarization parameters including the signal power, ellipticity, handedness, and orientation of the polarization ellipse. In cases where the information of interest to the investigator depends upon the relatively slow modulations of a carrier and not upon the frequency of the carrier itself, the preprocessing of the spectral information as described here allows the investigator to sample the data at a much reduced rate, or with a narrower bandwidth, without loss of information. We have implemented the circuits described in our investigation of electromagnetic waves in the ULF (3 mHz–3 Hz) frequency band and have achieved a reduced demand for storage and processing capacities in the project.
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07.50.Ek Circuits and circuit components
84.30.Sk Pulse and digital circuits
07.50.-e Electrical and electronic instruments and components
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Mixing liquids in microseconds

Peter Regenfuss, Robert M. Clegg, Mack. J. Fulwyler, Francisco J. Barrantes, and Thomas M. Jovin

Rev. Sci. Instrum. 56, 283 (1985); http://dx.doi.org/10.1063/1.1138345 (8 pages) | Cited 29 times

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An instrument is described in which two solutions can be homogeneously mixed within several microseconds. The liquids flow separately through two coaxial capillaries with conical tips and then simultaneously around a sphere (50–100 μ in diameter) which has been positioned close to the end of the outer tip. The liquids flow with velocities of ∼100 m/s through the small passages (∼5 μ wide) separating the sphere and the wall of the outer capillary and mix in the turbulent liquid flow behind the sphere. The mixed liquids are then ejected as a narrow liquid jet for observation. Design characteristics and construction techniques are presented along with a discussion of the properties of the turbulent flow field and estimates of the expected practically realizable mixing times. The experimentally determined speed of mixing indicates that we have nearly achieved the proposed lower limits of the mixing time.
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47.80.-v Instrumentation and measurement methods in fluid dynamics
06.60.Ei Sample preparation (including design of sample holders)
47.70.Fw Chemically reactive flows
47.60.-i Flow phenomena in quasi-one-dimensional systems

Miniature fiber‐optic refractometer for measurement of salinity in double‐diffusive thermohaline systems

T. L. Bergman, F. P. Incropera, and W. H. Stevenson

Rev. Sci. Instrum. 56, 291 (1985); http://dx.doi.org/10.1063/1.1138346 (6 pages) | Cited 13 times

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Information on salinity and temperature distributions is important in the study of thermohaline systems. In order to overcome difficulties associated with existing measurement methods, a miniature fiber‐optic probe has been developed. The probe, which is capable of local quasisteady and fluctuating salinity and temperature measurements, is easily constructed, calibrated, and utilized. Probe measurements compare favorably with results obtained using a slant‐wire shadowgraph technique and clearly show local phenomena in double‐diffusive thermohaline systems.
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07.60.Hv Refractometers and reflectometers
42.81.-i Fiber optics
92.10.af Thermohaline convection

Optical output stabilization method for direct current arc lamps

Philip B. Oldham, Gabor Patonay, and Isiah M. Warner

Rev. Sci. Instrum. 56, 297 (1985); http://dx.doi.org/10.1063/1.1138347 (6 pages) | Cited 3 times

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A simple, effective technique for stabilizing the optical output of direct current (dc) arc lamps is described. The large output fluctuation due to arc wander in a commercially available lamp and power supply is minimized by the introduction of an alternating current (ac) waveform superimposed on the dc source voltage in conjunction with detector averaging. Arc stability is monitored indirectly by the detection of arc excited fluorescence from a standard sample. The monitored lamp output is typically maintained to within 1% relative standard deviation (RSD) by this method. Data are presented supporting the theory that arc wander is significantly reduced by the addition of an ac component to the dc lamp power. Various methods of ac introduction are discussed along with the design of a controllable oscillator circuit. The effects of variations in ac voltage and frequency on optical output stability are examined.
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52.80.Mg Arcs; sparks; lightning; atmospheric electricity

Systematic errors in conductimetric instrumentation due to bubble adhesions on the electrodes: An experimental assessment

P. S. Neelakantaswamy, A. Rajaratnam, S. Kisdnasamy, and N. P. Das

Rev. Sci. Instrum. 56, 303 (1985); http://dx.doi.org/10.1063/1.1138348 (4 pages)

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Systematic errors in conductimetric measurements are often encountered due to partial screening of interelectrode current paths resulting from adhesion of bubbles on the electrode surfaces of the cell. A method of assessing this error quantitatively by a simulated electrolytic tank technique is proposed here. The experimental setup simulates the bubble‐curtain effect in the electrolytic tank by means of a pair of electrodes partially covered by a monolayer of small polystyrene‐foam spheres representing the bubble adhesions. By varying the number of spheres stuck on the electrode surface, the fractional area covered by the bubbles is controlled; and by measuring the interelectrode impedance, the systematic error is determined as a function of the fractional area covered by the simulated bubbles. A theoretical model which depicts the interelectrode resistance and, hence, the systematic error caused by bubble adhesions is calculated by considering the random dispersal of bubbles on the electrodes. Relevant computed results are compared with the measured impedance data obtained from the electrolytic tank experiment. Results due to other models are also presented and discussed. A time‐domain measurement on the simulated cell to study the capacitive effects of the bubble curtain is also explained.
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07.50.-e Electrical and electronic instruments and components
47.55.dp Cavitation and boiling
82.45.-h Electrochemistry and electrophoresis

Development of an electrostatic positioner for space material processing

W. K. Rhim, M. Collender, M. T. Hyson, W. T. Simms, and D. D. Elleman

Rev. Sci. Instrum. 56, 307 (1985); http://dx.doi.org/10.1063/1.1138349 (11 pages) | Cited 23 times

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This paper describes an electrostatic positioning instrument which was developed at the Jet Propulsion Laboratory to enable experimenters to conduct containerless material science experiments in space. Samples that are to be studied are electrically charged and controlled by the electrostatic force produced by a set of properly arranged electrodes. Three different types of positioners are described, i.e., the dish type, the ring type, and the tetrahedral type. In all these systems, the positioning and the damping of the sample is accomplished by a feedback control system. The advantage of this electrostatic positioning method, in comparison to the other methods, such as acoustic and electromagnetic, lies in the fact that it can operate in a high vacuum and does not require the material to be electrically conductive as long as the material can carry a certain amount of charge.
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06.60.Ei Sample preparation (including design of sample holders)
81.90.+c Other topics in materials science (restricted to new topics in section 81)

Miniature liquid‐3He refrigerator

J. P. Torre and G. Chanin

Rev. Sci. Instrum. 56, 318 (1985); http://dx.doi.org/10.1063/1.1138350 (3 pages) | Cited 8 times

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The use of a cryopump and high‐pressure, internal storage of the cryogen makes it possible to miniaturize a one‐shot recyclable 3He refrigerator while at the same time improving its performance. Because of their simplified interface requirements, such refrigerators are readily incorporated into existing 4He cryostats, allowing a convenient extension of their operating range down to 0.3 K. An analysis of the parameters describing refrigerator performance (condensation time, heat transfer to the 4He bath, lifetime, and refrigeration power) leads to the definition of an optimized refrigerator. Measured performance characteristics of a miniature [2‐l standard temperature and pressure (STP) of 3He] refrigerator used in laboratory and stratospheric balloon‐borne experiments are given.
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07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment
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