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Mar 1965

Volume 36, Issue 3, pp. 259-404

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Use of Prism Pairs for Precise Pointing of an Optical Axis

H. Eugene Stubbs

Rev. Sci. Instrum. 36, 259 (1965); http://dx.doi.org/10.1063/1.1719546 (5 pages)

Online Publication Date: 29 December 2004

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The use of a pair of prisms to achieve precise pointing of an optical axis is analyzed. A sextant using prism pairs having an accuracy of 0.2″ is comfortably within the present state of the art. Even higher accuracies can be achieved at the expense of a limited maximum range in the sextant.

Properties of Wide‐Gap Spark Chambers

J. P. Garron, D. Grossman, and K. Strauch

Rev. Sci. Instrum. 36, 264 (1965); http://dx.doi.org/10.1063/1.1719549 (7 pages) | Cited 5 times

Online Publication Date: 29 December 2004

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The operation of spark chambers with gaps of up to 40 cm has been studied. By applying electric fields of the order of 10 kV∕cm particle spark tracks suitable for accurate curvature measurements have been obtained. The uniformity of the electric field represents a very important factor in determining the limit of accuracy of curvature measurements. By comparing two 40‐cm chambers located in a magnetic field against each other, it is found that the momentum of a 1‐BeV∕c cosmic ray can be measured to an accuracy of ±1.4% with one 40‐cm chamber located in a 13.3‐kG magnetic field. Sensitive times of 5 μsec are typical.

Use of a Large Gap Spark Chamber in an Intense Beam of Particles

T. M. Knasel, J. K. Walker, and M. Wong

Rev. Sci. Instrum. 36, 270 (1965); http://dx.doi.org/10.1063/1.1719550 (2 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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An application is considered where a beam of charged particles is passed through a large gap spark chamber. It is shown that the use of helium gas contained in a thin plastic bag in the region of the beam can reduce the efficiency of the spark chamber, in that region, to as little as 10−6 or less. The efficiency for track detection outside this region is maintained at 100% with the use of a gas mixture of 89% neon, 10% helium, and 1% argon.

First‐ and Second‐Order Magnetic Optics of a Circular‐Pole Uniform‐Field Magnet. I.

K. L. Brown

Rev. Sci. Instrum. 36, 271 (1965); http://dx.doi.org/10.1063/1.1719551 (4 pages)

Online Publication Date: 29 December 2004

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A calculation has been made of both the first‐ and second‐order optics of a uniform‐field circular‐pole magnet, using the impulse approximation for the fringe‐field effects. From this, the first‐ and second‐order resolution has been derived over the entire focal plane of the magnet as a function of the angle of deflection and the momentum of the particle.

Differential Heat Capacity Calorimeter for Polymer Transition Studies

S. J. Gill and K. Beck

Rev. Sci. Instrum. 36, 274 (1965); http://dx.doi.org/10.1063/1.1719552 (3 pages) | Cited 14 times

Online Publication Date: 29 December 2004

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A differential‐heat‐capacity calorimeter suitable for measuring the heats of thermally induced transition reactions of polymer solutions is described. The sensitivity of the calorimeter is such that an effect of 0.200 calories can be measured with a precision of ±1% on top of a large amount of heat (approximately 300 cal) needed to raise the temperature of the calorimeter 10°C.

Efficient Low Pressure Sputtering in a Large Inverted Magnetron Suitable for Film Synthesis

W. D. Gill and Eric Kay

Rev. Sci. Instrum. 36, 277 (1965); http://dx.doi.org/10.1063/1.1719553 (6 pages) | Cited 11 times

Online Publication Date: 29 December 2004

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Electrical and sputtering characteristics of a 10‐cm‐diam inverted magnetron configuration have been investigated in the transition region from positive to negative space‐charge modes. Radial voltage and ion energy distributions were obtained for both modes. The positive space‐charge mode resulted in the most efficient transport of sputtered material from cathode to anode. Dependence of space‐charge sign reversal on apparatus dimensions and magnetic field strength are discussed showing that operation in the 10−5 Torr range can be expected for a 40‐cm‐diam configuration. The deposition profile at the anode was in good agreement with the calculated profile showing that ion current and hence sputtering is uniform over the effective cathode area.

Tagging System for High Energy Photons

David O. Caldwell, John P. Dowd, Klaus Heinloth, and Michael D. Rousseau

Rev. Sci. Instrum. 36, 283 (1965); http://dx.doi.org/10.1063/1.1719554 (6 pages) | Cited 3 times

Online Publication Date: 29 December 2004

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An apparatus has been built to determine the energy of each photon in a bremsstrahlung spectrum which produces an interaction of interest in a hydrogen target. The technique was applied specifically to charged pion photoproduction with photons of 2 to 5 BeV. The tagging system utilized a monoenergetic (to ± 1%) positron beam which produced photons and associated recoil positrons in a thin radiator. The recoil positrons were momentum analyzed and detected by a 19‐counter hodoscope. The difference between the energies of an incident and a recoil positron is the photon energy, and this was determined to ±2.5%. Since the photon beam is relatively weak, the interactions it produces must be detected with good efficiency. Such a large‐solid‐angle spark chamber, magnet, and counter system, which was used to measure the photoproduced pions, is also described.

Electric Furnace for Operation in Oxidizing, Neutral, and Reducing Atmospheres to 2400°C

T. B. Reed and R. E. Fahey

Rev. Sci. Instrum. 36, 289 (1965); http://dx.doi.org/10.1063/1.1719555 (2 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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A simple resistance‐heated furnace has been developed for operation at temperatures up to 2400°C in oxidizing as well as neutral or reducing atmospheres. The sample to be heated is placed in a dense zirconia tube, which is mounted inside a vertical split‐tube tantalum heating element. Any desired atmosphere may be used inside the zirconia tube without damaging the heating element, which is operated in argon. The heating element, which is also protected by the zirconia tube from attack by vapors from the sample, is surrounded by tantalum heat shields in a water‐cooled outer shell. A temperature of 2400°C was reached in a 2.22‐cm‐i.d. zirconia tube at a power level of 8 kW, and 2200°C was reached in a 3.5‐cm tube using 6.5 kW.

Hysteresis Loop Tracer for Thin Films in Ultrahigh Vacuum

J. A. Copeland, C. K. Kuo, and E. J. Scheibner

Rev. Sci. Instrum. 36, 291 (1965); http://dx.doi.org/10.1063/1.1719556 (4 pages) | Cited 7 times

Online Publication Date: 29 December 2004

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The hysteresis loop tracer described in this paper has two unique features: first, the pickup coil leaves one face of the film exposed thus allowing the film to be deposited while the pickup coil is in place; secondly, the high sensitivity (noise equivalent to 5×10−13 Wb) allows measurements to be made on very thin films or on films having a very small saturation magnetization. The construction of the hysteresis loop tracer is discussed in detail and its effectiveness evaluated.

Microwave Discharge Cavities Operating at 2450 MHz

F. C. Fehsenfeld, K. M. Evenson, and H. P. Broida

Rev. Sci. Instrum. 36, 294 (1965); http://dx.doi.org/10.1063/1.1719557 (5 pages) | Cited 128 times

Online Publication Date: 29 December 2004

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Five simple microwave cavities for producing discharges in gases were tested in He and H2 at pressures from 1 μ to 1 atm. Three of the cavities are commonly used, and two have been recently designed. One of the newly designed cavities offered a considerable improvement over early models with respect to compactness, ease of attachment to the system, and efficiency.

Automatic Optical Density Integrator

Sid Deutsch

Rev. Sci. Instrum. 36, 299 (1965); http://dx.doi.org/10.1063/1.1719558 (9 pages)

Online Publication Date: 29 December 2004

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An instrument for the automatic integration of amino acid chromatograms is described. Translation of the optical density from logarithmic to linear digital units is accomplished via a logarithmic potentiometer and voltage‐to‐frequency converter. Cycles are counted in a decade counter and the accumulated total is printed out when each curve ends. The chromatogram baseline is continuously corrected to compensate for drift. The operator can select any one or any combination of photocells for integration. The equipment features 11.6‐sec‐holding circuits and a high gain amplifier in which a signal whose period is 40 min long is sampled at a 0.25‐cps rate and is synchronously detected with a relay.

Improved Torsion Viscometer for Polymer Studies

R. L. Forgacs

Rev. Sci. Instrum. 36, 307 (1965); http://dx.doi.org/10.1063/1.1719559 (7 pages)

Online Publication Date: 29 December 2004

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A torsion pendulum type viscometer was developed to permit determination of dynamic viscosity and dynamic modulus of solid and liquid polymers. Sample temperature is automatically controlled within less than 1°C to any temperature in the −80 to +100°C range. Forced oscillation of the pendulum at frequencies from 3×10−6 to 3 cps or higher is possible, also, freely decaying oscillation and creep testing. The viscometer is unique in that an extremely sensitive (<1″) and stable photoelectric angle detector is combined with a thermoelectric temperature control system, which dispenses with vibration‐inducing moving fluids. This makes possible measurements with shear strain amplitudes as low as 10−6 to 10−7, and results in improved low frequency angular measurement accuracy, limited by the ambient level of room vibrations.

Conversion of the Bausch & Lomb Dual Grating Spectrograph for the Direct Reading of Nonuniform Line Profiles

Clifford J. Cremers

Rev. Sci. Instrum. 36, 314 (1965); http://dx.doi.org/10.1063/1.1719560 (3 pages)

Online Publication Date: 29 December 2004

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A description is given for the modification of the Bausch & Lomb dual grating spectrograph so that it may be used to directly measure longitudinal spectral line profiles with fixed phototube detectors. These measurements are often necessary in plasma diagnostics. The modified instrument has a single, compact, out of the way drive system that tilts the grating. This allows any number of lines to be recorded simultaneously. The time for scanning a cross section in the radiating source is on the order of 30 sec.

Generation and Diagnosis of Synthesized Plasma Streams

J. M. Sellen, W. Bernstein, and R. F. Kemp

Rev. Sci. Instrum. 36, 316 (1965); http://dx.doi.org/10.1063/1.1719561 (7 pages) | Cited 19 times

Online Publication Date: 29 December 2004

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A contact‐ionization source is described which generates a cesium ion stream characterized by a high degree of order in the ion motion. Electrons are added to form a quiescent, collisionless plasma stream. Diagnostic instruments are described for demonstrating the properties of the plasma streams. Ion densities range from 5×107 to 1×1011 ions∕cm3 in the source region, at accelerating voltages from 100 V to a few thousand volts, depending on the experimental application. Conical expansion of the beam reduces the densities in downstream regions. Electron temperatures in the beams range downward from the ∼2500°K emissive wire temperature. Means are described for increasing electron temperatures to several times this value, with resultant increase in beam divergence.

High Efficiency, Low Background GM Counter

V. J. Landis and R. C. Jensen

Rev. Sci. Instrum. 36, 323 (1965); http://dx.doi.org/10.1063/1.1719562 (3 pages)

Online Publication Date: 29 December 2004

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A gas flow, GM counter having a low background, a 4π counting configuration, and a convenient sample changing arranagement has been constructed and tested. The counter consists of two disk‐shaped detectors hinged so that the sample is completely enclosed by the detector windows. The beta counting efficiency is about 94% for a weightless sample. The counting characteristics, stability, and configurational efficiency are comparable to conventional designs. The relative figure of merit of the counter is such that, within a given time period, two to four times as many samples can be counted to the same statistical accuracy as was possible with 2π type counters.

Magnetic Field‐Tracking Nuclear Resonance Gaussmeter

August H. Maki and Richard J. Volpicelli

Rev. Sci. Instrum. 36, 325 (1965); http://dx.doi.org/10.1063/1.1719563 (3 pages) | Cited 9 times

Online Publication Date: 29 December 2004

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A feedback system is described by means of which a marginal oscillator may be referenced to the frequency of a nuclear resonance occurring in a magnetic field, and is thus useful as a magnetic field tracking nuclear resonance gaussmeter. An instrument is described which uses the proton resonance in water to track fields in the vicinity of 3500 G. The tracking range of the oscillator is 2 Mc about a center frequency of 14.5 Mc with an estimated tracking error of ±5 cps over this range at low tracking speed. A tracking rate as high as 50 kc∕sec2 is possible with a tracking error of about 20 cps. A digital‐to‐analog conversion of the oscillator frequency has been used to present EPR spectra on an x axis linear in magnetic field, thus compensating for poor magnetic field regulation.

Zeolite Gettering for the Production of an Ultrahigh Vacuum

Thomas H. Batzer and Robert H. McFarland

Rev. Sci. Instrum. 36, 328 (1965); http://dx.doi.org/10.1063/1.1719564 (3 pages)

Online Publication Date: 29 December 2004

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During the past four years, two groups at the Lawrence Radiation Laboratory have extended, independently, the uses of zeolite gettering devices toward the production of an ultrahigh vacuum. This paper discusses their collective results.

Amplitude and Decay Rate Analysis of Low Level Exponentially Decaying Radio‐Frequency Signals

Howard C. Berg

Rev. Sci. Instrum. 36, 330 (1965); http://dx.doi.org/10.1063/1.1719565 (5 pages)

Online Publication Date: 29 December 2004

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A method is described which allows routine measurements of the relative amplitudes and absolute decay rates of low level exponentially decaying radio‐frequency signals to be made to within an accuracy of 1%. The signals are converted to audio frequency, narrow banded, rectified, and integrated over two successive periods of time. The theory of the measurement, which is given in detail, shows how the analysis can be made in the presence of noise which is white over a frequency bandwidth large compared to the inverse decay times. The general features of the circuits are described, and a schematic is given for a nearly ideal full‐wave linear rectifier.

Precision Measurement of Lattice Imperfections with a Photographic Two‐Crystal Method

J. A. Bearden and Albert Henins

Rev. Sci. Instrum. 36, 334 (1965); http://dx.doi.org/10.1063/1.1719566 (5 pages) | Cited 5 times

Online Publication Date: 29 December 2004

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A photographic two‐crystal spectrometer method employing the penetrating W Kα1 line has been developed. In the present investigation this technique was used to test large crystals with areas up to 25×50 mm in reflection and volumes up to 25×3.5×5 mm in transmission; angular deviations in the lattice as small as 0.5″ were detected. The first crystal was a nearly perfect calcite 30×70×10 mm used in the second order and located 100 cm from the tungsten x‐ray tube and also 100 cm from the second crystal (one tested) which was usually set in the −2 order. The 200‐cm distance from the focal spot to the second crystal separated the α1α2 lines and allowed the α2 line to be blocked out when testing a calcite crystal. In most tests the crystals were of different d∞'s, and a small dispersion resulted, but essentially gave the rocking curve expected from the Darwin‐Prins single‐crystal diffraction pattern. A NaI detector and a scaler were used to locate the peak and half‐intensity points of the rocking curve. A photographic film was placed between the detector and test crystal, and an exposure of 5 to 20 min was made at each of the three positions. Structure in the image gave a measure of the imperfections and their location on the surface of the test crystal. Approximately 100 samples of calcite, quartz, silicon, and germanium crystals have been tested, of which only six or seven approximated perfection. The sensitivity and speed of the method appear superior to any thus far developed, and it provides not only an excellent test procedure for selecting crystals for precision x‐ray wavelength measurements and high resolving power studies, but also for further perfecting synthetic crystal ‐growing techniques.

Technique for Determining Spin‐Lattice Relaxation Times

George A. Candela and Robert E. Mundy

Rev. Sci. Instrum. 36, 338 (1965); http://dx.doi.org/10.1063/1.1719567 (5 pages) | Cited 9 times

Online Publication Date: 29 December 2004

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Experiments were performed so that the static dc susceptibility of a paramagnetic material could be measured as a function of microwave power absorbed at electron spin resonance. The spin‐lattice relaxation τ1 can be expressed by τ1 = [(χ0−χp)/PaΓm]MsBdc2 where Pa is the microwave power necessary to change the field independent static susceptibility from χ0 to χp. χp is the steady state static susceptibility of the sample when it is absorbing Pa amount of microwave power. Bdc is the homogeneous dc field produced by the laboratory magnet, Ms is the weight of the sample, and Γm is a constant whose value depends solely upon the system of units used. The relaxation time is determined by directly measuring Pa, Ms, B, χ0, and χp∕χ0. The apparatus, the experimental techniques, and the accuracy of the measurements are described in some detail.

Magnetic Field of Noncylindrical Coils

W. J. C. Grant and M. W. P. Strandberg

Rev. Sci. Instrum. 36, 343 (1965); http://dx.doi.org/10.1063/1.1719568 (4 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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An exact calculation is presented for the magnetic field produced by a pair of rectangular coils. The calculation is not based on approximations tailored for the central region of the configuration. For current sheets of rectangular cross section, we obtain a closed analytical expression for the fields which is exactly valid for all points on the principal coordinate planes, and for all possible combinations of coil parameters. The calculation is extended to sources of arbitrary thickness by numerical integration. Detailed numerical application is made to the calculation of field homogeneity in the central region of the configuration.

Gamma‐Ray Absorption Instrument for Determining Fluid Saturation of Cores

P. J. Closmann and W. R. Orr

Rev. Sci. Instrum. 36, 346 (1965); http://dx.doi.org/10.1063/1.1719569 (10 pages)

Online Publication Date: 29 December 2004

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An instrument is described for measuring fluid saturation in cores by means of gamma‐ray absorption. Results of this technique are compared with those from electrical resistance measurements. Good agreement is found for gas‐liquid systems under conditions of comparatively slow saturation change. For rapidly moving fronts the instrument responds quickly to the arrival of a saturation gradient, but does not give an accurate measure of saturation in the region of the front.

Drift‐Free Mössbauer Spectrometer

F. C. Ruegg, J. J. Spijkerman, and J. R. DeVoe

Rev. Sci. Instrum. 36, 356 (1965); http://dx.doi.org/10.1063/1.1719570 (4 pages) | Cited 24 times

Online Publication Date: 29 December 2004

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In order to eliminate drifts encountered in electromechanical Mössbauer spectrometers, a drive has been developed which is drift free with regard to velocity as well as position. The spectrometer can be driven in two modes: constant acceleration and constant velocity. The constant acceleration input signal is the analog output of the address scalers of a multichannel analyzer running as a multiscaler (time mode). The constant velocity is obtained from a photocell slit system which drives the input of the spectrometer with a rectangular wave. In both modes, the photocell system is used to eliminate all position drifts by starting each new cycle from the same position. To analyze the velocity of the spectrometer a voltage‐to‐frequency converter and multichannel analyzer are used.

Piezoelectric Gauge for Measuring Cylinder Drag in a Fluctuating Airstream

A. R. Hanson

Rev. Sci. Instrum. 36, 359 (1965); http://dx.doi.org/10.1063/1.1719571 (5 pages)

Online Publication Date: 29 December 2004

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A piezoelectric gauge is described which is capable of measuring directly the fluctuating drag on a circular cylinder in an airstream whose velocity varies periodically. The gauge will measure forces in the milligram range having frequencies from 15 to 1000 cps. Design features of the gauge are discussed. A few results are given for the Reynolds number range of 1.5 to 115.

Automatic Phase‐Measuring System for an 8‐mm Carrier Wave and its 4‐mm Harmonic

G. Lisitano

Rev. Sci. Instrum. 36, 364 (1965); http://dx.doi.org/10.1063/1.1719572 (4 pages) | Cited 3 times

Online Publication Date: 29 December 2004

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This paper describes a measuring system which automatically displays the phase variation of two different electromagnetic waves radiated together in the measuring channel. The two waves are an 8‐mm carrier wave and its second harmonic 4‐mm wave. The latter is produced by distortion of the carrier signal before its entrance into the measuring channel. The carrier wave is sawtooth frequency modulated. By using a long reference path a low frequency sinusoidal interference signal is produced for both waves. Tuned amplification does not affect the phase information of the interference signal and the high sensitivity needed for the second harmonic detection is achieved by biasing of the detector crystals. The drive power may be as low as 10 mW and the phase measurement is to large extent independent of amplitude variation for both waves.
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