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Nov 1963

Volume 34, Issue 11, pp. 1175-1286

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Charging and Acceleration of Microparticles

James F. Vedder

Rev. Sci. Instrum. 34, 1175 (1963); http://dx.doi.org/10.1063/1.1718171 (9 pages) | Cited 26 times

Online Publication Date: 29 December 2004

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Development work on charging and acceleration of microparticles gives promise of a micrometeoroid simulator capable of producing velocities well into the meteoric range. Velocities up to 7 km∕sec have been attained with highly charged micron‐size diamond particles with a 70‐kV accelerating voltage. Single particles electrodynamically contained in a high vacuum are charged positively by an ion current to give charge‐to‐mass ratios approaching 400 C∕kg. Once charged, the particle is extracted from the containing field and accelerated by a high potential. Preliminary work on charging microparticles of other materials demonstrates the possibility of producing high charge‐to‐mass ratios on many substances by this technique.

Apparatus for Observing Phase Transitions of Incandescent Materials

George N. Rupert

Rev. Sci. Instrum. 34, 1183 (1963); http://dx.doi.org/10.1063/1.1718172 (5 pages) | Cited 8 times

Online Publication Date: 29 December 2004

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The temperature vs time curve of a cooling or heating incandescent material is displayed either on a cathode ray oscilloscope or a strip chart recorder. Temperatures at which phase transitions occur are seen as discontinuities in the curves. The temperature‐sensing device is a photomultiplier tube. The sample is heated in an eddy current concentrator by induced radio‐frequency currents. Light from the sample is divided by a beam splitter between the phototube and an optical pyrometer which is used for temperature calibration. The temperature range displayed for a fixed starting temperature may be reduced by opposing the phototube's output voltage with an adjustable fixed voltage. Typical cooling curves are included.

Measurement of Magnetic Thin Film Rotational Properties and Uniformity

David M. Ellis and Clifford J. Bader

Rev. Sci. Instrum. 34, 1188 (1963); http://dx.doi.org/10.1063/1.1718173 (3 pages) | Cited 3 times

Online Publication Date: 29 December 2004

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A previous paper by the authors [Rev. Sci. Instr. 33, 1429 (1962)] described an instrument which relates magnetization vector position in a thin film to rf mixing behavior under a crossed‐wire probe. The instrument permits nondestructive observation of small areas of the film and affords high angular resolution. This paper describes provisions for automatically indicating and recording the magnetization angle as the film is traversed by the probe. These provisions extend considerably the usefulness of the instrument in studies of film behavior and uniformity.

Anomalous Residual Currents in the Ultrahigh Vacuum Use of Bayard‐Alpert Ionization Gauges

Thomas E. Hartman

Rev. Sci. Instrum. 34, 1190 (1963); http://dx.doi.org/10.1063/1.1718174 (6 pages) | Cited 12 times

Online Publication Date: 29 December 2004

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Anomalously high residual collector current is observed with a Bayard‐Alpert ionization gauge after the gauge has been exposed to a relatively high pressure gas which will chemisorb on the grid of the gauge. The evidence indicates that the principal portion of the anomalous residual current results from the subsequent release of the adsorbed species as high velocity ions. A small fraction of the fast ions collide with the collector resulting in a positive charge flow from the grid to the collector which is pressure independent. The more strongly chemisorbed gases are found to replace those which have been previously adsorbed. Oxygen results in the largest and most persistent anomalous residual current.

Optimization of Particle Injection into a Synchrotron

A. J. Lichtenberg

Rev. Sci. Instrum. 34, 1196 (1963); http://dx.doi.org/10.1063/1.1718175 (4 pages)

Online Publication Date: 29 December 2004

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A technique is developed for obtaining the phase space density distribution within the acceptance of a synchrotron if the distribution of the emittance is known. It is shown that the matching of an injector emittance to a synchrotron acceptance depends not only on the phase space boundary but also on the phase space density distribution. The problem of maximizing the charge accepted by a synchrotron with respect to the initial accelerating voltage is considered. Two cases are treated analytically which, while highly idealized, illustrate the general method and give upper and lower bounds on the voltage. A numerical computation is carried out to obtain the optimum synchrotron voltage at injection for a practical synchrotron injection system.

High Temperature Vacuum Furnace with Metallic Sheet Resistance Elements

J. F. Bacon, R. D. Veltri, and J. Y. Whittier

Rev. Sci. Instrum. 34, 1200 (1963); http://dx.doi.org/10.1063/1.1718176 (2 pages)

Online Publication Date: 29 December 2004

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A resistance‐heated furnace is described in which samples, 3☒ in. long by 2☒ in. in diameter, can be heated to 2800°C in an atmosphere of purified inert gas or in a vacuum of 3×10−5 mm Hg at temperature. Furnace heating elements are four flat sheets of tungsten or tantalum and are easily fabricated. Replacement of these elements and full restoration of vacuum (1×10−7 mm Hg for cold furnace) can be accomplished in 1 h.

Effect of Absorption and Incoherent Scattering on X‐Ray Line Profiles

Robert H. Bragg and Charles M. Packer

Rev. Sci. Instrum. 34, 1202 (1963); http://dx.doi.org/10.1063/1.1718177 (6 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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Formulas are derived for correcting observed x‐ray line profiles for distortion caused by low specimen absorption coefficient in both the asymmetrical Bragg and Laue cases. In the symmetrical Bragg case (incident and reflected x‐ray beams make equal angles with the specimen surface) the present results reduce to those obtained by Keating and Warren. By making suitable approximations, all of the usual intensity formulas for the Bragg and Laue cases are obtained. It is shown that the absorption corrections for the integrated intensity can be obtained directly from measurements of the background radiation.

Scanning Single‐Crystal Multichannel X‐Ray Spectrometer

N. Spielberg and J. Ladell

Rev. Sci. Instrum. 34, 1208 (1963); http://dx.doi.org/10.1063/1.1718178 (5 pages)

Online Publication Date: 29 December 2004

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The design of a scanning, single‐crystal, multichannel x‐ray spectrometer for spectrochemical analysis is discussed. This design makes use of two or more sets of reflecting planes in the same crystal, and an individual detector is used for each set of planes. Such an instrument permits the choice of optimum resolution and detection conditions for different spectral regions, without compromising source design and without the introduction of mechanical complexity. It is possible also to scan different portions of the spectrum simultaneously. The features of such an instrument are contrasted with other types of spectrochemical analysis instruments, and some results obtained using such an instrument are described.

Study of Contamination Rates in an Electron Microscope

R. L. Patterson and C. M. Wayman

Rev. Sci. Instrum. 34, 1213 (1963); http://dx.doi.org/10.1063/1.1718179 (3 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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A study of contamination rates in a Hitachi HU‐11 electron microscope under various conditions was made. A decontamination device is described which lowers the contamination rate by more than a factor of two. The construction of this apparatus is such that accessories like a multiaxis tilting stage and specimen tensile straining device can be used concurrently.

Fast Response, Blackbody Furnace for Temperatures up to 3000°K

Allen J. Metzler and J. Robert Branstetter

Rev. Sci. Instrum. 34, 1216 (1963); http://dx.doi.org/10.1063/1.1718180 (3 pages) | Cited 2 times

Online Publication Date: 29 December 2004

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An inductively heated graphite furnace having a ⅜‐in.‐diam source of blackbody radiation for pyrometer calibration is described. The furnace is fabricated from simple, easily demountable parts and may be operated at 1800°K for 6 h with only infrequent attention; temperatures to 3000°K may be obtained for shorter periods. Source temperatures are stable and are rapidly attained. The time constant is approximately 2☒ min. Special atmospheres are not required for furnace operation since graphite oxidation is minimized through furnace design.

Heat Flow in Connected Media of Different Temperature‐Dependent Conductivities

R. B. Lazarus

Rev. Sci. Instrum. 34, 1218 (1963); http://dx.doi.org/10.1063/1.1718182 (2 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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In slab or cylindrical geometry, it is shown that the total heat flow through parallel, homogeneous channels is the same, regardless of the state of thermal contact between them, even if the channels have conductivities which are different functions of temperature.

Fatigue and Saturation in Photomultipliers

J. P. Keene

Rev. Sci. Instrum. 34, 1220 (1963); http://dx.doi.org/10.1063/1.1718183 (3 pages) | Cited 17 times

Online Publication Date: 29 December 2004

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The characteristics of some EMI photomultipliers when operated continuously with large cathode and collector currents are described. It is shown that cathode currents up to about 10 μA∕cm2 are possible with some types of tubes, the only limitation being cathode deterioration under intense illumination. In other types surface resistivity and space charge prevent operation above about 0.02 μA∕cm2. Data on collector saturation are given and the effect of dynode heating by large currents with consequent reduction in secondary emission factor is also described.

Design and Construction of High Magnetic Field Traveling Wave Lines

L. M. Lidsky and D. J. Rose

Rev. Sci. Instrum. 34, 1223 (1963); http://dx.doi.org/10.1063/1.1718184 (5 pages)

Online Publication Date: 29 December 2004

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A pulsed, capacitively loaded helical line capable of generating 5000‐G pulses is described. The line velocity is 15 cm∕μsec. Titanate ceramics are used as the dielectric elements. The analysis and design take into account the often overlooked effect of inductive coupling between line elements. A formalism suitable for numerical computation of complicated systems is illustrated. The design can be extended to give a variable velocity 9‐kG line.

Simple Automatic Frequency Control System for Reflex Klystrons

R. K. Waring

Rev. Sci. Instrum. 34, 1228 (1963); http://dx.doi.org/10.1063/1.1718185 (2 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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A simple automatic frequency control system for reflex klystrons is described. A sample of the microwave power is reflected from a reference cavity that has a modulated resonant frequency. The detected signal is phase sensitively demodulated in a transistorized demodulator that can be inserted directly into the reflector lead of the klystron.

Streak Camera for Laser Emission Studies

James L. Helfrich and Gordon F. Blizard

Rev. Sci. Instrum. 34, 1229 (1963); http://dx.doi.org/10.1063/1.1718186 (4 pages)

Online Publication Date: 29 December 2004

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An inexpensive streak camera was designed and built with the specific purpose of examining laser emissions. A 10‐ft sweep radius and a 6‐ft film plane provided good spatial resolution and at the same time recorded the entire event. Sweep rates were variable to greater than 0.5 in.∕μsec. Periodic self‐modulation, mode variations, and changes in emitting points have been observed.

Precision Measurement of the Cleavage Plane Grating Spacing of Potassium Acid Phthalate

Alan J. Bearden and F. N. Huffman

Rev. Sci. Instrum. 34, 1233 (1963); http://dx.doi.org/10.1063/1.1718187 (2 pages) | Cited 13 times

Online Publication Date: 29 December 2004

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The clevage plane grating spacing of potassium acid phthalate (KAP) has been measured in nine orders of diffraction and d∞ found to be (13289.51±0.05 xu) at 26°C. The use of these crystals as diffraction elements for the wavelength range 6 to 25 Å is discussed. Measurement of the lattice spacing is by diffraction angle determinations in many orders with Cu Kα1 radiation. An angular precision of 0.1″ is attained. The index of refraction was calculated from the crystal constants and is consistent with the observed orders of diffraction.

Apparatus to Measure the Thermal Conductivity of Powders in Vacuum from 120 to 350°K

Kenneth Watson and Curtis A. Bauman

Rev. Sci. Instrum. 34, 1235 (1963); http://dx.doi.org/10.1063/1.1718188 (4 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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An apparatus, enclosed in a sand‐cast aluminum vacuum chamber capable of retaining pressures of 10−5–10−6 Torr, was used to measure the thermal conductivity of powder samples in vacuum. The base of the sample was heated by the temperature bath on which it rested and the top surface of the sample radiated into a cavity which was maintained at liquid nitrogen temperature (77°K). The thermal conductivity of the powders was calculated from the emitted flux, the sample thickness, and the bath temperature.

Magnetic Shielding by a Superconducting Cylinder

L. L. Vant‐Hull and J. E. Mercereau

Rev. Sci. Instrum. 34, 1238 (1963); http://dx.doi.org/10.1063/1.1718189 (5 pages) | Cited 4 times

Online Publication Date: 29 December 2004

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Eddy current magnetic shielding by a rotating conductor has been utilized to create a low magnetic field region in the interior of a hollow cylinder. The enhancement of this effect by cooling to the superconducting state has been studied and applied to a superconducting device which easily generates and maintains an extremely low magnetic field region as a laboratory environment. The operation of certain commercial Hall probes at helium temperatures is discussed, and a novel method of measuring bulk resistivities as low as 10−14 Ω‐m is suggested.

High Temperature Vacuum Furnace for Diffusion Studies

Thomas C. Piper and John Dyben

Rev. Sci. Instrum. 34, 1243 (1963); http://dx.doi.org/10.1063/1.1718190 (3 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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A high temperature vacuum furnace using electron bombardment heating has been designed and constructed for studies of diffusion in refractory materials. The furnace is designed to operate in the temperature range of 1200 to 2300°C for prolonged periods of time. The specimen temperature is controlled to ±2°C by a servo system using a thermocouple attached to the specimen crucible for the servo input.

Beam Profile Monitor for Linear Electron Accelerator

Dowell E. Martz and J. Darrell Robinson

Rev. Sci. Instrum. 34, 1246 (1963); http://dx.doi.org/10.1063/1.1718191 (3 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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The use of a lead sulfide detector in a device for monitoring the intensity distribution of high energy electron beams from a linear accelerator is described. Experimental measurements of the beam profile for a 6‐MeV linear accelerator are presented.

Timing Slow Pulses for Fast Coincidence Measurements

Michael G. Strauss

Rev. Sci. Instrum. 34, 1248 (1963); http://dx.doi.org/10.1063/1.1718192 (6 pages) | Cited 5 times

Online Publication Date: 29 December 2004

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The circuit described defines accurately the time of arrival of slow pulses. The circuit consists of a compensated delay univibrator generating a signal whose width increases with the input pulse height so that it ends at a time almost independent of the input trigger amplitude. The trailing edge of this signal shifts only 10 nsec when the input is varied from 0.5 to 10 V, and less than 5 nsec when it is varied between 1 and 9 V. The univibrator has been incorporated in a simple fast‐slow coincidence circuit. Resolving times (2τ) of 10–30 nsec have been obtained with Co60 and NaI detectors without losing coincident events.

Automatic Synchronous Excitation of Suspended Systems

F. V. Hunt

Rev. Sci. Instrum. 34, 1254 (1963); http://dx.doi.org/10.1063/1.1718193 (4 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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The sensitivity and the signal‐to‐noise ratio of electrically deflected measuring instruments, such as magnetometers or galvanometers, can be increased significantly by reversing the exciting current periodically at the fundamental resonance frequency of the suspended system and observing the peak amplitude of the oscillatory dynamic deflection. If these current reversals are made to occur exactly at the midpoints between successive zeros of deflection, the oscillations of the suspended system will be stably maintained at the resonance frequency with a ratio of dynamic to static deflection of approximately 4∕δ, where δ is the logarithmic decrement for free oscillation. This note describes electronic apparatus devised for controlling automatically the required quadrature timing of the current reversals. The circuits comprise a photocell‐actuated Schmitt trigger, a bistable flip‐flop, a timing capacitor, and a voltage comparator. Small timing errors due to finite slit width and hysteresis in the voltage comparator are of opposite sense and can be made to cancel.

Solid‐State Detectors for Beta‐Ray Spectroscopy below 4.2°K

J. Chin, A. T. Hirshfeld, and D. D. Hoppes

Rev. Sci. Instrum. 34, 1258 (1963); http://dx.doi.org/10.1063/1.1718194 (2 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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Surface barrier detectors operated at temperatures below 4.2°K are found to be sensitive to beta radiation throughout the volume of the silicon wafer and to give good resolution for conversion electrons (8.3 keV FWHM at 482 keV). The pulse height and resolution for a 1‐mm‐thick wafer are found to improve slightly with increasing reverse bias in the region of 300 to 530 V.
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Frequency Modulated NMR Oscillator without Amplitude Modulation

F. N. H. Robinson

Rev. Sci. Instrum. 34, 1260 (1963); http://dx.doi.org/10.1063/1.1718196 (1 page) | Cited 12 times

Online Publication Date: 29 December 2004

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Technique in the Use of Two Low‐Melting‐Point Solders

Edward Catalano and Emmett W. Wrenn

Rev. Sci. Instrum. 34, 1260 (1963); http://dx.doi.org/10.1063/1.1718197 (2 pages)

Online Publication Date: 29 December 2004

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