bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of the Index of Refraction of Some Molten Ionic Salts
Authors: Marcoux Jules
Published: February 2004

A simple method for measuring the index of refraction of molten salts is described. The indices of CaCl2, KBr, NaCl, and KCl are given at wavelengths ranging from 4000 to 7000 Å. Dispersion curves are given. Comparison is made with values obtained by another method.
A Solid State Light Pen and Computer Interface for the Tektronix 611 Storage Oscilloscope
Authors: Leskovec R. A. , Bevington P. R.
Published: February 2004

A solid state light pen has been developed to accommodate the phosphor characteristics of the Tektronix 611 storage oscilloscope. Computer interfacing for the 'scope includes remote control of the storage mode and expansion of both X and Y axes by a factor of 1–8 with variable trace positioning.
A Thermistor Anemometer for the Measurement of Very Low Air Velocities
Authors: Martino Francisco S. , McNall Preston E.
Published: February 2004

A new thermistor anemometer is described for measuring low air velocities of 0–100 cm/sec. A theoretical performance curve (anemometer output vs air velocity) was calculated for the instrument. When compared with the experimental performance data, good correlation existed. Several characteristics of the anemometer were investigated experimentally. The instrument displayed excellent sensitivity and good stability (reproducibility of the calibration curve at a given ambient temperature). The output was not affected by the air flow direction. The anemometer output was affected by changes in ambient temperature, and the use of calibration curves for various ambient temperatures is suggested.
A Precision Variable Luminance Source for Photometric Applications
Authors: Goodell William V.
Published: February 2004

A variable luminance source having precise photometric characteristics is described. The instrument utilizes the principle of the integrating sphere, efficiently using the flux from a 45 W quartz-halogen lamp to provide luminances from 1 to 500 fL in a continuous range. The color temperature was kept within ±100 K over the entire luminance range by geometric means without the introduction of aberrative optical elements. Luminance uniformity and stability of ±2.5 and ±0.5%, respectively, were maintained over a 42 mm output aperture for the tungsten spectrum from 0.4 to 1.4 μ.
Circuit for Approximate Computation of Reciprocal of Time Delay to Maximum Cross Correlation
Authors: Tompkins W. R. , Intaglietta M.
Published: February 2004

A circuit was developed to measure the inverse time delay to maximum cross correlation between two stationary time varying voltages. The first voltage is delayed in a sample-and-hold circuit whose sampling frequency is swept. When the delay between the two signals is smaller than a quarter of the period of the fundamental, the sample-and-hold voltage is directly multiplied with the downstream voltage. When the delay is greater than a quarter of the period of the fundamental, the sample-and-hold signal is multiplied by the sample-and-hold value of the second signal, sampled at the same rate, 180° later. The filtered product for both cases has a maximum when the sampling frequency is inversely proportional to twice the delay to maximum cross correlation.
Apparatus to Rotate Samples Rapidly at Temperatures Less than 2 K in High Transverse Magnetic Fields
Authors: Potter Wendell H.
Published: February 2004

A system is described that allows rapid rotation of a sample at speeds up to 103 rps at temperatures less than 2 K in large transverse magnetic fields. It uses an He gas turbine with hydrostatic He gas bearings. A very compact, efficient counterflow heat exchanger was developed to cool the bearing and drive gas to 15 K. The system was developed specifically to produce high proton polarizations using the spin refrigerator technique, but is applicable to other experimental situations requiring high speed rotation at low temperatures in large transverse magnetic fields.
An Apparatus for Magnetic Measurements at High Pressure
Authors: Vaughan R. W. , Lai C. F. , Elleman D. D.
Published: February 2004

A nonmagnetic high pressure cell capable of being used for a variety of magnetic measurements to over 100 kilobars is described. A Bridgman anvil type of cell, it has a 3–5 mm3 sample volume and is suitable for both pulsed and wide line nuclear magnetic resonance (NMR) measurements. In addition to a detailed description of the apparatus used for wide line NMR measurements, the use of the high pressure cell for magnetoresistance and susceptibility measurements is described.
A Wien Filter for Use as an Energy Analyzer with an Electron Microscope
Authors: Curtis G. H. , Silcox J.
Published: February 2004

An electron optical system is described which is suitable for energy loss analysis in an electron microscope. A focusing spectrometer of the Wien type has been added underneath the column of a Hitachi HU11A electron microscope. After passing through the microscope, the electrons are slowed down before entering the spectrometer and reaccelerated to the detection point. Appropriate control of the electron trajectories into the Wien analyzer is achieved with a quadrupole field lens which makes it possible to use a long entrance slit. The energy resolution of the analyzer is limited by the width of the entrance slit which is adjusted to match the beam spread (1.5 eV). It can be made large (250 μ) compared with that of the Möllenstedt analyzer (5 μ), thereby passing much higher intensity through the analyzer and increasing the system flexibility.
Precision Beam Location
Authors: Sickafus E. N.
Published: February 2004

A method for precise positioning of a beam on a given target is described. The technique employs a time dependent bias applied to the relative target beam position and frequency tuned detection of an associated flux that is coherently sensitive to changes in the primary beam. A location reference is determined which is the centroid of the convolution product of the target shape function and the beam profile function.
A Miniature Turbulence Gauge Utilizing Aerodynamic Lift
Authors: Siddon Thomas E.
Published: February 2004

An advanced version of the aerofoil probe turbulence gauge is described. The new device uses an axisymmetric lifting body sensor of 2.4 mm diameter coupled directly to a miniature preamplifier unit (6.35 mm diam). The output voltage varies linearly with the v or w component of turbulence. The device has uniform sensitivity and good signal-to-noise ratio over a nominal frequency range of 10–10 000 Hz. A discussion of calibration procedures and application considerations is included.
Random Pulse Train Generator with Linear Voltage Control of Average Rate
Authors: Hanby J. A. , Redman S. J.
Published: February 2004

An electronic instrument which generates a train of constant amplitude pulses occurring at random times is described. The average pulse rate of this process is a linear function of a controlling voltage. The intervals between successive pulses form a renewal process and the probability density of these intervals may be varied from an exponential distribution to a gamma distribution of variable form. Statistical measurements on the pulse train are described which support the claims on its statistical properties.
Automatic Counting and Sizing of Airborne Ferromagnetic Particles
Authors: Fratucello Giovanni , Giovanelli Giorgio
Published: February 2004

A continuous and automatic instrument for counting and sizing airborne ferromagnetic particles has been developed. It measures magnetic flux variations caused by ferromagnetic particles crossing a search coil; the size of the particles is derived from pulse height analysis. The response of the instrument is linear over a wide range of particle sizes; particles down to 10 μ in diameter can be detected.
A Stable Low Temperature Gas Stream System with Variable Temperature Control
Authors: Silver Lawrence , Rudman Reuben
Published: February 2004

A general purpose automatic low temperature system, which generates a stable stream of cold gas, can be used for maintaining frost-free samples at any temperature between ambient and 100 K. In this system cold nitrogen gas, obtained from boiling liquid nitrogen, is warmed to room temperature, controlled by standard noncryogenic components, and recooled by passing it through a heat exchanger immersed in the liquid nitrogen. The system also incorporates a novel level controller consisting of a magnet riding on the level indicator float which activates magnetic reed switches attached to the exterior of this indicator. The application of this apparatus in the field of x-ray diffraction is described.
Automatic Apparatus for the Determination of Helium Diffusion in Solids
Authors: Crawford R. W. , Frazer J. W. , Holt J. B.
Published: February 2004

An apparatus has been designed and built to determine automatically the rate of release of helium from various solids as a function of temperature. The diffusion of He in single crystals of neutron irradiated LiH is used to describe the operation of the apparatus. Samples can be maintained in a vacuum or in an automatically maintained gas (other than noble gas) atmosphere and held at temperatures from 200 to 1400°C. Helium evolved from the sample is periodically removed. A quantitative determination and standardization for He are automatically performed. If a gas atmosphere is used, this is removed from the helium by use of a titanium sublimation pump. The He which remains is then measured with a low resolution high sensitivity residual gas analyzer (partial pressure gauge). The system is capable of measuring at least 10−10 cm3 STP helium.
Digital Pulses Delayed with Substantially Reduced Deadtime
Authors: De Volpi A. , Caya G. , Rush C. , Rudnick S.
Published: February 2004

A delay module, NIM compatible, which can retard digital pulses through the entire range of 0.1 μsec–10 msec has been developed. The novel feature of the unit is an internal distribution system for six delay monostables that substantially reduces the deadtime which otherwise would be imposed for at least the duration of the delay. For example, if the product of count rate times deadtime is 0.9, the added deadtime loss due to this delay module can be about 0.1% (a 500-fold improvement over a single delay monostable). There are two modes of operation which depend upon the method of deadtime avoidance: scaling or cyclic distribution. Both methods yield similar results. There is also a test mode for calibration of the unit as well as for accurate determination of the delay interval. By the inclusion of appropriate gating arrangements, rapid and accurate delay calibrations can be performed by a random-pulse averaging method used in conjunction with a precision oscillator. The design of the circuit, operating experience, method of calibration, and results of calibration are included in the report.
A Triaxial Bridge Accelerometer
Authors: Westlund Clay D.
Published: February 2004

A triaxial bridge-type accelerometer is described. It is used in a falling sphere experiment to determine atmospheric density, temperature, and pressure. A reference mass, internal to the accelerometer, is displaced from a null position when the sphere experiences drag acceleration as it falls through the earth's atmosphere. Displacement, measured along each of the three axes, is related to drag acceleration and to air density. The data from the initial flight indicate a substantial improvement in sensitivity over the transit-time accelerometer previously used. Discussion is given on the construction, operation, and in-flight performance of the device.
Apparatus for Determination of Residual Drag Torque on Small Spinning Spheres in Magnetic Suspension
Authors: Fremerey J. K.
Published: February 2004

An apparatus for measuring the frequency decay of magnetically suspended freely spinning steel spheres is presented. A residual drag torque, which considerably exceeds the gas friction torque in ultrahigh vacuum, has been determined by means of a new measuring system for small frequency changes, which features high resolution power even at low rotor speed. The decay ratio −ω̇/ω has been recorded for several spheres with different diameters over a frequency range from 0.2 to about 105 Hz. Apart from some characteristic deviations, which have been related to certain experimental conditions, a linear frequency dependence of the decay ratio −ω̇/ω=a0+a1rω has been detected in the described apparatus (r being the sphere radius) with a0≃3×10−9 sec−1 and a1≃3×10−12 m−1. An explanation is given for this type of drag torque. Measurements are reliable within ±6×10−11 sec−1 up to rω≃700 m/sec. Stabilities better than ±5×10−12 sec−1 during one day have been recorded. A long term stability of the latter magnitude is required to verify the existence of an ω6 proportional energy dissipation, which was deduced by Keith in 1963 from relativistic gravitational theories.
A Wide Band Correlator
Authors: Fukao Masayuki
Published: February 2004

A wide band correlator based on an orthogonal expansion of the correlation function to be analyzed is described. The resultant correlation function is displayed on an oscilloscope screen in ``live'' time. A frequency band from some kilohertz to 1 MHz can be dealt with only by changing the time constant of analyzing orthogonal filters. Some discussions about truncation error of orthogonal expansions and a treatment for the case of periodic functions are described.
A Nanosecond Risetime Megavolt Voltage Divider
Authors: Pellinen D. G. , Heurlin S.
Published: February 2004

A small linear resistive voltage divider has been used in vacuo for measuring pulsed voltages exceeding 1 MV on electron accelerators. The monitor appears to be linear until breakdown and has a bandwidth greater than 60 Hz–150 MHz. A method of correcting for nonconservative induced potentials is described as well as several independent calibration methods.
Minimum Chromatic Aberrations of Magnetic Quadrupole Objective Lenses
Authors: Moses Ronald W.
Published: February 2004

Orthogonal magnetic quadrupole lens systems that could serve as electron microscope objectives are treated theoretically. After certain constraints are placed on the quadrupole field strength, the calculus of variations is applied to obtain systems with minimum chromatic aberrations. A digital computer was used to calculate optimum orthomorphic and anamorphotic objective type systems. The resulting orthomorphic systems have four lenses while the corresponding anamorphotic systems have three. The chromatic aberration only varies by a factor of 2 in this study indicating its relative insensitivity to choice of lens systems. It is found that the optimum quadrupoles have about 3.6 times as much chromatic aberration as round lenses with comparable fields and dimensions.
Electrostatic Probe for Measuring Ionization Rates behind Reflected Shock Waves
Authors: Matsuda S. , Gutman D.
Published: February 2004

A flat plate electrostatic probe for monitoring the specific rate of ionization behind reflected shock waves is described here. The use of the probe involves initiating an ionization reaction behind reflected shock waves and drawing the electrons formed in the process to a flat plate collector at the end of the shock tube. The electron current to the collector directly yields the time evolution of both the specific rate of ionization in the gas heated by the reflected shock wave and the concentration of the electrons in the heated gas, had the system not been perturbed by the electron removal process. The electrostatic probe is of simple construction and has a combination of sensitivity and space-time resolution not available using other techniques. It has been used to monitor the time evolution of electron production during the induction period of the C2H2+O2 reaction in the electron concentration range 105–107 cm−3 with a time resolution near 1 μsec. A modified probe could be used over a wider range of electron concentrations.
Planar Shock Wave Experiments Using Very Small Bore Guns
Authors: Hopkins Alan K. , Swift Hallock F.
Published: February 2004

Small caliber (7.62–13.7 mm) smoothbore powder guns have been developed to generate planar shock wave data in solid materials. Basically the experiments consist of launching flat plates of materials whose shock properties have been predetermined against targets made from materials with unknown properties mounted beyond the gun muzzle. A rotating-mirror streak camera is used to monitor the impact velocity and the recoil velocity of the target rear surface. These results, together with shock properties of the known material, are sufficient for determining a point on the shock Hugoniot of the unknown material when the assumption is made that target rear surface velocity is twice material velocity. The impact process is reversed (i.e., unknown material is launched against standard material when this assumption is not valid). To date, impact velocities have been limited to 2.5 km/sec because a powder gun was used for projectile launching but impact velocities can be extended to 7 or 8 km/sec by using a small light-gas gun.
How to Track Bacteria
Authors: Berg Howard C.
Published: February 2004

A microscope is described which automatically remains focused on individual motile bacteria. The container in which the bacteria are suspended is moved in such a way that the position of a given organism remains fixed; x, y, and z drive signals provide a measure of its displacement relative to the suspension medium. Records are shown of the motion of Escherischia coli.
Optical Readout of Laser Velocimeter Signals
Authors: Hauer Allan , Burr Ronald J.
Published: February 2004

An optical readout system for the analysis of laser Doppler velocimeter (LDV) signals is described and test results are given. The signal from the LDV is displayed on a TV screen and recorded photographically. The photographic negative is placed in a Fourier transform optical system which displays the frequency spectrum of the negative on a screen or photographic material. Flow velocities are then calculated from the frequency values displayed by the system and these velocities are shown to agree very closely to velocity measurements made simultaneously using a Pitot tube.
Light Collection from Large Cylindrical Scintillators
Authors: Friesenhahn S. J.
Published: February 2004

The parameters determining the light collection efficiency from large cylindrical scintillators are experimentally determined and the effects of varying these parameters are examined using a theoretical model of the scintillator. The temporal behavior of the scintillator is also calculated and methods of improving both the light collection and time response are suggested.
The Production of High Current, High Quality Beams of Ions and Neutral Particles
Authors: Coupland J. R. , Thompson E.
Published: February 2004

This paper describes results obtained with a hot cathode constricted arc plasma source and a single aperture three electrode accel-decel extraction system. The energy range covered is 5–25 keV for positive ions and 1.7–12.5 keV for neutral beams. Ion currents of the order of 80 mA H3+ and 100 mA He+ at the higher energies have been obtained through a 3.8 cm diam aperture at a distance of 180 cm from the source. The performance as a neutral injector has been evaluated by using the present PHOENIX II experiment. Finally, the relationship between experiment and theory and the limitations of this type of source are discussed.
Mass and Charge Dependent Ion Discrimination in a Linear Pulsed Time-of-Flight Mass Spectrometer
Authors: Van Brunt R. J. , Lightner G. S. , Whitehead W. D.
Published: February 2004

Two potential sources of mass and charge discrimination in a linear pulsed time-of-flight mass spectrometer have been analyzed in detail. The first is a well known effect due to spreading of the ion beam in the drift tube. The ion flux density distribution at the detector has been calculated as a function of the ion source dimensions, initial ion kinetic energy, and drift tube length and voltage. The second effect results from motion of the ions in the ion source region prior to being accelerated into the drift tube. It is shown that by appropriate choice of the source parameters and operating conditions it is possible to store ions in the source region prior to extraction and thereby enhance ion count without introducing severe discrimination effects.
Carbon Resistors as Pressure Gauges
Authors: Stankiewicz J. , White R. L.
Published: February 2004

A survey has been made of the properties of certain resistors (manufactured by the Allen-Bradley Company) under hydrostatic pressure up to 11 kilobars at 295, 77, and 4.2 K. It is found that the resistance of the resistors (nominal value 220 Ω) decreases markedly with pressure and they may provide very sensitive pressure gauges. The reproducibility during a single pressure cycle is completely satisfactory, although the resistors show hysteresis effects when the pressure is removed.
A Secondary Emission Analog for Improved Auger Spectroscopy with Retarding Potential Analyzers
Authors: Sickafus E. N.
Published: February 2004

An objectionable feature of electron spectra taken with a retarding potential analyzer, for example, as in Auger electron spectroscopy, is the large background that is characteristic of the general shape of the secondary electron distribution function. It is shown that an electron analog of the secondary electron emission from a specimen can be injected at the signal source of a retarding potential analyzer so as to cancel the secondary emission function. The result is that the annoying background that characterizes Auger electron spectra taken with retarding potential analyzers is removed, the error in the magnitude of Auger peaks due to secondary emission background is eliminated, ``washed-out'' fine structure accompanying large Auger signals may be recovered, and uniform amplifier gain is useful throughout the energy range of the detector circuit. The technique employs one of two analog functions for an approximation to the secondary electron emission and does not attempt an exact fit. The mathematical properties of these functions are described as well as criteria for choosing the appropriate function for the best approximation. It has been found that the functional behavior of the major component of the secondary electron energy spectrum from Ni (110) (i.e., ignoring superimposed Auger electron contributions) is essentially constant from 10 to 1000 eV. Consequently, there is no experimentally observed demarcation between true secondary emission and rediffused primaries. The general energy distribution function can be represented as N(E)=A(E+E0)−m.
Precision Measurement of Internal Diameters of Long, Small Bore Metal Tubing
Authors: Edsinger R. E. , Guildner L. A. , Anderson R. L.
Published: February 2004

Internal diameters of a long, small bore metal tube were calculated from the measured capacitances between it and a cylindrical coaxial probe of known characteristics. The tube and the probe were used as the electrodes of a three-lead capacitor, measurable with high accuracy in a transformer ratio arm bridge. For tubes of 0.1 cm bore or less, average diameters as a function of position can be determined by this method with an over-all uncertainty of ±6×10−5 cm over lengths of 1 m. The method can readily be extended to larger bores and greater lengths.
A Time Sharing Fluorometer for the Readout of Intracellular Oxidation-Reduction States of NADH and Flavoprotein
Authors: Chance B. , Graham N. , Mayer D.
Published: February 2004

Cellular fluorochromes, pyridine nucleotides (PN), and flavoproteins (Fp) reflect the redox state of the cytoplasmic space and mitochondria of the intact cells and tissues and afford a direct readout of essential parameters of cell metabolism. A time sharing fluorometer which alternates every 8 msec the overlapping emission and excitation wavelengths of both fluorochromes enables nearly simultaneous recording of the two components. From a spot of several millimeters in diameter an adequate signal-to-noise ratio can be obtained at a response time of less than 0.1 sec. In conjunction with the regenerative flow apparatus, the fluorescence of the components can be recorded in times down to 20 msec. Applicability to reaction kinetics in perfused organs and in suspensions of mitochondria as well as to other systems with double fluorescence labels is indicated.
High Sensitivity Microwave Gated Radiometer for Low Temperature Plasma Afterglow Studies
Authors: Delpech J.-F. , Gauthier J.-C.
Published: February 2004

We describe a new microwave gated radiometer for traveling wave measurement of the radiation temperature of low temperature plasma afterglows independent of plasma absorptivity and reflection coefficients. Since this radiometer is unaffected by a medium power heating microwave, it is particularly well suited for keeping a close control on temperature during microwave cross modulation experiments.
Temperature Gradient Vacuum Furnace for Diffusion Studies to 2000°C
Authors: Meyer R. O. , Voglewede J. C.
Published: February 2004

An rf induction-heated furnace has been designed that produces a stable linear temperature gradient greater than 1000° C/cm and a maximum specimen temperature of 2000°C. Methods of measuring temperature in a temperature gradient have been evaluated and the performance of the furnace and its power requirements are discussed.
A Simple Gas Quenching Furnace for Reactive Materials
Authors: Rose Robert L. , Goldberg Alfred
Published: February 2004

An apparatus is described in which solid samples of reactive materials are quenched following heating in a small drop-away vacuum furnace chamber. The principal feature is that the furnace is supported by the differential pressure between the furnace chamber and its surroundings. Thus, when the quenching gas is injected over the sample in the furnace chamber the vacuum is instantly broken, causing the furnace to drop away from the sample. By using chilled helium gas, quenching rates up to 1.8×104°C/sec have been achieved with 0.25 mm thick samples. Higher cooling rates should be attainable by the use of thinner samples and higher gas velocities and possibly by improving the quench nozzle design. The simplicity of the unit and the small volume to be evacuated are attractive features.
An Instrument for Measuring Pressure in Turbulent Boundary Layers
Authors: Kostiuk D. P. , Hummel R. H. , Azad R. S.
Published: February 2004

A pressure transducer, consisting of a peizojunction sensing element, has been developed for meauring both static and transient pressures. In the static mode of operation the calibration curve showed a ±1.5% FSO (full scale output) independent linearity, a 3% FSO hysteresis, and a repeatability of 0.5% FSO. Dynamically, the transducer exhibited a thermal sensitivity shift of 0.27% FSO/°C.
A Magnetic Densimeter for Low Temperatures and High Pressures
Authors: Haynes William M. , Stewart John W.
Published: February 2004

A magnetic suspension technique has been developed for use in making absolute density measurements on cryogenic fluids at low temperatures and elevated pressures. Adapting a method, previously used at room temperature, for PVT work in this region required several modifications. This apparatus can be used at any temperature below ambient and at pressures up to 340 atm. The density of saturated liquid nitrogen at 77.46 K has been determined in order to evaluate its performance.
A Combined Energy and Angle Analyzer for Scattered Electrons
Authors: Harting Erik
Published: February 2004

An instrument is described which permits energy analysis, by electrostatic deflection, of any of six beams of scattered electrons. In the particular design discussed, the beams define scattering angles between 40 and 140°, in 20° intervals. Various parameters of electron trajectories, including effects of small magnetic fields, have been computed and design criteria for optimum angular and energy resolution are presented.
Permalloy Film Deposition by Flash Evaporation
Authors: Condas George A. , Yarbrough Raymond B.
Published: February 2004

A flash evaporation technique was developed for the production of high purity, unfractioned Permalloy films. A high boat temperature was found to be necessary to prevent fractionation of the nickel and iron in the production of the vertically deposited films. Low water vapor content was also found to be necessary in the residual gas of the vacuum system to prevent the refractory metal of the boat from appearing in the deposited film.
An Electron Energy Analyzer for Photoelectron Energy Distribution Studies on Solids
Authors: Feuerbacher B. , Fitton B.
Published: February 2004

A 127° electrostatic cylindrical analyzer has been adapted for photoemission measurements. The resolution of the unit is 1.3% at 20 eV, increasing to 3.5% at 2 eV. The transmission is about 9% for energies higher than 6 eV. Integral photocurrents down to 10−15 A can be analyzed with a signal-to-noise ratio of 100. Digital data acquisition allows differentiation of the measured energy distribution spectra to enhance structure. The result is equivalent to an ac modulation technique with a considerable improvement in signal-to-noise ratio for a given integration time. Data on platinum are used as an example.
The Preparation of Metallic Prolate Spheroids
Authors: Sekula S. T. , Kernohan R. H. , Cantrell E. S.
Published: February 2004

A technique is described for the electrical discharge machining of prolate spheroid specimens from metallic rods using conventionally milled electrodes. Specimens of Nb, Ta, Re, and Nb–Ta alloys have been satisfactorily prepared. For single crystals of Nb, x-ray studies indicate the absence of any recrystallization after heat treatment of the prolate spheriods to remove strains.
A Crystal Cleaver and Electron Analyzer Assembly for Photoemission Studies on Vacuum Cleaved Crystals
Authors: Barnes Mervyn R. , Laude Lucien D.
Published: February 2004

A crystal cleaver and electron analyzer assembly is presented which allows good reproducibility of energy distribution curves of photoelectrons emitted from 10−11 Torr cleaved single crystals. The analyzer resolution is shown to be better than 50 meV for electron kinetic energy up to 2.5 eV. Additional facilities include crystal temperature control between −100 and +150°C.
Apparatus for Matrix Isolation Studies of High Temperature Species
Authors: Carstens Dean H. W. , Gruen Dieter M.
Published: February 2004

A new system suitable for studies of matrix isolated metal atoms is described and evaluated. The system incorporates a closed cycle helium refrigerator used to cool the sample block down to, or slightly below, 20 K and an electron beam sublimator to produce atomic beams of most of the refractory metals. The advantages of the system are its compactness and ease of operation.
Low Impedance Supply for Tunnel Junctions
Authors: Blackford B. L.
Published: February 2004

A circuit is described which employs an operational amplifier arranged as a voltage follower to obtain output impedances as low as 0.001 Ω. Direct drift and noise levels are such that the circuit can be used as both a dc and ac voltage source for tunnel junction measurements. A comparison is made with a similar ac conductance bridge recently reported in the literature and a simple modification of the latter circuit is suggested.
An Apparatus for Microwave Studies at High Pressures and Low Temperatures
Authors: Compy Elvin M. , Hansen Uwe J.
Published: February 2004

An apparatus for high pressure microwave experiments has been developed which can be operated at pressures up to 2 kilobars at 4.2 K using helium as the pressure transmitting medium. The high pressure chamber contains a rutile microwave resonator oscillating at ∼35 GHz. Microwave radiation is coupled into the resonator via a self-sealing conical dielectric waveguide. The apparatus has been used in preliminary measurements of the effect of pressure on cyclotron resonance in bismuth.
Digital Servo for Photogrammetric Instruments
Authors: Real R. R. , Fujimoto Y.
Published: February 2004

A form of digital servo with printed disk dc motor drive, incremental measurement, nonlinear feedback, and digital integrated circuit logic is found eminently suited to application in photogrammetric instruments. Complexity ranges from unity transfer through nonlinear transfer to use of a computer in the control loop. A steering circuit for drawing in a plane is also discussed.
A New Apparatus for Studying Excitation in Ion-Atom Collisions at Low Energy Using the Ion-Photon Coincidence Method
Authors: Vassilev G. , Baudon J. , Rahmat G. , Barat M.
Published: February 2004

A new apparatus is described whose purpose is the study of ion-atom excitation processes. A single photon emitted by the excited target atom is detected in coincidence with the ion scattered at a given angle. Preliminary results are given for the He+–He collision at 300 eV and scattering angle from 6 to 15° with excitation of the 33P state and emission of the 33P−23S line (3889 Å).
The Sensitivity of the End-On Shock Tube Detection Technique
Authors: Gutman David , Matsuda Shimpei
Published: February 2004

The sensitivity of an end-on detection technique used to monitor light emission behind reflected shock waves is described. Using this detection method, emission from a test gas heated by a reflected shock wave is monitored through an observation window mounted in the end wall of the shock tube. The geometric factor of the end-on detection system which relates the emission intensity within the test gas to the actual monitored intensity is derived and is shown to be constant under a number of experimental configurations. For the case of an exponentially growing emission signal, the sensitivities of the end-on and more conventional side-on detection techniques can be directly compared. For typical conditions encountered in studying the exponential growth of emission occurring during the C2H2+O2 induction period, the end-on detection system is shown to be 100 times more sensitive than a side-on apparatus for experiments in which a detector with a small surface area is used (e.g., a liquid nitrogen cooled InSb ir detector). For detectors with large surface areas (e.g., photomultipliers with end windows), the end-on technique is over 500 times as sensitive as side-on methods.
Time Domain Compensation of Cable Induced Distortions Using Passive Filters for the Transmission of Fast Pulses
Authors: Amsel G. , Bosshard R. , Rausch R. , Zajde C.
Published: February 2004

A method is described for suppressing the long tails which appear when signals are transmitted through cables. The principles of tail suppression are presented in a general frame and may be applied to various pulse transmission systems. The determination of the passive compensating filters is obtained by approximating the system impulse response with a convolution product, one factor being completely invertible. The compensating networks are realized by cascading impedance matched (50–50 Ω, for instance) bridged T type filters of easy construction. For a 105 m long RG-8 cable the 10 to 90% risetime was reduced from 18 to 2.5 nsec using only two filters, with a total attenuation of factor 2. It is shown that, in favorable cases, once an optimal filter for a given cable is found, other filters may be deduced from it for similar cables of different length and diameter (RG-8 and RG-58 C, for example); the theory and the measurement technique of the corresponding scaling factors are described. Various other applications are shown, including the compensation of an air cable in the subnanosecond region.
A Square Wave Dissociation Field Effect Pulse Generator for Use with Spectrophotometric Detection
Authors: Olsen Steven L. , Silver Ronald L. , Holmes Lloyd P. , Auborn James J. , Warrick Percy , Eyring Edward M.
Published: February 2004

A 50 kV square wave pulse generator and associated control circuitry for use in spectrophotometric dissociation field effect experiments has been constructed. The design differs from previous pulse generators in that cumbersome delay cables are not used. A 0.005 μF plastic capacitor is charged to a voltage adjustable from 30 to 52 kV. When the desired voltage is reached, a triggered spark gap is fired, connecting the capacitor to the chemical cell. At a preset delay time, continuously adjustable from 0 to 29 μsec, a second spark gap is fired, shorting the cell and causing the voltage remaining on the storage capacitor to be discharged through a 100 Ω resistor. This apparatus produces an exceptionally clean pulse with a rise- and fall-time of less than 22 nsec and does not produce the troublesome reflections associated with devices using delay cables. This high voltage pulse perturbs the equilibrium between reacting species in the chemical cell, and the return to equilibrium is observed spectrophotometrically. Chemical relaxation times faster than 30 nsec have been reliably measured with this device.
A New Diode for the Production of High Power Relativistic Electron Beams
Authors: Friedman M.
Published: February 2004

A new type of low impedance diode has been developed to produce pulsed relativistic electron beams. Using a multicathode system, the diode impedance was lowered to ∼4 Ω. Currents of ∼60 kA and voltages of ∼250 kV have been obtained.
A Circular Dichroism Spectrometer for the Vacuum Ultraviolet
Authors: Johnson W. Curtis
Published: February 2004

We have developed a circular dichroism spectrometer which will make measurements in the ultraviolet to 1350 Å. It is built primarily from commercially available components and is particularly simple in design. The instrument is linear and has a noise level over most of its range of less than 1×10−5 OD units for a 16 Å spectral slitwidth and 10 sec time constant. The absorption and circular dichroism spectra of (+) 3-methylcyclopentanone to 1350 Å are presented.
Thermally Controlled Precision Slits and Apertures
Authors: Münzenberg G. , Wollnik H.
Published: February 2004

A slit system is described in which the slit jaws and baseplate are made of materials of different thermal expansion coefficients. By changing the temperature of this slit system the slitwidth can be controlled. The operating range is from 1 μ to approximately 0.1 mm. The system is rugged, bakable, and still extremely precise; thus it is especially useful for uhv systems. It may be controlled remotely without further accessories. A thermally controlled slit system built for use in a mass spectrometer has been constructed and is described.
Lithium Vapor Cell and Discharge Lamp Using MgO Windows
Authors: Slabinski Victor J. , Smith R. Lowell
Published: February 2004

This paper describes a simple technique for the construction and use of a closed, yet demountable vapor cell with MgO single crystal windows. This cell can be used as a resonant scattering cell or as a discharge lamp. As a discharge lamp, it is competitive with the Cario-Lochte-Holtgreven type of flow lamp.
A Simple Ion Gun
Authors: Khan Mahboob , Schroeer Juergen M.
Published: February 2004

A simple electron bombardment ion gun based on a Bayard-Alpert ion gauge is described. The gun produces a total beam current of about 1 μA of Ar+ with a current density of 1 to 5 μA/cm2 and a diameter of about 1 cm, at an argon pressure of 5×10−6 Torr. The energy half-width of the beam is about 10 eV for ion energies between 500 and 1500 eV. The source is suitable for the production of ions from any gas.
Q-Machine Cathode Producing Large Radial Electric Fields
Authors: Jassby D. L.
Published: February 2004

A segmented cathode, consisting of two insulated concentric tantalum plates, is described. The tantalum sections are heated by radiation from a tungsten back plate, which in turn is heated by electron bombardment. The insulating material is alumina (Al2O3), which is effective up to 2100 K. Arbitrary voltage may be applied across the gap between the concentric front sections. When used as the hot end plate in a Q machine, this cathode maintains large radial electric fields in the plasma interior.
Nanosecond Gating of Proximity Focused Channel Plate Intensifiers
Authors: Lieber Albert J.
Published: February 2004

Vidicon coupled, proximity-focused channel plate image intensifiers are currently being gated by 4 nsec FWHM pulses. Resolution achieved is better than 9 line pairs/mm on the intensifier photocathode.
Field Emission Deflection Energy Analyzer
Authors: Kuyatt C. E. , Plummer E. W.
Published: February 2004

A Simpson-Kuyatt type spherical deflection energy analyzer has been adapted to a field emission source. A special decelerating lens allows the analyzer to be used over a wide range of electron energies and energy resolutions. For an electron energy of 2000 eV, a resolution of 20 meV has been demonstrated, while better resolution can be obtained for lower energies (∼10 meV at 1000 eV). Special techniques and new design features were employed to make the new analyzer compatible with ultrahigh vacuum (∼10−12 Torr).
Computation Aids for the International Practical Temperature Scale of 1968 in the Range of 13.81 to 273.15 K
Authors: Jones F. L. , Manning R. E.
Published: February 2004

A method is presented to use more conveniently the International Practical Temperature Scale of 1968 (IPTS-68) interpolating equations in the temperature range of 13.81 to 273.15 K (−259.34 to 0°C). Equations for each of the four temperature segments allow calculation of temperature from the measured thermometer resistance and calculation of resistance ratio and resistance at each temperature.
Oxygen Permeation through Silver
Authors: Beavis L. C.
Published: February 2004

This paper describes the gas analysis of oxygen flowing through a silver permeation membrane into an ultrahigh vacuum system. The initially contaminated silver emits gases such as hydrogen sulfide, sulfur dioxide, and carbon oxides more copiously than oxygen during the first hour of operation. After the initial conditioning of the membrane, high purity oxygen is obtained. The ultrahigh vacuum system shows long term effects of early exposure to sulfur bearing gases even after several hours of bakeout.
Filter-and-Hold Technique for Television Densitometry
Authors: Tompkins W. R. , Intaglietta M.
Published: February 2004

A simplified television densitometer was developed utilizing a filter-and-hold technique. The system circumvents the use of complex digital circuitry by using a fading memory filter which yields an approximate integral of the optical density in a window in the area of interest. The response is linear for features whose optical density changes in the parallel direction to the raster lines, and linear for 40% changes of optical density in the vertical direction.
Design of Rectangular Current Capacitor Banks
Authors: Cormack G. D. , Miller A. D. , Tan K. O.
Published: February 2004

The design equations for a capacitor bank current source capable of producing an essentially flat-top, kilo-ampere-range current pulse having a duration of the order of tens of microseconds are presented. Magnitude, rise time, duration, and droop of the pulse are considered.
A Simple Arrangement for Flash-Photolysis Measurements at Different Temperatures
Authors: Prell G. , Zanker V.
Published: February 2004

Flash-lamp, the reaction vessel, and the mapping mirror of a flash-photolysis apparatus are together cooled down by nitrogen gas. In the temperature range from 90 to 300 K reproducible relative quantum yield measurements are possible in an easy way.
Technique for Minimizing Air Gaps in Cavity Perturbation Measurements on GaAs and Si
Authors: Slagsvold B. J. , Schwerdtfeger C. F.
Published: February 2004

A cavity assembly for microwave perturbation measurements of temperature dependent dielectric constants in semiconductors is described. By means of a mechanism attached to the cavity, errors due to contact impedances between the sample and cavity walls are minimized. Measurements on GaAs and Si are presented and shown to be in good agreement with results obtained by other methods.
A Constant Volume Valve
Authors: Markus Walter
Published: February 2004

A constant volume valve is described for pressures to 1400 bar with a volume change between the open and closed positions of less than 0.15 mm3. The leak rate through the seat is less than 5×10−5 mole/sec. The valve is of a very simple design. The type described here is pneumatically operated.
Liquid X-Ray Diffraction Techniques for Overviewed Samples
Authors: Lawrence R. M. , Relford J. R. , Habegger S. C.
Published: February 2004

Overviewing techniques are used in achieving agreement between the forms of the relative and absolute intensity curves in liquid x-ray diffraction studies. To view the entire scattering volume of an irradiated sample, diffractometer slit combinations are selected on the basis of intensity vs sample height curves. Elimination of the sample absorption correction and the associated optical restrictions yields scattering patterns that have the same form as their corresponding absolute intensity curves over the entire range in scattering angle.
Simple Unipolar Pulsed Plasma Accelerator
Authors: Jurak K. , Offenberger A. A.
Published: February 2004

The design and operation of a current pulse forming network using two trigatrons for unipolar pulse generation in plasma accelerators are described. Only the first trigatron has external triggering. The resulting current pulse is approximately 100 kA of 35 μsec duration and has a shorter rise than fall time. Calculated characteristics show good agreement with measured values.
Accurate Calculation of Properties of the Two-Tube Electrostatic Lens II. First-Order Focal Properties and P-Q Curves
Authors: Natali S. , Di Chio D. , Uva E. , Kuyatt C. E.
Published: February 2004

Using digital methods, electric fields and paraxial electron trajectories in the two-tube electrostatic lens have been calculated, and the first-order (Gaussian) focal properties accurate to at least 0.1% were obtained for voltage ratios from 1.5 to 50. The results are presented in the form of P-Q (object-image position) curves for maximum ease of use.
Measurement System for Derivative Studies
Authors: Korb H. W. , Holonyak N.
Published: February 2004

A system for measuring I-V, dI/dV, and d2I/dV2 characteristics of two-terminal devices is described. An operational amplifier integrator is used to produce a sweep voltage. For derivative measurements the dc bias voltage is modulated by a constant ac voltage signal. Current is detected by a near-zero input impedance circuit with adjustable gain. A simple circuit utilizing an IGFET at zero drain voltage as a voltage controlled resistor compensates for harmonic content in the oscillator signal. It also enhances the detectability of weak harmonic signals in the presence of a strong fundamental signal by rejecting more than 90% of the strong signal. The system has been used to measure devices with impedances from a few ohms to over 105 Ω.
Design Parameters for the Cylindrical Mirror Energy Analyzer
Authors: Risley John S.
Published: February 2004

Design parameters are presented for various geometrical arrangements of the cylindrical mirror electron energy analyzer. The theory and operation of this high quality instrument are discussed and compared with an experimental device. Similar properties of a parallel plate analyzer with second order focusing are reviewed.
Theory of Coincidence Counts and Simple Practical Methods of Coincidence Count Correction for Optical and Resistive Pulse Particle Counters
Authors: Bader Henri , Gordon Howard R. , Brown Otis B.
Published: February 2004

The exact equation for primary coincidence count correction is derived, and it is shown that secondary coincidence correction can be calculated with an accuracy depending only on statistical counting errors. A coincidence correction equation is developed in the form of a series of unknown terms, but of known structure. The unknown terms can be eliminated by solving simultaneous equations obtained by counts after dilution of the gas or liquid sample containing particles in suspension, or by counts on the undiluted fluid by varying the size of the instrument sensing volume. These methods suggest useful improvements in the construction and use of particle counters.