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Oct 1972

Volume 43, Issue 10, pp. 1407-1548

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Theory of Coincidence Counts and Simple Practical Methods of Coincidence Count Correction for Optical and Resistive Pulse Particle Counters

Henri Bader, Howard R. Gordon, and Otis B. Brown

Rev. Sci. Instrum. 43, 1407 (1972); http://dx.doi.org/10.1063/1.1685455 (6 pages) | Cited 7 times

Online Publication Date: 4 November 2003

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The exact equation for primary coincidence count correction is derived, and it is shown that secondary coincidence correction can be calculated with an accuracy depending only on statistical counting errors. A coincidence correction equation is developed in the form of a series of unknown terms, but of known structure. The unknown terms can be eliminated by solving simultaneous equations obtained by counts after dilution of the gas or liquid sample containing particles in suspension, or by counts on the undiluted fluid by varying the size of the instrument sensing volume. These methods suggest useful improvements in the construction and use of particle counters.

Residual Drag Torque on Magnetically Suspended Rotating Spheres

J. K. Fremerey

Rev. Sci. Instrum. 43, 1413 (1972); http://dx.doi.org/10.1063/1.1685456 (5 pages) | Cited 5 times

Online Publication Date: 4 November 2003

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An almost quantitative explanation of the residual drag torque on freely spinning steel spheres in magnetic suspension is given by comparing previously published experimental data with theoretical results of Keith (1963). Accordingly, the residual drag torque is mainly caused by the earth's rotation. The associated decay ratio −ω∕ω increases quite linearly with the rotor angular velocity ω. A distortion of the rotational symmetry of the supporting magnetic field enhances the decay ratio. This effect decreases with increasing rotor speed. The influences of rotor imperfections and of lateral rotor vibrations are also considered.

Simultaneous Measurements of Temperature and Velocity in Heated Flows

Rene Chevray and Narinder K. Tutu

Rev. Sci. Instrum. 43, 1417 (1972); http://dx.doi.org/10.1063/1.1685457 (5 pages) | Cited 35 times

Online Publication Date: 4 November 2003

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Although measurements in nonisothermal flows have been made with constant current hot wire anemometers, the signals obtained are not amenable to linearization and do not permit continuous and simultaneous measurements of velocity and temperature. The instrument described here, consisting of two hot wire probes operated in different modes provides separate and simultaneous signals directly proportional to velocity and temperature for the frequency range of interest (0–10 kHz). This instrument was tested in a controlled environment and the results proved very satisfactory.

Laser Radar (LIDAR) for Mapping Aerosol Structure

R. J. Allen and W. E. Evans

Rev. Sci. Instrum. 43, 1422 (1972); http://dx.doi.org/10.1063/1.1685458 (11 pages) | Cited 9 times

Online Publication Date: 4 November 2003

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This paper describes a third‐generation experimental Q‐switched, ruby laser radar or lidar useful for air pollution mapping and meteorological studies. This system differs from its predecessors in that it incorporates (1) automatic inverse‐range‐squared receiver gain compensation, (2) coaxial transmitter and receiver optics, (3) automatic scanning and pulsing at equal angle increments or time intervals for fixed operation, and at equal distances traveled for mobile operation, and (4) video disk storage and instant replay of scan sequences. Details of these improvements are included. Photographs of typical displays are also included to illustrate atmospheric returns recorded during range‐height mapping of a smoke plume from an industrial plant, showing a cross section of the plume's structure; plan position mapping of the effluents from several industrial plants, indicating those emitting particulates; and distance‐height mapping, showing differences in pollution and changes in the height of the inversion layer obtained while driving through a city.

An Apparatus for the Study of Hydrogen‐Metal Reactions

J. W. Reichardt, J. E. Marceau, and T. B. Mason

Rev. Sci. Instrum. 43, 1432 (1972); http://dx.doi.org/10.1063/1.1685459 (5 pages)

Online Publication Date: 4 November 2003

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An apparatus has been designed and constructed which measures the rate of the reaction of hydrogen with metals, such as titanium, which form metal hydrides. The measurement is done using a flow technique. The data are recorded and analyzed using a real time interface with a digital computer. The accuracy of the rate measurement is within ±3×10−5 Torr liter∕sec.

Instrument Response Functions for Potential Modulation Differentiation

J. E. Houston and Robert L. Park

Rev. Sci. Instrum. 43, 1437 (1972); http://dx.doi.org/10.1063/1.1685460 (7 pages) | Cited 37 times

Online Publication Date: 4 November 2003

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An exact method is outlined for handling the effect of amplitude on the results of potential modulation differentiation. The method involves the derivation of the response functions for the various spectral components corresponding to a unit impulse input. Actual analytical expressions are derived for these components corresponding to both cosine and square wave modulation functions. The formalism is demonstrated to be applicable to arbitrary input functions and of particular value in situations where signal‐to‐noise requirements forbid the use of small modulation amplitudes.

A Lecher Wire Microwave Interferometer for Measurements of Electron Density and Electron Temperature in a Flowing Transient Plasma

A. Y. Cheung and David W. Koopman

Rev. Sci. Instrum. 43, 1444 (1972); http://dx.doi.org/10.1063/1.1685461 (7 pages) | Cited 8 times

Online Publication Date: 4 November 2003

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A microwave diagnostic system for measurement of electron density and temperature in a transient plasma flow, generated by a laser pulse focused on a solid target, has been constructed using a twin conductor (Lecher wire) probing element coupled to X‐band waveguide components by tapered parallel planes. The analysis of the operation of the probing section has required the solution of a symmetric seven layer dielectric problem, which models the transmission, reflection, and attenuation of the microwave signal by plasma located around Lecher wires. Simultaneous measurements of the phase and amplitude of the transmitted signal, together with an experimental configuration which accurately defines the interaction of the plasma with the Lecher wire section, have made possible the reliable determination of plasma properties with a spatial resolution of ∼0.5 cm and a temporal resolution of ∼5×10−8 sec.

The Design and Construction of an Ultrastable Air‐Bearing Turntable

K. D. Saunders and R. C. Beardsley

Rev. Sci. Instrum. 43, 1451 (1972); http://dx.doi.org/10.1063/1.1685462 (3 pages) | Cited 1 time

Online Publication Date: 4 November 2003

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The design of an ultrastable but inexpensive air‐supported turntable for rotating fluid dynamics experiments is presented. The rotational stability of this turntable is a few parts in 105, about an order of magnitude better than other turntables commonly in use.

A Bakable Changeover Valve for High Precision Mass Spectrometric Comparison of the Isotopic Composition of Gases

P. J. Begbie, R. D. Beckinsale, N. J. Freeman, and R. E. Powell

Rev. Sci. Instrum. 43, 1454 (1972); http://dx.doi.org/10.1063/1.1685463 (2 pages) | Cited 1 time

Online Publication Date: 4 November 2003

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The construction of a bakable changeover valve for high precision mass spectrometric comparison of the isotopic composition of gases is described. The leakage across the valve seats is about an order of magnitude smaller than the values published for similar valves in use, and the ``mixing correction'' which can be a significant correction to the experimental data is negligible.

A New Technique to Photograph Small Particles in Motion

S. Temkin and J. M. Reichman

Rev. Sci. Instrum. 43, 1456 (1972); http://dx.doi.org/10.1063/1.1685464 (4 pages) | Cited 1 time

Online Publication Date: 4 November 2003

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A new method to photograph small particles in motion is presented and shown to be feasible. The method combines the advantages of the two methods presently in use. It provides several consecutive photographs of a particle on a single negative, so that particle trajectories are easily obtained and analyzed. Further, the method uses backlight illumination, so that the shape of the particle is recorded on each exposure. The technique requires no special equipment other than that commonly used to photograph small particles. However, the method requires better synchronization than other methods, and cannot be used for all particle sizes. In the case of liquid droplets falling in air, the method is suitable for droplets 100 μ in diameter or larger. The feasibility of the method is demonstrated by recording the trajectories of a droplet falling with and without the effects of a horizontal electric field.

Automatic Impedance Measurements Using Thermal Noise Analysis

F. Micheron and L. Godefroy

Rev. Sci. Instrum. 43, 1460 (1972); http://dx.doi.org/10.1063/1.1685465 (6 pages) | Cited 6 times

Online Publication Date: 4 November 2003

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An apparatus permitting measurements of current and voltage thermal noise of two terminal devices has been built using a correlator amplifier and a controlled amplitude white noise generator. It allows accurate determinations of device impedance components, especially of nonlinear devices such as thin ferroelectric capacitors.

An Automatic Balanced‐Filter Device Featuring Three Levels of Attenuation and an Automatically Operating Beam Stop with an Adjustable Range

Mario Buscemi

Rev. Sci. Instrum. 43, 1466 (1972); http://dx.doi.org/10.1063/1.1685466 (3 pages)

Online Publication Date: 4 November 2003

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A compact balanced filter device for use with an automated x‐ray diffractometer is described. Besides the balanced filters, the device also contains two automatically controllable attenuators providing three levels of attenuation. It also features an automatically operating beam stop which is not dependent upon the electrical system and adjusts to blank out the incident beam from 0° to ±6° two theta. Simplicity of design permits easy duplication.

Multichannel Photon Counter for Luminescence Decay Measurements

J. A. W. van der Does de Bye, A. C. P. van den Bosch, C. M. Hart, M. Saitoh, A. Slob, and P. Verhoog

Rev. Sci. Instrum. 43, 1468 (1972); http://dx.doi.org/10.1063/1.1685467 (7 pages) | Cited 5 times

Online Publication Date: 4 November 2003

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A photon counting 10 channel buffer memory enables the storage of periodically excited fast decays from weak luminescent sources in commercially obtainable multichannel analyzers, digital oscilloscopes, and other instruments with relatively slow memories. Integrated E2CL gate circuits serve as the building blocks and make a time resolution of about 10 nsec possible. Light emitting diodes were used to simulate exponential decays for the testing of the measuring system.

An Apparatus for Electron Energy Analysis in Glow Discharge Plasmas

D. D. Neiswender and F. C. Kohout

Rev. Sci. Instrum. 43, 1475 (1972); http://dx.doi.org/10.1063/1.1685468 (6 pages) | Cited 8 times

Online Publication Date: 4 November 2003

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An apparatus has been designed and built for the analysis of electron energies in low temperature glow discharge plasmas. The technique involves sampling the plasma via a molecular leak and energy analyzing the electrons by a retarding potential field. Integral retarding potential curves can be plotted directly on an X‐Y recorder, or the integral signal can be differentiated electronically to yield a curve which is proportional to the electron energy distribution. The characteristics of the apparatus, including its resolving power, are discussed, and some preliminary results are described.

A New Method for Current ``Crowbar,'' Utilizing Reflected Shock Waves

Koichi Kasuya and Toshimitsu Murasaki

Rev. Sci. Instrum. 43, 1481 (1972); http://dx.doi.org/10.1063/1.1685469 (1 page) | Cited 2 times

Online Publication Date: 4 November 2003

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A new method is proposed for crowbar techniques utilizing the ionization behind reflected shock waves in air. We can easily crowbar discharge currents when we make the time of the current peak coincide with the arrival of the shock wave at the crowbar gap.

Switching Jitter in Spark Gap Triggered by a TEM00‐Mode Mode‐Locked Ruby Laser

D. Milam, C. C. Gallagher, R. A. Bradbury, and E. S. Bliss

Rev. Sci. Instrum. 43, 1482 (1972); http://dx.doi.org/10.1063/1.1685470 (3 pages) | Cited 4 times

Online Publication Date: 4 November 2003

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The first study of jitter in a laser triggered spark gap switched by pulse trains from a mode‐locked ruby laser is described. The spark gap was fired by producing gas breakdown in a high pressure argon‐nitrogen mixture between the pole pieces. Jitter was measured as a function of the position of the lens used to focus the laser beam and as a function of the ratio of the applied voltage to the self‐breakdown voltage of the gap. Jitter values of less than 2 nsec were obtained under optimum conditions provided that the gap was fired by the early part of the pulse train.

Method and Apparatus for Reducing Errors Introduced in Cutting of X‐Ray Oriented Single Crystals

Murry N. Adams and Grover C. Wetsel

Rev. Sci. Instrum. 43, 1485 (1972); http://dx.doi.org/10.1063/1.1685471 (4 pages)

Online Publication Date: 4 November 2003

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A method is described whereby monocrystalline samples such as those used in microwave‐ultrasonic studies can be prepared with surfaces cut accurately parallel to known crystallographic planes. The apparatus makes use of an optical autocollimator traveling on precision ways to align the x‐ray camera and saw and to check the sample surface after the cut. By following the procedure described, one can readily obtain a parallelism of the cut surface to the plane prescribed by x‐ray orientation that is of the order of minutes of arc.

An Electronic Correlator for Photoelectric Correlation Measurements

S. Chopra and L. Mandel

Rev. Sci. Instrum. 43, 1489 (1972); http://dx.doi.org/10.1063/1.1685472 (3 pages) | Cited 34 times

Online Publication Date: 4 November 2003

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An instrument has been developed for determining intensity correlation functions of a light beam with high accuracy. It is based on digital storage of the arrival times of up to six photoelectric pulses following a start pulse. The times are stored in the memory of a multichannel analyzer, such that the histogram of arrival times is a direct measure of the form of the intensity correlation function. The correlator allows data to be accumulated at a much higher rate than in a time‐to‐amplitude converter.

A Method for Measuring the Spatial Dependence of the Index of Refraction with Double Exposure Holograms

F. P. Küpper and C. A. van Dijk

Rev. Sci. Instrum. 43, 1492 (1972); http://dx.doi.org/10.1063/1.1685473 (6 pages) | Cited 1 time

Online Publication Date: 4 November 2003

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An extension of Luneburg's lens calculation to weakly refractive media offers the possibility of determining the spatial dependence of the index of refraction n if there exists a linear relation between (n−1)2 and r2. Experiments are described to prove the idea. The method provides a test for the radial dependence of the refractive index as well as (in the case of a suitable distribution) a measurement of the characteristic parameter that defines this dependence. The procedure is based on the detection of a change of the focal length of a system by double exposure interferometric holography. Focal lengths longer than 103 m can be detected. The application of the method to measure electron densities of plasmas is discussed.

Printed Circuit Board Evaluation by Holographic Interferometry

D. S. Lo

Rev. Sci. Instrum. 43, 1498 (1972); http://dx.doi.org/10.1063/1.1685474 (3 pages)

Online Publication Date: 4 November 2003

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Application of real time holographic interferometry for the examination of a printed circuit board is described. The procedures and the resulting holographic interferograms of two specific studies are presented: (1) The heat conduction of a spacer used for mounting transistors on a heat sink, and (2) the detection of inner layer short circuits on a multilayer printed circuit board.

An Adjustable Gas Inlet System for an Isotope Mass Spectrometer

M. L. Coleman and J. Gray

Rev. Sci. Instrum. 43, 1501 (1972); http://dx.doi.org/10.1063/1.1685475 (3 pages) | Cited 2 times

Online Publication Date: 4 November 2003

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A versatile gas inlet system has been devised that overcomes many of the difficulties associated with other methods. A metering valve has been inserted between one of the two capillaries and the source of an isotope mass spectrometer. Tests have shown that the valve not only controls flow rate but also determines the proportion of molecular to viscous flow, in such a way that the fractionating effects of the inlet systems are equalized regardless of the differences between their reservoir pressures. Some of the advantages are ease of balancing capillaries (allowing the use of glass) and elimination of bellows or mercury pistons, allowing baking of the whole inlet system. The device may be automatically controlled for continuous balancing of flow rates.

A Precision Current Pulse Generator for NMR Self‐Diffusion Measurements by the Pulsed Gradient Technique

Gerald B. Matson

Rev. Sci. Instrum. 43, 1504 (1972); http://dx.doi.org/10.1063/1.1685476 (5 pages) | Cited 4 times

Online Publication Date: 4 November 2003

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An apparatus is described for delivering controlled pulses of current into an inductive load. Digital logic is utilized for control of the pulse duration, and current feedback is used to control the magnitude of the pulse. The apparatus was designed to enable NMR self‐diffusion measurements to be obtained by the pulsed gradient technique, and diffusion results are shown for number 15 white mineral oil using pulse durations of 10 msec and magnitudes of over 25 A.

A Randomly Dispersive Strip Line for Studies of Propagation in Fluctuating Media

R. E. McIntosh, J. M. Wilk, and L. W. Pickering

Rev. Sci. Instrum. 43, 1509 (1972); http://dx.doi.org/10.1063/1.1685477 (5 pages)

Online Publication Date: 4 November 2003

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An experiment designed to measure the statistical properties of rf pulses transmitted through a fluctuating dispersive medium is described here. The experimental system utilizes a microwave strip line in which the region separating the two conductors contains a randomly inhomogeneous, gaseous discharge.

A Light Scattering Photometer Using Photographic Film

A. Brunsting and P. F. Mullaney

Rev. Sci. Instrum. 43, 1514 (1972); http://dx.doi.org/10.1063/1.1685478 (6 pages) | Cited 2 times

Online Publication Date: 4 November 2003

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A light scattering photometer which uses a 5 mW helium‐neon laser as a light source and red‐sensitive film as the detection system is described. The film records the scattered intensity for scattering angles from 3° to 80° and from 100° to 177°. Corrections are made for refraction effects in the light scattering cell. Developed film is read with a densitometer, and film density is converted to relative scattering intensity. The quality of the light transmitted through the developed film in the densitometer is examined. This device has been tested using uniform 10.9 μ diam polystyrene spheres. The measured pattern agrees quite well with theoretical predictions.

Application of Dual Parameter Analyzers in Solid‐State Laser Tests

Stuart A. Schleusener and Kenneth O. White

Rev. Sci. Instrum. 43, 1520 (1972); http://dx.doi.org/10.1063/1.1685479 (4 pages) | Cited 2 times

Online Publication Date: 4 November 2003

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New applications of a 128×128 channel, computer controlled, dual parameter analyzer used to record, compute, and display solid state laser emission and propagation data are described. The pulse height analysis coincidence mode is used to make spike amplitude measurements on reference and propagated signals or make spike coincidence measurements on two spectrometer output signals. An X‐Y contour mode display provides a real time visual indication of results for wavelength dependent absorption tests, cavity mode tests, and beam cross section studies. A description of an operating system and initial test results are presented.
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