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May 1974

Volume 45, Issue 5, pp. 621-718

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A 0.6 T omnidirectional superconducting magnet system

D. K. Wagner

Rev. Sci. Instrum. 45, 621 (1974); http://dx.doi.org/10.1063/1.1686700 (5 pages) | Cited 4 times

Online Publication Date: 11 November 2003

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The design and construction of a superconducting magnet system, producing a maximum magnetic field of 0.6 T with any desired direction, is described. The magnet consists of a pair of Helmholtz coils, which can be rotated about a fixed solenoid. The azimuthal angle of the field is selected manually by rotation of the Helmholtz coils, and the polar angle is selected electronically by adjusting the currents in the Helmholtz coils and solenoid appropriately. The latter is accomplished automatically by means of the associated power supply, which is described in detail. The accuracy of the magnet system is approximately 0.8 mT or ☒% of the field magnitude, whichever is greater. This system has proved to be indispensable for studies of the rf size effect in pure metals at low temperatures. temperatures.

Nonlinear scattering dipole for electromagnetic field measurements in plasmas

Reiner L. Stenzel

Rev. Sci. Instrum. 45, 626 (1974); http://dx.doi.org/10.1063/1.1686701 (5 pages) | Cited 2 times

Online Publication Date: 11 November 2003

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Absolute electric field measurements of a 2 GHz electromagnetic wave in a nonuniform plasma are described. A remote measurement technique with minimum perturbations is used in which the information is obtained at the launching antenna from the backscattered signal of a small movable dipole in the radiation field. The weak scattering signal of the test dipole is discriminated against reflections from metallic walls and the plasma cutoff layer by introducing a small frequency shift (Δω∕ω≃10−3) at the dipole. The dipole contains a passive nonlinear reactive element (varactor diode) which generates multiple sidebands when irradiated with two frequencies. The nonlinear behavior of the sidebands is used to obtain an absolute calibration for the electric field strength at the dipole. Mismatch effects due to the density dependent dipole radiation resistance are minimized by terminating the dipole with a high impedance.

A fast recovery pulsed nuclear magnetic resonance sample probe using a delay line

I. J. Lowe and M. Engelsberg

Rev. Sci. Instrum. 45, 631 (1974); http://dx.doi.org/10.1063/1.1686702 (9 pages) | Cited 37 times

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A sample probe for pulsed nuclear magnetic resonance that replaces the normal resonant circuit by a lumped parameter delay line is described. Theoretical analysis shows that the delay line probe has a signal‐to‐noise ratio and conversion efficiency of power into rotating magnetic field equivalent to a resonant circuit of Q =(2π) (delay time) (Larmor frequency). However, the delay line probe has a much wider bandwidth, much shorter transient decay time, and faster recovery from the rf excitation pulse. Experimental results are included that demonstrate submicrosecond recovery times for the observation of the signal.

Pressure‐resisting glass cell for high pressure, high resolution NMR measurement

Hiroaki Yamada

Rev. Sci. Instrum. 45, 640 (1974); http://dx.doi.org/10.1063/1.1686703 (3 pages) | Cited 36 times

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The technique of using a pressure‐resisting glass cell for high resolution NMR measurement up to 2000 kg∕cm2 has been established. The high pressure NMR experiment is shown to be safely conducted on the ordinary high resolution spectrometer. In this report, detailed illustration of the glass cell is described along with the explanation of the device to transmit the pressure, generated in the standard high pressure equipment, to the glass cell located in the high resolution NMR probe.

Apparatus for neutron diffraction at high pressure

D. B. McWhan, D. Bloch, and G. Parisot

Rev. Sci. Instrum. 45, 643 (1974); http://dx.doi.org/10.1063/1.1686704 (4 pages) | Cited 24 times

Online Publication Date: 11 November 2003

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Powder neutron diffraction data have been obtained on cesium metal above the two transitions at 42.5 and 43 kilobar using a piston cylinder apparatus. A Lucalox cylinder (high density Al2O3) (35.4 mm o.d., 6.35 mm i.d.) is radially supported by compressing two steel plates with a hydraulic ram leaving a neutron window between the plates ∼6 mm high. A 17° included angle was used between the cylinder and support plates. A tungsten carbide piston, driven by a second hydraulic ram, raised the pressure on the sample at three times the rate of increase of the support pressure.

Velocity measurement by self‐tracking correlator

W. R. Tompkins, R. Monti, and M. Intaglietta

Rev. Sci. Instrum. 45, 647 (1974); http://dx.doi.org/10.1063/1.1686705 (3 pages) | Cited 47 times

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A continuously variable time delay correlator was designed for the purpose of measuring velocity. The inverse transit time (velocity) between upstream and downstream detectors is continuously adjusted by a feedback loop which maintains constant the level of cross correlation at two equal intervals from the peak correlation. Variable delay is achieved by changing the clock frequency which controls a digital shift register delay line. The output of the system is linear and identical to that calculated with parallel logic cross correlation computers.

A 400 rad flash x‐ray system for pulse radiolysis

H. Hinsch, H. E. Scheel, and E.‐G. Niemann

Rev. Sci. Instrum. 45, 650 (1974); http://dx.doi.org/10.1063/1.1686706 (3 pages) | Cited 1 time

Online Publication Date: 11 November 2003

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Design and working principle of a flash x‐ray system is described. A two‐stage Marx generator is used, the charging voltage is 150 kV, the stored energy 1125 J. Anode and cathode are arranged coaxially. The anode consists of a tungsten coated aluminium tube of 20 mm i.d. into which the substances to be irradiated are placed. Measurements of electrical and radiation parameters are described. The x‐ray dose per pulse is 400 rad, the half‐width of the pulse is 0.2 μsec and the mean quantum energy 44 keV. An example for the application of the system in microsecond pulse radiolysis is presented.

Pulsed‐discharge infrared OH laser

T. S. Wauchop, H. I. Schiff, and K. H. Welge

Rev. Sci. Instrum. 45, 653 (1974); http://dx.doi.org/10.1063/1.1686707 (3 pages)

Online Publication Date: 11 November 2003

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The laser emission of vibrationally excited OH in the electronic ground state, produced in pulsed electric discharges through O3☒H2 gas mixtures, has been studied using two transverse discharge systems. Discharges were produced in two electrode and multipin transverse configurations. Stimulated emission between the ν = 3→ν = 2 and ν = 2→ν = 1 levels was observed in the 3 μ wavelength region. The output has been investigated as a function of composition and pressure of O3☒H2 mixtures, addition of foreign gases, and discharge energy. Output intensities were compared to that of the HF laser emission produced from H2☒SF6 in the same discharge system. The two discharge configurations gave similar intensities; this OH laser was shown to have approximately 10−2 times the power of the HF† laser.

Design of a fast voltage clamp for biological membranes, using discontinuous feedback

R. Brennecke and B. Lindemann

Rev. Sci. Instrum. 45, 656 (1974); http://dx.doi.org/10.1063/1.1686708 (6 pages) | Cited 16 times

Online Publication Date: 11 November 2003

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The construction of a voltage clamp with discontinuous feedback is described. Its main feature is a pulsed membrane current with an amplitude proportional to the voltage error, which is determined by integration in the pulse intervals. A current pulse of 8 μsec length repeating every 24 μsec is used. Gain switching assures a fast response to large errors, as well as high steady state accuracy. Membrane voltage changes by 150 mV in 8 μsec to 1% of the final value. 50 μsec after such a step, a change of resistive membrane current can be read reliably. Performance is demonstrated with equivalent networks of biological membranes and with applications to black lipid membranes and epithelial membranes.

A photoionization source of monoenergetic electrons

A. C. Gallagher and G. York

Rev. Sci. Instrum. 45, 662 (1974); http://dx.doi.org/10.1063/1.1686709 (7 pages) | Cited 17 times

Online Publication Date: 11 November 2003

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A photoionization source of monoenergetic electrons is described and design criteria for such sources are discussed. The present design produces a beam of ≃10−12–10−13 A by photoionization of a metastable (1D2) barium beam inside the cavity of a He☒Cd laser operating at 3250 Å. The photoelectrons are produced with 17 meV kinetic energy and a calculated energy spread of <1 meV. Energy analysis is provided by measuring the width of the 11.08 eV argon resonance. The observed width of this resonance has, to date, been limited to ∼6 meV, but tests are reported which indicate that this width is largely due to Doppler spreading in the target atomic beam and potential gradients across the collision volume.

A pulsed EPR spectrometer

Martin Huisjen and James S. Hyde

Rev. Sci. Instrum. 45, 669 (1974); http://dx.doi.org/10.1063/1.1686710 (7 pages) | Cited 54 times

Online Publication Date: 11 November 2003

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A pulsed electron paramagnetic resonance spectrometer is described, and applications of the instrument to the determination of longitudinal relaxation times of dilute solutions of free radicals and of spin‐labeled proteins using the saturation‐recovery method are discussed. The spectrometer employs a bimodal cavity; the pumping and observing microwave powers are coherent; and all modulating frequencies, delays, and aperture widths are derived from a master clock. Free‐induction‐decay signals may be observed in such equipment, and special techniques are introduced to avoid interference of these signals with the saturation‐recovery signals.

A Fourier transform spectrophotometer for astronomical applications, 700–10 000 cm−1

Stephen T. Ridgway and R. W. Capps

Rev. Sci. Instrum. 45, 676 (1974); http://dx.doi.org/10.1063/1.1686711 (4 pages) | Cited 3 times

Online Publication Date: 11 November 2003

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An FTS system has been constructed and operated in the range 700–10 000 cm−1. It has been used primarily for the observation of astronomical objects. Detector‐noise‐limited performance has been realized through the entire spectral range, and thermal background compensation has been achieved satisfactorily. Two features are emphasized: (1) the flexibility of the spectrometer in both spectral range and choice of resolution, and (2) the photometric quality.

An apparatus for observing relatively rapid hydrogen‐deuterium exchange in biopolymers

Nobuhiro Suda, Mamoru Nakanishi, and Masamichi Tsuboi

Rev. Sci. Instrum. 45, 680 (1974); http://dx.doi.org/10.1063/1.1686712 (3 pages)

Online Publication Date: 11 November 2003

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A simple apparatus is described for bringing a protein or a nucleic acid molecule abruptly from an H2O medium into a D2O medium and at the same time to introduce the resultant D2O solution rapidly in a sealed cell for an infrared absorption measurement. It has a small Sephadex column and three magnet valves, and biopolymer molecules are forced to pass the column and pushed into the infrared cell with D2O by means of an external pressure of nitrogen gas. By the use of this apparatus an infrared absorption measurement can be started at 10 sec from the ``zero‐time,'' when the biopolymer molecules are brought into contact with the D2O molecules.

An instrument for recording the motions of microorganisms in chemical gradients

Peter Lovely, F. W. Dahlquist, Robert Macnab, and D. E. Koshland

Rev. Sci. Instrum. 45, 683 (1974); http://dx.doi.org/10.1063/1.1686713 (4 pages) | Cited 4 times

Online Publication Date: 11 November 2003

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A relatively simple instrument is described which records the three‐dimensional trajectories of swimming microorganisms. An important feature is the large sample chamber; this permits prolonged tracking in stable, defined gradients of chemotactic stimulants. Data concerning the motility and chemotaxis of the bacterium Salmonella typhimurium are presented.

Doppler‐tuned x‐ray spectrometer

Robert W. Schmieder

Rev. Sci. Instrum. 45, 687 (1974); http://dx.doi.org/10.1063/1.1686714 (15 pages) | Cited 9 times

Online Publication Date: 11 November 2003

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A novel spectrometer designed especially for a fast foil‐excited beam source has been studied and tested. The spectrometer makes use of a large Doppler shift to bring the emission spectrum into coincidence with known features of the absorption spectrum of a suitable filter material. Tuning is accomplished by varying the angle between the beam and the detector, with the filter material between the source foil and the detector. Knowledge of the beam velocity, angle, and the absorption spectrum of the filter is sufficient to determine the emission spectrum from the beam. The resolving power easily exceeds 103 and probably can exceed 105 with some effort, making this spectrometer competitive with conventional crystal diffraction devices. A prototype has been constructed, and tested at the Berkeley HILAC. In the initial experiments, the 21P1 − 11S0 line of heliumlike argon at 3.3 keV, produced by passing a 412 MeV argon beam through a thin carbon foil, was brought into coincidence with the silver LIII absorption edge near 3.4 keV. The expected sudden jump in the count rate when the detector was moved past 58° was observed. This device can be used either for wide range, low resolution scans, or for narrow range, high resolution work, and its range of applicability can be easily extended to higher and lower energies.

Apparatus for fatigue tests in vacuum at low temperatures

V. Bachmann, M. Böhmer, and D. Munz

Rev. Sci. Instrum. 45, 702 (1974); http://dx.doi.org/10.1063/1.1686715 (3 pages) | Cited 1 time

Online Publication Date: 11 November 2003

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Experimental apparatus is described for push‐pull fatigue tests between room temperature and 77 K and in a pressure range between 760 and 5 × 10−8 Torr. The specimen grips are cooled with liquid nitrogen. The variation of the temperature is less than ±2°C in the whole temperature range. To ensure good heat insulation, the loading rod is divided by a system of steel rings interspaced with glass balls. First results with an aluminium alloy are presented.
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A fast opening mechanical shutter system for flash photolysis experiments

S. Yatsiv and J. J. Ewing

Rev. Sci. Instrum. 45, 705 (1974); http://dx.doi.org/10.1063/1.1686716 (2 pages) | Cited 6 times

Online Publication Date: 11 November 2003

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A rotating disk mechanical shutter system has been developed to trigger flash photolysis experiments and prevent scattered light from blinding photomultipliers mounted on a monochromator. Trigger pulses are provided by He∕Ne laser light passing through a pinhole in the disk. The monochromator entrance slit is exposed after a variable delay time by a slot in the disk. The system provides fast slit opening times (a few μsec), μsec jitter in delay times, and very high discrimination against unwanted light (rejecting unwanted signals ∼104 times the desired signal). The system is ideal for flash or laser photolysis experiments which must utilize very weak line sources as kinetic probes.

A gated electron beam technique for Auger electron spectroscopy

B. W. Byrum

Rev. Sci. Instrum. 45, 707 (1974); http://dx.doi.org/10.1063/1.1686717 (2 pages) | Cited 1 time

Online Publication Date: 11 November 2003

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The necessary circuitry to implement recording of useful Auger electron spectra in the minimum practical time is described. The technique minimizes electron beam exposure of the sample, thus minimizing changes of the sample surface which can result from extended exposure to the electron beam.

A simple resistance probe for measurements from 4.2 to 300 K

Michael Mitchell

Rev. Sci. Instrum. 45, 708 (1974); http://dx.doi.org/10.1063/1.1686718 (2 pages) | Cited 2 times

Online Publication Date: 11 November 2003

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A simple apparatus for making resistance measurements from 4.2 to 300 K in liquefied gas storage Dewars is described.

Dielectric loss tangent measurements for elctro‐optic modulator crystals

James Ralph Teague and Robert R. Rice

Rev. Sci. Instrum. 45, 710 (1974); http://dx.doi.org/10.1063/1.1686719 (2 pages) | Cited 1 time

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A new optical test has been devised to measure the dielectric loss tangent for low loss, high dielectric electro‐optic crystals over a wide frequency range. In this method, the loss tangent is calculated from temperature data obtained by optically detecting a laser beam transmitted through the crystal between crossed polarizers while a narrow pulse rf signal is applied to the crystal.

A useful 350 MHz scaler

Alan R. Baldwin and Richard Madey

Rev. Sci. Instrum. 45, 711 (1974); http://dx.doi.org/10.1063/1.1686720 (3 pages)

Online Publication Date: 11 November 2003

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A single decade 350 MHz scaler has been designed and used to extend the pulse rate capability of present scaling instruments. The scaler counts fast negative pulses and has a pulse pair resolution of less than 3 nsec. The complete circuit and operating characteristics are described.

A sapphire to niobium vacuum seal for the temperature range 2–2000 K

Louis Bogart and Ilan Ben‐Zvi

Rev. Sci. Instrum. 45, 713 (1974); http://dx.doi.org/10.1063/1.1686721 (2 pages) | Cited 4 times

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A single step brazing process has been developed for producing vacuum tight seals between sapphire and niobium. These assemblies can be cycled between liquid helium temperatures and 1725° C, and show good stability and low vapor pressure at high temperatures.

A logarithmic time base generator or counter

Walter N. Trump and Lewis Fowler

Rev. Sci. Instrum. 45, 714 (1974); http://dx.doi.org/10.1063/1.1686722 (3 pages) | Cited 5 times

Online Publication Date: 11 November 2003

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A number of output pulses linearly related to the logarithm of elapsed time or of input pulse count is generated by a circuit including two counters and a comparator. A fraction 1∕a of the input pulses is applied to a continuous counter. A second, cycling counter receives all input pulses above a selected starting count, counts to equality with the continuous counter, and resets with production of an output pulse. Repetition of the cycle yields an output pulse series according to the equation ti∕t0=[a∕(a − 1)]i, where t represents time or pulse count depending upon the source of pulses, periodic or aperiodic, and i is the number of output pulses. Conformance to the logarithmic relation log (ti∕t0)=i log [a∕(a − 1)] is within 0.01%−0.1% for reasonably large input counts. This circuit has been applied to generation of a logarithmic time base for direct linear plotting of data from thermal conductivity measurements of liquids by the transient hot‐wire method.

A mercury U‐tube manometer with a high sensitivity throughout the pressure range from 0 to 800 Torr

Isao Yasumoto and Keizo Nagai

Rev. Sci. Instrum. 45, 717 (1974); http://dx.doi.org/10.1063/1.1686723 (2 pages) | Cited 1 time

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A mercury U‐tube manometer applicable to the pressure range from 0 to 800 Torr has been successfully designed. One branch of a 25 mm wide glass U‐tube contains a constant reference height platinum electrode, and the other branch contains a depth micrometer for measuring the variable column length of mercury in the manometer. The sensitivity was experimentally found to be 0.003 mm throughout the pressure range from 0 to 800 Torr under appropriate conditions.
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Erratum: Use of a microchannel plate for ion beam tuning of analytical mass spectrometers

William H. Aberth and Russell R. Sperry

Rev. Sci. Instrum. 45, 718 (1974); http://dx.doi.org/10.1063/1.1686724 (1 page)

Online Publication Date: 11 November 2003

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