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Oct 1968

Volume 39, Issue 10, pp. 1407-1595

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The Northwestern University 50 cm Liquid Helium Bubble Chamber

R. J. Walker, M. M. Block, I. R. Kenyon, D. Koetke, J. Keren, P. Malhotra, P. Mazur, and H. Winzler

Rev. Sci. Instrum. 39, 1407 (1968); http://dx.doi.org/10.1063/1.1683121 (11 pages) | Cited 3 times

Online Publication Date: 10 November 2003

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The Northwestern University 50 cm liquid helium bubble chamber had its engineering run at the University of Chicago cyclotron in October 1965, after a construction and testing period of just under 2 yr. The chamber dimensions are approximately 50×25×32 cm, and the water‐cooled magnet can provide a field of 30 kG. The chamber and magnet, which weigh about 2.2×105 N, can be lifted into a beam site while in operational condition, and the chamber and magnet require a space of only 7.6×4.5 m in the beam line. The expansion is performed by a bellows located above the magnet. A repetition period of 1.2 sec∕pulse has been achieved continuously. The optical system uses dark field illumination with three cameras which view the entire chamber with a maximum stereo angle of 16°. The cameras use 35 mm film and have a demagnification of 1∕12. The chamber has produced approximately 106 useful photographs in three separate runs, and these pictures are currently being analyzed.

The Monopole Mass Spectrometer

P. H. Dawson and N. R. Whetten

Rev. Sci. Instrum. 39, 1417 (1968); http://dx.doi.org/10.1063/1.1683122 (6 pages) | Cited 1 time

Online Publication Date: 10 November 2003

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Monopole mass spectrometer characteristics were determined by analyzing ion trajectories under various operating conditions. The trajectories were computed by numerical integration of the Mathieu equations of motion. The mode of operation was chosen to correspond with that in general use, with ion injection being parallel to the axis of the instrument. The simulation was made specific by considering a monopole under operating conditions such that an ion with m∕e=72 spends 12 rf cycles within the field. Information was obtained concerning peak shape, sensitivity, and resolution. The influence of entrance and exit slit dimensions and of rod‐Vee block spacing was determined.

New Ferroelectric Hysteresis Curve Tracer Featuring Compensation and Virtual Sample Grounding

Y. T. Tsui, P. D. Hinderaker, and F. J. McFadden

Rev. Sci. Instrum. 39, 1423 (1968); http://dx.doi.org/10.1063/1.1683123 (2 pages) | Cited 13 times

Online Publication Date: 10 November 2003

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A new compensable hysteresis curve tracer for ferroelectric measurements is described. This was developed because of the need to measure ferroelectricity in slightly conducting materials. Unlike conventional hysteresis circuits, one side of the sample is virtually grounded through the use of an operational amplifier. The voltage source is grounded and there are no restrictions imposed on the oscilloscope input impedances in comparison with their respective sources. An additional feature of this new tracer is that both compensated and uncompensated hysteresis loops can be displayed simultaneously on a dual beam oscilloscope.

Current Sweep Circuit with Sweep Speed Feedback

J. D. Leslie, H. J. T. Smith, and B. Van Beek

Rev. Sci. Instrum. 39, 1425 (1968); http://dx.doi.org/10.1063/1.1683124 (5 pages)

Online Publication Date: 10 November 2003

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A current sweep circuit is described which allows the quick and accurate recording of narrow current peaks in the I‐V characteristic of a Josephson tunnel junction driven by the circuit. A feedback feature senses the current peaks and slows the sweep rate in these regions to allow for the finite slewing speed of the X‐Y recorder. The performance of the circuit is demonstrated using a simple test arrangement.

Digital Reader of Oscilloscope Trace Photographs

F. C. Jobes

Rev. Sci. Instrum. 39, 1429 (1968); http://dx.doi.org/10.1063/1.1683125 (5 pages)

Online Publication Date: 10 November 2003

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A device for reading ordinary Polaroid oscilloscope trace photographs has been assembled from an oscilloscope, an oscilloscope camera, a 400 channel analyzer, and some control circuitry. This device reads the coordinates of 400 points along a trace by scanning in the y direction until the trace is found for each of 400 x positions. A photomultiplier tube looking through the back of the Polaroid print detects the trace. The reading, which is stored digitally in the analyzer until printed out, has an accuracy of better than 1%. This technique can be adapted to other types of trace photographs and can use other digital devices as well.

Versatile Double Crystal X‐Ray Goniometer

W. L. Bond

Rev. Sci. Instrum. 39, 1434 (1968); http://dx.doi.org/10.1063/1.1683126 (3 pages) | Cited 2 times

Online Publication Date: 10 November 2003

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A double crystal goniometer is described. It has been found useful for determining the degree of perfection of crystals. It can detect deviations of atomic planes of the order of 1″ and differences of spacing of the order of 5 parts∕1 000 000. The goniometer is very easily adjusted for any crystal and is quite stable with respect to temperature changes and vibration.

Vibrating Sample Magnetometers

J. E. Noakes, A. Arrott, and C. Haakana

Rev. Sci. Instrum. 39, 1436 (1968); http://dx.doi.org/10.1063/1.1683127 (3 pages) | Cited 5 times

Online Publication Date: 10 November 2003

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In order to eliminate the sensitivity to field noise and microphonics of a vibrating sample magnetometer it is sufficient to add trimming coils which are adjusted to produce no signal when the applied field is deliberately driven at the frequency ω0 which is to be used for vibrating the sample. A mechanical chopper which discriminates against all even harmonics and against third harmonics is discussed. The use of eddy currents to precisely align a sample in a null measurement of magnetization is described.

Microminiature Pirani Gauge for Measurements of Low Pressures

G. T. Rayfield, F. P. Boynton, and O. W. Potter

Rev. Sci. Instrum. 39, 1438 (1968); http://dx.doi.org/10.1063/1.1683128 (3 pages)

Online Publication Date: 10 November 2003

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The design and operation of a small Pirani gauge, suitable for surface pressure measurement in low density flows, are described. The gauge is made from two microminiature lamp elements. One element senses the external pressure, and the other provides temperature compensation. The electrical circuitry is essentially a Wheatstone bridge. The pressure range is approximately 0.1–10 Torr, with a possible accuracy of 2%.

AgCl Seal: A Simplifying Improvement

Bernard Caras

Rev. Sci. Instrum. 39, 1441 (1968); http://dx.doi.org/10.1063/1.1683129 (2 pages) | Cited 2 times

Online Publication Date: 10 November 2003

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A simplification and∕or improvement for AgCl seal to glass is presented. Metallization of the seal area was avoided. Instead, preferential spreading of molten AgCl on glass was achieved via local surface grinding of the glass seal area. Direct visual and microscopic inspection of the entire seal was made possible by elimination of the opaque metallization.

Four‐Sequential‐Output Generator for Research in Electroanesthesia

Sid Deutsch

Rev. Sci. Instrum. 39, 1443 (1968); http://dx.doi.org/10.1063/1.1683130 (6 pages)

Online Publication Date: 10 November 2003

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Focusing is important in electroanesthesia research because it is conjectured that we should achieve high current density in some internal structure and zero current elsewhere. If current is applied sequentially to many opposing electrodes on a solid conducting sphere, the current density magnitude at the center of the sphere is three times the average current density under each electrode. This technique thus appears to focus current although, in reality, the individual current flow lines diverge. Because of the presence of low resistance pathways in an actual brain, however, the results using the homogeneous sphere model are only qualitatively correct. A four‐sequential‐output unit is described. The outputs are individually controlled so that it is possible to alter the internal current density distribution, in the experimental subject, by decreasing one output while increasing another. Each output supplies maximum values of 250 V peak open circuit and 50 mA peak short circuit.

Apparatus for Inducing High Uniaxial Compressive Stresses in Crystals

J. F. Schetzina, J. P. McKelvey, and M. W. Cresswell

Rev. Sci. Instrum. 39, 1448 (1968); http://dx.doi.org/10.1063/1.1683131 (5 pages) | Cited 2 times

Online Publication Date: 10 November 2003

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A vise capable of exerting uniaxial forces in excess of 2×109 dynes and operable between 77 and 300 K is described. The strain induced in the crystal being compressed is measured via a strain gauge bonded directly to the surface of the specimen. The applied stress may be varied smoothly to greater than 1010 dynes∕cm2 and a resistance bridge resolves the induced strain in the stress direction to 2×10−6. Some preliminary high stress piezoresistance data for p‐type germanium are included.

Vibrating Coil Magnetometer for Measurements on Type II Superconductors

D. E. Farrell

Rev. Sci. Instrum. 39, 1452 (1968); http://dx.doi.org/10.1063/1.1683132 (5 pages) | Cited 3 times

Online Publication Date: 10 November 2003

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Problems involved in the measurement of magnetization in type II superconductors are briefly considered. A simple vibrating coil magnetometer has been developed for use at temperatures above 1.5 K with a sensitivity of 10−4 emu, permitting quantitative tests to be made of some recent developments in the theory of type II superconductors.

Cell for Dielectric Measurements in the High Radio Frequency Region

C. T. O'Konski and Adrian Edwards

Rev. Sci. Instrum. 39, 1456 (1968); http://dx.doi.org/10.1063/1.1683133 (3 pages) | Cited 8 times

Online Publication Date: 10 November 2003

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The design and construction of a dielectric cell and adaptor suitable for use with the Boonton RX meter are presented. The geometry of the cell can be varied easily to accommodate a wide range of permittivity. Data illustrating the cell performance are included for several known liquids.

Techniques of Ultrasonic Paramagnetic Resonance

H. C. Meyer, P. F. McDonald, and P. L. Donoho

Rev. Sci. Instrum. 39, 1459 (1968); http://dx.doi.org/10.1063/1.1683134 (2 pages)

Online Publication Date: 10 November 2003

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Ultrasonic paramagnetic resonance (UPR) techniques are given for recording the derivative of UPR absorption with respect to magnetic field and for measurement of spin relaxation rates. The X‐band pulse echo, spin relaxation spectrometer utilizes high power pulses from one magnetron to saturate the spin system. Low power pulses from another magnetron are then used to monitor the recovery from saturation by varying the delay between the saturating and monitoring pulses.

New Type of High Speed Valve

N. Inoue and T. Uchida

Rev. Sci. Instrum. 39, 1461 (1968); http://dx.doi.org/10.1063/1.1683135 (4 pages) | Cited 6 times

Online Publication Date: 10 November 2003

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A new type of high speed operating valve for theta pinch devices in plasma physics research is described. The valve is thin enough to be set between the theta pinch coil and the discharge tube. The operation of the valve depends on the force exerted between two parallel electric currents. The gas is injected from the wall of the discharge tube so that an amount of gas is initially confined in the discharge region. Azimuthal distribution of the gas admitted is found to be uniform by measurement with a fast ion gauge. The opening time of the valve is less than about 350 μsec. The amount of gas admitted for a given setting is reproducible to less than ±5%.

Mass Selector for Ion Beam Experiments

Lowell P. Theard

Rev. Sci. Instrum. 39, 1464 (1968); http://dx.doi.org/10.1063/1.1683137 (8 pages) | Cited 1 time

Online Publication Date: 10 November 2003

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A mass selector which efficiently produces mass filtered beams of both primary and secondary ions in the medium current ranges is described. Currents up to 10−6 A for the mass filtered beam can be obtained with beam energies of 3–5 keV. Ions are produced in a hot cathode, gas discharge ion source of relatively simple construction, and are extracted as a parallel beam. Mass analysis is accomplished over a short pathlength with a compact, high current, sector field electromagnet which is entirely contained within the analyzer chamber. An electrostatic quadrupole lens is used for optimum shaping of the incident ion beam for high transmission through the magnetic sector. A second quadrupole lens is used to restore parallelism to the mass filtered ion beam and is mounted beyond the image slit, which was made wide enough to pass the entire image focused beam. The instrument has no object slit, as the entire incident beam is brought to a crossover at the object position. Beam transmission through all elements in the analyzer chamber, including the two quadrupole lenses, the sector magnet, and the image slit, is approximately 50%. Oscillating beam scanners are used to measure the beam density profile and to monitor the mass spectrum. The resolving power for spatial separation is about 60. Secondary ions such as N4+ and CH5+ can be generated with intensities comparable to those of primary ions.

Functional Ion Laser Based upon a Thermionic Hollow Cathode Discharge

D. A. Huchital and J. Dane Rigden

Rev. Sci. Instrum. 39, 1472 (1968); http://dx.doi.org/10.1063/1.1683138 (6 pages) | Cited 11 times

Online Publication Date: 10 November 2003

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An ion laser based upon a thermionic hollow cathode discharge is described. The anode and the cathode are a pair of hollow metal cylinders that are spaced by a series of metal apertures along the axis of a solenoid. The laser is necessarily operated in a flowing gas mode; argon or krypton flows through the cathode tube and is pumped out through a high conductance sideport. The arc runs from the inside of the cathode tube at a point where the gas pressure is approximately 1 Torr. The characteristics of a variety of cathode types are discussed. The collimating structure consists of a number of relatively widely spaced metal apertures supported either on insulating rods or resting directly on the vacuum wall. The device is simple and completely demountable. A number of multiwatt versions of this design are discussed. The results of controlled life tests are presented and the expected useful lifetime of the laser is discussed.

Resolution Determination in Field Emission Energy Analyzers

Russel D. Young and C. E. Kuyatt

Rev. Sci. Instrum. 39, 1477 (1968); http://dx.doi.org/10.1063/1.1683139 (4 pages) | Cited 54 times

Online Publication Date: 10 November 2003

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The influence of energy analyzer transmission function on measured field emission energy distributions has been evaluated by folding a Gaussian transmission function into the field emission total energy distribution. The resulting distributions at 0, 4.2, 20.3, 77, and 300 K are plotted as a function of the field‐ and work‐function‐dependent parameter d, and for the special case ϕ=4.40 eV, F=3.0×107 V∕cm. A criterion is established for determining the width of an analyzer transmission function from distributions measured at the above temperatures. It is shown that the slope of the log of the energy distribution is changed by less than 1% when the analyzer width is changed from 0 to 100 mV.

Fast Metallic Contact Solid Dielectric Switch for High Voltage and Current

Ivars Henins and John Marshall

Rev. Sci. Instrum. 39, 1481 (1968); http://dx.doi.org/10.1063/1.1683140 (4 pages) | Cited 6 times

Online Publication Date: 10 November 2003

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A metallic contact solid dielectric switch with a closing time of 10.13±0.31 μsec is described. An electrically exploded foil is used to drive a 0.317 cm thick aluminum plate through 0.076 cm polyethylene insulation into solid contact with the other switch electrode. The switch has been used as a series switch in a 20 kV circuit with a current of 1.2×106 A rising in 40 μsec. In a ``crowbar'' application it has carried 40 kA with a 1∕e decay time of 45 msec.

Liquid Helium Cryostat for Resistance Thermometer Calibration

C. R. Duda

Rev. Sci. Instrum. 39, 1484 (1968); http://dx.doi.org/10.1063/1.1683141 (4 pages) | Cited 1 time

Online Publication Date: 10 November 2003

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A cryostat designed primarily for intercomparison of platinum resistance thermometers in the range 10 to 300 K is described. A vented, ``inverted'' Dewar is introduced as a simple means to provide both rapid cool‐down and thermal isolation without the necessity of temporary vacuum seals. Adiabatic conditions are automatically maintained, resulting in a system easily stabilized to within 30 μK∕min throughout the entire range.

Multichannel Electronic Counter Chronograph for Determining Detonation Velocities in Explosives

H. R. Fuehrer and D. L. Emmons

Rev. Sci. Instrum. 39, 1488 (1968); http://dx.doi.org/10.1063/1.1683142 (3 pages)

Online Publication Date: 10 November 2003

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The multichannel time intervalometer (MTI) was designed and fabricated for use in detonation wave measurements. The electronic chronograph was designed to measure short elapsed time events, relative to a start pulse which results from detonation, occurring during relatively long observation periods. The MTI used a quartz crystal as a frequency source and employs high speed transistor components which are capable of providing accurate measurements of detonation velocities. Attaining this capability in a portable unit with its direct read‐out feature enhances the experimenter's ability to study short duration events such as explosive behavior.

High Temperature Debye‐Scherrer X‐Ray Camera

Josef Intrater and Deane K. Smith

Rev. Sci. Instrum. 39, 1491 (1968); http://dx.doi.org/10.1063/1.1683143 (4 pages)

Online Publication Date: 10 November 2003

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A multipurpose, high temperature, Debye‐Scherrer camera has been constructed which has a temperature range from −100 to 1050°C. Temperatures may be controlled to less than 1 C° with gradients essentially nonexistent. Samples are hung vertically to minimize any chance of sagging, and are rotated in a ball bearing guided mechanism. The unit may be operated in high vacuum or in special atmospheres. The film cassette is detachable and self‐positioning. Using the camera fiducial marks, accuracies to 1 part in 5000 are obtainable. The film cassette covers the range from −45°2θ to 135°2θ with the region from −12°2θ to 12°2θ blocked by the beam stop. Exposure times are comparable with standard Debye‐Scherrer cameras. The general construction is relatively simple. Furnace elements are easily replaceable. Water cooling paths are straightforward with all connections between detachable parts of the unit being external. The cover assembly which supports the specimen and its drive mechanism is self‐aligning to assure correct centering of the specimen in the camera.

MOSFET Operation at 4.2 K

Robert R. Green

Rev. Sci. Instrum. 39, 1495 (1968); http://dx.doi.org/10.1063/1.1683144 (3 pages) | Cited 9 times

Online Publication Date: 10 November 2003

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MOSFETS operate at 4.2 K and act as impedance transformers for high impedance (1010Ω) ir detectors. Several types, both n‐channel and p‐channel, have operated successfully at this temperature and withstood the thermal shock of repeated cycling from room temperature. Low device power dissipation and relatively low noise can be achieved by optimizing drain current (ID) and drain‐to‐source voltage (VDS) for the particular device. Power dissipations as low as 0.4 mW have been recognized.

Method of Applying a Modern Potentiometer for Resistance Thermometry

H. L. Daneman and G. C. Mergner

Rev. Sci. Instrum. 39, 1498 (1968); http://dx.doi.org/10.1063/1.1683145 (3 pages) | Cited 1 time

Online Publication Date: 10 November 2003

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In resistance thermometry, a potentiometer can have certain advantages over a resistance bridge. The method described consists of using the ratio of the ``measure'' to the ``standardize'' voltage of a conventional dc precision potentiometer to measure the ratio of a thermometer resistance to a resistor of known value connected in series with the thermometer. By appropriate selection of potentiometer and thermometer currents, potentiometer range, and known resistor, a measurement direct reading in ohms, or Rt∕R0, is obtained. Normal potentiometer measuring procedure is used. Reversal of thermometer current to avoid influence of thermoelectric effects may be included. Tables are provided which indicate temperature resolution achievable by this method at various temperatures and levels of nominal thermometer resistance. Advantages and disadvantages compared with a bridge method are presented and discussed, as are experimental results using the two methods.

Apparatus for Adiabatic Rotation of a Sample in a Magnetic Field at Liquid Helium Temperatures

M. H. Halloran and J. E. Kunzler

Rev. Sci. Instrum. 39, 1501 (1968); http://dx.doi.org/10.1063/1.1683146 (4 pages) | Cited 8 times

Online Publication Date: 10 November 2003

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An apparatus for adiabatic rotation of a sample in a magnetic field at liquid helium temperatures is described. It has been used for the observation of magnetothermal oscillations of metal single crystals as a function of their orientation in a magnetic field. While the sample is being rotated, magnetothermal oscillations as small as 10−6 K were observable; nonsteady (random) heat transfer or heat generation (heat pulses) under favorable conditions was found to be less than 10−5 K (a few milliergs). It appears that the apparatus is useful for a variety of other experiments where it is desirable to change the orientation of a sample in a solenoid either adiabatically or isothermally.
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