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Dec 1969

Volume 40, Issue 12, pp. 1531-1652

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Measurement of Large Angle Atomic Scattering Using Axially Symmetric Magnetic Fields

T. O. Bush, O. Heinz, G. W. Rodeback, and C. J. Cook

Rev. Sci. Instrum. 40, 1531 (1969); http://dx.doi.org/10.1063/1.1683855 (11 pages) | Cited 1 time

Online Publication Date: 10 November 2003

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A technique using the focusing properties of a nonuniform axially symmetric magnetic field to study large angle (θ>32°, lab) scattering of ions from atoms and molecules is described. The scattering cell is placed on the magnetic axis at the position of maximum field and ions in the momentum interval ∣Δp∣ at ∣p∣ scattered into a conical shell Δθ at θ are counted by a detector placed down along the axis in a region of low field. The solid angle is increased by a factor of several hundred over conventional scattering techniques of comparable angular resolution due to the azimuthal symmetry of the apparatus. The magnetic vector potential and the trajectory equation for a charged particle in this type of inhomogeneous, axially symmetric field are derived. As a preliminary test the known differential scattering cross section for He+ on the He was measured from 40 to 52° (lab) at 300 eV. Results of measurements of the absolute differential scattering cross sections for Li+ on He from 36 to 41.7° at 200 and 300 eV, corresponding to CM scattering angles of 90 to 160°, are presented.

Spectroscopic Method for Simultaneous Determination of Species Concentration and Temperature in a Cyclic Combustion Process

D. S. Smith and E. S. Starkman

Rev. Sci. Instrum. 40, 1541 (1969); http://dx.doi.org/10.1063/1.1683857 (4 pages) | Cited 2 times

Online Publication Date: 10 November 2003

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An optical method for the simultaneous determination of species concentration and temperature in a high pressure transient combustion and expansion process is described. The experimental system utilizes a mechanically chopped (2000 Hz) external radiation signal to perturb the self‐emission signal from the combustion gas of an internal combustion engine. Distinguishing between the emission and absorption signals simultaneously provides a capability for determination of species concentration by absorption and of optical temperature by an emission‐absorption technique.

Spherical Multipole Magnets for Plasma Research

M. Sadowski

Rev. Sci. Instrum. 40, 1545 (1969); http://dx.doi.org/10.1063/1.1683858 (5 pages) | Cited 8 times

Online Publication Date: 10 November 2003

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Spherical multipole (SM) magnetic fields are used for plasma containment. Such magnetic fields are produced by magnetic dipoles symmetrically placed on the sides and the edges of regular polyhedrons. In the paper, field configuration of the high order SM systems is considered and some basic problems regarding the design of SM electromagnets are discussed. Relations are given relating magnetic field, power input, current‐ and temperature‐ time characteristics. The construction and operation of the ``Kaktus'' magnet are also described.

Continuous Resistive Surface Deflection Unit

C. E. Catchpole and D. H. Ceckowski

Rev. Sci. Instrum. 40, 1549 (1969); http://dx.doi.org/10.1063/1.1683859 (3 pages)

Online Publication Date: 10 November 2003

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The operation of an assembly using a uniform resistive surface to provide deflection of an electron beam is discussed. Essentially, the assembly consists of electroded plates of doped lead glass fused together and fired in hydrogen to produce the continuous resistive surface. Results indicate that when this assembly is employed in an image dissector tube, a 30° deflection can be obtained on either side of the central axis. The assembly was also operated with a vidicon gun and a test pattern was reproduced with very little distortion.

A Low Pressure Ionization Gauge

D. L. Swingler

Rev. Sci. Instrum. 40, 1552 (1969); http://dx.doi.org/10.1063/1.1683860 (3 pages) | Cited 1 time

Online Publication Date: 10 November 2003

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An ionization gauge is described which uses an ion gun designed for end extraction. An out‐of‐sight ion collector is used to extend the x‐ray limit normally present in simpler structures. The gauge head has a sensitivity of 60 Torr−1 without a secondary suppressor electrode or 20 Torr−1 with a secondary suppressor. The gauge head is not difficult to make, uses a simple power supply, and does not require any focusing adjustment. Ion trajectories, plotted by a digital computer, are used to give an insight into the efficient operation of the structure.

Gas Fed Multichannel Hollow Cathode Arcs

J. L. Delcroix, H. Minoo, and A. R. Trindade

Rev. Sci. Instrum. 40, 1555 (1969); http://dx.doi.org/10.1063/1.1683861 (8 pages) | Cited 3 times

Online Publication Date: 10 November 2003

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A new type of gas fed hollow cathode (multichannel cathode) has been studied. Such cathodes operate with a lower voltage drop and higher maximum current density than conventional one‐channel cathodes and have a longer lifetime as well. Moreover, multichannel cathodes allow operation within a wide range of discharge currents and with extremely low gas flow rates. A theoretical analysis clarifies the principles of the operation of this type of cathode. The experimental results are explained and some general rules are presented for the cathode design.

Low Temperature Thermal Conductivity of Several Greases

M. M. Kreitman

Rev. Sci. Instrum. 40, 1562 (1969); http://dx.doi.org/10.1063/1.1683862 (4 pages) | Cited 7 times

Online Publication Date: 10 November 2003

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The temperature dependence of the thermal conductivity of silicone vacuum grease, Cry‐Con grease (a copper loaded electrically insulating grease), and Eccotherm TC‐4 (a specially formulated paste based on silicones and fillers) has been measured at liquid helium temperatures. It is concluded that the (thermal) greases examined have thermal conductivities in bulk corresponding approximately to those of thermal insulators. The successful use of thermal bonding greases to effect heat transfer at liquid helium temperatures and below requires very thin layers of the greases, in order to avoid the deleterious effect of their poor thermal conductivity in bulk.

Design and Analysis of a High Intensity Fast Oxygen Atom Source

David R. Miller and Dan F. Patch

Rev. Sci. Instrum. 40, 1566 (1969); http://dx.doi.org/10.1063/1.1683863 (4 pages) | Cited 23 times

Online Publication Date: 10 November 2003

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A mixture of 5% O2 in He has been used in a rf discharge at pressures from 15 to 70 Torr to produce a free jet source of a high intensity energetic beam of atomic oxygen. Intensities of 1017 atoms∕sec∕sr are predicted and energies of 0.33 eV have been measured. A time‐of‐flight analysis of the beam properties is presented and indicates that the source temperature is near 620 K.

A Laser Earth Strain Meter

Jon Berger and R. H. Lovberg

Rev. Sci. Instrum. 40, 1569 (1969); http://dx.doi.org/10.1063/1.1683864 (7 pages) | Cited 7 times

Online Publication Date: 10 November 2003

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A laser interferometer for the study of earth strain is described. Changes in the length of an 800 m arm are measured by counting fringes in the interference pattern with a least count of 4×10−10. The output is linear and has a flat response from dc to 1 MHz and a dynamic range of 106. The laser wavelength is controlled by reference to a passive optic resonator contained in a stable environment. The wavelength stability is a few parts in 1010 for periods up to a laser lifetime (∼3000 h).

A New Type of Surface Ionization Detector

J. Politiek and J. Los

Rev. Sci. Instrum. 40, 1576 (1969); http://dx.doi.org/10.1063/1.1683865 (4 pages) | Cited 10 times

Online Publication Date: 10 November 2003

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The ionization coefficient of a potassium atom impinging on a hot Pt‐8% W wire is independent of its energy below 3 eV (3850 m∕sec) and dependent on it above 3 eV. This is due to the fact that a high energy atom can reflect from the wire without being ionized. By using a tungsten cylinder as an ionizer and a niobium wire in the middle of it as a collector, incident atoms which are not ionized can be prevented from leaving the cylinder without being detected because subsequent collisions with the wall will take place and result in ionization. By means of this type of standard detector, which has a multiplication factor of about 30, the reflection coefficient of a potassium atom incident on a Pt‐8% W wire is determined as a function of its velocity. For a potassium atom with an energy of 23.6 eV (10 800 m∕sec) this reflection coefficient is about 16.5%.

Calorimeter for Simultaneous Measurements of Stored Energy and Resistance

E. A. Ryan and J. J. Jackson

Rev. Sci. Instrum. 40, 1580 (1969); http://dx.doi.org/10.1063/1.1683867 (5 pages) | Cited 3 times

Online Publication Date: 10 November 2003

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An adiabatic calorimeter using digital data acquisition and programmed heating for measurement of stored energy in the range 350–1000 K is described. In addition to combining the advantages inherent in digital acquisition systems with the advantages of an adiabatic calorimeter, samples were heated by Joule heating permitting (1) simultaneous measurement of stored energy and resistance and (2) calibration of the system including losses. This arrangement, when applied to measure the stored energy and resistance associated with defects introduced in samples by quenching, plastic deformation, or radiation damage, has sufficient sensitivity not only to measure the total stored energy but also to yield a spectrum of the energy release as a function of temperature. Calibration data indicated that energy release rates as small as 10 μW could be measured. Measured losses which were nearly independent of temperature totaled approximately 5.5 μW. Resistance measurements were reproducible to better than 10 parts in 10.6

Writing Speed Determination of Sweeping Image Cameras Using a Photomultiplier Tube Calibrator

S. P. Marsh

Rev. Sci. Instrum. 40, 1584 (1969); http://dx.doi.org/10.1063/1.1683868 (2 pages) | Cited 1 time

Online Publication Date: 10 November 2003

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A photomultiplier tube was used to detect light from an image sweeping over slits distributed across the image plane of the camera. The time interval between photomultiplier signals was measured using a Tektronix 545 oscilloscope. The resulting writing speed was determined with an error of less than 0.15% and showed a sec2θ variation over the image plane.

Quasilog Scaler

Richard Weissman

Rev. Sci. Instrum. 40, 1586 (1969); http://dx.doi.org/10.1063/1.1683869 (5 pages)

Online Publication Date: 10 November 2003

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Data systems using information from long scaler chains often do not require the full resolution obtained by reading out the lower order bits of the chain when the accumulated count is large. However, if the count is small the lower order bits must be used. To reduce the total number of bits needed for a required resolution, a logarithmic readout can be used. The brute force logic to provide logarithmic readout would be cumbersome, particularly for aerospace application. A reduced logic system following a set of generalized equations to provide quasilogarithmic readout of any conventional binary scaler is described, which permits extremely simple circuitry with size, weight, and power requirements suitable for aerospace and similar applications. An example is shown of a complete circuit using a 20‐stage scaler with five‐bit logarithmic readout.

Microwave Helices in Electron Spin Resonance Studies at High Pressure or Very Stable Temperatures

William Z. Plachy and Tjeerd J. Schaafsma

Rev. Sci. Instrum. 40, 1590 (1969); http://dx.doi.org/10.1063/1.1683870 (5 pages) | Cited 4 times

Online Publication Date: 10 November 2003

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Special purpose ESR systems which make use of helical slow wave devices are described. One such system can be used to study liquids at pressures in excess of those employed in ordinary cavity systems. An ESR cell with temperature fluctuations and gradients of less than 10−3°C is also described.

A Recording Detection System for Quantitation of Electron Microscope Image Contrast Using a Retractable Micro‐Faraday Cage Probe

H. M. Johnson, G. G. Hausner, and D. F. Parsons

Rev. Sci. Instrum. 40, 1594 (1969); http://dx.doi.org/10.1063/1.1683871 (3 pages) | Cited 5 times

Online Publication Date: 10 November 2003

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A recording electrometer system is described based on a retractable micro‐Faraday cage probe mounted in the beam stop port of a Siemens Elmiskop IA electron microscope. A vibrating reed electrometer is used to measure the current collected by the probe. Intensity data at different points in the image are collected by moving the image over the fixed probe by manipulation of the specimen stage controls. The total system has a noise less than 3×10−15 A, a 10 sec full scale response time, and provides immediately observable image intensity data which can be converted into contrast.

A Reliable Flashlamp Pumped Tunable Organic Dye Laser

A. Goldstein and F. H. Dacol

Rev. Sci. Instrum. 40, 1597 (1969); http://dx.doi.org/10.1063/1.1683872 (2 pages) | Cited 5 times

Online Publication Date: 10 November 2003

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An improved flashlamp pumped dye laser is described. Reliable long term operation has been attained by using a low inductance capacitor bank. A linewidth of 0.3 Å and a beam divergence of 2.5×10−3 rad result from more uniform optical pumping in the flashlamp. Tuning ranges of several organic dyes are presented.

Flash Calorimeter for Measuring Triplet Yields

James B. Callis, Martin Gouterman, and J. D. S. Danielson

Rev. Sci. Instrum. 40, 1599 (1969); http://dx.doi.org/10.1063/1.1683873 (7 pages) | Cited 22 times

Online Publication Date: 10 November 2003

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A fast, sensitive differential calorimeter is described which permits the observation of heating caused by the relaxation of the lowest triplet states of organic molecules formed by flash excitation. From the ratio of slow to total heating after flash excitation, we calculate Φt, the quantum yield of triplet formation. The detection of the small amounts of heat involved (∼10−5 cal) is accomplished by means of a capacitor microphone transducer which measures volume changes caused by the heating. The response time (∼100 μsec) is determined by the lowest cavity resonance of the sample cell. At room temperature we find for anthrance in ethanol Φt=0.66, while for acridine orange in glyerol Φt=0.23.

An On‐Line Data Recording System

W. Krag, N. Daggett, R. N. Davis, and F. Perkins

Rev. Sci. Instrum. 40, 1606 (1969); http://dx.doi.org/10.1063/1.1683874 (4 pages)

Online Publication Date: 10 November 2003

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A relatively simple system for recording experimental data from an optical spectrometer has been built and operated. The data are transmitted by telephone at a maximum rate of about four points∕sec to a central computing facility where they are recorded on magnetic tape. Several simultaneous users can be accepted. A brief description of the interface between the experiment and the computing facility is presented.

The Effect of Variable Fluid Properties on the Sensitivity of MHD Flowmeters

William J. Thomson and Gordon R. Bopp

Rev. Sci. Instrum. 40, 1609 (1969); http://dx.doi.org/10.1063/1.1683875 (5 pages)

Online Publication Date: 10 November 2003

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For ducts operated as MHD flowmeters, it is demonstrated that the sensitivities are substantially affected by variable fluid viscosity and electrical conductivity. The analysis considers a mathematical model based on fully developed laminar MHD flows with constant heat flux boundary conditions. By considering the pertinent equations in dimensionless form and assuming a power law dependency of the fluid properties on temperature, flowmeter sensitivities are calculated as functions of the Hartmann number, duct aspect ratio, and the magnitude of the property variations. It is shown that, even for small property variations, the flowmeter sensitivities deviate significantly from constant property values. For larger variations, they can be as much as 60% below ideality for heated walls and 30% above for cooled walls.

New Two‐Point Calibration Method for Platinum Resistance Thermometers for the Range 75–400 K

J. P. Pratt and D. C. Ailion

Rev. Sci. Instrum. 40, 1614 (1969); http://dx.doi.org/10.1063/1.1683876 (3 pages) | Cited 1 time

Online Publication Date: 10 November 2003

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In this paper we describe a new method for calibrating high quality platinum resistance thermometers to ±0.01°C over the temperature range 75–400 K. This method requires resistance measurements at only two temperatures (liquid nitrogen and the ice point) in contrast to other methods which require measurements at four temperatures. The method is based on the invariance of Cragoe's Z‐functions (resistance ratios) with respect to different high quality platinum thermometers. In addition our method uses the new International Practical Temperature Scale of 1968 (IPT‐68). We checked our calibration at two intermediate temperatures (liquid oxygen and the fusion point of mercury) and measured deviations of less than ±0.01°C from our calibration.

A Live Time Controlled Scanning Rate for a Whole Body Counter

M. E. Sveum and P. E. Bramson

Rev. Sci. Instrum. 40, 1616 (1969); http://dx.doi.org/10.1063/1.1683877 (2 pages)

Online Publication Date: 10 November 2003

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Scanning whole body counters tend to sacrifice sensitivity and introduce measurement error through the use of constant drive rate mechanisms which do not readily compensate for changes in electronic deadtime. An electronic drive rate control has been developed at Battelle‐Northwest Laboratory which largely eliminates this problem. The control automatically adjusts the relative drive rate to correspond to multichannel analyzer live time and is easily programmed for subject height and count duration. Digital circuitry, utilizing integrated circuits, controls the speed of a heavy duty stepping motor by controlling the motor stepping frequency. A scanning whole body counter utilizing the typical constant drive rate tends to underestimate the body or organ burden of a subject whose deposition caused abnormally high analyzer deadtime. A counter utilizing the live time control will spend proportionally more real scanning time over an area of high deposition, resulting in a desired amount of ``scanning live time'' for which the counter calibrations apply.

Plasma Parameter Slide Rule

D. R. Nordlund and O. P. Breaux

Rev. Sci. Instrum. 40, 1618 (1969); http://dx.doi.org/10.1063/1.1683878 (5 pages) | Cited 1 time

Online Publication Date: 10 November 2003

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A slide rule has been developed to facilitate rapid calculation of basic plasma parameters such as electron number density, Debye length, and the number of particles in a Debye sphere. These parameters can be readily calculated within an accuracy of 1.5% for most practical situations involving the application of plasma probes. In addition the slide rule can be used to determine whether Coulomb collisions preclude application of collisionless probe theory in plasma diagnostics.

A Floating Microcompass for Measuring Millioersted Magnetic Fields in Millimeter‐Cube Sampling Volumes

G. E. Helmke and E. O. Schultz‐DuBois

Rev. Sci. Instrum. 40, 1622 (1969); http://dx.doi.org/10.1063/1.1683879 (4 pages)

Online Publication Date: 10 November 2003

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A magnetic compass is described which permits the measurement of small magnetic fields with relatively high accuracy and in sample volumes of small linear dimensions. In a particular model, 300 mOe were measured with better than ±2% accuracy and at a distance of less than 1 mm from the source of the magnetic field. Novel features in this compass are its reduced size and the liquid suspension. By the action of surface tension, the magnetic needle floats on the rotationally symmetric meniscus of a water surface in a capillary. The suspension offers centering, damping of motion, and elimination of static friction. The paper gives design view points and technology, discusses the measurement method and error sources, and presents examples of measurements.

A Narrow Band Far Infrared Interferometer for Electron Density Measurements

Merrill L. Andrews and Sanborn C. Brown

Rev. Sci. Instrum. 40, 1626 (1969); http://dx.doi.org/10.1063/1.1683880 (5 pages)

Online Publication Date: 10 November 2003

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An interferometer has been constructed with reflection optics and lamellar gratings to operate in the wavelength range of 175–400 μ. The gratings serve not only as beam splitters and recombiners but also as filters to separate out a narrow band of radiation. In this way a simple wide band Hg arc lamp can be used as the source. Because of the required response time for afterglow plasmas, a Putley detector measures the radiation. An application of the interferometer has been made to measure electron densities in repetitively pulsed plasma with λ = 200 μ and a time response of 3 μsec. The electron line density sensitivity is 3×1013 cm−2 and line densities have been measured up to 1015 cm−2, still substantially below the instrumental limit.

Degradation of Laser Optical Surfaces

T. L. Barber

Rev. Sci. Instrum. 40, 1630 (1969); http://dx.doi.org/10.1063/1.1683881 (2 pages) | Cited 2 times

Online Publication Date: 10 November 2003

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Problems of optical surface degradation became apparent while measurements were being made with a laser. After examination, it was concluded that the defects fell into two categories—those caused by atmospheric dust, and those resulting from the effects of cleaning solvents. A procedure is described which minimizes both of these problems.
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