bluuebunny/crossref_metadata_2025 huggingface dataset:
Computerized Acoustic Spectrometer for Polymeric Solids at Low Temperatures
Authors: Schlein Helmar , Shen Mitchel
Published: February 2004

A force, flexural resonance spectrometer at acoustic frequencies with an automatic data acquisition system is designed to measure the dynamic mechanical properties of polymeric solids from 10 to 500 K. The sample is clamped at its nodal points and driven by a voltage-controlled oscillator through an electromagnetic transducer. Two small iron tabs are glued to either ends of the sample to provide magnetic coupling. A similar transducer is used to receive the response of the sample. The bandwidth method is employed to determine the internal friction. An electronic circuit is devised to measure the frequency at the maximum amplitude and those at the half-power points of the amplitude-frequency curve. These readings, as well as the voltage output from the thermocouple, are digitally recorded on a paper-tape punch. Data are then transferred onto cards and processed on a computer. Results are displayed in analog form via a CalComp plotter. Measurements for polyethyl methacrylate, polyethylene, and paraffin wax are reported.
The Angular Response of Spherical Plate Electrostatic Analyzers
Authors: Theodoridis George C. , Paolini Frank R.
Published: February 2004

We examine the transmission characteristics of spherical plate electrostatic analyzers, for external particle sources, as functions of angular coordinates α and β, and particle energy E. The angle α is in the plane of the particle's trajectory; β is in the plane containing the point of incidence and perpendicular to the radius vector from the center of electrostatic force. We express the total energy-geometrical factor F, which is the ratio of transmitted particle flux (particles/sec) to directional intensity (particles/cm2·sec·sr·keV), in the functional form F≡GαβEAβ0ΔαΔE,where βo, and Δα are angular parameters and ΔE the energy resolution, all appropriately defined. We give methods for determining the function G and present some specific examples. We show that G is of the order of unity. A surprising result is that βo, which is a measure of the angular aperture in β space, may differ appreciably from the value expected intuitively on the basis of the angular dimensions of analyzer plates. The angles α and β are locally defined with respect to each arbitrary point of incidence within the entrance aperture. We also give a general method for finding the detailed angular response of spherical plate analyzers in a frame of reference fixed with respect to the analyzer plates.
Microwave Measurement of Permittivity and Electrical Conductivity in Shock Compressed Liquids
Authors: Hawke R. S. , Mitchell A. C. , Keeler R. N.
Published: February 2004

A microwave technique for measuring the permittivity and electrical conductivity of shock compressed fluids is described. The results of experiments on carbon tetrachloride are presented and compared with previous work. The technique has a range of 1 to 104 in relative dielectric constant and 4×10−5 to 4×102 Ω·cm−1 in conductivity.
An Application of Optical Telemetry to Shock Tube Measurements
Authors: Dannenberg Robert E. , Katzman Howard
Published: February 2004

An optical carrier, single-channel telemetry system is described. It provides complete electrical isolation between data acquisition instrumentation and data storage or recording facilities. The system, which has a bandwidth from dc to 50 kHz, has been used successfully in a shock tube facility where high voltage isolation is required for protection of instrumentation.
Internal Energy Standardization of Multichannel Gamma Ray Spectra by Use of the 0.511 MeV Annihilation and 40K Peaks
Authors: Grismore R. , Weitz W. E. , Folsom T. R.
Published: February 2004

A computer method is described for making after-the-fact adjustments for incorrect zero energy intercept and instrumental gain to experimental gamma ray pulse height spectra from NaI (Tl) scintillation spectrometers. The method makes use of the 0.511 MeV annihilation peak and 1.46 MeV 40K photopeak as internal energy reference standards, both of which peaks are available to NaI (Tl) scintillation detectors. The technique has been tested experimentally and appears to be of practical use for routine energy standardization of long counting time gamma ray spectra between 0.1 and 2.0 MeV.
Thermistor Thermometer for Linearized Magnetic Recording and Telemetry
Authors: Alon Yosef , Jonas Malkiel
Published: February 2004

A simple instrument for the remote sensing, magnetic recording, and linear display of temperature is described, which is well suited for synchronous recording of temperature and dependent phenomena. A range of 40°C is displayed both during recording and playback, accuracy and resolution being a fraction of a degree. No recalibration or adjustments are needed. Small power consumption (30 mW from a single battery) suggests field uses, possibly unattended. Construction is easy and standard components are used throughout.
Pressure Viscometer for Viscosities between 1 and 104 P
Authors: McDuffie G. E. , Barr T.
Published: February 2004

A high pressure viscometer is described capable of measuring viscosities over the range 1 to 104 P at pressure to 3500 kg/cm2 and at temperatures between −60° and 100°C. The device is constructed from commercial high pressure tubing and is mounted in a commercial thermal air bath. Calibration is made at atmospheric pressure with the liquid under test against a series of Canon-Fenske viscometers. Accuracy of the measurement is better than 1% at all viscosities in the range of the device.
Measurement of the Velocity and Attenuation of Ultrasonic Pulses in the Presence of Noise
Authors: Williamson R. C.
Published: February 2004

The well developed techniques of coherent detection and signal averaging may be used to extend the range and accuracy of measurements of ultrasonic velocity and attenuation. Significant improvements in signal-to-noise ratio are obtained by averaging a coherently detected echo train in a signal averager such as a multichannel analyzer or boxcar integrator. A standard circuit of this type is described and analyzed. Comparison of coherent detection and rectification shows the inherent advantages of coherent detection for signal-to-noise enhancement.
Low Cost High Linearity Solid State Digital Double Boxcar
Authors: Samuelson Gary L. , Ailion David C.
Published: February 2004

In this article, we describe a digital solid state double boxcar of infinite holding time and very high linearity. It uses a Hewlett-Packard (HP2212 A-M3) voltage-to-frequency converter (VFC) whose output is accumulated on a running counter, thereby providing signal averaging with an infinite holding time. The combination of FET signal gates with zero offset and the highly linear VFC results in a linearity of better than ±0.01% over an input range of ±1.0 V, which is a considerable improvement over that available with other digital boxcars. Integrated circuit pulse generators of high stability provide gating times from a fraction of a microsecond to many seconds. A unique monitoring system allows ease of adjustment with a simultaneous ``master'' display of all gating and signal functions. Other features of this boxcar are extreme compactness, low cost, and very high stability.
Low Cost Integrated Circuit Versatile Pulse and Frequency Counter
Authors: Samuelson Gary L. , Ailion David C.
Published: February 2004

In this paper we describe a compact multipurpose counter whose design is based on the use of plastic integrated circuits. The circuit contains about $90 worth of semiconductor components and is very easy to wire; nevertheless, it is extremely versatile. It consists of dual 107 and 105 counters which can be used separately as two counters, or in series as a single 1012 events counter. Frequencies up to 10 MHz can be read to the accuracy of the crystal used (typically better than 0.005%). Time intervals can be measured—either the width of a single pulse or the time interval between the positive (or negative) slopes of two pulses. The circuit can also be used as a digital integrator, since the average count of pulses in a series of numerous pulse train events can be automatically evaluated after 10, 100, 1000, or 10 000 events.
Thin Lithium Targets Sealed in Nickel for Low Oxygen Contamination
Authors: Weisser David C. , Hobbie Russell K.
Published: February 2004

A technique is described for making pure lithium targets in the range of 100 μg/cm2 by encapsulation in a sputtered nickel film. The oxygen impurity is about 2%.
Low Temperature Setup for Electron Irradiation and Subsequent Photoconductivity Studies of Semiconductors
Authors: Vajda P. , Lori J.
Published: February 2004

A cryostat is described for irradiations with electrons at liquid helium temperatures and subsequent photoconductivity and infrared absorption studies in the range from 20 to 400 K. Heat is removed from the sample by conduction through a copper tail touching the bottom of the liquid helium container. A mechanical ``switch'' enables the thermal separation of the sample assembly from the helium bath during the annealing studies. A rotatable outer-tail piece permits irradiation with electrons through aluminum windows avoiding damage to the optical NaCl windows. The beam dosimetry and monitoring equipment are described in detail.
Device for Electrical Conductivity Measurements of Glasses during Heating and Cooling
Authors: Wagstaff F. E. , Charles R. J.
Published: February 2004

A system has been developed for electrical conductivity measurements of molten glasses in which electrode effects and nonuniform sample temperatures have been minimized. The sample shape is a small thin disk held between flat platinum electrodes to give low thermal inertia and minimum temperature gradients. Controlled heating and cooling are provided by a programmed dc power supply. Conductivity and temperature are measured periodically and punched on a paper tape which serves as the computer input. All calculations are performed in the computer and the output is logσ vs 1/T and activation energy vs temperature. Conductivities of 10−1 to 10−6 (Ω·cm)−1 have been measured in the temperature range of 1000 to 300°C.
A Modified Ultrasonic Pulse-Echo-Overlap Method for Determining Sound Velocities and Attenuation of Solids
Authors: Chung D. H. , Silversmith Donald J. , Chick Bruce B.
Published: February 2004

The ultrasonic pulse-echo-overlap method described by Papadakis [J. Acoust. Soc. Amer. 42, 1045 (1967)] has been modified to permit simultaneous measurement of the time delay and the relative voltage ratio between any pair of returning echoes in the pulse-echo train. All the components involved in the present modification are commercially available items, and this instrumentation system for the ultrasonic pulse-echo-overlap method is compatible with the pulse superposition method.
A Heavy-Ion Energy Loss Spectrometer
Authors: Park John T. , Schowengerdt F. D.
Published: February 2004

A high resolution system for the measurement of the energy loss spectra of 20–250 keV heavy ions incident on gas targets is described. The high resolution is obtained by decelerating the ion beam to a low, well defined energy before performing the energy analysis. The energy loss spectrum is determined by changing the accelerator energy to compensate for energy lost in collisions with the gas atoms. The system is arranged so that normal fluctuations in the accelerator's power supply do not affect the energy resolution. The resolving power of the system is 2.5×104. The primary proton beam has a detected WHM of 2 V at 50 kV. An energy loss spectrum is shown for which the collision-excited 11S-21P transition in helium is clearly resolved.
Curve Resolver for Mixtures of Damped Sine Waves
Authors: Moore C. D. , Malmberg J. H.
Published: February 2004

A system for analyzing waveforms consisting of mixtures of exponentially damped sine waves is described. The instrument generates a set of damped sine waves of variable amplitude, frequency, damping decrement, and phase. These waveforms are added and displayed on an oscilloscope. Their parameters can be adjusted to obtain a waveform which matches the curve to be analyzed. The component waveforms are then analyzed one at a time. The instrument has been used to analyze interferometer curves arising in the course of plasma wave experiments.
An Energetic Model for Rapid Mixing
Authors: Duffey Donald , Staerk Hubertus
Published: February 2004

A model for rapid mixing of liquids is developed to relate driving pressure and time needed for complete mixing. A quantitative statement of this relationship is obtained by replacing turbulence with diffusion and employing Stokes' law for the viscous forces. Mixing times predicted by the model compare reasonably well with several values reported for different jet-type mixer designs.
Free Radical Beam Source
Authors: Kalos Ferenc , Grosser Arthur E.
Published: February 2004

A source of pure beams of thermal alkyl radicals for molecular beam scattering experiments is described. A parent compound, (CH3)2Hg, (CH3)3Bi, CH3I, or (C2H5)2Hg, was pyrolyzed in an array of small Ta tubes, and a beam of the products entered a slotted disk type velocity selector. Selection at 1500 m/sec chemically purified the radical beam by removing parent molecules and high mass decomposition products. The best purities, found by modulated beam mass spectrometry, average to 94±8 mole% CH3, and in these runs the estimated intensities were 2−7×1015 radicals/sr·sec, or 3−10×1013 radicals/cm2·sec at the detector. Light hydrocarbons (C1,C2) were the major impurities, their concentration increasing with methyl flux.
Device Which Tests and Records Radial Symmetry in Electron Micrographic Images
Authors: Adams L. R. , Forte G. M. , Glaeser R. M.
Published: February 2004

A stroboscopically illuminated turntable is described; accurate and easily manipulated variation of the flashing frequency relative to the turntable frequency is achieved by photoelectric triggering of the lamp. The device is suitable for both visual and photographic evaluation of objects that may possess ``hidden'' degrees of radial (rotational) symmetry.
A Marx Three Component Oscillator for Internal Friction Measurements at Low and High Temperatures in High Vacuum
Authors: Povolo F. , Gibala R.
Published: February 2004

An apparatus for the measurement of internal friction in the kilohertz frequency range is described. The Marx three component piezoelectric technique is used and the apparatus is designed for measurements at low and high temperatures in high vacuum. A graphical technique for calculating the damping from the measured voltages is presented and is used in a manner that improves the accuracy with which amplitude independent and amplitude dependent damping can be separated.
Tracer Diffusion Studies on Metals Using a Microtome
Authors: Graham D.
Published: February 2004

A microtome has been used to remove 2 μ sections from metal specimens as part of a radiotracer diffusion study. The technique is described in detail and includes a design for an orientation stage to obtain sections parallel to the diffusion interface. The equipment has been used successfully on Zr, Ti, Fe, Pd, Ag, and Cu, and diffusion profiles for self-diffusion in Fe, Zr, and Ag are given. This instrument extends the sectioning method into the area of diffusion zone analysis previously occupied exclusively by abrasion techniques.
Bimetal Strip Hydrogen Gas Detectors
Authors: Shaver P. J.
Published: February 2004

It is shown that bimetal strips which use palladium—silver alloys as the active component are sensitive detectors of gaseous hydrogen. Concentrations of hydrogen in STP nitrogen as low as 50 ppm have been detected with this technique. Fast response times are obtained at bimetal strip operating temperatures of 200–300°C. The experimentally observed steady state behavior of these strips is in good agreement with theory.
Transient Response of Magnetic Probes
Authors: Ferrari L. A. , Zucker M. S.
Published: February 2004

The response of a magnetic probe to a source that varies harmonically with time is calculated including transient effects. It is found that when the applied frequency is 10% of the natural resonant frequency of the probe the maximum distortion in the integrated signal is ≈ 10%.
Infrared Emission from a V-Shaped Metal Groove Compared with That from a Flat Surface of the Same Metal
Authors: Hurlock S. C. , Rao K. Narahari , Burkhard Donald G. , Shealy David L.
Published: February 2004

A source of continuous infrared radiation has been designed and constructed. The element operating in a high vacuum is a molybdenum ribbon heated by passing a high current through it. A comparison is made between the near infrared emissions from a V-shaped and from a flat portion of the ribbon.
A Modified Microinterferometric Technique for Measurement of Diffusion Coefficients of Liquids
Authors: Travnicek E. A. , Fan L. T.
Published: February 2004

Measurements of diffusion coefficients of liquids have been difficult and time consuming. A laser interferometric system with which diffusion coefficients of liquids may be measured with greater ease and accuracy than by the use of previously reported systems was developed. The system developed was tested by measuring the diffusion coefficients of benzene in cyclohexane. A helium—neon gas laser was used as a light source. Its use permitted accurate computation of instantaneous profiles of concentration vs position in the diffusion cell of the system. These profiles were derived from photographs of interference fringe lines taken during experimental runs.
New Techniques and Apparatus for Examining the Elevated Temperature Deformation of Metals
Authors: Solomon A. A.
Published: February 2004

A new method is described for examining the deformation dynamics of metals at elevated temperatures. Tensile loads are applied to a specimen using a closed loop electrohydraulic servosystem. An optical furnace and proportional controller are used for temperature control, and a linear variable differential transformer is used to sense specimen length. System control is found to be sufficient to perform several new types of tests, and permits a more fundamental reexamination of the stress relaxation and strain rate sensitivity tests.
A 5 μsec Dual Beam Flash Photoelectric Apparatus
Authors: Yip R. W.
Published: February 2004

A dual beam flash photolysis apparatus for photoelectric recording is described. The use of a millisecond flashlamp as the analysis light source combined with a heavily decoupled 6 stage photomultiplier dynode chain offers the advantage of good uv output, convenient pulsed light source permitting high current photomultiplier operations without additional gating instrumentation, minimum photolysis of the sample, and extremely high intensity, which increases signal with respect to shot noise, scatter, and electrical interference. Dual beam operations reduce the baseline variations due to analysis source fluctuations. For transients longer than 1 msec, dc light sources are used. The photolysis flash energy is 200 J in a light pulse of 5 μsec wide at ⅓ of its peak value.
Coaxial Cathode Design for Plasma Sources
Authors: Chen Francis F.
Published: February 2004

An electron bombardment heated cathode structure is described which is capable of producing an electron emitting surface 5.7 cm in diameter at 2700 K, with ±5 K azimuthal temperature uniformity. The coaxial structure allows access along the axis, is assembled from modular components machinable on a lathe, and requires no water cooling internal to the vacuum system. The ``cathode'' is particularly suitable as an emitting end plate for a thermionic plasma (Q machine).
Modified Rapid Quenching Apparatus
Authors: Baker James N. , Mighton Charles E. , Bitler William R.
Published: February 2004

A ``splat'' cooling apparatus has been designed which minimizes sample contamination by using levitation melting and which produces a solid of essentially uniform thickness. Typical foil dimensions obtained were 1 cm×1 cm×25 μ.
Phase-Plane Method of Exponential Waveform Measurement
Authors: Huen Tony
Published: February 2004

In physical measurements of exponentially decaying pulses, two questions naturally arise: (1) Is the waveform really just a simple exponential? (2) And if so, what is the time constant? It is shown here both of these questions can be answered easily by using a phase-plane plot rather than by the conventional time-function display.
Equipment for the Quantitative Photometric Measurement of Reflectivity by Polarized Light Microscopy
Authors: Larson L. T.
Published: February 2004

A system has been designed for the quantitative photometric measurement of light reflected from microscopically small areas of metals and opaque minerals mounted and prepared in polished sections. The equipment has been designed to operate in the visible region of the spectrum (400–700 nm wavelength) and to use microscopically defined, plane polarized, vertically incident light. The system embodies a double beam, null balancing, photometer array; a mechanically driven microscope stage; and a direct X—Y chart readout of the reflectivity of the specimen relative to microscope stage position.
Time Variant Filters for Generating Bipolar Pulses with Signal-to-Noise Ratios of Unipolar Pulses in Nuclear Pulse Amplifiers
Authors: Blalock T. V. , Nowlin C. H.
Published: February 2004

A time variant filter employing a simple gating technique was developed to produce bipolar pulses with signal-to-noise (S/N) ratios as good as those of unipolar pulses. The gated bipolar pulse discussed herein has an S/N ratio of a unipolar pulse shaped like the first lobe of the bipolar pulse. For the special case of symmetrical bipolar pulse shaping, the improvement in S/N ratio over the single measurement of the bipolar signal produced by conventional time invariant filters is 41.4%, and the improvement over the time invariant peak-to-peak measurement is 22.5%. The S/N ratio of the symmetric bipolar triangular pulse discussed in this paper is within 7.5% of the S/N ratio of the theoretically optimum unipolar pulse, but the system must be direct coupled from the radiation detector to the linear gate if count rate dependent peak shifts are to be avoided.
A Dilatometer Method for the Precision Measurement of the Densities of Liquids to 400°C and 352 kg/cm2
Authors: Bell J. T. , Biggers R. E. , Rogers T. G. , Rom A. M.
Published: February 2004

A specially designed titanium dilatometer for measuring densities of liquids and solutions from room temperature to 400°C and at pressures to 352 kg/cm2 has been built and operated. The liquid volume of a weighed solution of known composition is determined by taking an x-ray photograph to show the position of the vapor-liquid interface in the calibrated section of the dilatometer. The density is then calculated after correction for mass transfer between the liquid and vapor states. The furnace assembly and accompanying instrumentation were designed and constructed to maintain the entire length of the dilatometer in an essentially isothermal state at each temperature, and to permit an accurate, representative measurement of the temperature and pressure. The density of water was determined from room temperature and pressure to the critical point. The results agreed to within an average accuracy of 1.0% with the most recent steam table values; considerably better agreement was obtained at lower temperatures.
A Method for Studying Field Effects on Film Resistors
Authors: Kazmierowicz Casimir W.
Published: February 2004

A technique for measuring the voltage coefficient of resistance associated with precision film resistors is discussed. A standard dc method is used to measure the resistance at various currents. Temperature changes due to Joule heating are minimized by submerging the resistor in a boiling liquid so that most of the power is dissipated in supplying the heat of vaporization to the liquid rather than in changing its temperature. Examples are given which show that increasing temperatures cause positive changes in resistance while increasing voltages produce negative changes. This indicates that the effects due to temperature and voltage are indeed separated. A variation of the basic measuring technique is discussed whereby, within reasonable approximations, voltage coefficients can be recorded automatically.
Instrumentation for Single Crystal X-Ray Diffraction at High Pressures
Authors: Weir C. E. , Piermarini G. J. , Block S.
Published: February 2004

A diamond anvil high pressure cell made of beryllium, a special goniometer head, and a Buerger-type precession camera designed for x-ray diffraction by single crystals at high pressures are described in some detail. The most important problems still to be solved are discussed.
Application of Microwave Reflection Technique to the Measurement of Transient and Quiescent Electrical Conductivity of Silicon
Authors: Naber J. A. , Snowden D. P.
Published: February 2004

A microwave reflection technique for measuring both the transient and quiescent electrical conductivity of semiconductors in a temperature range from 4.2 to 450 K is described. This technique eliminates the difficulties due to non-Ohmic contacts when making electrical measurements on semiconductors, particularly silicon.
A Miniature Transducer for Measuring Low Transient Pressures
Authors: Hofland R. , Glick H. S.
Published: February 2004

Miniature pressure transducers which are suitable for measuring pressures on models placed in rarefied shock tunnel flows are described. Special attention is given to the problems of mechanical vibration, convective heating, and miniaturization. It is shown that by using a matched pair of piezoelectric crystals in conjunction with special first-stage circuitry a pressure transducer can be built which, for example, is 5.1 mm in diameter and has the following characteristics: (1) a pressure sensitivity of 1.64 mV/Torr, (2) an acceleration sensitivity of less than 0.0425 mV/g at frequencies up to 200 Hz, and (3) a negligible response to heat flux rates up to 1.33 Δp MW/m2, where Δp is the measured pressure increment in units of torricelli.
Mössbauer Spectroscopy with Monochromatic Circularly Polarized Radiation
Authors: Shtrikman S. , Somekh S.
Published: February 2004

A technique for carrying out Mössbauer experiments with monochromatic polarized radiation is described. Mössbauer spectra of longitudinally magnetized YIG (yttrium iron garnet) employing circularly polarized radiation are given.
Fabry-Perot Cavity for Dielectric Measurements
Authors: Breeden K. H. , Langley J. B.
Published: February 2004

A technique is described for measuring complex permittivities of low loss dielectric materials with a semiconfocal Fabry-Perot resonator. Equations are derived for calculation of dielectric constant and loss tangent. Results are presented for slip-cast fused silica at 94 GHz.
Thin Film Temperature Sensor
Authors: Kennedy Bruce W.
Published: February 2004

Development of a thin film temperature sensor for rocket borne application is discussed. A description of sensor material, response time, substrate material, and flight instrumentation is presented. Construction techniques are briefly described. Results of rocket flights are discussed and indicate that the temperature profiles obtained with the thin film sensor compare favorably with those obtained with the existing bead thermistor temperature sondes.
Analysis and Performance of a Split-Detector Spot Analyzer
Authors: Sihvonen Y. T.
Published: February 2004

A system of two detectors separated by a narrow gap provides information regarding the diameter and flux distribution of small focused light spots. Differential signal variations in response to gap position for three flux distributions are theoretically analyzed: constant intensity, linearly diminishing intensity, and Gaussian. A PbZrTiO3 pyroelectric split detector was fabricated for analyzing spots as small as 6 μ (half-intensity diam). Data taken on a focused He–Ne laser spot (≈25 μ half-intensity diam) are compared with expectation curves. Suggestions for improving resolution and sensitivity are made.
An Investigation into the Causes of the Aging Phenomena of Self-Quenching Geiger-Müller Counter Tubes; C2H5CN a Better Quench Gas than C2H5OH
Authors: Lox F. E. , Eeckhaut Z.
Published: February 2004

The decrease of the quenching agent found in aged counters (approximately 2×108 counts registered) is of the order of 0.5%. This cannot account for their bad functioning. Only changes on the anode surface (polymer deposit) and in the gas phase (new products formed by counter discharge) are responsible for the deterioration of aged self-quenching G-M counters. The first mentioned changes are neutralized by simply glowing the wire, the latter may be overcome by the choice of a suitable quenching agent. C2H5CN gives better results than C2H5OH.
Simple Mass Spectrum Linearizer
Authors: Meisels G. G. , Giessner B. G. , Leger L. J.
Published: February 2004

An inexpensive modification of a commercial mass spectrometer is described which permits linear display of ion intensity vs m/e on an X-Y recorder. Its evaluation shows that the major limitations arise from recorder specifications. For magnetically scanning instruments, mass assignments can be made within ±0.006% utilizing the maximum zero offset of 85% of the largest mass of interest. Peak positions are independent of scanning speed up to 30 m/e units/min and can be assessed within 0.1% of the mass range covered.
Production of Isolated Pairs of Water Drops Having Unequal Radii
Authors: Abbott Charles E.
Published: February 2004

A technique has been developed for producing freely falling pairs of water drops with unequal radii. Radius ratios as large as 10 to 1 can be obtained with drops having radii in the range 0.1–1.0 mm. Continuous production of drop pairs is possible, with the desired repetition rates selected by electronic controls and unwanted drop pairs deflected out of the observation volume. Successive pairs, thus produced, are sufficiently identical that a sequence of photographs has been obtained with an effective elapsed time between exposures of 100 μsec, the equivalent of 10 000 frames/sec in terms of high speed photography.
A Constant Stress Creep Apparatus for Superplastic Metals
Authors: Dudderar T. D.
Published: February 2004

In conducting constant stress creep tests of ductile metals means must be provided to alter the applied load in response to changes in specimen geometry. Over the years a variety of automatic devices has been developed which compensates for the limited range of geometrical change usually encountered. Interest in superplastic metals exhibiting homogeneous plastic deformations of several hundred percent and total extensions of up to 2000% at almost zero applied stress levels creates the need to extend the techniques of creep testing. In this investigation it was desired to keep the test apparatus as simple as possible to permit its use in a variety of test programs, including elevated temperature and combined creep-fatigue experiments. As a result, a design was developed which permitted the application of very low stresses stimulating quasistatic creep rates over a 20 to 1 strain range, as well as higher stress configurations required to produce significantly elevated creep rates. Test results with a low stress prototype provide creep data for a superplastic lead-tin alloy over a range of very low strain rates both with and without superimposed fatigue.
An Apparatus for Neutron Diffraction from Single Crystals
Authors: Khan D. C. , Erickson R. A.
Published: February 2004

The problem of coincidence reflections with a Bragg peak is discussed and an apparatus is described for an automatic averaging over the ``umweganregung'' and ``aufhellung'' peaks to come very close to the true Bragg intensity. Results of an experiment are considered to prove the validity of the method. A refrigerator arrangement is described for work below room temperature.
A Rotating Sample Holder Using Flexible Fiber Optics for the Excitation and Detection of Photoluminescence at Liquid Helium Temperatures
Authors: Tynan Eugene , Welber Benjamin
Published: February 2004

We describe a sample holder useful for the study of the angular dependence of photoluminescence at liquid helium temperatures. The system is characterized by a high collection efficiency and is particularly well suited to situations where there is only vertical access to the experimental space.
Ultracentrifuge Data Acquisition from a Central Control System
Authors: Windsor Alfred A. , Jensen Lin C. , Hoopes David A. , Lindgren Frank T.
Published: February 2004

Three analytic ultracentrifuges are controlled and useful operating measurements recorded by a central control and data acquisition system. Rotor speed, temperature, picture number of each schlieren photograph, and time of each measurement are recorded on cards by a printing summary punch machine. A Fortran IV computer program processes the data, yielding graphs of rotor speed and temperature vs time and the accumulated value of ωFS−2∫ω2(t)dt for the mean time of each schlieren photograph. These data permit error detection as well as more accurate schlieren analysis of lipoprotein distributions and flotation rates.
An Inexpensive, Easily Wound, Superconducting Magnet for Dip Experiments
Authors: Merrill John R.
Published: February 2004

This paper presents a design for a small superconducting magnet. The magnet is used for dip experiments into a storage Dewar with the access tube removed from the neck. The solenoid is corrected by means of two extra coils wound on the outside. Correction coils increased the usable volume over which the field is uniform to 0.1% by a factor of about 50. The magnet is uniform to 0.1% over the full radial bore and for almost 2 cm along the axis. All the information necessary to wind the magnet is given; the magnet reported was wound by novices. The total cost of the magnet was about $20; the magnet achieved more than 15 kG.
Fast Neutron and Gamma Ray Risetime Differences for 8 to 10 MeV Pulses in a Large NaI(Tl) Crystal
Authors: Jaszczak R. J. , Nutt R. , Macklin R. L.
Published: February 2004

A dissimilarity in the risetime distribution of 8 to 10 MeV pulses from a 22.9 by 30.5 cm NaI(Tl) crystal due to fast neutrons and those due to gamma rays of equivalent energy has been observed. The time spectra were obtained using low and high level discriminators triggering at 100 keV and 2.5 MeV, respectively. The NaI (Tl) crystal was viewed by six matched RCA 4524 bialkali photomultiplier tubes. The time resolution of this system (using a small plastic scintillator to obtain one time reference) for 4.43 MeV gamma rays using leading edge timing is 2.5 nsec. The fast neutrons undergo inelastic collisions within the crystal prior to capture. The mean time between collisions for 3 MeV neutrons in NaI is 2.8 nsec; thus, the time interval between the two discriminators is longer for a typical fast neutron than for a gamma ray of equivalent energy. This results in a degradation of the time spectrum due to the fast neutrons. The 8 to 10 MeV gamma ray risetime distribution is symmetric, having a time resolution (FWHM) of 2.75 nsec. The neutron risetime distribution has a tail on the side corresponding to longer time intervals between the two discriminator outputs. It is shown that it is possible to reduce the number of pulses due to neutrons in the 8 to 10 MeV region by ⅓ by setting a time window. Estimates of an increased capability to discriminate through the use of a pulsed accelerator and a beam pickoff (thereby allowing the time interval between neutron emission and first inelastic scattering to be observed) are presented.
A Survey of Some Secondary Thermometers for Possible Applications at Very Low Temperatures
Authors: Rosenbaum Ralph L.
Published: February 2004

A survey has been made on the temperature dependent behavior of several new types of carbon resistors and germanium sensors to determine whether any particular type might be suitable as a secondary thermometer in the 0.01–1.0 K temperature interval. Each thermometer was specially constructed to improve the thermal contact to the sensing element. Several commercial germanium and carbon resistance sensors appear promising as thermometers in the very low temperature interval. In addition, it appears feasible to extend the use of 0.02 at.% Au–Fe thermocouples down to 0.05 K.
Electronic Circuit Breaker for Motor Load Protection
Authors: Kilgore Stanley B.
Published: February 2004

An electronic circuit breaker, designed to switch off the power to an electric motor when the mechanical load increases beyond the normal load, is described. The circuit operates rapidly and can sense an increase in mechanical load before it reaches destructive proportions. The sensitivity of the electronic circuit makes it necessary to incorporate a time delay that prevents the initial surge current from turning the motor off before it gets started.
A Microwave Amplitude Stabilizer
Authors: Bandelier Raymond , McConnell R. D. , Fischer Gaston
Published: February 2004

A device is described which allows the stabilization of the output of a microwave source at power levels up to 1 W. Variations of the source power are reduced by more than 30 dB with a time constant of about 20 μsec. The long term stability of the device is better than 10−4 over several hours. The device consists only of inexpensive commercially available components.
A Versatile Electrical Shutter for Optical Pumping Experiments
Authors: Fralick R. D. , Zipf E. C.
Published: February 2004

A versatile electro-optical shutter has been developed for use in optical pumping experiments. The shutter has a cutoff time of 25 nsec, a contrast ratio greater than 2×104 to 1, can be held opened or closed for continuously variable amounts of time, and can effectively shutter light with a large angle of divergence (up to 8°). The shutter consists of a commercially built Kerr cell controlled by a high voltage modulator. The modulator is a specially designed bistable switch which is capable of producing variable width 31 kV pulses and can be cyclically operated up to 250 Hz. The high stability of the shutter together with its other properties makes it particularly useful in optical pumping experiments in which digital signal averaging techniques are used.
Rotating Blade Spark Cutter for Hg and Alkali Metals
Authors: Shiller J. , Dooley J. W. , Tepley N. , Thomas R. L. , Fenner J.
Published: February 2004

Modifications of a spark cutter are described which facilitate preparation of oriented mercury and alkali metal crystals having geometries suitable for ultrasonic experiments.
A Specimen Holder for Low Temperature Electron Irradiation of Metallic Resistivity Specimens
Authors: Dworschak F. , Neuhäuser J. , Schuster H. , Wollenberger H. , Wurm J.
Published: February 2004

A mounting of metallic resistivity specimens is described which allows low temperature electron irradiation within the vacuum system of the particle accelerator. The heat generated in the specimens during irradiation is transferred to the specimen holder via solderable sapphire plates which provide a good thermal contact and also the electrical insulation required. The temperature distribution in the specimens is calculated for general parameters. The maximum specimen temperature can be monitored continuously during the irradiation. Good agreement is found between calculated and measured maximum temperature.
Assembly and Operation of a Simple, Multipurpose Zonal Ultracentrifugation System
Authors: Paris J. E.
Published: February 2004

A description is given for the correct assembly and operation of the variety of components of a zonal ultracentrifugation system, useful for several kinds of zonal particle separations. Simple, reproducible means are provided for the storing, volume measurement, and output control of the gradient, sample, and overlay solutions. These fluids do not come in contact with lubricated parts. The liquid flux along the lines is free from pressure pulses or local areas of turbulence. The various solutions are kept cold without installation of the whole setup in a temperature controlled environment. The system of connections is designed to be smooth and compact, with a minimum of dead spaces. The type and size of the necessary tubing connectors, stopcocks, etc. was chosen as to preserve lamellar flux of gradient solutions and to insure permanent tightness. The proposed system can be easily disassembled for the purpose of cleaning and a large number of experiments did not affect its hermeticity. All parts in contact with solutions are autoclavable for sterilization.
A Cold Cathode Invertron
Authors: Copeland G. E. , Fowler R. G.
Published: February 2004

A new gaseous discharge source has been developed for use in measurement of atomic and molecular electronic state lifetimes where the transitions occur in the range 1000–12 000 Å. The source is a coaxial aluminum cold cathode-anode device utilizing fast pulse circuits, magnetic field breakdown enhancement, and a flowing gas supply. Excitation of gaseous species is achieved by electron collisions in the discharge. The cold cathode device can be used with any gaseous species since its source of electrons is not a heated oxide-coated cathode. Excitation fall times of 2 nsec are obtained.
Spark Gap Power Switching for Conical θ-Pinch Plasma Gun
Authors: Kuswa Glenn , Stallings Charles
Published: February 2004

A simple, easily maintained air spark gap of ∼7 nH inductance was developed to switch 0.24 C stored charge at 20 kV in an LC circuit having a period of ∼4 μsec. A similar 3 nH spark gap with an auxiliary triggering circuit was used to clamp the magnetic flux within the load near the voltage minimum. Voltages up to 30 kV and currents to 5×105 A have been handled. Acoustic noise was minimized by completely enclosing the arc, and forced air venting removed corrosive gases and helped control the temperature to improve reproducibility.
Cyclotron Resonance Plasma Source with Variable Temperature and Density Profiles
Authors: Decker J. F. , D'Amico C. V.
Published: February 2004

A simple plasma source using microwave breakdown near cyclotron resonance in a low pressure gas has been developed. It consists of a tapered glass tube inserted through a waveguide that is terminated by a tunable short. By suitable choice of the degree of taper, the problem of strong temperature inhomogeneities (and sometimes hollow plasmas) frequently encountered with ECR plasma production can be overcome. Using relatively low microwave power levels, <3 W, the following ranges of electron temperatures and densities have been produced: 2 <Te <8.5 eV and 3 × 109 <Ne <4 × 1010 cm−3 (the density is power limited).
A Pulsed Optical Isolator for 1.06 μ Light
Authors: Fong P. K.
Published: February 2004

A pulsed Faraday effect rotator was built and used as an optical isolator for light at 1.06 μ. The pulse mode simplified the problem of creating the high magnetic field strengths necessary to allow the use of a relatively short, low absorbance rotator material. A forward-to-backward transmission ratio of 36 dB was obtained using a 0.32 cm diam laser beam.
An Automatic Shutter for Holography
Authors: Lin L. H. , Beauchamp H. L.
Published: February 2004

An automatic shutter intended for recording holograms with laser light is described. The shutter allows holographic recording material to be exposed until a preset exposure value is reached; it then automatically cuts off the laser beam. The automatic control on the exposure time is provided by a photoconductor cell placed near the recording material. Properly used, this shutter can eliminate the need to measure the light level illuminating the material. It also permits the laser power to vary over at least two orders of magnitude during the exposure without affecting the high diffraction efficiency of the recorded hologram.
A New Biaxial Strain Gauge
Authors: Sharpe William N.
Published: February 2004

Strain is measured by recording the motion of fringes produced by laser light incident on adjacent pyramidal indentations in a specimen surface. The gauge length of this noncontacting technique is of the order of 0.1 mm. The theory of the fringe formation and the relation of fringe motion to strain are given along with an experimental evaluation of the validity of the technique. Biaxial strains can be measured both for known and unknown principal strain directions.
Elementary Dilution Refrigeration
Authors: Anderson A. C.
Published: February 2004

The paper describes the construction and operation of a simple continuous dilution refrigerator which provides modest refrigeration to temperatures below 0.05 K. Both construction technique and cost are similar to what would be required to build a 3He evaporative refrigerator.
Fast Transient Recorder Using Magnetic Thin Films
Authors: Irons H. R. , Schwee L. J.
Published: February 2004

A simple compact recorder suitable as an alternative to the oscilloscope-camera combination is described. The risetime of the recorder is 2 nsec and it has a dynamic range of 30 dB. The information is read out either electronically or by observing a magnetic domain wall which represents the recorded signal.
Remote Weight-Handling Device for Calibration of Electronic Microbalance
Authors: Panosh R. L. , Pasteris J. M.
Published: February 2004

A device is described that permits the remote attachment of standard weights, for calibration purposes, on the beam of an electronic microbalance that is enclosed in a vacuum chamber. The weights can be manipulated in a reproducible and imperturbable manner. The device consists of a self-heating bimetallic element that controls the displacement of a suspension arm on which standard weights are suspended. The displacement of the arm is controlled electrically and can be operated in a vacuum tight chamber over a range of pressure.
The Measurement of Photocharge in AgBr
Authors: Tyler R. W. , Saunders V. I.
Published: February 2004

A method for measuring the total number of negative or positive charges liberated in large silver halide single crystals by shallowly absorbed radiation is described. The use of thin samples allows all the photocharges to be displaced the full thickness of the crystal and induce a certain amount of charge on a series capacitor, whose potential is measured with an oscilloscope. Data at room temperature are obtainable by the use of pulse techniques. Details are given of apparatus used for these experiments and earlier photographic experiments. Repetitive, well formed square pulses up to 500 V and 1 msec or 5000 V and 3 μsec are obtained. Synchronization with light flashes can be controlled to within a fraction of a microsecond.
Production of an Extensible Matrix by Laser Drilling
Authors: Longfellow J.
Published: February 2004

A CO2 laser has been adapted for use in high speed drilling of fine holes in thin rubber sheeting. The drilled sheeting is useful for vacuum handling microminiature semiconductor components. Holes are drilled at the approximate rate of 25/sec, and the total time required for drilling 31 400 holes of 90 μ diameter on 0.25 mm centers is 38 min.
Gas Scattering as a Limit to Trace Sensitivity in Analytical Mass Spectrometers
Authors: Ruedenauer F. G.
Published: February 2004

The distribution of elastically scattered ions in the image plane of a one-directional focusing mass spectrometer is calculated. The spectrometer is of the homogeneous magnetic sector type with the exit slit inside the field. It is shown that elastic scattering of beam ions by residual gas molecules results in peak broadening incompatible with the requirement of a high abundance sensitivity. A special two-sector instrument with reduced scattering contribution is proposed.
A Fabry-Perot Cavity for Millimeter and Submillimeter ESR Spectrometers
Authors: Amity I.
Published: February 2004

A cavity for ESR spectrometers for work in millimeter and submillimeter waves is described. The design principles are explained and results for 75 GHz are demonstrated. The experimental Q at room temperature is higher than 6000.