bluuebunny/crossref_metadata_2025 huggingface dataset:
100 kHz Homodyne, 35 GHz Reflection-Cavity Spectrometer with Phase-Lock of the Reference Signal and Low Frequency Field Modulation
Authors: Praddaude H. C.
Published: February 2005

A 35 GHz, reflection-cavity type microwave spectrometer is described. We use a 35 GHz ferrite modulator in the signal arm to produce a double sideband (±100 kHz) suppressed carrier signal to reduce the 1/f microwave crystal noise. Solid metal cavities and low frequency modulation of the externally applied magnetic field are used to reduce leakage from the cavity, thereby reducing susceptibility to microphonics and allowing more freedom in the choice of cavity modes suitable for a wide variety of experiments with metallic or dielectric samples. This instrument employs a 35 GHz ferrite phase shifter to phase lock the microwave signal in the reference arm of the bridge for observation of absorption signals An analogous scheme for phase-locking at dispersion signals is also suggested. A narrow passband, low noise, active filter, with a Q factor of approximately 106, is used as part of a feedback loop around the 100 kHz receiver. This minimizes the possibility of saturation of the receiver due to less than critical coupling to the microwave cavity. Practical advantages of the present unit in low temperature spectroscopy, particularly with regard to helium bubbling and helium level change, are stressed. Comparative sensitivity tests of this unit with the standard 200 Hz magnetic field modulation systems show that, at cavity power levels smaller than 5 mW, a factor of ten improvement can be attained. At higher microwave power levels the improvement available is hampered by microphonics in the bridge. The theoretical analysis of the microwave bridge operation, of various key components, and of the electronic system is presented in the text and in the appendices.
Contactless Measurement of Resistivity of Slices of Semiconductor Materials
Authors: Miyamoto Nobuo , Nishizawa Jun-Ichi
Published: February 2005

In this resistivity measurement, a pair of semicircular measuring electrodes is connected to a series or parallel resonance circuit composed of an inductance L and a variable capacitance C. A sample is coupled capacitively with the electrode with no direct contact. The authors' method is similar to the Q meter method in principle, but uses a comparative measurement. Some analyses of this method and the experimental results are reported: (1) the measurable range of resistivity is limited by an electrode structure and a frequency, (2) the resistivity measurement over a range as wide as 0.3 to 1500 Ω-cm can be carried out by using both the series and the parallel resonance circuits, (3) for a thin sample below 3 mm in thickness, the resistivity can be measured by using a calibration, (4) the influence of different surface treatments is not seen if the surface remains flat.
Properties of Gold-Chromium Alloy Pressure Gauges
Authors: Davis Lance A. , Gordon Robert B.
Published: February 2005

The pressure and temperature dependence of the electrical resistance of the alloy Au+2.1% Cr have been measured. After low temperature heat treatment, the resistance of this alloy passes through a minimum as a function of temperature. As pressure is increased, the temperature at which the resistance minimum occurs becomes progressively higher. Metallographic study shows that a necessary condition for the occurrence of this resistance minimum is the formation of a finely dispersed second phase. As a material for electrical resistance pressure gauges, the gold-chromium alloy is characterized by low temperature sensitivity, absence of shift of the zero-pressure resistance, and nearly linear and reasonably large pressure response. However, it also displays hysteresis during pressure cycling and a tendency for the pressure calibration to drift.
Measurement of Radiant Energy Emitted by Xenon Flashlamps
Authors: Aslin H. K.
Published: February 2005

Two types of radiometer were used to measure the radiant energy produced by high energy helical xenon flashlamps operating in the pulse mode. Metal cylinders plated with platinum black are accurate to 2%, but can be used only at low incident energy and power. Graphite slugs are less accurate because of uncertainties in the reflectivity of graphite, but are more durable, and have been used successfully at incident radiant energy of 126 J/cm2 and peak power of 50×103 W/cm2.
Measurement of Dielectric Constant and Loss Factor of Powder Materials in the Microwave Region
Authors: Conger Norman L. , Tung Shao E.
Published: February 2005

A system has been developed to measure the dielectric properties of powder materials using X band microwave frequencies. The measurement is conducted in a microwave cavity oscillating in the TM012 mode and resonant at 9.4kMc. Relatively small amounts of material are needed, and samples are introduced into the cavity using a quartz tube. The limitation of the perturbation theory as a basis for computation is examined experimentally. The suitability of different equations correlating the apparent dielectric constant of the powder material with the intrinsic values of the solid (crystalline or fused solids) is demonstrated by the data.
Goniometer Assembly for NQR Zeeman Studies
Authors: Peterson G. E. , Bridenbaugh P. M.
Published: February 2005

The study of Zeeman splitting of NQR lines in single crystals at times provides information about the nature of certain chemical bonds. Such analyses require a goniometer to orient the crystal with respect to the magnetic field. The description of a goniometer which is easily constructed and is sufficiently accurate for many studies is given.
Two Directional Beam Convergence by Sector Shaped Uniform Magnetic Field
Authors: Ezoe Hirohiko
Published: February 2005

In order to increase the ion transmission in a mass spectrometer, an ion optical system which renders the output ion beam from a magnet parallel to the median plane is proposed, and its general design formulae and processes are presented. The characteristics and the merits of the present system over the conventional two directional beam focusing arrangement are discussed and some numerical examples are given.
Ion Tracer Anemometer for the Measurement of Low Density Air Flow
Authors: Lilienfeld Pedro , Solon Leonard R. , DiGiovanni Hugo J.
Published: February 2005

A density independent anemometer for use at altitudes between 20 and 50 km has been developed and successfully operated on an air sampling research balloon flight. Its operation is based on the pulsed generation of ions within the air stream and their subsequent detection at a measured distance. Closed loop retriggering of the electric discharge results in a pulse train whose frequency varies directly with the air velocity. Semiconductor circuitry is used throughout, including an automatic discharge restarting circuit. Designed for monitoring velocities between 5 and 50 m/sec, the instrument range can be conveniently extended in both directions by suitable repositioning of the anemometer probes.
New Experimental Method for Perturbation Measurements in Cavity Resonators
Authors: Veyron B. , Voisin G.
Published: February 2005

We present a new experimental equipment for field strength measurements in low Q cavity resonators by means of the perturbation method. The main part of this equipment is an admittance meter which enables us to perform both amplitude and direction measurements by an extremum method.
Nanosecond Fluorimeter
Authors: Hundley Lee , Coburn Tim , Garwin Edward , Stryer Lubert
Published: February 2005

A nanosecond fluorimeter suitable for measuring the emission kinetics of chromophores which have excited state lifetimes longer than 1 nsec is described in this paper. The acquisition and processing of the nanosecond data were accomplished in entirety by computers. The pulsed light source, an oxygen spark-gap lamp operated in a relaxation mode, is simple to construct and use. The lamp exhibits high intensity over a broad spectral range, as well as a short pulse duration. In the wavelength interval from 230 to about 470 mμ, there were 6×1011 photons per pulse at a repetition rate of 2.1 kHz. The spectrum of the lamp was approximately flat between 200 and 600 mμ. The rise and fall times of the light pulse, as measured with a planar photodiode, were 0.7 and 1.1 nsec. The accompanying current pulse had rise and fall times shorter than 0.43 nsec. A 1P21 photomultiplier tube was used as the detector in the fluorimeter. The output of the 1P21 was connected to a sampling oscilloscope that was triggered by a synchronous current pulse from the light source. The analog output of the sampling oscilloscope was digitized, stored, and averaged on a LINC computer, and then transferred to magnetic tape for processing on an IBM 7090. The nanosecond data were analyzed in terms of a convolution integral which took into account the shape of the exciting light pulse as seen by the detection system. The use of the apparatus is illustrated by two examples: 1, 4-bis-2- (4-methyl-5-phenyloxazolyl) benzene, which has a lifetime of 1.5 nsec; and 1-anilino-8-naphthalene sulfonate bound to serum albumin, which has a lifetime of 17.1 nsec.
Production of Monodisperse Sprays
Authors: Dabora E. K.
Published: February 2005

A technique for producing monodisperse sprays is described. The technique makes use of Rayleigh's criterion for the breakup of capillary jets by mechanically vibrating a number of uniform size capillary needles arranged in parallel. It was used to produce sprays in the size range of 290–950 μ, but in principle there is no reason why this range cannot be extended. The regime of spray sizes where drop coalescence is likely to take place is delineated, and methods of minimizing coalescence are described.
Pulsed, High Intensity Source of Soft X Rays
Authors: Beckner Everet H.
Published: February 2005

A description is given of the techniques and apparatus employed to generate a high density keV plasma capable of serving as an intense source of soft x rays. The spectral distributions of the emission spectra have been analyzed and details of the analysis are presented. The distributions are characteristic of 5–10 keV optically thin plasma continua with line radiation superimposed. Source intensities of from 0.1 to 5 MW are readily produced, lasting for a few tenths μsec; these intensities are a strong function of the material used for discharge tube electrodes, varying as Z4 for Z≤30. Finally, cursory experiments were conducted to examine the feasibility of filtering these spectra to obtain a monochromatic radiation source.
Bearing Cage Follower-Platform for Bearing Studies
Authors: Staph Horace E. , Munsch George F.
Published: February 2005

A separately driven shaft was located facing an operating test bearing, with the centerlines of the shaft and the bearing collinear. The shaft speed was synchronized with that of the bearing cage. Thus lead wires from cage-mounted transducers could be brought to signal telemetering systems for remote readout. The shaft speed synchronization with the cage was obtained by reflecting light signals off the cage side wall onto three photocells, which signals were amplified to provide 3-phase power to drive the shaft motor. The system is described in detail. An example of the system used to measure inner race and cage temperatures of a ball bearing at speeds to 15 000 rpm is given.
Measurement of the Mechanical Properties of Solids at High Pressure
Authors: Gordon Robert B. , Mike Leslie F.
Published: February 2005

Apparatus for making precision measurements of the stress-strain curves of solids under high pressure has been developed. Constant deformation rate is obtained by use of an electric motor drive system operating within the pressure vessel. Forces are measured with a resistance strain gauge load cell also within the vessel. The equipment may be adapted for making compression or tension tests, stress relaxation and creep experiments, microhardness measurements, and observations of internal friction in solids under true hydrostatic pressure.
New Conical Camera for Single-Crystal Orientation by Means of X Rays
Authors: Arguello C.
Published: February 2005

This paper describes a modification of the back reflection Laue camera in which the film is placed on a conical surface, thereby providing a direct stereographic projection of the crystal without the use of nets or the measurement of angles. A larger number of reflections is also obtained for this camera as compared with the flat camera. A quantitative discussion of the geometry of the diffraction patterns obtainable with this camera is presented.
AC Superconducting Solenoid for Kilogauss Field Modulation
Authors: Kurtin Stephen , Foner Simon , McNiff Edward J.
Published: February 2005

The design of an ac superconducting solenoid capable of producing oscillatory magnetic fields having peak-to-peak amplitudes as large as 1000 G at frequencies up to 500 Hz with only moderate dissipation is discussed. It is shown that a simple, inefficient coil geometry (thin solenoid) is suitable. Tests with an ac superconducting solenoid used as a modulation coil in a 60 kG superconducting magnet are described. Results indicate that the performance of copper at 4.2°K is far surpassed by Nb-25% Zr over a wide range of operating conditions.
Small Magnetic Impact Forming Device
Authors: Harrison Ernest , Derbyshire Stephen W.
Published: February 2005

The design of a small, electromagnetically driven impact apparatus is described. The unit was designed as a laboratory unit to compact small samples of powdered materials to high density. A capacitor bank energy source is discharged into a solenoid coil. The resulting field is used to accelerate a plunger which impacts on the punch and die assembly containing the material to be compacted.
Wide Line NMR Induction and Bridge Spectrometer for the Frequency Range 2–90 MHz
Authors: Torgeson D. R.
Published: February 2005

A wide band, variable frequency nuclear magnetic resonance spectrometer is described for use with either a crossed-coil induction probe in the frequency range 2 to 40 MHz or a parallel T rf bridge from 2 to 90 MHz. A novel use of simple rf circuits is described wherein the receiver amplifier has useful gain to 95 MHz and the transmitter amplifier has useful gain to 45 MHz. A simple modification of the Varian Associates 8 to 16 MHz induction probe for use with this circuit to 40 MHz is described. Sensitivity of the instrument with both the probe and bridge compares most favorably with a commercial induction spectrometer. The circuit is essentially free of microphonic noise.
Highly Efficient, Inexpensive, Medium Current Ion Source
Authors: Hirsch Robert L. , Meeks Gene A.
Published: February 2005

A newly designed ion source has provided deuterium ion currents up to 10 mA at input powers of about 100 W. The device utilizes a diffuse, filament-excited dc discharge produced in the 10−3 Torr pressure region and incorporates an ion extractor as a part of the plasma chamber. The extractor and discharge chamber exit aperture form a converging lens that shapes the ions into a small diameter beam, which exits the chamber through a small orifice in the extractor. The combination of low operating pressure and small diameter exit orifice results in low neutral gas leakage. Simplicity of design and operation renders the unit relatively inexpensive to build and maintain. Because the discharge is diffuse, it can be readily scaled up or down in size and modified for the extraction of a variety of beam shapes.
Simple Bridge for Pulsed Nuclear Magnetic Resonance
Authors: Jeffrey K. R. , Armstrong R. L.
Published: February 2005

An asymmetrical rf bridge for pulsed magnetic resonance experiments is described. The balancing adjustments, which can be made quickly and easily, ensure a proper impedance match to transmitter and receiver. The bridge is particularly well suited for pure nuclear quadrupole resonance experiments.
Transistorized Current Stabilizer for X-Ray Tubes with Directly Heated Cathodes
Authors: Yee Kenneth W. , Deslattes Richard D.
Published: February 2005

An instrument is described which stabilizes the emission current in x-ray tubes with directly heated cathodes. Transistors are used in the amplifier and loading circuits. Emission currents from 20 to 1000 mA are maintained constant to within 0.1% for periods of at least a half hour.
15N Target for Electron Scattering
Authors: Dally E. B. , Croissiaux M.
Published: February 2005

A 15N target system has been made for high energy electron scattering. The target material was ammonia 15NH3 liquefied by dry ice. The target windows were closed with very thin stainless steel foils.
Laser-Excitation of the Raman Spectra of Molten Salts
Authors: Clarke J. H. R. , Solomons C. , Balasubrahmanyam K.
Published: February 2005

An apparatus is described for determining the Raman spectra of molten salts at temperatures up to ca. 1000°C, using a focused laser beam. The sample volume is 5 ml or less; a technique is described for filtering melts immediately before the spectral measurements. To demonstrate the performance of the apparatus, spectra were obtained for carbon tetrachloride (25°C), molten sodium nitrate (350°C), molten mercuric bromide (270°C), and molten sodium sulfate (900°C). Intensely red-colored molten mercuric iodide was also characterized (it exhibits one polarized Raman band at 146 Δcm−1). For these tests, 6943 Å exciting radiation from a pulsed ruby laser was employed, but the apparatus can in principle be used with other lasers of different frequency. Comparison with spectra obtained using conventional mercury arc excitation shows that the laser compares favorably in the time needed to record spectra, and that spectra are more readily obtainable from high temperature melts and colored systems.
Variable Temperature EPR Cryostat Cavity
Authors: Weil J. A. , Schindler P. , Wright P. M.
Published: February 2005

An EPR cavity for operation at temperatures ranging from 20°K to room temperature is described. Sample cooling is achieved with a ``Cryo-Tip'' Joule-Thomson refrigeration system. The cavity can be used with a standard Varian V-4500 spectrometer.
Apparatus for Guarded Polarization Measurements
Authors: Vest Robert W. , Graham Henry C.
Published: February 2005

A circuit is presented for making guarded polarization measurements in situ on samples which vary from 10 to 108 Ω over the temperature range of the experiment. The time dependence of the voltage at constant current (or the current at constant voltage) can be followed from less than 1 msec to several days. Combined leakage resistance 105 times smaller than the sample resistance results in less than 1% error in the measurements. The circuit should prove generally useful whenever automatic guarding is required over a wide frequency range (including dc).
Improved Displays for Measuring Power Spectra of Complex Nonstationary Signals
Authors: Kenney J. F. , Deaton T. K. , Miller J. E.
Published: February 2005

In scientific research it is frequently desirable to make an accurate measurement of the power spectrum of a complicated time-varying signal. The performance of a Sona-Graph audio spectrum analyzer can be upgraded for this purpose by changing the output format from a carbon-deposited paper that is burned by an electric arc to an oscilloscope and camera system. The time resolution is improved, and direct amplitude measurements are now possible. The utility of the system is demonstrated by analysis of samples of VLF and ULF emissions. The technique can be used in many fields of scientific research, such as geophysics, oceanography, biology, medicine, and acoustics.
Feedback Control Theory for Constant-Temperature Hot-Wire Anemometers
Authors: Freymuth Peter
Published: February 2005

A feedback control theory for constant-temperature hot-wire anemometers is developed in the form of a linear differential equation of the third order. This theory allows a more detailed and clearer description of the anemometer's behavior than can be obtained by the frequency response method which has been applied until now to constant-temperature hot-wire anemometers. The theory is presented for the case of an equal arm bridge in the feedback system. Although the theory is restricted to small velocity fluctuations, it is assumed that large fluctuations may be measured correctly within approximately the same frequency range as small ones. The theory is applied to the optimization of the frequency response of constant-temperature hot-wire anemometers by means of a square wave test.
Superconducting Homogeneous InTl and PbBi Films Evaporated from a Single Source
Authors: Kopf L.
Published: February 2005

Techniques are described for the evaporation of homogeneous alloy films from a single source. InTl, a substance whose components have very different vapor pressures, and PbBi, whose components have more similar vapor pressures, were successfully deposited as thin films by these techniques. Comparisons of superconducting transition temperatures with published data confirm that the films are indeed homogeneous.
Multicrossover Cryotron—a High Gain Single Stage Amplifier
Authors: Newhouse V. L. , Mundy J. L , Joynson R. E. , Meiklejohn W. H.
Published: February 2005

Present high gain cryotron amplifiers use dc biased cascaded crossed film cryotrons, and cannot be operated below 1 kHz because of low frequency noise. It is shown that in situations where minimum input inductance is not required, a much simpler circuit, using a crossed film cryotron with many crossovers, can be used as a single stage high gain amplifier. It is found that, if gate bias is applied in the form of pulses, helium bubble formation, which is the cause of low frequency noise, is inhibited. Also the chopping action of the gate pulse allows the amplification of dc signals. The multicrossover cryotrons described have 512 crossovers and exhibit bandwidths of 1 MHz and transimpedances of up to 10 mV/mA. It has been possible to explain their nonmonotonic gain-temperature dependence in terms of penetration depth and thermal propagation effects.
Periodic Integrating Device for Measurement of Rapidly Varying Count Rates
Authors: Kukla Cassimer M.
Published: February 2005

A device for the measurement of rapidly varying counting rates is described. The input signals, which need not be of constant size or shape, are converted into pulses of constant width and constant current. The pulses are applied to an integrating capacitor where, at the end of an integral period, the voltage of integration is sampled and stored. The sample is in storage for an integral period and is displayed on a chart recorder, while the integrator is accumulating counts for the next sample. With this method the recorder is required only to indicate the number of counts per period. The device has been used in conjunction with a conventional scintillation counter, a radio-active tracer, and a chart recorder to obtain an instantaneous and permanent record of blood flow patterns in the heart.
Bidirectional Detector of Ultrasonic Particle Motion in Solids
Authors: Robinson Donald J.
Published: February 2005

A compact bidirectional detector of ultrasonic particle motion in solids has been developed and used in connection with a three-dimensional seismic model study. It comprises a matched pair of bimorph crystals and sum and differencing circuits to separate vertical and horizontal motions. The ability of the apparatus to display motion trajectories similar to those predicted by theory is demonstrated.
Single Axis, Two Crystal X-Ray Instrument
Authors: Deslattes Richard D.
Published: February 2005

Design features of a two crystal instrument capable of measurements of diffraction angles to an accuracy of the order of 0.1″ are presented. The instrument is of simple geometry, employs a stable and massive chassis, and derives its precision from components of general availability. Diffraction angles are generated in 1° increments by a precise indexing mechanism and interpolated by means of a sine arm driven by a micrometer.
Low-Temperature Liquid-Vapor Deformation Calorimeter
Authors: Wolfenden A. , Appleton A. S.
Published: February 2005

A single-step calorimeter has been constructed and developed to measure the energy relations involved in the deformation of metals in tension at low temperatures. The instrument has been used to measure the energy stored during the deformation of copper and aluminum single crystals as a function of strain and orientation at 78°K. The results have been analysed with respect to errors and reproducibility and compared with data from previous investigations.
Fiber Optics in Field Ion Microscopy
Authors: Hren J. J. , Newman R. W.
Published: February 2005

A fiber optic window has been fitted to a stainless steel field ion microscope permitting the use of direct contact photography for recording the image. The elimination of intermediate optics coupled with the use of large format sheet film results in shorter exposure times and increased quality of the field ion micrograph. The fiber optic window itself is briefly described along with some experimental results.
Cosmic Rays as a High-Energy Particle Source
Authors: Cowan E. W. , Moe M. K.
Published: February 2005

A large cloud-chamber-ion-chamber stack has been designed and operated to measure the properties of the interactions in light materials of cosmic-ray protons and pions in the energy range greater than 140 GeV. The usable flux of these particles at sea level is limited to the measured value of (1.3±0.1)×10−4 m−2 ster−1 sec−1 by the requirement that each particle be unaccompanied by time-coincident particles in the aperture of the apparatus of 0.22 m2- ster. With the use of this flux and the apparatus described, an interaction cross section for protons in carbon can be measured for energies up to 300 GeV in about a year. In the use of the ionization spectrometer, large fluctuations in the absorption curve have been observed that preclude the use of the shape of the curve alone to measure the energy of individual events.
Magnetic Steering Device for Electron Coincidence Experiments
Authors: Watson R. L. , Rasmussen J. O. , Bowman H. R. , Thompson S. G.
Published: February 2005

The highly convergent fringing field produced by a 100 kVA C-magnet has been used to guide electrons emitted at a source around a 90° arc to a Si(Li) detector. This source-detector configuration is often desirable because it enables the electron detector to be effectively shielded from other radiations emitted at the source. The electron motion in this device consists of a superposition of a trochoidal motion and a vertical oscillation through the magnet symmetry plane. The high detection efficiency of the system (∼5%) makes it particularly well suited for applications in electron coincidence experiments. Utilization of the device in a study of internal conversion in coincidence with fission is described, and several other applications are suggested.
Photographically Rectifying Weissenberg Films
Authors: Greenberg Berton
Published: February 2005

A photographic device for converting x-ray Weissenberg photographs into undistorted representations of the reciprocal lattice is described in detail.
Calibration and Differential Field Measurement of High Magnetic Fields by Means of a Periodic Size Effect in Gallium
Authors: Foner S. , McNiff E. J.
Published: February 2005

The periodic size effect in pure single crystal gallium plates is applied to high field calibration and particularly to accurate differential measurements of high magnetic fields. A simple rf probe is described which is used to measure the characteristics of the size effect and to demonstrate the applicability of the method to such measurements up to about 100 kG to an accuracy of at least 1%. By combining aluminum powder and Mylar tape as markers in the rf probe, NMR calibration of the unit can be made during a single field sweep. The rf probe is small and readily adapted to a wide variety of field geometries. In addition to a brief description of the probe, the characteristics of the periodic size effect in gallium are summarized and the rf and dc dependence of the oscillatory amplitude of the periodic size effect are also discussed.
Retardation Lens Used to Improve the Abundance Sensitivity of a Mass Spectrometer
Authors: Freeman N. J. , Daly N. R. , Powell R. E.
Published: February 2005

A retardation lens has been placed between the resolving slit and the ion detector in a mass spectrometer. It has been used to reject ions that have lost significant energy by collision with residual gas atoms in the system. Several types of lens have been investigated. A considerable increase in the abundance sensitivity on both the high and low mass side of a peak results from the use of this device.
Automatic Acceleration and Speed Control for an Analytic Ultracentrifuge
Authors: Windsor Alfred A. , Rich Thomas H. , Doyle Robert E. , Lindgren Frank T.
Published: February 2005

A complete profile of automatic acceleration for an analytic ultracentrifuge is established with an electronic speed control system. Motor current is controlled by a Sola (resonant transformer) resonant current source during acceleration and when the rotor reaches full speed the Sola saturates, forming a constant voltage regulator. As full speed is approached, a closed loop system is introduced which compares the frequency of a magnetic-geartooth counter to a reference circuit and then applies the error as voltage increments to the drive motor. To evaluate performance, a computer program was developed to compare manual control with the automated system. Results indicate greater accuracy in the automated system for the integrated ω2dt during the acceleration phase of ultracentrifuge operation, and extremely stable and accurate control of final speed (to within 10 ppm or less).
Thermal Transport Across Superconducting Solder Joints Near 0.1°K
Authors: Steyert William A.
Published: February 2005

Heat transfer rates across various types of soft solder joints are investigated between 0.06 and 0.5°K using a 3He−4He dilution refrigerator. For Cd-Bi junctions and thin (10 μ) Sn-Pb junctions, the heat flux per unit area and unit temperature difference is 4.7×106 T2.74 erg/sec. This rate is about twice that predicted by the theory of Little. Junctions of Sn-Pb and Sn-In about 40 μ thick have a much lower conductance. The thermal conductivity of bulk Sn-Pb solder is found to be 9900 T2.31 erg/sec-cm-°K.
Micropenetrometer for the Characterization of Polymer Surfaces
Authors: Cuthrell R. E. , Greulich F. A. , Lynch A. W.
Published: February 2005

A micropenetrometer was constructed using a linear variable differential transformer mounted on a balance arm. Surface contours obtained with this instrument indicate the size of surface irregularities and deviations from planarity. The sizes of colloidal particles in the micron range were determined for a thermosetting epoxy polymer.
Resistance Heated Sublimator
Authors: Warren K. A. , Denison D. R. , Bills D. G.
Published: February 2005

The design and performance of a large area, low voltage device for controllably subliming metals or nonmetals at temperatures up to 1400°C is described. The sublimator consists of a BeO ceramic core internally heated by six resistive elements connected in parallel to eliminate hot spot and instability problems. The material to be sublimed is affixed to the core as a split tube, sheet, strip, wire, or powder slurry and is heated uniformly by thermal conduction. Problems of heat flow, thermal runaway, and high temperature chemical reactivity of adjacent sublimator elements are considered together with solutions obtained. Performance data are presented for a titanium sublimation application in which sublimation rates of 6.8×10−7 g/sec at 450 W increasing to 8.3×10−5 g/sec at 950 W were obtained. Usable lifetimes in excess of 30 000 h of continuous operation are possible.
Faraday Effect Hysteresigraph
Authors: Beck J. W.
Published: February 2005

The optical Faraday effect hysteresigraph is an instrument for measuring the static thermomagneto-optic properties of thin transparent magnetic film samples. Via an oscilloscope, it displays 60 Hz magnetic hysteresis loops of the samples over a temperature range of 20°C±40°, with peak magnetic fields of 2600 Oe. Its use of thermoelectric elements results in a compact package, highly effective for rapid change and accurate control of sample temperature.
Series Expansions for the Solid Angle Subtended by a Circular Disk at a Point Directly Above the Periphery
Authors: Grosjean C. C.
Published: February 2005

It is the purpose of this paper to establish a new series development representing the solid angle subtended by a circular disk at a point situated directly above and in the immediate vicinity of the periphery. After having recalled Masket's series expansion which is applicable only for distances larger than the diameter of the disk, a few initial terms of the new series expansion are deduced starting from an integral representation of the solid angle and applying some formulas from the theory of Legendre's complete elliptic integrals. In this way, it is shown that the series must contain logarithmic terms besides integer powers of the distance variable. Then, after having transformed the problem under study into an equivalent problem of electrostatics, the complete infinite series representation of the solid angle is deduced from its expression as a Fourier integral by applying a new expansion theorem to the latter. The paper ends with an interesting verification of the obtained result.
SPECS, a Versatile Space-Qualified Detector of Charged Particles
Authors: O'Brien B. J. , Abney F. , Burch J. , Harrison R. , LaQuey R. , Winiecki T.
Published: February 2005

A versatile instrument code named SPECS (for Switched Proton Electron Channeltron Spectrometer) has been developed for measurement of charged particles in space. Particles entering the device pass between a pair of deflection plates across which is established a voltage Vi. Particles of a given charge and different energies are then deflected into a set of five channeltron devices located on one side of the deflection plates, while particles of the opposite polarity but comparable energies are deflected into a funneltron located on the opposite side of the plates. Thus, electrons and protons are detected simultaneously in a total of six differential energy intervals. The voltage Vi is then changed over six steps: ±35 V, ±350 V, and ±3500 V. In this way electrons are measured over an energy range of about 50 electron volts (eV) to about 100 000 eV. Protons are measured over the same energy range, with the lowest detectable energy set by the intrinsic channeltron efficiency of detection of positive ions at some hundreds of electronvolts. The thirty-six energy channels can be measured in an adjustable cycle time as short as 1 sec. Stepping can be internally or externally synchronized. Different versions of the device have been built for numerous rocket and satellite applications, with weight between 900 and 1600 g, and power less than 1.5 W. Five small units have been flown to date on Javelin rockets, and the larger will be put into orbit in the satellites code-named Owls 1 and 2 and Aurora 1, while another set will be deployed by the astronauts on the lunar surface. The scientific advantages and flexibility of the units are described.
Measurement of Thomson Heat in Metallic Systems
Authors: Maxwell G. M. , Lloyd J. N. , Keller D. V.
Published: February 2005

The fundamental concepts of the Thomson heat and the basic equations governing the heat flows associated with its generation are presented. From these considerations, two different approaches to the direct measurement of the Thomson coefficient are demonstrated. The methods include a nonequilibrium technique in which the measurements are based on the initial temperature changes associated with the application of a potential gradient to a metal specimen in a thermal gradient and a technique in which the equilibrium temperature difference associated with the reversal of current flow form the basis for the calculation of the Thomson coefficient. The latter case leads to a very simple equation relating the Thomson coefficient to the change in equilibrium temperature associated with reversal of current flow. A simple calorimeter was designed and utilized to test the validity of the analysis and to compare these results with the electric current variation technique which was reported previously. The Thomson coefficients for nickel were observed as −32 ±12% μV/deg (40.1°C); −40.0±5% μV/deg (20°C) and −58.0±2% μV/deg (10°C). Those for lead were observed as −0.36±11% (41.0°C) and −0.31±3% (20°C).
Interference Accelerometer
Authors: Bruce C. F.
Published: February 2005

A simple form of accelerometer using interference fringes of a Fabry-Perot system is described, in which accelerations as small as 10−5 msec−2 (10−6 g) can be measured. The variations in the light flux transmitted by the vibration-sensitive interferometer due to relative plate displacements as small as 0.25 nm (10−8 in.) are photodetected and finally displayed as a waveform on an oscilloscope. A frequency analyzer in the detection system enables any chosen harmonic component to be studied and measured. The unit can be calibrated readily in terms of the wavelength of light during measurement for any given frequency. The unit has been used to measure low vibration levels in laboratory rooms where the amplitude and frequency range of the main disturbances usually were in the ranges 0–0.05 μ (0–2 μin.) and 0–50 Hz, respectively.
Technique for Absolute Temperature Measurements at Microwave Frequencies
Authors: Haroules George G. , Brown Wilfred E.
Published: February 2005

Measurement of the absolute temperature of microwave noise sources under field conditions is usually achieved at the expense of tedious rf attenuation measurements and the incorporation of cryogenic equipment in the measurement system. Measurement accuracy is determined by the precision to which the effects of passive rf attenuation are known. The technique described does not require this knowledge of the effects of rf attenuation on instrument calibration. The feasibility of this technique has been established by tests performed with a modified Dicke radiometer. The technique establishes the radiometer indicator output zero as a direct reading of absolute zero and provides calibration of the indicator scale directly in degrees Kelvin. Laboratory calibration of an appropriately modified radiometer and measurement of noise temperature near absolute zero are discussed.
Window Seals for Ultrahigh Vacuum Use
Authors: Roberts R. W. , Harrod J. F. , Poran H. A.
Published: February 2005

Sealing techniques are described for joining windows of lithium fluoride, magnesium oxide, and quartz to Pyrex glass, FN glass, quartz, and silver. These seals withstand repeated bakeouts at 300–350°C and can be used in ultrahigh vacuum systems.
Apparatus to Determine Excess Molar Volumes. Application to the H2-N2 Mixture
Authors: Mastinu G.
Published: February 2005

An apparatus for measuring excess volumes of dissolved gases in liquids at low temperature, for pressures below 100 atm and for concentrations about 1%, is described. The apparatus has been tested measuring the excess volume for A-N2 and H2-N2 systems.
Electron Emissive Surface Electric Field Meter
Authors: Ogawa Howard S. , Sellen J. M. , Cole Robert K.
Published: February 2005

The performance of a surface electric field strength meter, utilizing a broad unfocused beam of electrons, has been evaluated analytically and experimentally. The meter is capable of measuring E fields up to 100 V/cm and possesses a sensitivity of ∼0.1 V/cm in the field regime near E=0. The meter response to time varying electric fields is limited by the finite transit time (<10−7 sec) of the electrons from the source to the detector plates. Simple formulae for the errors introduced in the measurement of time dependent electric fields by finite transit time effects and by displacement currents are presented and indicate errors of ∼0.1 V/cm for E fields rising at 106 V/cm sec. Sensitivity of the meter to magnetic field perturbations along three mutually perpendicular directions has been evaluated. The meter response has been examined in a plasma flow simulating spacecraft through the ionosphere.
Wide-Range Multi-Input Pulse Height Recording System
Authors: Humphreys Russ
Published: February 2005

This paper describes a system which can photographically record with one dual-beam oscilloscope the amplitudes of 10 simultaneous photomultiplier pulses over a four-decade dynamic range with an accuracy of ±1.5% over the entire range. The signal processing time is 2.2 μsec. The basic circuit is a logarithmic pulse-height-to-time converter with two triggering levels, requiring twelve transistors per input channel. The dynamic range of the device could be easily extended to six decades, and the two-level technique can be applied to digitized recording systems and pulse height analyzers. The circuit has been found to meet the above specifications over a temperature range from −19 to +38°C.
Langmuir Probe for the Measurement of Electron Density and Electron Temperature in the Ionosphere
Authors: Prakash Satya , Subbaraya B. H.
Published: February 2005

A Langmuir probe system has been developed for measurement of electron densities and electron temperatures in the lower ionosphere. While the probe works like the Smith probe, it has various practical advantages. It is an all electron system working on a single floating power supply. This makes the actual system simpler and allows for more thorough prelaunch checkouts while the rocket is on the launch pad. Further, this system can feed an additional guard electrode without the use of any additional electronics. It has greatly helped in reducing the current leakage and the effect of the distributed capacity at the input of the amplifier. Also the sweep used is such that capacitive discharge currents between the sensor and the rest of the system do not appear in that part of the sweep where retarding potential analysis is done for determination of electron temperature. Within this system it is possible to control the sensor voltage with the output of the amplifier and keep it at space potential. In principle this method can be used to determine both the electron density and electron temperature simultaneously and continuously.
Small Particle Sizing Using Turbidimetric Layered Sedimentation
Authors: Schleusener Stuart A. , Read Alvin A.
Published: February 2005

Application of turbidimetry to layered sedimentation for use in small particle sizing is investigated both theoretically and experimentally. The cavity of a 6328 Å He-Ne gas laser is used to detect the low light losses experienced during layered sedimentation tests.
Photodiode Holder with 300 psec Rise Time for Laser Studies
Authors: Lubin M. J. , Leising W.
Published: February 2005

A simple photodiode holder design is presented which exhibits less than 300 psec risetime response utilizing an ITT FW-114A photodiode.
Design of a Sonic Pressure Gauge
Authors: Noiseux Denis U. , Maidanik Gideon
Published: February 2005

The design of a gauge capable of measuring gas pressures in the range from atmospheric pressure to 10−4 mm Hg by acoustic techniques is presented. The principles of acoustic transmission in the classical and geometrical relaxation regimes of gas dynamics are reviewed for the case of a confined volume of gas. The geometrical conditions for the feasibility of a sonic pressure gauge following a linear law are obtained. Practical limitations in the sound source used give rise to a change in the sensitivity of the gauge in the transition from classical to geometrical relaxation regime. Transducer and electronic design and a calibration curve of the gauge are given. The experimental results are in general agreement with the analysis.
Silicon-Controlled Rectifier Circuitry for Producing Pulsed Magnetic Fields
Authors: Rothwarf F. , Bateman C. O. , Ford D. , Milke P.
Published: February 2005

A switching circuit using a high powr silicon-controlled rectifier to discharge a high energy (5 kJ), low voltage (450 V) capacitor bank into pulse coils immersed in liquid helium is described. A free-wheeling diode assures that the pulses remain unidirectional. The circuit has successfully operated with inductance-resistance-capacitance (LRC) combinations yielding pulses having rise times τR and decay times τD in the ranges 0.80 msec ≤τR≤0.25 sec and 2.2 msec ≤τD≤1.2 sec, respectively. Another SCR is used to shunt unwanted capacitor energy to an auxiliary circuit at any desired time during the pulse duration. This function is used to protect the pulse coils from overheating and to conserve liquid helium. The use of special, fixed-geometry copper coils is described which enables one to obtain initial rates of change of the applied magnetic field Ḣ0 which varied over many orders of magnitude (102<Ḣ0<108 Oe/sec). The circuit, while generally useful in most solid-state studies requiring pulsed-magnetic fields, was used to study flux-jumping, rate effects, and critical currents in tubes and wires made of type II superconducting materials. Some of these experiments are described.
Characteristics of Traveling Wave Helices in ESR Spectrometers
Authors: Pearlman Michael Reisman , Webb Robert H.
Published: February 2005

Design criteria for construction of helices for microwave spectrometers are discussed with particular attention to large magnetic fields required for double resonance work. Some coil-to-guide matching techniques are evaluated with regard to efficiency, sensitivity, and simplicity. Techniques of coil and match evaluation are discussed in detail.
Simulation of Nucleonic Cascades as a Means of Studying Fluctuations
Authors: Linsley John
Published: February 2005

A method is described for generating electrical signals with waveform analogous to the longitudinal distribution of particles in fluctuating nucleonic cascades. Measurements carried out on the signals are equivalent to Monte Carlo calculations for the cascades. Results are applicable in the study of cosmic ray air showers. Signal fluctuations arise from fluctuations in quantities that represent atmospheric level and inelasticity of the dominant nucleon—nucleus interactions.
High Sensitivity Compression Fixture
Authors: Lautenschlager E. P. , Adsit N. R.
Published: February 2005

An apparatus to measure compression loads accurately in a controlled atmosphere is described. The design places the load cell inside the test chamber. The apparatus has been used for testing materials up to 1200°C.
Magnetic Slit
Authors: Brechna H. , Cobb J.
Published: February 2005

A magnetic slit for momentum definition and beam separation is described. The 2.5-m magnetic slit was designed and built at the Stanford Linear Accelerator Center to be used in combination with a pulsed bending magnet to guide a 20-GeV/c electron beam with a dispersion of 3% to three experimental areas.
Sensitive Linear Flowing-Stream Photometer for Amino Acid Analyzers
Authors: Hamilton Paul B.
Published: February 2005

A sensitive flowing-stream photometer, [based on the photometric analyzer of Glasser, Kanzler, and Troy, Rev. Sci. Instr. 33, 1062 (1962)], with linear output suitable for monitoring the effluent from ion exchange columns after reaction with ninhydrin in the chromatographic analysis of amino acids, is described. Because of the linear output the analog display, in absorbance units, is printed on even grid paper on the strip chart recorder. The range is from 0 to 1.5 absorbance; at 2.5 absorbance the departure from linearity is 2.2%. The absorbance of the reaction stream at 4400 and 5700 Å is determined. At 5700 Å a split beam arrangement allows two levels of sensitivity to be recorded independently and simultaneously, each to any degree of attenuation below maximum so that a wide range of concentration can be accommodated. Drift and noise for the range 0 to 0.01 absorbance noise is approximately 2% of full scale, equivalent to 0.0002 absorbance. Other potential applications of the instrument include monitoring microbial growth and studying the kinetics of reactions whose time constants lie within the scope of the instrument. Demountable connectors allow the original dual wavelength mode of operation to be restored. In this mode the ratio of absorbance at two different wavelengths of a solute can be determined.