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May 1966

Volume 37, Issue 5, pp. 545-683

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Improvements in Linear Electric Shock Tube Drivers

Richard G. Fowler

Rev. Sci. Instrum. 37, 545 (1966); http://dx.doi.org/10.1063/1.1720247 (4 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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A series of improvements in electric shock tube drivers is described, comprising a segmented series discharge driver for long duration flows, a segmented parallel discharge driver for large diameter shock tubes, a switchless shock tube for maximum circuit efficiency, and a metal walled driver for radiant energy conservation.

Electronic Hysteresigraph Holds dB∕dt Constant

P. Mazzetti and P. Soardo

Rev. Sci. Instrum. 37, 548 (1966); http://dx.doi.org/10.1063/1.1720248 (5 pages) | Cited 20 times

Online Publication Date: 29 December 2004

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An electronic instrument able to trace on a X‐Y recorder all types of magnetic curves of ferromagnetic materials and having better performance than ordinary ballistic equipments is described. The main features of the instrument are (a) the ability to trace any magnetic curve keeping the induction flux derivative constant, which minimizes the errors due to eddy currents in the specimen, and (b) the extremely low drift of the integrating circuit, which allows it to trace hysteresis loops of specimens of normal dimensions in times as long as 30 min, yet maintaining the accuracy within 1%. Sensitivity, accuracy, errors due to eddy currents, and comparison with ordinary ballistic methods are discussed in detail in the text. Many experimental results are also given.

Apparatus for Continuous Differentiation of Data Curves

C. H. Chervenka

Rev. Sci. Instrum. 37, 553 (1966); http://dx.doi.org/10.1063/1.1720249 (3 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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A new mechanical device is described which rapidly yields the derivative of a data curve in the form of a continuous plot. This table top differentiator, the operation of which is mostly manual, depends in principle upon the measurement of the slope of successive tangents to the curve. Slopes of numerical values between −1 and 5 are measured conveniently. The device has been applied to the differentiation of interference patterns from the analytical ultracentrifuge.

Alternating Gradient Electrostatic Accelerating Tube

D. Boyd and J. V. Kane

Rev. Sci. Instrum. 37, 555 (1966); http://dx.doi.org/10.1063/1.1720250 (4 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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The processes of electron multiplication and electron loading in acceleration tubes have been investigated theoretically. These effects limit the maximum voltage at which Van de Graaff generators can operate. A new design for an accelerating tube is proposed which by virtue of its closely spaced electrodes has the advantage of ease of calculation and flexibility of boundary condition. Computer calculations were done for this tube to study electron multiplication trajectories. We have found that an axial alternating electrical field gradient can limit such avalanches by periodically trapping the electrons.

Technique for Streak Camera Writing Rate Calibration Using Pulsed Laser

A. B. Christensen and W. M. Isbell

Rev. Sci. Instrum. 37, 559 (1966); http://dx.doi.org/10.1063/1.1720251 (3 pages) | Cited 3 times

Online Publication Date: 29 December 2004

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A technique is described whereby the writing rate of a rotating mirror streak camera can be determined with the use of a pulsed laser and a knowledge of the speed of light. The result of using the technique to calibrate a 35 mm streak camera is discussed.

Refrigerated Inlet Arrangement for Mass Spectrometric Studies of Unstable Species at Low Temperatures

H. A. McGee, T. J. Malone, and W. J. Martin

Rev. Sci. Instrum. 37, 561 (1966); http://dx.doi.org/10.1063/1.1720252 (6 pages) | Cited 2 times

Online Publication Date: 29 December 2004

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A refrigerated mass spectrometer inlet apparatus is described which also functions as a multipurpose low temperature reactor and a rough separative device. The arrangement has proven to be a powerful tool in the study of the synthesis, reactivity, and energetics of compounds that are stable only at very low temperatures.

Method of Plotting Field and Current‐Induced Phase Transition in Superconductors

Werner Kolb

Rev. Sci. Instrum. 37, 567 (1966); http://dx.doi.org/10.1063/1.1720253 (2 pages)

Online Publication Date: 29 December 2004

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A method is outlined to plot the dependence of the critical field of a superconductor on its critical current automatically on the screen of an oscilloscope. Critical field and current, respectively, control the X and Y input of the oscilloscope whereas the beam intensity is controlled by the voltage drop across the superconductor. Use of short current and field pulses eliminates disturbing thermal effects. The device is particularly useful for routine measurements on cryotron circuits.

Hydraulic Ram Design for Modern High Pressure Devices

H. Tracy Hall

Rev. Sci. Instrum. 37, 568 (1966); http://dx.doi.org/10.1063/1.1720254 (4 pages)

Online Publication Date: 29 December 2004

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Equations are developed for designing hydraulic rams of maximum thrust for a given external cylinder diameter. For push type rams, the optimum ratio of outside to inside wall diameter w is 1.554, and the maximum fluid pressure P to be used is 0.4142 times the allowable hoop stress ft in the cylinder. For pull type rams in which the allowable tensile stress fb in the pull bar (cylinder rod) and the allowable hoop stress ft in the cylinder wall are equal, w=1.414 and P=0.333 ft. When these allowable stresses are not equal, more complicated relationships exist and are discussed in the text.

Technique for Simultaneously Measuring Ion Densities, Metastable Atom Densities, and Light Emission in Decaying Gaseous Plasmas

G. F. Sauter, R. A. Gerber, and H. J. Oskam

Rev. Sci. Instrum. 37, 572 (1966); http://dx.doi.org/10.1063/1.1720255 (8 pages) | Cited 25 times

Online Publication Date: 29 December 2004

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An apparatus for simultaneously measuring the time dependence of (a) ion densities, (b) metastable atom densities, and (c) the intensities of spectral lines and bands during the decay period of a gaseous plasma is described. It is comprised of a quadrupole mass spectrometer for the ion density measurements and a light spectrometer for light emission and fractional light absorption studies. The reliability of the results obtained by mass spectrometer probing of a decaying plasma was checked by comparing the results obtained in helium with those obtained by other measuring methods. The data were found to be consistent and showed that this technique can be a significant tool for the study of collision processes occurring in decaying plasmas. Moreover, the simultaneous application of mass and light spectrometric methods gives information about the time dependences of the various plasma constituents at the same plasma region.

Explosive Driven Shock Tubes

Russell E. Duff and Arlyn N. Blackwell

Rev. Sci. Instrum. 37, 579 (1966); http://dx.doi.org/10.1063/1.1720256 (8 pages) | Cited 4 times

Online Publication Date: 29 December 2004

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Several different high explosive driven shock tubes have been developed as sources of short duration, supersonic, high pressure pulses which can be used to load large, massive objects with accelerations up to many thousand g's. These shock tubes are particularly appropriate for simulating strong blast effects on hardened structures. An important characteristic of these shock tubes is the use of detonation products as the primary working fluid. Therefore, this represents one of the few instances in which the ``cold flow'' of a shock tube has been used for aerodynamic testing. Extensive design calculations are presented, and experimental measurements in a number of configurations are in good agreement with the calculations. The facilities tested have produced peak dynamic pressures of 70 to 2000 bar for half‐time durations from a few hundred microseconds to several milliseconds. Tube diameters have varied from 0.6 to 2 m, and the lengths have ranged between 3 and 15 m. All of the shock tubes are, at least in part, expendable. However, they can be quickly constructed to meet given flow requirements at costs quite modest when compared with those of competitive techniques for producing high accelerations of large objects.

Optimized Pulsed NMR Single Coil Circuit Design

K. W. Gray, W. N. Hardy, and J. D. Noble

Rev. Sci. Instrum. 37, 587 (1966); http://dx.doi.org/10.1063/1.1720257 (2 pages) | Cited 16 times

Online Publication Date: 29 December 2004

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A single coil pulsed NMR sample circuit is described which allows optimization in the transmitting and the receiving modes. In the transmitting mode the circuit is matched to the transmitter output impedance, 50 Ω, and in the receiving mode it is matched to the optimum input impedance of the preamplifier.

Effect of Intermodulation on Measurement of Small Hall Coefficients with Double ac Method

Rudolf G. Suchannek

Rev. Sci. Instrum. 37, 589 (1966); http://dx.doi.org/10.1063/1.1720258 (2 pages) | Cited 7 times

Online Publication Date: 29 December 2004

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The effect of intermodulation on the double ac method is described with emphasis on the mixing of the sample current frequency with the frequency of the magnetic field in the current circuit of the apparatus. The resulting voltages at the same frequency as the Hall voltage are coupled to the Hall voltage measuring circuit by the probe misalignment and the mutual inductance of the leads. Methods to eliminate the disturbing effects due to intermodulation are discussed.

Spatially Resolved Density Measurements of Deuterium Plasma Using Energetic D+ Beam

R. L. Hickok, F. C. Jobes, and J. F. Marshall

Rev. Sci. Instrum. 37, 591 (1966); http://dx.doi.org/10.1063/1.1720259 (5 pages) | Cited 2 times

Online Publication Date: 29 December 2004

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The density distribution of cylindrically symmetric deuterium plasmas can be measured by probing the plasma with an energetic deuterium beam and observing the protons from the D(d,p)T reaction. This technique measures the absolute deuterium density with good spatial resolution and is independent of the electron and ion velocity distributions. Using this method, we determined to within 10% the density distributions of a high current deuterium arc for three different operating conditions. A comparison of these density distributions with optical intensity distributions shows that the optical intensity decreases faster with radius than the deuterium density.

Gas Density Stabilizer for Flow Proportional Counters

Richard D. Deslattes, Bert G. Simson, and Robert E. LaVilla

Rev. Sci. Instrum. 37, 596 (1966); http://dx.doi.org/10.1063/1.1720260 (4 pages) | Cited 16 times

Online Publication Date: 29 December 2004

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A controller for gas density (pycnostat) is described with particular view to gain stabilization in flow proportional counters. The device is capable of operation at small flow rates and at pressures both above and below atmospheric. Constructional details and performance measurements are reported.

Voltage Output Characteristics of Axial Gradient Heat Flux Transducers

Phillip A. Kinzie and Estanislao N. Sosa

Rev. Sci. Instrum. 37, 599 (1966); http://dx.doi.org/10.1063/1.1720261 (5 pages) | Cited 3 times

Online Publication Date: 29 December 2004

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An analysis is given for transducers employing thermoelectric temperature difference sensing as a measure of heat flowrate. A theoretical equation relating transducer output voltage to the applied heat flowrate is developed, based upon a simple model. This equation is shown to be a nearly linear function in the case of transducers employing copper‐constantan‐copper difference thermocouples. Experimental calibration data obtained using a conductive heat source are then compared with theory. The theoretical and experimental results are found to be in general agreement. It is concluded that transducers of this type demonstrate a voltage output function which is linear within the order of ±1%.

Motion Picture Projection of Multiple Spark Camera Film

J. Christopher Kent

Rev. Sci. Instrum. 37, 604 (1966); http://dx.doi.org/10.1063/1.1720262 (2 pages)

Online Publication Date: 29 December 2004

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A method is described for motion picture projection of multiple spark camera film records. Motion picture projection of these nonstandard film records can enhance their usefulness by aiding visualization of the photographed event. Such projection can be accomplished by using the objective lens group of the multiple spark camera (or a duplicate lens group) as a projection lens group. The addition of a viewing screen, an illumination source, and an appropriate shuttering device enables the film to be projected as a motion picture sequence.

Dual Purpose Nuclear Magnetic Resonance and Nuclear Quadrupole Resonance Spectrometer

B. L. Barton

Rev. Sci. Instrum. 37, 605 (1966); http://dx.doi.org/10.1063/1.1720263 (2 pages)

Online Publication Date: 29 December 2004

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A technique is described for converting a single coil, wide line NMR spectrometer into a dual purpose nuclear magnetic resonance and nuclear quadrupole resonance spectrometer. The nuclear quadrupole resonance spectrometer uses a coherent, self‐detecting, self‐quenching, superregenerative Colpitts oscillator. The quench frequency is varied by changing the resistance between the control grid and ground. The nuclear quadrupole resonance spectrometer described is applicable to the study of internal motions in solids, which requires information on both the change in the quadrupole resonance frequency and line width.

Multistage Gun for Production of Low Energy Ion Beams

H. B. Haskell, O. Heinz, and D. C. Lorents

Rev. Sci. Instrum. 37, 607 (1966); http://dx.doi.org/10.1063/1.1720264 (8 pages) | Cited 14 times

Online Publication Date: 29 December 2004

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An ion gun using separate acceleration and deceleration stages to produce ion beams in the 1–100 eV energy region has been constructed and tested. The gun is based on an existing electron gun design but uses a thermal emitter Li2O⋅Al2O3⋅nSiO2 (n = 2 and n = 4) as a source of Li+ ions. Current densities of 10−8−10−6 A∕cm2 at beam energies of 2–100 eV were obtained and both the spatial and the energy distributions of the ions were investigated. Minimum beam radii (typically about 1 mm) occurred a few centimeters from the last aperture. Beam profiles were measured as a function of axial distance and well collimated beams up to 16 cm in length were obtained. The energy spread in the beam was found to be 0.22 eV (total width at half maximum intensity), in good agreement with the expected thermal energy spread from the source which operates at about 1200°C. Mass analysis shows that beam purities are in excess of 99% 7Li+ for isotopically enriched emitter material. Theoretical calculations of space charge effects on image distance and image size are presented as well as design parameters and graphs for the operation of the gun under various conditions.

High Temperature‐High Pressure Cell for Measuring Densities of Metals by Radiation Counting Technique

I. G. Dillon, P. A. Nelson, and B. S. Swanson

Rev. Sci. Instrum. 37, 614 (1966); http://dx.doi.org/10.1063/1.1720265 (6 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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Equipment and techniques have been developed for measurement of densities of metals at high temperatures (up to 2200°K). The equipment and techniques were demonstrated using alkali metals but are generally applicable not only to most metals but also to many other substances. Determination of vapor and liquid densities of alkali metals at high temperatures and pressures was accomplished by measuring the radiation emanating from the vapor and liquid phases of a radioactive alkali metal contained in a high pressure cell fabricated from a molybdenum‐30 wt.% tungsten alloy. The procedure was used to obtain vapor and liquid phase densities of the alkali metals at temperatures up to 2200°K and pressures up to 500 atm, which approach critical conditions. The radiation counting method involves sealing the metal whose density is to be measured in a containment capsule, irradiating the capsule and metal to produce a gamma emitting isotope of the metal, charging the capsule into the high temperature cell, and counting the activity of the vapor phase and the liquid phase at temperatures ranging from room temperature up to the critical point. A calibration of density vs irradiation level is performed at low temperatures where accurate liquid density data are available.

Sieving for Particle Size Distribution in 10 Through 1 μ Region

H. B. Carroll and I. B. Akst

Rev. Sci. Instrum. 37, 620 (1966); http://dx.doi.org/10.1063/1.1720266 (4 pages)

Online Publication Date: 29 December 2004

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Sieves were used to determine particle size distributions smaller than 44 μ (usually considered the subsieve region) through 1 μ. In particular, sieves having openings of 10 through 1 μ were used to measure the distribution of high explosive particles which are approximately spherical. Particle size distributions agreed well with distributions obtained by microscopy and photosedimentometry. The sieves are electroformed ``micromesh'' screens in 7.6 cm diam nesting cylinders, like standard sieves in the large ranges. The proper choices of elutants, dispersion techniques and agents, and sample size have been important in obtaining reproducible results. Samples as large as 0.4 g are satisfactory. The time required to obtain a distribution analysis is somewhat dependent on sample size. With samples much larger than are usual with other ``subsieve'' measurement methods—e.g., 0.4 g—one technician completes two analyses with one set of sieves (<44 through <1 μ) in a normal day.

X‐Ray Spectrometer Attachment for Elmiskop I Electron Microscope

E. Fuchs

Rev. Sci. Instrum. 37, 623 (1966); http://dx.doi.org/10.1063/1.1720267 (4 pages) | Cited 3 times

Online Publication Date: 29 December 2004

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With the aid of an x‐ray spectrometer attachment for the electron microscope (Elmiskop I), it is possible to perform quantitative analyses of the chemical elements in a specimen. The spectrometer attachment is based on the semifocusing method. It is equipped with six analyzing crystals and two counters which may be exchanged during operation. It is possible to analyze for all elements with an atomic number greater than 11. The minimum mass detectable is 10−14 g.

Flowmeter for Measurement of Low Velocities in Liquids with Weak Electrical Conductance

Ugo Magrini

Rev. Sci. Instrum. 37, 627 (1966); http://dx.doi.org/10.1063/1.1720268 (5 pages) | Cited 2 times

Online Publication Date: 29 December 2004

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The performance of a probe for measuring low velocities in weak electrolytes is reported; its sensing element, dipped into the fluid, consists of two Pt electrodes supplied with direct current. The calibration was made for two types of probes in water and dilute solutions of H2SO4 and NaCl. Data are presented concerning the reproducibility of the measurements and the sensitivity of the apparatus at different current intensities. The possibilities of using the probe to yield the kinematic properties of a liquid in motion are studied.

Design of Photomultiplier Socket Assembly with High Gain and Clean Output Signals for Tubes Viewing Organic Scintillator Light Pulses

William A. Gibson

Rev. Sci. Instrum. 37, 631 (1966); http://dx.doi.org/10.1063/1.1720269 (5 pages) | Cited 3 times

Online Publication Date: 29 December 2004

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Two of the major problems in designing a socket assembly for a 56AVP photomultiplier viewing light pulses from an organic scintillator have been investigated. They are (1) optimization of the dynode voltage distributions for gain and pulse shape over a wide range of tube gains, and (2) proper grounding of the dynode bypass capacitors and coupling of the coaxial signal leads to the anode and dynodes so that clean signals appear at the output. The effects of varying the dynode voltage distributions were studied and results of improper distributions are discussed. A dynode voltage distribution is given which gave near optimum gain and pulse shape for several different 56AVP's viewing the light pulses from an organic scintillator illuminated by 239Pu alpha particles over a wide range of supply voltages and with anode currents up to 1 A. An electrical and mechanical layout is presented which results in electrically clean pulses from the 14th dynode and anode as well as clean integrated pulses from the lower dynodes; in addition, high gain is realized with adjustment of only the last dynode‐to‐anode voltage. Photographs of the output signals are shown for a wide range of tube gains, and curves of the relative gain and risetime as a function of tube voltage are given.

Characteristics of Grid Controlled Ionization Gauge in Nitrogen

J. A. Weinman

Rev. Sci. Instrum. 37, 636 (1966); http://dx.doi.org/10.1063/1.1720270 (4 pages)

Online Publication Date: 29 December 2004

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The operating characteristics of a grid controlled ionization gauge in nitrogen at pressures between 2×10−3 and 4 Torr are presented. Positive ions were produced by a primary electron current, space charge limited by a control grid. The positive ion current was thus independent of filament temperature over a moderate range of filament heating currents. Elastic scattering reduced the ionization path of the electrons at pressures greater than 0.03 Torr. A secondary discharge established by suitably chosen electric fields compensated for the reduced ionization efficiency of the gauge above this pressure. The gauge thus yielded a positive ion current which increased monotonically from 1.7×10−9 to 4.3×10−7 A with increasing pressure throughout the investigated range of pressure.

Probe Cryostat to Fit He Supply Dewar

J. A. Schmitz and D. R. Ford

Rev. Sci. Instrum. 37, 640 (1966); http://dx.doi.org/10.1063/1.1720271 (4 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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A design for an economical cryostat‐probe is presented. Approximately 0.5 liter of liquid 4He is required to cool the probe and sample assembly. Sample temperatures are varied by using a heater and a thermal leak, with no appreciable loss of 4He noted during the heating‐cooling cycles. Temperature regulation was held to ±0.005°K for extended periods of time. Provisions for magnetic field measurements have been included in the design of the probe.
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