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Dec 1967

Volume 38, Issue 12, pp. 1697-1812

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Construction of the Guide Field for a Low Inductance Air‐Core Plasma Betatron

L. A. Ferrari, K. C. Rogers, and A. Jermakian

Rev. Sci. Instrum. 38, 1697 (1967); http://dx.doi.org/10.1063/1.1720648 (6 pages)

Online Publication Date: 29 December 2004

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The guide field for a low inductance (55×10−9 H) air‐core plasma betatron is constructed by placing flux‐concentrators within the interior of a single‐turn solenoid. The betatron field coil is energized by the discharge of a 75 μF, 20 kV capacitor bank. The quarter period of the field‐coil capacitor bank system is 4 μsec and the peak magnetic and electric fields at the equilibrium orbit (r0=4.83 cm) are ≈3250 G and 60 V∕cm, respectively. Techniques used to make accurate (±0.1%) measurements of transient magnetic field distributions are also described.

Gelatin‐Free Ion‐Sensitive Plates for Mass Spectrography

R. E. Honig, J. R. Woolston, and D. A. Kramer

Rev. Sci. Instrum. 38, 1703 (1967); http://dx.doi.org/10.1063/1.1720649 (5 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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Several methods have been explored to produce gelatin‐free thin‐film plates of superior performance for the detection of positive ions. Of these methods, vacuum deposition of silver halides has been found to be the most flexible system and has been examined in an extended series of tests. Particle size, sensitivity, and shape of the response curve were studied as a function of various experimental parameters, such as evaporation temperature, thickness of layer, substrate temperature, ion energy, developing conditions, and others. The plates obtained by this technique have particle sizes of about 1 μ and yield sensitivities, for 20 keV ions, approaching those of Ilford Q2 plates at 50% blackening. When blackening B is plotted vs log E (E=exposure in coulombs), the slope of the resulting response curve is considerably steeper than that found for Q2 plates. The thin‐film plates produced have a number of advantages over the commercially available Schumann‐type plates: the background blackening of unexposed areas approaches that of clear glass and has an unusually low noise level; spectral line sharpness is greatly improved; the plates show practically no halation, have good conductivity and excellent vacuum properties; and there are no storage problems.

Response of Ion‐Sensitive Plates as a Function of Ion Energy

J. R. Woolston, R. E. Honig, and E. M. Botnick

Rev. Sci. Instrum. 38, 1708 (1967); http://dx.doi.org/10.1063/1.1720650 (6 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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To attempt a better understanding of the mechanism of ion detection with ion‐sensitive plates, a study was made of sensitivity as a function of ion energy, and of blackening as a function of exposure. Various commercially available and experimental plates used in mass spectrography were investigated. A dc beam of Cs+ ions was used to expose evenly areas 0.1 by 0.25 cm on the plates, which were placed between the ion beam monitor collector and the magnetic sector entrance boundary of an AEI type MS7 double‐focusing mass spectrograph. Thus, after leaving the ion source, the ions traversed only the electrostatic sector portion of the instrument. For the sensitivity study, exposures were made with ion energies ranging from 0.1 to 20 keV on Ilford Q2, Kodak SWR, Kodak‐Pathé SC5, and RCA thin‐film plates made by the direct evaporation of AgBr onto glass (described in a companion paper by Honig, Woolston, and Kramer). In addition, blackening as a function of exposure was determined at various energies for each ion‐sensitive material. The relationship observed between sensitivity and ion energy, when plotted in double‐logarithmic fashion, is not a simple linear function, as has been stated by previous investigators, but exhibits a complex behavior.

Magnetic Viscosity in Sensitive Suspensions

Titus Pankey

Rev. Sci. Instrum. 38, 1713 (1967); http://dx.doi.org/10.1063/1.1720651 (3 pages) | Cited 2 times

Online Publication Date: 29 December 2004

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A previously described suspension employing permanent magnets is shown to be a sensitive device for measuring magnetic viscosity. A large increase in viscosity concomitant to the loading of the suspended mass with nonmagnetic weights suggests that some of the observed viscosity originates in the mechanism of magnetic suspension per se.

Broadband Nuclear Resonance Dispersion Detector

R. J. Blume and D. T. Edmonds

Rev. Sci. Instrum. 38, 1716 (1967); http://dx.doi.org/10.1063/1.1720652 (4 pages)

Online Publication Date: 29 December 2004

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The detector is a Robinson limited oscillator with a single tuning control to which has been added an untuned ``transmitter'' coil orthogonal to the usual sample coil. Oscillation is maintained by a combination of Robinson feedback and weak mutual coupling of the two coils. The rf fields of the two coils are in time phase; the transmitter field is much the stronger. Dispersion signals were obtained in tests to 20 MHz at least as easily as were absorption signals with a conventional autodyne. The circuit is especially well suited to frequency‐swept searches for narrow, easily saturable lines (since the dispersion signal does not saturate) and those requiring high H1 with unimpaired sensitivity (since the ``receiver'' sees the entire nuclear signal, but only a small fraction of the ``transmitter'' output).

Operating Parameters of dc‐Excited He‐Ne Gas Lasers

R. L. Field

Rev. Sci. Instrum. 38, 1720 (1967); http://dx.doi.org/10.1063/1.1720653 (3 pages) | Cited 9 times

Online Publication Date: 29 December 2004

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The output power of the 6328 Å helium‐neon gas laser has been investigated as a function of capillary diameter, total pressure, and He‐Ne partial pressure ratio at optimum dc discharge currents. The optimum value of pTd (total pressure × capillary diameter) remains constant, and the scaling laws, power ∝ d, optimum current ∝ d are approximately satisfied for the four diameters investigated. The results suggest that optimum laser output is always achieved at the same value of electron mean energy and at a constant fractional ionization. This study permits a clearer understanding of the relationship between various helium‐neon discharge parameters and the 6328 Å laser output power, and by extrapolation allows the prediction of optimum gas fill for other capillary diameters. These results should also be useful in analyzing the effect of gas cleanup on tube life.

Measurement of Torques at Low Temperatures

Claire D. Metz

Rev. Sci. Instrum. 38, 1723 (1967); http://dx.doi.org/10.1063/1.1720654 (3 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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A method is described for producing calibrated torques at low temperatures using the interaction between an applied magnetic field and a superconducting torus. The torque produced is proportional to the square of the applied magnetic field and can thus be varied continuously over a wide range by varying the current which produces the magnetic field. It can be used in a null method to measure any torques of interest, such as the torques produced by second sound on a Rayleigh disk or on a radiation balance. The principal advantages of this method are that a wider range of torques is available with a given assembly and that the null position is more easily obtained.

Solid State Microwave Refractometer

M. J. Vetter and M. C. Thompson

Rev. Sci. Instrum. 38, 1726 (1967); http://dx.doi.org/10.1063/1.1720655 (2 pages) | Cited 5 times

Online Publication Date: 29 December 2004

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A solid state 9.4 GHz microwave refractometer has been developed using a new technique for phase measurement. Noise level in a passband of 0.3 to 30 Hz is about 0.03 N‐unit rms using a 10 mW microwave source with losses of 30 dB between source and sampling cavity. It is easily adapted to measuring multiple sampling cavities simultaneously, thus allowing absolute and relative refractive indices (in various combinations) to be observed at several locations.

Fast Vacuum‐uv Light Source for Gas Phase Flash Photolysis

K. H. Welge, J. Wanner, F. Stuhl, and A. Heindrichs

Rev. Sci. Instrum. 38, 1728 (1967); http://dx.doi.org/10.1063/1.1720656 (3 pages) | Cited 9 times

Online Publication Date: 29 December 2004

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A flash photolysis device is described which makes irradiation down to the LiF‐cutoff (∼1100 Å) in long reaction vessels feasible. The number of quanta per flash entering the reaction cell between ∼1100 and 1400 Å and ∼1100 to 1650 Å is measured by chemical actinometry. The light pulse has a 1∕e duration of less than 2 μsec, largely independent of the discharge energy and the length of the light source.

Resonance Relaxation Sounder for the Multiple Ionospheric Probe

J. Hugill and M. J. Field

Rev. Sci. Instrum. 38, 1731 (1967); http://dx.doi.org/10.1063/1.1720657 (5 pages) | Cited 2 times

Online Publication Date: 29 December 2004

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Design parameter selection, block diagram, special circuit description, and calibration procedure are given for rocket instrumentation used to measure plasma resonances in the E‐region.

Increasing the Accuracy of Crystal Orientation Procedures Using the Weissenberg Camera

Bi‐Cheng Wang and A. W. Cordes

Rev. Sci. Instrum. 38, 1736 (1967); http://dx.doi.org/10.1063/1.1720658 (2 pages)

Online Publication Date: 29 December 2004

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A one‐film method for orienting single crystals using an oscillation film obtained with a Weissenberg camera is described. Highly precise orientation corrections are obtained by using the curvature of the nonzero lines, which is more sensitive to crystal orientation than the zero layer line curvature used in other methods. The equations used for the corrections are derived, rather than empirical, and a general equation for the shapes of the lines caused by a misoriented crystal is given.

Use of Pure Copper as a Standard Substance for Low Temperature Calorimetry

Douglas L. Martin

Rev. Sci. Instrum. 38, 1738 (1967); http://dx.doi.org/10.1063/1.1720659 (3 pages) | Cited 22 times

Online Publication Date: 29 December 2004

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Measurements in the temperature range 0.4 to 3°K have shown that the specific heat of American Smelting and Refining Co. 99.999+% pure copper in the ``as received'' condition may be higher than the specific heat of samples which have been vacuum annealed or vacuum cast from this material, possibly due to the presence of a dissolved gas. The specific heat of copper has been increased (by a percent or so) by heating in a hydrogen atmosphere. The effect of very low levels of transition metal impurities on the specific heat is discussed.

Unsymmetrical Friction and Pressure Calibration in Internally‐Heated Piston‐Cylinder Type High‐Pressure Devices

Carl W. F. T. Pistorius, Eliezer Rapoport, and J. B. Clark

Rev. Sci. Instrum. 38, 1741 (1967); http://dx.doi.org/10.1063/1.1720660 (3 pages) | Cited 21 times

Online Publication Date: 29 December 2004

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It is shown that the procedure of evaluating pressure losses in internally‐heated piston‐cylinder devices by assuming symmetrical friction is in error below ∼500°C. Previous results may be in error by as much as ∼5 kilobars at 40 kilobars and 25°C. A method of calibration is described which evaluates such unsymmetrical pressure losses.

Source of Carbon Resonance Radiation

A. Greenville Whittaker and Paul Kintner

Rev. Sci. Instrum. 38, 1743 (1967); http://dx.doi.org/10.1063/1.1720661 (4 pages)

Online Publication Date: 29 December 2004

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A hollow‐cathode carbon resonance lamp was constructed, and the effect of anode configuration, filler gas (helium, argon, and neon), filler‐gas pressure, and lamp current on the intensity of enission lines in the region 1560 to 2000 Å was studied. The carbon resonance triplet at 1657 Å could be obtained with good intensity, as could the carbon line at 1931 Å. The spectrum also showed a number of molecular bands, one of which interfered slightly with the carbon resonance line at 1657 Å. The bands could be removed, however, by reducing the pressure of the filler gas.

Vacuum Diode Detector for Measuring High Intensity Gamma‐Ray Flux

P. J. Ebert and A. F. Lauzon

Rev. Sci. Instrum. 38, 1747 (1967); http://dx.doi.org/10.1063/1.1720662 (6 pages) | Cited 5 times

Online Publication Date: 29 December 2004

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An insensitive gamma‐ray detector for measurement of fast rising, transient gamma‐ray fluxes has been developed. Linear signals ≥5×102 A have been observed, corresponding to a 1.25 MeV dose rate of >1016 R∕h. The detector can also be used in the steady state mode where signals ≤10−12 A can be measured. This current corresponds to a 60Co dose rate of ∼20 R∕h. Detector design criteria, sensitivity as a function of energy, linearity, and time response are also discussed.

Quadrupole Magnet Misalignment Tolerances

Philip F. Meads

Rev. Sci. Instrum. 38, 1752 (1967); http://dx.doi.org/10.1063/1.1720663 (5 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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The field produced by a quadrupole magnet is antisymmetric with respect to reflection through either of two orthogonal planes whose intersection is the optical axis of the magnet. Failure to perfectly align these planes for a given quadrupole magnet with the cardinal planes of the beam system incorporating that magnet induces an error field that perturbs the beam. The effects of misalignments of a number of quadrupoles are derived by including the induced error fields in the equation of motion. The results are expressed in terms of the known linear optical properties of the beam system and are sufficient for determining the tolerances required on each constituent quadpole magnet.

Recording Method for Studying the Kinetics of Gas Producing Reactions

Abraham Wilson

Rev. Sci. Instrum. 38, 1757 (1967); http://dx.doi.org/10.1063/1.1720664 (4 pages)

Online Publication Date: 29 December 2004

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An apparatus for making recorded kinetic measurements on reacting systems involving gases and solids or liquids has been constructed and tested by studying the decomposition of benzene diazonium chloride. In operation, helium is flowed through one side of a thermal conductivity detector (TCC), an equilibration tube containing solvent (if necessary), through the reactor, and back through the other side of the TCC. The measurement is made under conditions of programmed ambient temperature. The resulting recorder pen displacement is proportional to the concentration of gas in the helium stream, and, with appropriate apparatus design, to the rate of evolution of nitrogen. The skewed bell curve which results can be analyzed for the kinetic data. At each temperature (time) the pen displacement is a direct measure of the reaction velocity. The measurement has thus resulted in a transformation from a differential to an algebraic kinetics expression. The area under the curve to any temperature (time) is proportional to the total amount of gas produced. In a calibrated apparatus, one thus has a continuous analysis of the reaction. Treatment of the data to obtain an Arrhenius expression is a fairly straightforward procedure, programmable for computer solution. The example of reaction chosen is the decomposition of benzene diazonium chloride. The results are compared with literature values.

Stabilized Constant Acceleration Mössbauer Drive

Y. Hazony

Rev. Sci. Instrum. 38, 1760 (1967); http://dx.doi.org/10.1063/1.1720665 (4 pages) | Cited 7 times

Online Publication Date: 29 December 2004

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A closed feedback loop for the zero velocity drift of a constant acceleration Mössbauer spectrometer has been developed. Using a transducer with a built‐in limit switch and the modified logic circuitry of a multi‐scaler‐analyzer, the feedback loop responds to the zero velocity drift of the entire system as a whole rather than to each component independently. A long‐term zero velocity stability of ±0.001 mm∕sec has been obtained.

Pyroelectric Laser Calorimeter

Robert W. Astheimer and Robert E. Buckley

Rev. Sci. Instrum. 38, 1764 (1967); http://dx.doi.org/10.1063/1.1720666 (5 pages) | Cited 4 times

Online Publication Date: 29 December 2004

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A laser calorimeter has been developed based on the pyroelectric effect. This radiation sensing mechanism is independent of the temporal and spatial distribution of incident energy. Calibration with sources of known power and comparison with other methods of measurement indicate an absolute accuracy of better than ±5%.

System for Continuous Recording of Critical Current Curves of Superconductors

R. W. Shaw and H. L. Laquer

Rev. Sci. Instrum. 38, 1768 (1967); http://dx.doi.org/10.1063/1.1720667 (2 pages)

Online Publication Date: 29 December 2004

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A method is described which allows the direct and continuous recording of the critical current versus magnetic field curves for superconductors. The system uses an electronic integrator to control a current supply so as to produce a selected small voltage across the sample. It presents an improvement in both speed and ease of obtaining critical current curves.

Magnetic Measurements under Hydrostatic Pressure: Intensity of Magnetization and Anisotropy

N. Kawai and A. Sawaoka

Rev. Sci. Instrum. 38, 1770 (1967); http://dx.doi.org/10.1063/1.1720668 (3 pages) | Cited 7 times

Online Publication Date: 29 December 2004

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A new technique was developed to make magnetic observations of weakly magnetized materials under hydrostatic pressure up to 12 kilobars in a wide temperature range from liquid helium temperature up to 200°C. We have designed a special type of nonmagnetic pressure vessel in which the materials to be measured were pressurized. For measuring magnetization, the above pressure vessel was connected to a torsion pendulum and its deflection in a magnetic field was measured. For measuring the anisotropy of ferromagnetic crystals, the vessel was connected to an air‐jet supported magnetometer having an unbonded strain gauge detector and its torque moment in a uniform magnetic field was determined.

Flame Ionization‐Pulse Aerosol Particle Analyzer (FIPAPA)

Walter L. Crider and Arthur A. Strong

Rev. Sci. Instrum. 38, 1772 (1967); http://dx.doi.org/10.1063/1.1720669 (4 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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An instrument is described that counts automatically according to size aerosol particles of certain specific chemical compositions. The technique employed depends on converting to current pulses the ions produced from airborne particles passing through the combustion zone of a flame. Because the amplitude of the current pulse resulting from an ionized particle passing through a flame is dependent on both the mass and the ionization potential of the particle, the FIPAPA can aid in submicron aerosol particle identification when used in combination with instruments employing other sensing zone types. By use of electronic pulse‐height circuits, these current pulses are subsequently counted in six ranges of magnitude. The minimum size particle detectable was found to be 0.15 μ diam for KOH and 0.25 μ diam for NaCl.

Helium Vapor Cooled Current Leads

K. R. Efferson

Rev. Sci. Instrum. 38, 1776 (1967); http://dx.doi.org/10.1063/1.1720670 (4 pages) | Cited 11 times

Online Publication Date: 29 December 2004

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See Also: Erratum

Show Abstract
A new technique is described for constructing vapor cooled leads used to introduce electrical currents into liquid helium. Using this method, leads can be constructed to carry optimum currents ranging from low values (less than 100 A) to very high values (several thousand amperes). The current carrying elements are small (No. 38) silver‐plated copper wires woven into the shape of cylindrical tubes (i.e., electrostatic shielding). This fine division of the current carrying elements allows very good heat exchange with the helium boil‐off gas. Helium losses are approximately 2.71×10−3 liter∕h A for a pair of leads operating at the optimum current.

Improved Method of Measuring X‐Ray Tube Focus

William Parrish

Rev. Sci. Instrum. 38, 1779 (1967); http://dx.doi.org/10.1063/1.1720671 (4 pages) | Cited 4 times

Online Publication Date: 29 December 2004

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The intensity distribution and dimensions of the x‐ray tube focus can be recorded accurately and rapidly by scanning with a pair of molybdenum rod slits and a scintillation counter. Two methods were used: (1) the image‐forming slit mounted near the x‐ray tube remains fixed and the image is scanned with another slit mounted on the detector; (2) both slits and detector are translated as a unit across the focus. The vignetting was analyzed and can be made negligible in both methods. Magnification of the image is not possible with method (2), but it has the advantage of minimum vignetting and easier alignment.

AC Methods for the Determination of Photoelectron Energy Distributions

Ranga Nathan and C. H. B. Mee

Rev. Sci. Instrum. 38, 1783 (1967); http://dx.doi.org/10.1063/1.1720672 (3 pages) | Cited 7 times

Online Publication Date: 29 December 2004

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The sensitivity of the Spicer‐Berglund retarding‐potential method for the determination of photoelectron energy distributions may be improved by an order of magnitude by a more effective cancellation of the capacitative component of the signal. A double modulation technique, in which energy distributions can be traced from saturated photocurrents of the order of 10−11 A, is also described. This method can be employed to eliminate steady thermionic or photoelectric currents many orders of magnitude greater than that under investigation.
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