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Feb 1974

Volume 45, Issue 2, pp. 151-320

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A new method of Johnson noise thermometry

C. J. Borkowski and T. V. Blalock

Rev. Sci. Instrum. 45, 151 (1974); http://dx.doi.org/10.1063/1.1686578 (12 pages) | Cited 11 times

Online Publication Date: 11 November 2003

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A new method of Johnson noise thermometry was developed and experimentally evaluated. The absolute temperature Ts was determined by measuring the available thermal noise power, i.e., the product of the open‐circuit thermal noise voltage and the short‐circuit thermal noise current generated by a sensing resistor at temperature Ts. The measured thermal noise power from the thermometer is a linear function of absolute temperature. This new method is independent of the sensing‐resistor composition, the mass and nature of the charge carriers, and, in principle, the ohmic value of the resistor. Consequently, the method has a wide range of application, including use in the realization of an absolute thermodynamic temperature scale and especially in the measurement of high temperatures, particularly in nuclear reactors where the properties of sensor materials not only change due to the aging effects induced by the high temperatures but also change drastically because of radiation damage and transmutation. An evaluation of the method was performed with the sensor and signal processor both located in an area of high electrical background noise. The signal cable connecting the sensor to the signal processor was about 0.5 m in length. The deviations of the experimental data were not more than ± 0.10% from a straight line calibration through absolute 0 K in the temperature range ΔT from 725 to 1275 K. In the range ΔT, the maximum error in the indicated temperature for a 100% increase in the value of the sensing resistor at a fixed temperature was ± 0.60% and for a 50% decrease, was −1.00%. The feasibility of separating the thermal noise signal from electrical background noise induced in a long signal cable was demonstrated with the sensor and signal processor connected with a 30 m long coaxial cable. With the extraneous noise power in the cable, more than an order‐of‐magnitude greater than the thermal noise power, the uncertainty in temperature due to the extraneous noise was less than 1% at 100 C.

A time resolved spectrometer for high intensity relativistic electron beams

Jack V. Walker and Jack Stevens

Rev. Sci. Instrum. 45, 163 (1974); http://dx.doi.org/10.1063/1.1686579 (8 pages) | Cited 5 times

Online Publication Date: 11 November 2003

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A spectrometer system designed to measure the time‐dependent kinetic energy of electrons from high current pulsed relativistic beam accelerators is described. The spectrometer, consisting of a three‐element vacuum Compton diode, is simple, rugged, and self‐driving. Calibration data are presented covering the energy range of 150 keV to 16 MeV. Applications and limitations of the spectrometer are discussed.

Model of response of an electric field mill operating during suborbital flight

Thomas P. Sheahen

Rev. Sci. Instrum. 45, 171 (1974); http://dx.doi.org/10.1063/1.1686580 (7 pages) | Cited 4 times

Online Publication Date: 11 November 2003

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A rotating‐vane electric field mill was used to measure the electric field at the base of a series of vehicles as they passed through the ionosphere and reentered the atmosphere. Anticipated rapid and large variations in measured electric fields required a time response of a few milliseconds and a dynamic range from 40 to 50 000 V∕m. These conflicting goals were met by using a bipolar logarithmic amplifier with limited memory. Presented here is a mathematical model of the electronics, which was used to unfold the electric field values from the telemetered outputs. The instruments also met other design constraints and functioned correctly on all flights.

True centroid‐sync used to cancel wander in a spot‐image analyzer

Robert W. Harris

Rev. Sci. Instrum. 45, 178 (1974); http://dx.doi.org/10.1063/1.1686581 (4 pages)

Online Publication Date: 11 November 2003

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A method is described for analyzing the projected focal spot of a light beam spread by propagation through atmospheric turbulence. The degradation in the spot caused by the wander of its centroid is analyzed separately from the average spread of the intensity distribution about the centroid. The technique presented utilizes a unique analog circuit for measuring the time‐centroid of the pulse which represents a one‐dimensional scan of the light spot.

Removable interdigital electrodes for surface wave studies

I. N. Greenberg and F. P. Lipschultz

Rev. Sci. Instrum. 45, 182 (1974); http://dx.doi.org/10.1063/1.1686582 (2 pages)

Online Publication Date: 11 November 2003

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We have fabricated interdigital electrode structures on polished glass plaques. By placing the plaques next to the surface of a piezoelectric material and exciting the electrode of the transmitting plaque with pulsed rf energy of the appropriate frequency, good acoustic surface waves are received at a similar plaque at the opposite end of the sample. The plaque electrodes are fragile but reusable if handled with care.

Theory of a membrane‐voltage clamp with discontinuous feedback through a pulsed current clamp

R. Brennecke and B. Lindemann

Rev. Sci. Instrum. 45, 184 (1974); http://dx.doi.org/10.1063/1.1686583 (5 pages) | Cited 30 times

Online Publication Date: 11 November 2003

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We present a voltage clamp (potentiostat) for biological membranes which works on a new principle. Its feedback loop contains a current clamp which drives a train of brief current pulses through the membrane (typically 8 μsec duration and 8 μsec intervals). In each interval between two current pulses, the difference between membrane voltage and command voltage is sampled and determines the amplitude of the next current pulse. Since the membrane capacitance acts as an analog store between current pulses, the membrane voltage oscillates near the desired value in a triangular waveform. It is independent of resistive voltage drops at electrodes or fluid layers developing in series to the membrane (or the electrode) to be clamped. The clamp does not tend to oscillate, in contrast to clamps with continuous feedback after compensation for series resistors. A precise measurement of membrane capacitance is possible.

A continuous two‐photon‐fluorescence monitor

Richard E. Palmer

Rev. Sci. Instrum. 45, 189 (1974); http://dx.doi.org/10.1063/1.1686584 (2 pages) | Cited 1 time

Online Publication Date: 11 November 2003

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A technique is described in which two‐photon‐fluorescence traces are recorded by means of an image‐intensified vidicon instead of photograph techniques. The traces can be recorded directly at a rate up to 60 Hz for use in aligning a repetitively pulsed mode‐locked Nd+3:YAG laser.

An x‐ray spectral measurement system for nanosecond plasmas

David J. Johnson

Rev. Sci. Instrum. 45, 191 (1974); http://dx.doi.org/10.1063/1.1686585 (4 pages) | Cited 27 times

Online Publication Date: 11 November 2003

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A 15‐channel Ross filter∕silicon diode detection system has been developed for measuring nanosecond pulsed x‐ray spectra in the energy range from 4.5 to 116 keV. The theory and practical aspects of Ross filters and silicon diode detectors are discussed as applied to this system. The data read‐out system consists of a current integrator array, a simultaneous multichannel digital voltmeter, and oscilloscopes. The system is designed for compatibility with a small computer to allow real time spectral measurements. The x‐ray spectrum of a 24 kJ dense plasma focus has been obtained with this system and a theoretical thick target electron beam x‐ray spectrum fit to the experimental data. The best fit is obtained with an E−2 power law electron beam spectrum extending from 5 to 125 keV.

A cloud chamber control system

Donald E. Hagen, Andrew C. Tebelak, and James L. Kassner

Rev. Sci. Instrum. 45, 195 (1974); http://dx.doi.org/10.1063/1.1686586 (3 pages)

Online Publication Date: 11 November 2003

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We describe an analog control system for the temperature control of an expansion cloud chamber. During the expansion, the sample gas and the chamber walls are cooled at the same rate so as to maintain adiabaticity. The control system measures the wall temperature with transistor temperature sensors, calculates the gas temperature from the gas pressure using the adiabatic gas law, and generates a control signal proportional to their difference. The control precision is sufficient to allow the chamber to be used in the study of atmospheric phenomena.

Low natural frequency vibration isolator or seismograph

Paul Lorrain

Rev. Sci. Instrum. 45, 198 (1974); http://dx.doi.org/10.1063/1.1686587 (5 pages) | Cited 4 times

Online Publication Date: 11 November 2003

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This passive vibration isolator, or stable table, attenuates horizontal displacements as well as tilt due to bending of the floor under shifting loads. It has a transmissiblity of 0.1 for horizontal displacements at a frequency that can be as low as 0.1 Hz. Higher frequencies are attenuated as 1∕f2. The stable platform floats on a simple air bearing that rests on a pair of I beams supported on the concrete beams of the building. A weak horizontal restoring force is exerted on the platform by two light vertical springs. The device can also be used as a two‐dimensional seismograph, or as a sensitive tilt meter.

Electronic circuit using charged pins for determining impact planarity in shock wave experiments

E. J. Shuler, W. Mock, and W. H. Holt

Rev. Sci. Instrum. 45, 203 (1974); http://dx.doi.org/10.1063/1.1686588 (4 pages) | Cited 1 time

Online Publication Date: 11 November 2003

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An electronic circuit using charged pins has been designed to permit the accurate determination of the impact planarity (tilt) in shock wave experiments. The tilt circuit generates voltage pulses with risetimes of approximately 3 nsec. The circuit is described and its operation is discussed.

The electron beam fluorescence method as applied to molecular scattering experiments

P. B. Scott, T. R. Mincer, and E. P. Muntz

Rev. Sci. Instrum. 45, 207 (1974); http://dx.doi.org/10.1063/1.1686589 (3 pages) | Cited 4 times

Online Publication Date: 11 November 2003

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A molecular beam system using electron beam excitation to observe the rotational state distribution of incident and scattered beams of nitrogen is described. The incident nitrogen beam is skimmed from a nozzle source and has low translational and rotational temperatures. Cryopumping of the scattering chamber is necessary to maintain a sufficiently low partial pressure of wall scattered nitrogen in the detection region. The electron gun is of special design for attaining (typically) 15 mA at 1200 eV energy in a millimeter diameter beam. Recording instrumentation is of analog type, the signal to noise ratio of a scattered beam is typically of order 40 using a 5 sec integration time constant. The system has been used to infer the anisotropy of nitrogen‐rare gas intermolecular potentials.

A portable laser light‐scattering probe for turbulent diffusion studies

B. T. Yang and R. N. Meroney

Rev. Sci. Instrum. 45, 210 (1974); http://dx.doi.org/10.1063/1.1686590 (6 pages)

Online Publication Date: 11 November 2003

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A new instrument has been devised, based on light scattering principles, to measure real‐time concentration variation in a turbulent flow. Used for turbulent diffusion measurements in a wind tunnel boundary layer, it can also be utilized for other turbulent mixing studies as well. The instantaneous concentration was detected by means of a 5 mW He☒Ne gas laser as a light source, dioctyl phthalate aerosols as tracer particles, fiber optics as the scattered light transmitter, and a photomultiplier as a scattered light sensor. The instrument was designed to be moved to any location in a wind tunnel to measure steady or unsteady diffusion processes.

Interferometric measurement of fully turbulent free convective heat transfer coefficients

W. Z. Black and Jack K. Norris

Rev. Sci. Instrum. 45, 216 (1974); http://dx.doi.org/10.1063/1.1686591 (3 pages) | Cited 4 times

Online Publication Date: 11 November 2003

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A Mach‐Zehnder interferometer provides information about the local temperature surrounding a heated body. When using this type of interferometer, the measurement of turbulent heat transfer coefficients is often difficult to achieve, and as a result most interferometric studies of heat transfer rates have been limited to laminar flow. A differential interferometer, on the other hand, provides a measure of the temperature gradient and this type of interferometer produces fringe patterns that are an excellent means of observing the flow structure within a turbulent free convection boundary layer. Parallel fringe patterns can easily be converted to local heat transfer coefficients. Heat transfer coefficients measured in air above an isothermal inclined flat plate are presented. These are in excellent agreement with previously published results.

Stability of fringe counting interferometers

John W. Edgerton and Kenneth L. Andrew

Rev. Sci. Instrum. 45, 219 (1974); http://dx.doi.org/10.1063/1.1686592 (4 pages) | Cited 1 time

Online Publication Date: 11 November 2003

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Two configurations of an automatic bidirectional, fringe‐counting corner‐cube interferometer are compared. They differ only in the method of quadrature phase introduction. The one using polarization coding has good phase stability at optical path differences as large as 955 mm, the one using adjacent beams has such poor phase stability as to render it useless at path differences greater than 700 mm. A useful well‐defined alignment procedure is given for the corner‐cube interferometer.

An experimental technique for monitoring dynamic cracks

R. E. Lavengood, D. Peretz, F. L. Brissey, and E. M. Wu

Rev. Sci. Instrum. 45, 223 (1974); http://dx.doi.org/10.1063/1.1686593 (3 pages) | Cited 1 time

Online Publication Date: 11 November 2003

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A technique is presented which, by means of plating and etching processes, permits the creation of a wide variety of crack propagation gauges. High precision gauges of arbitrary size and shape are easily prepared. Specific gauge configurations are shown for center notch, edge notch, and cleavage type specimens. Optimum‐gauge design is discussed and typical readout circuits are shown.

Measurement of totally depleted silicon solid state detector thickness by x‐ray attenuation

Frederick A. Hanser and Bach Sellers

Rev. Sci. Instrum. 45, 226 (1974); http://dx.doi.org/10.1063/1.1686594 (6 pages) | Cited 1 time

Online Publication Date: 11 November 2003

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A method for measuring the thickness of silicon detectors by x‐ray transmission is described. The method has been calibrated by using silicon disks of known thickness. Use of a 10 keV fluorescent Ge K x‐ray source excited by a 10 mCi 238Pu source can give 1% accuracy from 50 to 700 μ Si, including a correction for an assumed, or independently measured, thickness of the front Au layer. With 14.4 keV nuclear γ rays from 400 μ Ci of 57Co 1% accuracy can be obtained from 200 to almost 1500 μ Si. With the two x‐ray measurements both the Si and the Au layer thicknesses can be measured. The method has been used to make an accurate thickness measurement of a nominally 100 μ Si detector which was used to make stopping power measurements for heavy (z > 1) ions in Si.

Effect of rf field inhomogeneities on spin‐echo measurements

T. E. Bull

Rev. Sci. Instrum. 45, 232 (1974); http://dx.doi.org/10.1063/1.1686595 (11 pages) | Cited 17 times

Online Publication Date: 11 November 2003

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The effect of radio frequency inhomogeneities on nuclear magnetic transverse relaxation time (T2) measurements has been investigated experimentally and numerically. Measurements using the Meiboom‐Gill modification to the Carr‐Purcell sequence have been emphasized; however, some other methods have been considered. The calculations have been performed assuming that the magnetization obeys (a) the Bloch equations and (b) the modified Bloch equations. In case (a) the errors resulting from rf field inhomogeneities were found to be small to moderate, and a method is presented whereby the upper limits to these errors can be determined experimentally. Furthermore, the errors are decreased considerably in a homogeneous main magnetic field adjusted to resonance and go to zero when T1 = T2. In case (b) the errors were considerably larger than in case (a) and the presence of a homogeneous main magnetic field did not necessarily decrease these errors. Even quite small rf field inhomogeneities were found to produce significant errors in the exchange times, chemical shift differences, and activation parameters derived from the transverse relaxation times.

Production of pulsed magnetic fields with a flat pulse top of 440 k0e and 1 msec duration

G. Dworschak, F. Haberey, P. Hildebrand, E. Kneller, and D. Schreiber

Rev. Sci. Instrum. 45, 243 (1974); http://dx.doi.org/10.1063/1.1686596 (7 pages) | Cited 6 times

Online Publication Date: 11 November 2003

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A capacitance discharge unit for the production of pulsed magnetic fields up to 440 k0e is described. The pulse formed by a passive network has a field plateau of approximately 1 msec duration for a half‐period of ∼ 3.5 msec and a field ripple of Δ H∕H ≤ 1%. The unit occupies approximately 10 m2, the total weight is 600 kg. It can be produced at low cost.

A frequency modulator coupled to an electron multiplier

T. Muranaka and M. Kanayama

Rev. Sci. Instrum. 45, 250 (1974); http://dx.doi.org/10.1063/1.1686597 (2 pages)

Online Publication Date: 11 November 2003

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A frequency modulator coupled to an electron multiplier has been developed to extract and measure the output current which is small, floating at high voltage, and contains various frequencies starting from dc. The measurable input current range is from 1 × 10−9 to 3 × 10−7A and the cutoff frequency is about 2 kHz when using a 1 mΩ resistor for converting input current to voltage.

Instrumentation for direct microscopic elemental analysis of frozen biological tissue

Thos. E. Hutchinson, Marvin Bacaner, John Broadhurst, and John Lilley

Rev. Sci. Instrum. 45, 252 (1974); http://dx.doi.org/10.1063/1.1686598 (4 pages) | Cited 13 times

Online Publication Date: 11 November 2003

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A system has been devised to provide direct observation of frozen biological tissue in the scanning electron microscope. Both transmission and secondary electron methods of signal collection have been obtained. In combination with energy elective fluorescent x‐ray analysis, the elemental constituents of subcellular regions less than 1000 Å in diameter have been analyzed in the transmission mode of operation. Transmission scanning electron micrographs of frozen muscle shows significant microstructural differences with conventionally obtained electron micrographs although dark bands, possibly corresponding to z zones of classically observed spacing, are seen.

An anaerobic stopped‐flow spectrophotometer

D. Michael, D. O'Donnell, and N. H. Rees

Rev. Sci. Instrum. 45, 256 (1974); http://dx.doi.org/10.1063/1.1686599 (5 pages) | Cited 6 times

Online Publication Date: 11 November 2003

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A reliable, all‐glass, stopped‐flow apparatus is described in which extremely air‐sensitive reactions can be studied under anaerobic conditions; it is also suitable for studying reactions involving oxygen in solution. The equipment can be used over the temperature range − 100 to + 100 °C.

Circular plotter and kinoform lens

Yoshiki Ichioka

Rev. Sci. Instrum. 45, 261 (1974); http://dx.doi.org/10.1063/1.1686600 (3 pages) | Cited 1 time

Online Publication Date: 11 November 2003

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A kinoform is an optical device that shapes the phase of a wavefront in any arbitrary manner. For making a kinoform, one first has to plot a black‐grey‐white pattern that is then photographed and bleached. Bleaching is a process that converts a photographic amplitude distribution into a corresponding phase distribution. Often a kinoform has circular symmetry, then called a ``kinoform lens.'' We describe a plotter that can provide a circular pattern suitable for kinoform lenses. Our circular plotter is easy to assemble from simple commercial components. We show two results: a Fresnel lens, and an aspherical corrector plate.

An apparatus for the simultaneous measurement of reflectance, absorbtance, and transmittance

William H. Thomason and James D. Macomber

Rev. Sci. Instrum. 45, 264 (1974); http://dx.doi.org/10.1063/1.1686601 (6 pages)

Online Publication Date: 11 November 2003

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A simple apparatus for the accurate measurement of the angular dependence of the reflectance, absorbtance, and transmittance of objects illuminated by a cw laser is described. Beam profiles and divergences can also rapidly be determined.

A work‐accelerated electron beam gun for optical measurements on molten zones

Gunther Rötzer

Rev. Sci. Instrum. 45, 270 (1974); http://dx.doi.org/10.1063/1.1686602 (4 pages) | Cited 2 times

Online Publication Date: 11 November 2003

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An electrostatically operated electron gun of the shielded filament type is described which embraces the advantages of no need of cooling the gun, relatively high collimation, and complete visibility of the zone of the sample which is heated by the gun.
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