bluuebunny/crossref_metadata_2025 huggingface dataset:
A Flight Calibration Device for Absolute Measurements at the Lyman-Alpha Wavelength
Authors: Metzger P. H. , Clark M. A.
Published: February 2004

A small device consisting of a lamp, filter, and external photodiode has been used successfully to monitor the sensitivity of a Lyman-alpha photometer on OGO-6 as well as a number of Air Force satellites. The operation of this calibration device is independent of lamp, filter, or window decay.
Heated Infrared Sample Cell for Volatile Fluorides
Authors: Swope Lawrence
Published: February 2004

Routine reaction rate comparison studies of highly corrosive gaseous fluorides, such as CIF3 and F2, extending to temperatures above 100°C required the development of an improved heated ir gas cell. The cell features cooled window gaskets composed of Teflon, all nickel construction, and a tapered sample space to reduce the internal volume. The internal temperature of the cell can be accurately determined and controlled by the use of parameter design charts to set the control variables. The cell, which has proven to be reliable and easy to operate for the intended service, has also been extended to applications requiring vaporizing air sensitive compounds onto the cooled windows for direct ir observation.
A Computer Controlled Interferometer System for Precision Relative Angle Measurements
Authors: Bird H. M. B.
Published: February 2004

An angle measuring interferometer system has been constructed for use in a high precision crystal-diffraction γ- and x-ray spectrometer. The angle measuring device has been designed to be free of most sources of systematic error (e.g., movements of the axes of rotation, thermal effects, etc.). Electronic circuits count ¼-fringe increments which correspond to a change in angle between two rotating platforms of Δφ=0.025″. A PDP-8 computer reads the incremental fringe count and corrects drifts in angle by applying analog signals to magnetostrictive transducers. Using the computer, the spectrometer can be made to scan over a succession of diffraction angles, remaining locked at each position under feedback control. Preliminary tests indicate that the over-all system is capable of making consistent diffraction-angle measurements within an accuracy of ±0.005″; this upper limit of stability is determined by the spectrometer resolution and the limited counting statistics obtained.
A Large Granite Stage and Measuring Microscope
Authors: Alston-Garnjost Margaret , Davis J. W. , Dauber P. M. , Smits R. G.
Published: February 2004

We have constructed a stage and measuring microscope servocontrolled by a PDP-8 computer. The travel of of the stage is 0.5×0.5 m(x,y) and the travel of the microscope objective is 7.5 cm (z). The measuring accuracy is 1 μ in the x-y plane and 5 μ along the z axis.
Alternating Current Losses in Thin Film Superconductors: New Calorimetric Measurement Technique
Authors: Meyer C. H. , Snowden D. P. , Sterling S. A.
Published: February 2004

A calorimetric technique has been developed for measuring the ac loss in short, cylindrical thin film superconductors carrying a transport current. Substrates used in the present study were 0.32 cm in diameter by 3.8 cm long. Loss in the range 10−8−10−4 W may be determined by measuring the temperature rise at the center of the sample, which causes a decrease in resistance of a carbon resistance thermometer mounted inside the hollow cylindrical substrate on which the superconductor is deposited. By maintaining the current contacts at 4.2 K and heating the center of the sample (in a vacuum can), loss may be determined from 4.2 K up to the transition temperature of the superconductor. Data below 4.2 K are taken by lowering the temperature of the coolant bath. This technique has been used extensively to study the temperature dependent ac properties of Nb3Sn. Typical loss data are shown.
Improvement of Photon Counting by Means of a Pulse Height Analyzer
Authors: Betzler K. , Weller T. , Conradt R.
Published: February 2004

By taking into account the pulse height distribution, the maximum available information from a photomultiplier is examined in the case of very low light intensities and is compared with that information which is obtained in the conventional photon counting method using an optimized triggering level. Using the proposed method, the relative error is diminished by about a factor 1.4, i.e., nearly a factor of 2 is gained in the measuring time in the case of an EMI photomultiplier 6256.
Cylindrical Mirror Analyzer with Surface Entrance and Exit Slots. I. Nonrelativistic Part
Authors: Sar-El H. Z.
Published: February 2004

The properties of the cylindrical mirror analyzer are discussed for the case where its entrance and exit slots are on the surface of the inner electrode. A comparison with the case where the slots are on the axis shows that although the axial arrangement is superior, the surface case is more compact. It seems also that sample alignment in the surface case is not as critical as in the axial arrangement.
A New Kind of Oscillating Crucible Viscometer
Authors: Gallina V. , Malvano R. , Omini M.
Published: February 2004

A new oscillating crucible viscometer, having a torus shaped crucible, is presented. The geometry of the torus allows a rigorous treatment of the fluidodynamical problem for an oscillating viscous liquid. The damping coefficient δ is shown to characterize two possible distinct zones of oscillation: In the first zone, δ rises when the viscosity η of the liquid rises; in the second one, δ is lowered by an increase of η. The second zone proves to be much more convenient for fixing the working point of the instrument because here the sensitivity is expected to be twice that of the first zone. Some preliminary experiments have confirmed the results of the theory.
Sweep Generator for Atomic Collision Studies
Authors: Ratcliffe C. A.
Published: February 2004

This article describes an electronic circuit to supply voltage to an electrostatic analyzer of the type commonly used in atomic collision experiments. The voltage produced is applied to the analyzer reflector to select the energy range of electrons which pass through it. The waveform of the voltage produced is triangular, i.e., a ramp of positive slope followed by a similar ramp of opposite slope. The repetition rate is about 1/sec. The primary features of the circuit are accurate triangle generator, an amplification system for adjusting the lower and upper limits of the triangle, a high voltage amplifier which can produce up to −4000 V output, an amplification system for producing a voltage proportional to the output to use with data acquisition equipment, and a readout system to which a digital voltmeter may be connected. Differential nonlinearity of the output triangle waveform is of the order of 0.1%. Direct use of the scaled sample for data reduction minimizes the need for higher accuracy.
Recording Flash X-Ray Burst Times with Scintillation Crystals
Authors: Taylor H. R. , Preonas D. D. , Swift H. F.
Published: February 2004

A scintillator crystal system whose output is monitored with a streak camera was developed to measure the times between a number of flash x-ray bursts used to radiograph dynamic mechanical events. Light flashes from NaI(Tl) crystals exposed to flash x-ray beams were conducted from the crystals through fiber optics bundles to the slit plane of a streak camera. The short duration of the x-ray and optical pulses allowed the streak camera to be run in the half-slit mode. Separations of the resultant images along the time axis of the camera film were measured to determine the times between flash x-ray bursts to accuracies of 35 nsec.
Measurement of Small Pressure Differences in a Gas Flow
Authors: Karabelas A. J. , Hanratty T. J.
Published: February 2004

A transducer, which is based on the measurement of liquid conductivity, has been developed for the accurate determination of very low pressure differences in gas flows. The main features of the instrument are its high sensitivity (∼2.5×10−4 mm Hg), its efficiency, and the simplicity of the design.
Production of Polydisperse Sprays
Authors: Pierce T. H.
Published: February 2004

A device which produces a spray with a controllable drop size distribution is described. This system is especially well suited for generating nonsmooth (e.g., bimodal) distributions, although smooth distributions can also be produced. Droplets of uniform size result from the rapid growth of an oscillatory disturbance in a free liquid jet. Simultaneous generation of droplets of various diameters by this method produces the polydisperse spray. The range of drop diameters is approximately 300–3000 μ.
Simplified Instrumentation for Low Frequency Spectrum Analysis
Authors: Parks Jack G. , Coulter Richard L.
Published: February 2004

Three techniques are described for the analog computation of Fourier series parameters of data signals stored on multichannel magnetic tape loops. Logic signals on the tape loop control the operation of circuits used to generate the Fourier sine integral. The techniques consist of using circuits which modify one of three variables: test frequency, test phase angle, or period of integration. Typical analog recordings are presented with the methods for determining amplitude (absolute), phase angle (relative to loop logic), and frequency (less than 1 kHz) of Fourier components.
A Thermal Conductivity Cell for Small Powdered Samples
Authors: Cremers C. J.
Published: February 2004

A thermal conductivity cell is described for making measurements of the thermal conductivity and thermal diffusivity of small samples of powdered dielectric materials. The principle used is that of the line heat source. A novel way is described for applying this method so that much smaller samples than normal may be tested. This size requirement is necessary for investigations involving limited samples as does the Lunar Science Program. The method is checked by measuring the conductivity of standard samples and comparing the results with those found in the literature.
Fabrication of Sputtering Sources by Plasma Spraying: Tantalum-Hafnium Mixtures
Authors: Locker L. D. , Malm D. L.
Published: February 2004

The possibility of fabricating sputtering sources by plasma spraying is investigated for the deposition of nitride films by reactive sputtering of tantalum-hafnium mixtures. Plasma sprayed and hot pressed sources were found to produce films with identical properties even though the plasma spraying process introduces more nonmetallic impurities into the source. Improvements in controlled atmosphere chambers for plasma spraying would enable this method to compete favorably with hot pressing in terms of cost, versatility in making various shapes and sizes, and elimination of bonding problems in the rf sputtering of dielectrics.
A Nanosecond Risetime Megampere Current Monitor
Authors: Pellinen D. G. , Spence P. W.
Published: February 2004

An integrating Rogowski coil has been used for measuring megampere current pulses in large electric fields. The coil has a risetime of about 2 nsec and a typical sensitivity of 300 V/MA.
High Frequency, Low Amplitude Strain Measurement with Strain Gauges
Authors: Duggins Ben D. , Bickle Larry W. , Mitchell Dennis E.
Published: February 2004

This note describes a strain gauge system that has been used to measure vibratory strains having a peak amplitude of 2×10−6 m/m and a dominant frequency of 44 kHz. The precautionary measures that were taken to improve the signal-to-noise ratio of the system are discussed, and the strain-gauge installation technique is described.
An Improved Burner Design for Testing Dynamic Burning Properties of Solid Propellants
Authors: Coates R. L. , Sayer L.
Published: February 2004

An improved T-burner design, which circumvents problems associated with ignition, has been demonstrated in recent tests at Thiokol Chemical Corporation. The T-burner utilizes a broad band tuned Helmholtz resonator to delay the onset of instability.
The Rotated Hot Wire Anemometer
Authors: Chevray René
Published: February 2004

The novel method of measuring turbulence intensities and shear stress by a rotating single hot wire anemometer presented by Fujita and Kovasznay [Rev. Sci. Instrum. 39, 1351 (1968)] was used to make turbulence measurements in the wake of a thin flat plate. While measurements of turbulence levels proved as accurate as could be expected, shear stress measurements made by this method were better than inferred from the analysis. Inclusion of higher order terms in it showed the resulting equation to be identical but the assumptions to be less restrictive.
A Simple Apparatus for Liquisol Quenching
Authors: Laine E. , Heikkilä E. , Lähteenmäki I.
Published: February 2004

A simple inexpensive liquisol quenching apparatus is described which produces thin flat specimens from metals and alloys. A small amount of the sample is melted in resistance heated graphite crucible. The liquisol quenching is achieved by squeezing the molten globule between the cold fixed anvil and the cold fast moving piston. The apparatus can be evacuated or supplied with an inert gas.
Method of Measuring the Optical Transmission of Microcrystals at Low Temperatures Using a Casting Resin
Authors: Vaccani S. , Wachter P.
Published: February 2004

A new method of embedding micro crystals in a casting resin is described. The resin proved to withstand liquid helium temperatures, thus optical transmission experiments could be performed at various temperatures.
Channel Electron Multiplier Operation in the Continuous Current Mode
Authors: Rowe J. E. , Christman S. B. , Plummer R. D.
Published: February 2004

The possibility of using the channel electron multiplier in the analog continuous current mode is pointed out. By combining this mode with the usual pulse counting mode, one can extend the dynamic range of the channel multiplier over several decades.
Replication as a Laser Window Cleaning Technique
Authors: Levy Stephen , Wright Roland H.
Published: February 2004

A laser window cleaning method that removes all the particles on the surface without leaving any residual films is described. The technique is borrowed from the standard replication process used in electron microscopy.
Precise Measurement of Heat Transfer Using Holographic Interferometry
Authors: Aung W. , O'Regan R.
Published: February 2004

A holographic interferometer suitable for the precise measurement of heat transfer is described. In this instrument interference occurs between beams which have traversed the same optical components and hence these components need not be of high quality. Compared with the conventional Mach-Zehnder interferometer, the present instrument is less expensive and simpler to construct, and yet the two interferometers yield comparable accuracy. For illustration, the holographic interferometer is used to study the free convection thermal boundary layer on a heated isothermal vertical flat plate. The results are in good agreement with an existing theory.
A Molecular Beam Scattering Apparatus with a Low Temperature Bolometer Detector
Authors: Cavallini M. , Meneghetti L. , Scoles G. , Yealland M.
Published: February 2004

A relatively simple and versatile differential scattering molecular beam apparatus for nonalkali systems is described in which a low temperature semiconductor bolometer is used as detector. Details are given on vacuum facilities, beam sources, and detector element. A few examples of measurements on rare gases are given and the possibilities of the apparatus discussed.
A Low Temperature Heat Pipe Used as a Thermal Switch
Authors: Kopf L.
Published: February 2004

A device, based on the heat pipe principle, is described in an application as a thermal switch at very low temperatures. The presence or absence of a high purity liquefied gas in the heat pipe is the basis for the switch being on or off.
A Method of Preparation of LaB6 Cathodes
Authors: Nasini M. , Redaelli G.
Published: February 2004

A technique for preparation of cathodes consisting of a tantalum LaB6 coated ribbon has been successfully tested. The cathode has shown good performances in high density gas discharge tube (as ion lasers) operations.
Diffuse Reflectance and Fluorescence Measuring Apparatus
Authors: Gorbics S. G. , Claffy E. W. , Attix F. H.
Published: February 2004

An apparatus is described for measuring the diffuse reflectance and/or fluorescence of small (15–30 mg) granulated or powdered samples of solid materials. The sample rests in the horizontal plane, thus requiring no special mounting procedure. Input light is provided by a quartz-iodine lamp through a monochromator having a range of wavelengths from 350 to 800 nm. A photomultiplier measures the light scattered from the diffusely reflecting walls of the sample chamber. The optical absorption spectrum of γ-irradiated lithium fluoride powder is shown as an example of performance, obtained in a study of the possible applicability of LiF M-,R2-, and N2-band absorption for radiation dosimetry purposes.
A Highly Sensitive Recording Balance for Very Heavy Loads
Authors: Malpica José Mireles
Published: February 2004

The sensitiveness of a balance is directly proportional to the lever arm and inversely proportional to the product of the distance of the axis of oscillation to the center of mass by the mass of the moving system. However, as the load increases, the central knife's edge and its support deform elastically, changing the line of contact to a surface with a larger frictional torque, decreasing the responsiveness of the balance to small increments of load. This is the main cause of loss of responsiveness as the load increases. It is possible to change the sensitiveness by means of a chain hung from an annular knife placed below the central knife, the other end of which can be raised or lowered. The elastic deformation of the central knife's edge and its support is avoided by turning the central knife's edge upward and making it touch lightly hard surfaces, supporting magnetically the weight of the moving system, thereby practically maintaining zero load responsiveness for all loads. By means of a servomechanism the beam is kept balanced and a suppressed zero record is made with a pen on a wide roll of paper which moves at uniform speed. It is thus possible to register the loss of mass of higher mammalians due to loss of water and metabolic processes.
Conductivity Measurements of Semiconductors by Microwave Transmission Technique
Authors: Srivastava G. P. , Jain A. K.
Published: February 2004

A simple, quick, contactless, and accurate method for the measurement of electrical conductivity of a semiconductor slab is presented in this paper. The method is based on the study of transmission of circularly polarized TE11 mode of microwave propagation in circular waveguide. Conductivity of n-type germanium and silicon samples and its temperature variation in the range 293–140 K have been successfully studied.
A Computer Controlled Automatic System for Measuring the Conductivity and Hall Effect in Semiconducting Samples
Authors: Shewchun J. , Ghanekar K. M. , Yager R. , Barber H. D. , Thompson D.
Published: February 2004

A unique computer controlled automatic system for measuring the conductivity and Hall effect in semiconducting samples is described. The system features a small process control computer which runs a temperature programmable liquid helium Dewar, a magnet, and a data acquisition system. Fifty temperature points can be preprogrammed in any desired distribution over the range 4.2–400 K. The control computer ensures that the system is virtually foolproof in terms of operator blunder and system malfunction. Data acquisition is on punched paper tape with hard copy output. Data, converted from paper tape to cards, are analyzed by a high speed computer. Turnaround times (from sample loading to full analysis of data) of as low as 6 h have been achieved.
A Simple Technique for Generating Nitrogen Atoms
Authors: White Kevin J. , Morgan Cornelius U. , Freedman Eli
Published: February 2004

It has been found that up to 1% nitrogen atoms can be generated by passing nitrogen gas over the heated filaments of a conventional 1000 W projection lamp. It appears that the filaments must attain a minimum voltage and temperature for the production of nitrogen but these conditions can readily be achieved by a variable voltage transformer.
A Clean Vacuum Electron Beam Column for Cathodoluminescence Investigations
Authors: Marciniak H. C. , Wittry D. B.
Published: February 2004

An instrument is described for investigation of cathodoluminescence at temperatures between 25 and 400 K and beam voltages to 50 kV. Contamination effects are minimized by the use of oil-free pumps, by isolation of the specimen region from sources of organic vapors, and by the use of baffles at liquid nitrogen temperature above and below the specimen region. Preliminary results on the cathodoluminescence of GaAs are reported and compared with the temperature dependence of the bandgap from optical absorption data.
A Time-Resolved Ross Filter System for Measuring X-Ray Spectra in Z-Pinch Plasma Focus Devices
Authors: van Paassen Hugo L. L.
Published: February 2004

The development of plasma pinch and other flash x-ray devices has created the need for a system capable of measuring the spectra of 50 nsec x-ray pulses. A Ross filter system used in conjunction with silicon diode x-ray detectors gives nanosecond time resolution in spectral intervals between 5.46 and 115.6 keV.
Soft X-Ray Image Intensifiers with High Time and Space Resolution
Authors: Bettinali L. , Pecorella F. , Rager J. P.
Published: February 2004

We describe in this paper a device giving time and space resolved soft x-ray pictures of rapidly varying intense sources based on the use of a channel plate intensifier. Ten nanosecond soft x-ray framing of a dense plasma focus has been obtained using a 200 μ pinhole for image formation limiting space resolution to 3 line pairs/mm. The principle of this device has been conceived in order to preserve the 10 line pairs/mm intrinsic space resolution determined by the channel plate.
Domain Studies in Thin Film Recording
Authors: Kaske A. D. , Oberg P. E. , Paul M. C. , Sauter G. F.
Published: February 2004

An observation technique utilizing the longitudinal Kerr magneto-optic effect was used in various studies of thin film recording. The semitransparent nature of the recording media allowed simultaneous observation of recorded domains and the write and read head gaps. Thin film heads were used to record in iron films having coercivities ranging from 60 to 160 Oe. The apparatus allowed quick determinations of maximum linear densities which were as high as 1550 flux reversals/cm. Recorded domain orientation with respect to the gap of a thin film read head was easily observed, and the corresponding output signals on an oscilloscope were photographed. The write-read-observe apparatus with a thin film read head was also helpful in detecting the magnetic field from Néel walls.
X-Ray Detectors with Bandpass Response Characteristics
Authors: Lindsey James S.
Published: February 2004

A detector that is sensitive to x rays in only a given energy range is described. It can be constructed to have a wide variety of passband widths and positions. It has a very low sensitivity (roughly 10−21 C/keV of incident energy) and is, therefore, useful in high flux applications and where nanosecond time resolution is important.
An Interfacing Unit for a 28 psec Feedthrough Sampling Head and a Random Sampling Oscilloscope
Authors: Andrews James R.
Published: February 2004

In time domain measurements of repetitive pulses there are situations when a signal delay line cannot be tolerated and a signal pretrigger is not available. In such situations, a random sampling oscilloscope system must be used. In the course of recent research activities, the author encountered the need to employ a remote, 50 Ω feedthrough, 28 psec transition time, wide-band sampling head with a random sampling oscilloscope system. Because the sampling head and the random sampling system were incompatible units from different manufacturers, an interfacing system was required to connect the two units. Presented here are a working design for the interface and operating results.
Window-Heat Sink Sandwich for Optical Experiments: Diamond (or Sapphire)-Semiconductor-Indium Sandwich
Authors: Holonyak N. , Scifres D. R.
Published: February 2004

A fixture for mounting thin semiconductor samples for luminescence and stimulated emission experiments is described. This fixture, a sandwich configuration, consists of a diamond or sapphire window, a thin (1–5 μ) experimental sample, and indium wetted onto copper. In comparison with previous methods for mounting thin samples for optical pumping, the new sandwich fixture affords higher heat dissipation capability (∼103 W/cm2) and total reflection at the sample edges and back surface, thus improving the sample Q and optical performance.
A Wide Range Superregenerative Nuclear Quadrupole Resonance Spectrometer
Authors: O'Konski C. T. , Scheffer T. J.
Published: February 2004

A versatile grounded grid Colpitts superregenerative oscillator-detector with varactor diode frequency modulation has been tested and is described here.
A Silver Chloride Seal
Authors: Aslam M.
Published: February 2004

A new method is described for making a silver chloride seal between two glass components having the same coefficient of thermal expansion, which uses rf heating of the sealing surfaces. The advantages of the sealing technique are outlined.
Visual Spectrometer for Use With a Pulsed CO2 Laser
Authors: Robinson A. M. , Bradette C. , Kirkwood E.
Published: February 2004

A block of graphite has been used to modify a spectrometer for visual observation of the wavelength emitted by a transversely excited high pressure CO2 laser.
A Free-Space Focused Microwave System to Determine the Complex Permittivity of Materials to Temperatures Exceeding 2000°C
Authors: Bassett Harold L.
Published: February 2004

The instrumentation, the design of the free-space focused microwave bridge system, and the technique for determining the complex permittivity of materials from ambient to 2500°C are described. The system employs a rotating disk sample which is located at the coincident focal point between two prolate spheroidal reflectors; the sample is heated on one side by oxyacetylene flames in such a manner that the microwave beam is not affected by the flames. Dynamic measurements are made of the sample insertion phase and insertion loss. A transient heat conduction analysis is used to determine the temperature profiles within the sample, and the electrical transmission data are correlated with the temperature profiles to give dielectric constant and loss tangent as functions of temperature. The relative dielectric constant and loss tangent of high purity slip-cast fused silica (density of 1.91 g/cm3) are determined to 2500°C. The relative dielectric constant vs temperature function is a segmented line and is 3.34 at ambient, increases linearly with temperature to 3.54 at 1500°C, 3.98 at 1600°C, 4.18 at 1700°C, and 4.32 at 2500°C. The loss tangent vs temperature function is also a segmented straight line when plotted on semilog paper with a value of 0.0005 at ambient and 0.09 at 2500°C.
A Time Interval Selector and Proportional Delay Generator
Authors: Roy N. L. , Becker D. G.
Published: February 2004

An instrument is described that performs the following timing functions: (a) selection of time intervals which lie within a preselected range; (b) upon occurrence of a selected time interval, generation of three real time triggers, two of which are delayed by separately adjustable multiples of the time interval and one of which coincides with the end of the interval. Function (b) is especially valuable in time coincidence work with poorly analyzed beams or with particles of indeterminate and widely varying velocity; an example of this type of application is discussed. Circuit values are given for a unit with time interval limits continuously variable within 1–10, 10–100, and 100–1000 μsec ranges and with time interval multiplying factors continuously variable from 0.1 to 1 or from 1 to 10; design equations are presented to facilitate modification of these values, as may be required for other applications.
A Scattered Light Polariscope for Three-Dimensional Birefringent Flow Studies
Authors: McAfee Wallace J. , Pih H.
Published: February 2004

This paper reports in detail the design and construction of a new scattered light polariscope for three-dimensional birefringent flow research. The unique features of this polariscope, which were employed to overcome the particular problems associated with birefringent flow analysis using scattered light, are pointed out. A photograph of typical birefringence patterns obtainable is shown. A comparison of theoretical and experimental results for a particular flow case is made indicating the accuracy that can be obtained using this polariscope.
A Proton Recoil Monitor for Neutron Flux Measurements
Authors: Jaszczak Ronald J. , Macklin R. L. , Taylor M. C.
Published: February 2004

Time-of-flight techniques have been used with a silicon surface barrier detector and a polyethylene radiator to determine the neutron flux from the Oak Ridge electron linear accelerator in the energy region between 200 keV and 7 MeV. The 200 mm2 surface barrier detector at 40 m and constant fraction timing electronics are used to measure time of flight, from which the neutron energies are inferred. A Monte Carlo program has been written to determine the efficiency, timing, and energy characteristics of the monitor system.
Stroboscopic Scanning Electron Microscopy at Gigahertz Frequencies
Authors: Robinson G. Y.
Published: February 2004

Techniques for achieving a microwave time resolving capability in a scanning electron microscope using the stroboscopic mode of operation are presented. By pulsing the primary electron beam with traveling wave electrostatic deflection plates, an over-all system bandwidth in excess of 2 GHz is achieved. A method to detect fast primary electron beam pulses is also reported. Time varying surface potential measurements using secondary electron emission are given to demonstrate the microwave frequency response.
Molecular Beams of Short Lived Radioactive Nuclides
Authors: Grover J. R. , Kiely F. M. , Lebowitz E. , Baker E.
Published: February 2004

The advantages of the use of molecular beams labeled with short lived (T½≈10−5−10−1 sec) nuclides in crossed beam studies of molecular interactions are discussed. Theoretical expressions useful for the design of effusive sources of such beams are presented. Experiments to verify the theory and develop apparatus capable of generating usefully intense beams are described, with particular reference to beams of HAt made with 0.032 sec 217At. Beams of 4×105 molecules/min incident on a spot 0.4 cm in diameter, 2.5 cm from the collimator, and with angular divergence of 4° have been achieved.
A Safety Shutter for Use on X-Ray Generators
Authors: Farnum E. H.
Published: February 2004

A simple shutter has been constructed to increase the safety of x-ray generators used in routine diffraction work. It has been designed to permit easy alignment of an x-ray camera while minimizing the possibility of accidental release of the x-ray beam. Failsafe and nearly foolproof, the shutter is particularly suitable where many operators may be using the same x-ray generator.
A Cryostat for Low Energy Electron Diffraction Work at Liquid Helium Temperatures
Authors: Strongin Myron , Dickey J. M. , Farrell H. H. , Arns T. F. , Hrabak G.
Published: February 2004

An apparatus is discussed which has been successfully used for low energy electron diffraction (LEED) experiments at liquid helium temperatures. Problems such as sample cleaning and thermometry are discussed, along with a description of the use of the apparatus in an experiment where argon crystals were grown on the niobium (100) face.
Self-Balancing Conductance Bridge for Low Temperature Thermometry
Authors: Chase R. L.
Published: February 2004

A self-balancing conductance bridge is described that operates at sufficiently low power levels to be useful for thermometry at very low temperatures. It uses a four-terminal configuration which largely eliminates the effect of lead resistance. Operation at a low frequency, synchronized with the 60 Hz power frequency, and the use of a wide dynamic range error detector make the bridge very insensitive to hum pickup and capacitive unbalance.
A Magnetic Monopole Detector Utilizing Superconducting Elements
Authors: Alvarez Luis W. , Antuna Maurilio , Byrns Roscoe A. , Eberhard Philippe H. , Gilmer Robert E. , Hoyer Egon H. , Ross Ronald R. , Stellrecht Hans H. , Taylor John D. , Watt Robert D.
Published: February 2004

An electromagnetic detector has been built to extend the search for magnetic monopoles to the lunar sample returned during the Apollo missions. It is sensitive to the minimum magnetic charge allowed by Dirac's theory and permits analysis of a sample without changing any of its properties. The apparatus consists of a superconducting niobium sensing coil with a core at room temperature, shorted by a superconducting mechanical switch and protected against the effects of variable ambient magnetic field by an adequate shield made of superconducting lead. Characteristic features, performance, and sample containers are described.
Balloon Flight Instrumentation for Solar Cell Measurements
Authors: Sarles F. W. , Haase W. C. , McKenzie P. F.
Published: February 2004

Instrumentation has been developed which automatically measures the V-I characteristics of a number of solar cells and transmits the resultant serialized data stream over an rf telemetry link. This particular system was designed for 64 cells; selection of cells is accomplished entirely by semiconductor circuits utilizing switched feedback techniques. Two hundred and fifty-two points are taken on the V-I characteristic, giving detailed information on slopes as well as actual values. Measurement accuracies are 0.03% of full scale for voltage and 0.1% of full scale for current; these do not represent attainable limits but are simply reasonable limits for this specific application. The system described was built to calibrate solar cells on a high altitude balloon flight, but the techniques can be applied equally well to ground or satellite applications.
A Low-Current Low-Energy-Spread Duoplasmatron Ion Source
Authors: Steinberg M. , Yap B. , Fleischmann H. H.
Published: February 2004

Design and operation of a simple duoplasmatron particularly suited for low energy atomic ion scattering experiments are described. With permanent magnets and air cooling, it produces ion currents of about 100 μA having an energy spread of only a few electron volts.
The Saturation Gain of Curved Channel Multipliers
Authors: Andresen R. D. , Page D. E.
Published: February 2004

A model is presented dealing with the saturation gain occurring in curved channel multipliers at high applied voltages. Assuming that space charge is the gain limiting process, the number of electrons within this cloud is calculated. There exists good agreement between experimental and theoretical saturation gain in the range of high voltage applied to the curved channel multiplier.
A Cross Correlation Chopper for Molecular Beam Modulation
Authors: Hirschy V. L. , Aldridge J. P.
Published: February 2004

Application of a cross correlation technique for improving the signal-to-noise ratios and for measurements of time-of-flight (TOF) spectra of thermal energy molecular beams is described. Results of modulating a thermal argon beam are presented. A reduction of the noise level by a factor of 7 beyond signal averaging is observed.
An Apparatus for Measuring Diffusion and Partition Coefficients of Dissolved Substances in Membranes
Authors: Špaček P. , Kubín M.
Published: February 2004

An apparatus has been described for rapid and accurate measurements of the diffusion and partition coefficients of dissolved substances in membranes, along with the general layout and arrangement of the equipment and the possibilities of use. The apparatus combines a diffusion cell and a twin membrane pump, and has been designed in such a manner as to reduce to a minimum the total volume of solution in the apparatus. It is used in connection with a sensitive external flow concentration detector.
A High Resolution Electron Spectrometer for Use in Transmission Scanning Electron Microscopy
Authors: Crewe A. V. , Isaacson M. , Johnson D.
Published: February 2004

The design and construction of a double focusing uniform field magnetic electron spectrometer are described. The pole pieces of the magnet are curved in an effort to correct all median plane aberrations and thereby increase the collecting power. The spectrometer has been installed on a scanning microscope which uses a field emission gun to produce a 100 Å probe. Energy analysis of the transmitted electrons as well as filtered diffraction patterns can be obtained from areas as small as 100 Å in diameter. In addition, the area under study can be observed directly in the scanning transmission mode, using electrons of any selected energy loss. A resolution of the spectrometer of 2 ppm at an electron energy of 20 keV is shown and the measured second order aberration coefficient is <5% of that of an equivalent straight edge sector magnet. Also, the solid angle for collection of electrons is about an order of magnitude greater than that of the equivalent straight edge magnet at any given resolution. Experimental results in all modes of operation are presented.
Piezoelectric Determination of Crystal Axes
Authors: Engan H.
Published: February 2004

Two different methods of orienting piezoelectric crystals are described. One method depends upon the symmetry of the phase velocity of elastic surface waves as a function of propagation direction in a crystal face. The other method utilizes the symmetry of the piezoelectric coupling strength. Measurements in the Z planes of α-quartz and LiNbO3 reveal accuracies better than 10′ for the determination of the nonoptic axes.
Capacitively and Inductively Foreshortened Cavities for Magnetic Resonance Spectroscopy
Authors: Guenther B. D. , Christensen C. R. , Jensen R. A. , Daniel A. C.
Published: February 2004

Two types of cylindrical reentrant cavities are described for magnetic resonance and ultrasonic applications in the 0.1–-1.0 GHz frequency region. The physical size of these cavities is reduced by introducing large capacitive and inductive elements into the cavity. Tuning, rf coupling, and temperature control techniques are described for operation at low temperatures.
Time Resolution of Plasma Potential Using Gridded Electrostatic Analyzers
Authors: Robinson J. E. , Clarke J. F.
Published: February 2004

A system is presented for the time resolution of plasma potential using gridded electrostatic analyzers. The novelty of this method is the separation of consecutive current-energy characteristic curves and their display on a CRT. Using a 20 kHz bias signal, 30–50 consecutive 25 μsec sweeps are displayed on a CRT in a 1 msec time interval. This is sufficient for the study of low frequency plasma fluctuations in transient confinement experiments. Application to the DCX-2 mirror machine is discussed.
A Secondary Reference Voltage Source Stable to 1 ppm
Authors: Raamot J.
Published: February 2004

The design of a simple parallel current regulation circuit has the following bandwidths: 10 MHz for voltage regulation, 0.2 Hz for the primary reference voltage circuit, and 20 Hz for amplifier noise. These characteristics compare very favorably to other voltage regulation circuits which are used in design of secondary reference voltage sources.
Accommodation Coefficient Measurements with a Sensitive Torsion Balance
Authors: Schmidt C. , Schiff H. I.
Published: February 2004

The normal impulse accommodation coefficient is measured with a torsion balance. Data for Ar, N2, O2, H2, N2O, CO2, stainless steel, and glass are given. The absolute error of the relative method used is Δσ′=0.05. The measurements occur at room temperature.
A Bleed-Type Pressure Transducer for In-Stream Measurement of Static Pressure Fluctuations
Authors: Spencer B. W. , Jones B. G.
Published: February 2004

The theory, design, and operation of a bleed-type pressure transducer for measurement of static pressure fluctuations in turbulent incompressible air flow are described. The transducer features miniature size (0.89 mm diam orifice), good sensitivity (3.0 mV/cm of water), minimal yaw sensitivity, and approximately uniform amplitude response from dc to 8 kHz using helium as the bleed fluid. Static and dynamic methods of calibration are described as well as an experimental arrangement for wind tunnel measurements.
Two Theoretical Analyses of the Output Signal from an Eddy Current Sensor
Authors: Baudelet C.
Published: February 2004

The theorical output signal of an eddy current sensor has been derived by two techniques. The physical analysis, which requires simplifying assumptions, leads to an expression suitable for numerical evaluation, while the dimensional analysis approach results in a similar formula that can serve as a guide to experiments.
A Mass Spectrometer for the Simultaneous Measurement of the Neutral and the Ion Composition of the Upper Atmosphere
Authors: Balsiger H. , Eberhardt P. , Geiss J. , Kopp E.
Published: February 2004

A mass spectrometer is described which measures the neutral and the ionized components of the upper atmosphere simultaneously (delay ∼20 msec). Its 1% mass resolution is 60 and its sensitivity is sufficient to measure small ion concentrations in the presence of high neutral gas densities. During rocket flights the shift in the mass scale between the ion peak and the corresponding neutral peak is a measure for the rocket skin potential.
A High Resolution Spectrometer for the Shorter Millimeter Wavelength Region
Authors: Huiszoon C.
Published: February 2004

A description is given of a molecular beam apparatus which extends high resolution absorption spectroscopy into the shorter millimeter wavelength region (up to 500 GHz). A parallel-plate-type absorption cell, allowing for Stark modulation, is used with the molecular beam passing between the plates. The half-width of the absorption lines is about 5 kHz at a resonance frequency of about 200 GHz.
An Inexpensive Energy Filter Lens for Large Diameter Electron Beams
Authors: Zeman H. D. , Jost K. , Gilad S.
Published: February 2004

The theory behind the use of a rotationally symmetric hyperbolic electrostatic field as an energy filter lens for electrons is discussed. The design of such a lens for use in eliminating inelastically scattered electrons from the output beam in a low energy electron scattering experiment is described. A filter lens designed, built, and tested by the authors is described. It has an entrance aperture of 1.27 cm diameter, an angular acceptance of ±2°, and a measured energy cutoff width of (0.27±0.02)%.
Production of Polycrystalline Iso-Oriented Films of Low Melting Point Compounds by Controlled Cooling of the Liquid
Authors: Lunelli Bruno
Published: February 2004

An apparatus is described which can be used for the easy and reproducible production of polycrystalline iso-oriented films of low melting point compounds by crystallization of the liquid in an iso-oriented temperature gradient. This method is suitable both for compounds which are liquids and those which are gases at room temperature. Suggestions which lead to the production of different crystal planes are given. Results obtained for carbon disulfide and vinyl chloride are presented.
Electrostatic Deflection Binary Alloy Evaporator
Authors: Erskine J. L. , Tracy John M. , Stern E. A.
Published: February 2004

A new technique for producing thin film binary alloys is discussed which used periodic deflection of an electron beam between two sources in a vacuum evaporator. This technique makes it possible to produce high quality binary alloys of predetermined ratios and with uniform composition throughout the thickness, as shown by x-ray diffraction analysis.
Vidicon Microscope for Counting Fluorescent Particles
Authors: Dyer D. L. , Fuller C. H.
Published: February 2004

Weakly fluorescent particles may be counted or displayed through use of the light integrating property of vidicons. This paper describes a fluorescence microscope-vidicon system designed for counting bacteria. It employs incident bright-field uv illumination with an inexpensive television (TV) system.
A Low Temperature Glass-Ceramic Capacitance Thermometer
Authors: Lawless W. N.
Published: February 2004

Dielectric measurements are reported on capacitance thermometers based on SrTiO3 crystallized from glass at 1100 and 1200°C. Multilayer experimental units, approximately 5×2×1 mm, were fabricated using pilot plant facilities and measured from 1.7 to 300 K. If both the capacitance and loss tangent are measured, the range of the 1100°C crystallized thermometer is from at least 1.7 to 300 K. For capacitance measurement alone, the thermometer range is below 72 K, and in this range the capacitance varies smoothly and monotonically with temperature, becoming linear below 5.2 K. The sensitivity is largest in this linear region and averages 250 pF·K−1 for the 1100°C crystallized thermometers. The self-heating at 4.2 K is about 70 pW (5 kHz, 7 mV) and decreases with decreasing temperature. The effect of a magnetic field on the thermometer was measured in an open Dewar of liquid helium at four frequencies in fields up to 80 kG. The measured changes were ≤±1 mK and are interpreted as fluctuations in the bath temperature rather than an intrinsic magnetocapacitance effect. The response time between 4.2 and 300 K is at least 70 K·sec−1. The main disadvantage of the thermometer is a transient (∼30 min) capacitance instability which is equivalent to a ≤30 mK change before stabilization. Once stabilized, the thermometer repeats to about ±2 mK when compared to a germanium thermometer, and repeats to ±13 mK on cyclically plunging into liquid helium (15 cycles) in the unstabilized case. This instability is apparently due to helium migration into the unencapsulated sensor body. The polar properties of glass crystallized SrTiO3, on which the thermometer is based, are briefly discussed, and comparisons are made with two other capacitance thermometers reported in the literature.
Simulating Atmospheric Radio Noise from Low Frequency through High Frequency
Authors: Bolton Earl
Published: February 2004

Generally it is too costly or otherwise not feasible to conduct performance tests on a radio communication system under conditions of actual atmospheric radio noise because this noise is nonstationary. Accurate simulation of desired conditions solves this difficulty. Magnetic tape recordings were made of atmospheric radio noise from low frequency through high frequency. The recordings were computer analyzed and were used as a model for the design of an atmospheric noise simulator. The simulation is valid and accurate for the limited available data base.
Paired Comparison Tests of the Relative Signal Detected by Capacitive and Floating Langmuir Probes in Turbulent Plasma from 0.2 to 10 MHz
Authors: Roth J. Reece , Krawczonek Walter M.
Published: February 2004

Paired comparison measurements of the spectrum of electrostatic potential fluctuations in a steady state turbulent plasma confined in a magnetic mirror geometry have been made with capacitive and floating Langmuir probes over the frequency range from 0.2 to 10.0 MHz. For the experimental conditions investigated (5×107≤ne≤5×108/cm3, 8≤Te≤38 eV, 350≤Ti≤930 eV, Bmax=1.0 T), no significant difference in the relative frequency response was observed below 4.0 MHz. At about this frequency, however, the signal detected by the floating Langmuir probe dropped off relative to that of the capacitive probe. The source resistance of the turbulent fluctuations sensed by the Langmuir probe was about 400 Ω. At higher frequencies (from 7.0 to 10.0 MHz) a signal was detected by the floating Langmuir probe that was not detected by the capacitive probe. This spurious signal may be confused with the turbulent fluctuations of the plasma in the absence of paired comparison tests.