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Feb 1968

Volume 39, Issue 2, pp. 145-279

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Cryostat for the Measurement of Thermal Conductivity and Specific Heat between 0.05 and 2°K

J. P. Harrison

Rev. Sci. Instrum. 39, 145 (1968); http://dx.doi.org/10.1063/1.1683301 (8 pages) | Cited 36 times

Online Publication Date: 10 November 2003

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A cryostat is described which is capable of measuring specific heat and thermal conductivity of dielectric crystals over the temperature range 0.05 and 2.0°K. Thermal conductivity is measured with a steady flow of heat through the sample, and specific heat by a pulse technique. Differential carbon resistance thermometry is used for both measurements. The performance is demonstrated on the thermal conductivity of LiF, and on the specific heat of two samples of nominally pure KCl.

Dry‐Powder Aerosol Dispersing Device with Long‐Time Output Stability

Walter L. Crider, Naomi P. Barkley, and Arthur A. Strong

Rev. Sci. Instrum. 39, 152 (1968); http://dx.doi.org/10.1063/1.1683302 (4 pages) | Cited 5 times

Online Publication Date: 10 November 2003

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Operating parameters and performance characteristics are described for a dry‐powder Fe2O3 aerosol disperser used for periods up to 23 h with minimal operator attention. Aerosol mass concentration fluctuations in a 3 m3 dynamic‐flow chamber were determined over 23‐h periods for the aerosol generator with and without electronic feedback circuits. From the data presented in this paper and from observations made during 2 weeks of continuous operation, this ``rust duster'' was found to be capable of continuously dispersing Fe2O3 powder into 1.5 m3 of air per minute to produce aerosols having median concentrations from about 0.7 to 3.0 mg m−3. Over most of this concentration range, with or without the feedback control circuit, the mass concentration of Fe2O3 aerosol was kept within the ±50% variability limit originally set as acceptable for chronic animal exposure conditions.

Two ``Whisker'' Straining Devices Suitable for Low Temperatures

E. P. Stillwell, M. J. Skove, and J. H. Davis

Rev. Sci. Instrum. 39, 155 (1968); http://dx.doi.org/10.1063/1.1683303 (3 pages) | Cited 9 times

Online Publication Date: 10 November 2003

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Two devices for straining ``whiskers'' are described. In the first device, the whisker is mounted on a Mylar film that is stretched by a differential screw. The entire device can be immersed in liquid helium, which eliminates thermal expansion problems in low temperature experiments. In the second device the whisker is mounted between two bimorphs of piezoelectric material. The piezoelectric puller is small enough to fit inside a 2.5 cm i.d. superconducting solenoid and still permit the entire device to be rotated about an axis perpendicular to the solenoid axis.

Pneumatically Operated Microelectrode Puller for Use in Electrophysiology

Max J. Lab and W. C. Maddison

Rev. Sci. Instrum. 39, 158 (1968); http://dx.doi.org/10.1063/1.1683305 (3 pages) | Cited 1 time

Online Publication Date: 10 November 2003

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Micropipettes suitable for intracellular use are pulled by a vacuum applied to the nozzles of two glass syringes. The ends of the glass tube are attached to the plungers, which are pulled home in opposite directions. The two pulls are in a straight line and can be varied in velocity and duration, producing microelectrodes of different shapes and sizes. The details of construction and operation are described.

System Approach to Fast Logic for Counter Experiments in High Energy Physics

W. Sippach and J. Sunderland

Rev. Sci. Instrum. 39, 161 (1968); http://dx.doi.org/10.1063/1.1683306 (4 pages) | Cited 1 time

Online Publication Date: 10 November 2003

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A fast counter logic system is described that separates the time correlation and logic questions. A loose trigger generates a set of time windows for gating narrow discriminator pulses into storage elements. The stored signals are then logically combined into event definitions that are strobed to produce system outputs. Special emphasis is placed on use of the system with a data handler. Modules built for a counter hodoscope experiment are also described.

Wide‐Range Pulse‐Shape Discrimination System

C. E. Hollandsworth and W. P. Bucher

Rev. Sci. Instrum. 39, 165 (1968); http://dx.doi.org/10.1063/1.1683307 (4 pages) | Cited 2 times

Online Publication Date: 10 November 2003

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A pulse‐shape discrimination system for use with organic scintillators is described which is based upon the true zero‐crossing detection of single delay‐line shaped pulses. Results of performance tests are presented in the form of contour diagrams which show the crossover‐time spectra of neutron and gamma‐ray induced events as a function of pulse amplitude. A technique to compensate for the variation of scintillation pulse shape with recoil‐proton energy is described. Good gamma‐ray rejection with nearly 100% recoil‐proton acceptance over a dynamic range of 100 is obtained.

Blanking Circuit for a Magnetic Electron Multiplier in a Time‐of‐Flight Mass Spectrometer

Joseph R. Haumann and Martin H. Studier

Rev. Sci. Instrum. 39, 169 (1968); http://dx.doi.org/10.1063/1.1683308 (2 pages) | Cited 1 time

Online Publication Date: 10 November 2003

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A blanking generator has been developed for use with a magnetic electron multiplier in a time‐of‐flight mass spectrometer. By blanking out superfluous portions of the mass spectrum, non‐linearity in the electron multiplier is minimized, gain is increased, and dirtying of the dynode strip is retarded.

Very Low Frequency Integrating Vibrating Sample Magnetometer (VLFVSM) with High Differential Sensitivity in High dc Fields

S. Foner and E. J. McNiff

Rev. Sci. Instrum. 39, 171 (1968); http://dx.doi.org/10.1063/1.1683309 (9 pages) | Cited 47 times

Online Publication Date: 10 November 2003

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A vibrating sample magnetometer is described which is specifically adapted for magnetic moment measurements in high dc fields. The sample is moved at very low frequencies between series opposing detection coils, the induced voltage is integrated, and each cycle is recorded so that the output can be further time‐averaged. Two novel aspects make this instrument particularly useful for high field measurements. First, the sample is moved beyond the center of the detection coils so that positioning errors, forces, and other incidental effects are eliminated. Second, a precise reference balance voltage is synchronously applied to the output signal to permit high‐resolution differential measurements of magnetic moment. In addition to a detailed description of the basic VLFVSM, a general discussion of flux integration techniques is presented. Operation of the VLFVSM with field modulation superimposed, variable temperature, variable pressure, additional electronic filtering, and under swept‐field conditions is discussed. Mechanical and electronic details and typical operating characteristics are included. The entire magnetometer has moderately high sensitivity, is extremely rugged, versatile, and eliminates sources of error present in many sample extraction techniques. All components, excluding the mechanical systems associated with the sample, are available commercially. This magnetometer has been applied to practically all types of high field magnetic moment measurements including differential susceptibility measurements in metals, alloys and insulators, superconductors, and highly anisotropic materials such as the rare earth metals.

A Flying‐Spot Scanner

C. N. Potter and D. E. Sawyer

Rev. Sci. Instrum. 39, 180 (1968); http://dx.doi.org/10.1063/1.1683310 (4 pages) | Cited 7 times

Online Publication Date: 10 November 2003

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A flying‐spot scanner used to study the electrical properties of semiconductor materials and devices is described. The instrument automatically deflects a collimated light beam in a raster pattern and focuses the raster on the photosensitive semiconductor surface. The electrical output from the semiconductor is amplified and used to form an image of the photoresponse of the sample on a cathode ray tube. The resolution of the system referred to the sample is about 5 μ.

A Pulse‐Height Analyzer for Charged‐Particle Spectroscopy on the Lunar Surface

T. M. Harrington and J. H. Marshall

Rev. Sci. Instrum. 39, 184 (1968); http://dx.doi.org/10.1063/1.1683311 (11 pages) | Cited 2 times

Online Publication Date: 10 November 2003

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The design and performance of a charge‐sensitive amplifier and a 256‐channel pulse‐height analyzer for use in a lunar surface analysis experiment are presented. Input is from silicon detectors used to measure the energies of up to 7 MeV alpha particles and protons. Anticoincidence logic is provided for the proton detection system to reject cosmic rays. The instrument operates in the space environment over a temperature range of −50 to +50°C. Over this range the instrument gain was stable to ±0.4%, and the offset varied less than 0.1 channels. Resolution of 35 keV was obtained with a 228Th alpha‐particle source. Total power for the system, which includes 10 amplifiers, 2 analog‐to‐digital converters, 4 discriminators, and data processing logic is approximately 2 W. Particular attention was given to reliability in the design and construction of the system. Large amounts of negative feedback and carefully selected and screened components were utilized to achieve this goal.

Inductance Thermometer

R. H. Willens, E. Buehler, and E. A. Nesbitt

Rev. Sci. Instrum. 39, 194 (1968); http://dx.doi.org/10.1063/1.1683312 (3 pages) | Cited 8 times

Online Publication Date: 10 November 2003

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Inductors with a large temperature coefficient of inductance have been fabricated with alloys which, as a result of rapid quenching from the liquid state, have new and unusual magnetic properties. These inductors have been incorporated in an oscillator which generates a frequency that depends upon temperature. The rate of frequency change with temperature, between room temperature and 1°K, is large enough to permit very accurate temperature measurements. The conversion of temperature to frequency makes possible easy transmission over long distances.

Null Pressure Optical Cell for Measurements on Liquids at Elevated Temperatures and Pressures

D. M. Gruen, D. S. Newman, and R. L. McBeth

Rev. Sci. Instrum. 39, 197 (1968); http://dx.doi.org/10.1063/1.1683313 (3 pages) | Cited 1 time

Online Publication Date: 10 November 2003

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An optical cell used in obtaining absorption spectra at temperatures up to 500°C and pressures up to 2100 kg cm−2 is described. The cell can be characterized as a ``null‐pressure'' device. The solution is contained in a sealed quartz cuvette and the pressure exerted by the solution within the cell is balanced by an external pressure of argon gas. The near ir spectra of water below and above the critical temperature are presented.

cw Microwave Spectrometer for Ultrasonic Paramagnetic Resonance

R. G. Leisure and D. I. Bolef

Rev. Sci. Instrum. 39, 199 (1968); http://dx.doi.org/10.1063/1.1683314 (7 pages) | Cited 23 times

Online Publication Date: 10 November 2003

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See Also: Erratum

Show Abstract
A description and detailed analysis of an acoustic cw microwave spectrometer is given. The spectrometer, although designed specifically to measure the small changes in acoustic velocity and attenuation characteristic of ultrasonic paramagnetic resonance, can be used also to measure absolute values of acoustic velocity and attenuation over wide ranges of frequency and temperature. The use of a calibrator in producing a known reference signal is described.

Asymptotic Theory of Beam Break‐Up in Linear Accelerators

W. K. H. Panofsky and M. Bander

Rev. Sci. Instrum. 39, 206 (1968); http://dx.doi.org/10.1063/1.1683315 (7 pages) | Cited 31 times

Online Publication Date: 10 November 2003

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The phenomenon of radial beam break‐up observed in terms of long, multi‐section electron linear accelerators has been analyzed using a multi‐cavity model. In this model the source of regeneration due to backward wave amplification is ignored. The dominant phenomenon involves build‐up of radial modes in each cavity as coupled by the electron beam. The resulting differential equations are integrated by the method of steepest descent and by a numerical iteration method. Scaling laws in terms of the pulse length, beam intensity, energy gradient, and length of the structure are derived.

Spectrothermal Emission Aerosol Particle Analyzer (SEAPA)

Walter L. Crider

Rev. Sci. Instrum. 39, 212 (1968); http://dx.doi.org/10.1063/1.1683316 (4 pages) | Cited 3 times

Online Publication Date: 10 November 2003

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An instrument that selectively counts, according to size, aerosol particles containing certain specific metals is described. The technique employed is based on the principle of spectrothermal emission of individual particles passing through the combustion zone of a hydrogen‐air flame. After the flash of light from each emitting particle passes through a monochromator, it is converted to a voltage pulse which is electronically counted according to height. The instrument sensitivity was determined for aerosols of NaCl, CaCl, CaO, Fe2O3, KOH, LiOH, MnO2, and MgO. The minimum size particle detectable varied from 0.10μ diam for NaCl to 1.22μ diam for MgO.

Thermistors as Circuit Elements in Low‐Frequency Circuits

Kamil Kraus

Rev. Sci. Instrum. 39, 216 (1968); http://dx.doi.org/10.1063/1.1683317 (5 pages)

Online Publication Date: 10 November 2003

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The properties of a polarizing NTC, as well as a PTC resistor, that arise from the fact that thermistors act as a negative resistance to low frequency signals, have been investigated and the impedances were deduced both theoretically and by experiment. The properties of the thermistors as a conductor and a capacitor were investigated and the conditions for oscillating at low frequencies were given. In addition, a phase‐advance network and an integrating network were proposed.

Fast Response Magnetometer Using Ferromagnetic Resonance in Thin Films

L. J. Schwee and H. R. Irons

Rev. Sci. Instrum. 39, 220 (1968); http://dx.doi.org/10.1063/1.1683318 (3 pages)

Online Publication Date: 10 November 2003

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A magnetometer of simple construction is described having a response time of the order of 4 nsec. In this instrument the impedance of a thin film biased near ferromagnetic resonance is a measure of the external field. At resonance the element may be matched to a transmission line. The voltage amplitude of the reflected wave varies linearly with change in the external magnetic field.

New Ionization Chamber Technique for the Measurement of Environmental Radiation

M. H. Shamos and A. R. Liboff

Rev. Sci. Instrum. 39, 223 (1968); http://dx.doi.org/10.1063/1.1683319 (7 pages) | Cited 1 time

Online Publication Date: 10 November 2003

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It is shown, contrary to usual low‐level ion chamber practice, that there are unique advantages to using highly electronegative filling gases, which enhance columnar recombination. Indeed, through the proper choice of gas and electric field strength, it is possible to discriminate almost completely against alphas originating in the walls without affecting the collection of beta‐ and gamma‐induced ionization. A number of chambers utilizing this technique have been constructed. The resulting characteristics, as well as comparisons with calibrated sources, indicate a complete absence of residual currents from wall contaminants. The fluctuations in background measurements are reduced by at least a factor of 3 over comparable air chambers.

Photographic Apparatus for the Study of Fracture in Metals

H. Ezrol, H. Margolin, R. W. King, R. Bunshah, and P. Venkatesan

Rev. Sci. Instrum. 39, 229 (1968); http://dx.doi.org/10.1063/1.1683320 (4 pages)

Online Publication Date: 10 November 2003

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A photographic apparatus capable of photographing metal specimens undergoing fracture has been constructed. It consists of an image converter camera, a light source, an apparatus to fracture the specimens and a synchronizing system. The image converter camera can take up to 8 pictures that have exposure times of 0.1, 0.3, 1, 3, or 10 μsec with interframe intervals of 0.5, 1.5, 5, 15, or 50 μsec. The only restriction on selection of exposure time and interframe interval occurs at an interframe time of 0.5 μsec for which the exposure time must be 0.1 μsec. Triggering of the image converter camera can be accomplished with a time delay or with a device which triggers at a preselected strain in the specimen. A photograph of a zinc crystal at −58°C with a crack travelling at 56 m∕sec is presented.

Ionization of Fast Neutral Atoms by Passage through a Hot‐Cathode Discharge

H. H. Fleischmann and R. Kribel

Rev. Sci. Instrum. 39, 233 (1968); http://dx.doi.org/10.1063/1.1683321 (6 pages) | Cited 1 time

Online Publication Date: 10 November 2003

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The possibilities and conditions for ionization of neutral hydrogen atoms in the energy range of 30–300 eV by passage through an auxiliary plasma are investigated. The general requirements for the plasma are determined by the scattering of the fast neutrals and ions to be detected: density, integrated along the path of the fast particles, several ×1012 cm−2; integrated neutral density [less than double sim] 1015 cm−2 electric fields [less than double sim] 1 V cm−1 and magnetic fields not more than a few hundred gauss. In this case, usable conversion ratios of several 10−3 seem possible. Experimentally, the conversion efficiency of a plasma produced by a hot‐cathode discharge is compared with the efficiency of a calibrated air stripping cell. At low energies, for the plasma cell, higher efficiencies by about an order of magnitude are found. Expected values for the conversion efficiencies are achieved for particle energies above 250 eV. At lower energies, similar values seem achievable using ion analyzers with wide acceptance angle.

Lapping Machine Attachment for Preparing Oriented Crystals

Donald E. Johnson

Rev. Sci. Instrum. 39, 238 (1968); http://dx.doi.org/10.1063/1.1683322 (2 pages) | Cited 1 time

Online Publication Date: 10 November 2003

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The description and use of a lapping attachment for the preparation of x‐ray oriented reference surfaces on crystal specimens is presented. The surfaces are prepared on specimens which have been mounted and oriented on a goniometer device. The resulting prepared surface provides a reference face for machine finishing a crystal sample with all faces in a known relation to the crystalline axis or planes. Test runs of various specimens have produced finished surfaces that have retained their original orientation within 0.1° of error.

Square and Sine Wave Modulation of the Beam from a 3 MV Van de Graaff Accelerator

H. J. Fraser, A. I. M. Ritchie, and S. Whittlestone

Rev. Sci. Instrum. 39, 240 (1968); http://dx.doi.org/10.1063/1.1683323 (5 pages)

Online Publication Date: 10 November 2003

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Methods of producing square and sine wave beam modulation of a 3 MV Van de Graaff accelerator are described. Square pulses are produced at frequencies from 100 kc to zero with up to a 100% duty cycle and a minimum pulse length of 8 μsec. The ratio of the off‐current level to the on‐current level is less than 5×10−4 and can be further reduced by a post‐acceleration deflection system to less than 10−5. The unit, which is triggered from a command pulse external to the machine, is in the top terminal of the Van de Graaff and has shown itself to be highly reliable over some 1000 h of machine operation. The sine wave modulation unit described here operates in the range 80–1000 cps with a modulation depth of up to 90% and higher harmonic contamination of less than 1%.

Condensable Gases in a McLeod Gauge

K. B. Wear

Rev. Sci. Instrum. 39, 245 (1968); http://dx.doi.org/10.1063/1.1683324 (6 pages) | Cited 1 time

Online Publication Date: 10 November 2003

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Condensable gases need not be precluded from a McLeod gauge operated in the mode described. Readings taken with a captured gas sample at different compression ratios may be used to identify the condensables, estimate their concentrations, and determine both the vacuum system pressure and the partial pressure due to noncondensable gases. Theory, vacuum system and gauge manipulation, data, and difficulties encountered are discussed.
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Superconductor‐Glass Vacuum Seals

P. R. Critchlow, J. Lees, and P. W. Matthews

Rev. Sci. Instrum. 39, 251 (1968); http://dx.doi.org/10.1063/1.1683325 (1 page)

Online Publication Date: 10 November 2003

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Abstract Unavailable

Pulse Limiter

R. M. Sundelin

Rev. Sci. Instrum. 39, 251 (1968); http://dx.doi.org/10.1063/1.1683326 (3 pages)

Online Publication Date: 10 November 2003

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Abstract Unavailable
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