bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical Photon Production in Anthracene by Electrons with Energies between 2 and 10 000 eV
Authors: Fisher T. R. , Kohler D.
Published: February 2004

The response of an anthracene scintillation detector to electrons with energies from 2 to 10 000 eV is reported. The detector response, instead of falling rapidly to zero at energies less than 1000 eV, approaches a constant value of 0.56 photon/incident electron at low energies. The response of the detector in this very low energy region apparently results from a new photon production mechanism which is not understood at present. Above 1000 eV, significantly better spectra are obtained than have been reported previously.
Some Characteristics of a Pulsed Xenon Lamp for Use as a Light Source in Kinetic Spectrophotometry
Authors: Hodgson B. W. , Keene J. P.
Published: February 2004

This paper presents details of the electrical and optical characteristics of Osram XBO 250, 14 V, 18 A, high pressure xenon arc lamps during 1 msec current pulses of several hundred amperes which are used as analyzing light sources in kinetic spectrophotometry. The lamps are operated continuously at their normal rating between pulses and the arc provides a path of high electrical conductivity for the pulse current. As a result the volume occupied by the discharge and the potential drop between the electrodes do not change very much during a pulse, whereas the radiance of the discharge increases by a large factor which depends on current and wavelength. At 450 A the increase in radiance is about 700× in the far ultraviolet, about 300× in the visible, and about 50× in the infrared. XBO 250 lamps operated in this way can withstand many thousands of pulses without excessive deterioration. A circuit for producing the current pulses is described.
Low Temperature Voltage Divider and Null Detector
Authors: Sullivan D. B.
Published: February 2004

This paper describes a low temperature voltage divider and null detector which are designed to accurately bring the low level voltage of the Josephson steps to the 1 V level. The divider uses the series-parallel interchange of resistors. Preliminary tests indicate that the resistors are stable to within one part in 107 and that the ratio is accurate to within one part in 106. The null detector utilizes a superconducting quantum interference magnetometer and is limited only by the Johnson noise in the cooled resistors.
LiNbO3 Light Modulator
Authors: Ninomiya Yuichi , Motoki Toshio
Published: February 2004

Up to this time, LiNbO3 has not been considered to be a desirable material for a light modulator because of its susceptibility to ``optical damage.'' We ascertained that the LiNbO3 light modulator could be constructed practically without optical damage when the crystal was heated to ∼170–180 °C. A pair of polished LiNbO3 single crystals were soldered on a piezoelectric resonance damper of copper with pure tin, and were encapsulated in a glass vacuum vessel which prevented turbulence by heated air. It was demonstrated that the performance of the modulator was fine, especially with regard to extinction ratio, temperature characteristics, frequency response, and so on. In this report, we describe the optical-damage-free LiNbO3 modulator generally, from the growth condition of a high optical quality crystal to the construction and the performances of the modulator.
Surface Ionization Type Ion Source of Ba+ Ions for Use in Collision Experiments
Authors: Feeney R. K. , Bacon F. M. , Elford M. T. , Hooper J. W.
Published: February 2004

A surface ionization type ion source, which produces a Ba+ ion beam of known chemical purity and excitation state, has been developed specifically for use in collision experiments. Barium vapor is surface ionized on a rhenium filament that is heated to approximately 1800°C by the passage of a direct current. The water cooled source provides ion currents of about 10 μA, and can be operated without differential pumping in a vacuum environment of (3–4)×10−9 Torr.
Simple Time-of-Flight Residual Gas Analyzer and Surface Monitor
Authors: Carrico J. P. , Johnson M. C. , Wolber W. G.
Published: February 2004

A simple, inexpensive time-of-flight device using channel electron multipliers as the electron source and the ion detector has been constructed for the analysis of residual and adsorbed gases.
Positive Pressure Cooling of Cryogenic Baths and Its Application to Solid State Lasers
Authors: Asher I. M.
Published: February 2004

The addition of helium gas to the vapor phase of a liquid nitrogen bath lowers the temperature by as much as 10 K. This was used to shift the frequency of a cooled ruby laser. The method provides an attractive alternative to the use of vacuum pumps.
Demountable Gallery Infrared Cell for Soft Semisolids
Authors: Tovrog T. , Krawetz A. A.
Published: February 2004

A demountable infrared cell with a galley cut in the rear salt window permits the spectral analysis of semisolids with good reproducibility and accurate control of sample film thickness and uniformity. Window breakage, which can be a problem when semisolids are used in standard infrared cells, is essentially eliminated.
A Dynamic Method for Measuring the van der Waals Forces between Macroscopic Bodies
Authors: Hunklinger S. , Geisselmann H. , Arnold W.
Published: February 2004

A new method for measuring the van der Waals forces between macroscopic bodies is described. In contrast to previous static methods we developed a new dynamic technique with a considerably higher reproducibility, sensitivity, and accuracy. With this experimental setup the van der Waals force between various specimens has been determined. In this paper we present the results on borosilicate glass at distances between 0.08 and 1.2 μ which are in good agreement with theory.
A Precision Densitometer for Gaseous Electron Diffraction
Authors: Foster H. Randolph , Kohl D. A. , Bonham R. A. , Williams M. L.
Published: February 2004

A high precision, single beam densitometer is described for gaseous electron diffraction which averages transmission by spinning the photographic plate in order to measure densities between 0.1 and 1.4 on scattering patterns with a precision approaching the limit set by electron statistics. An automatic plate reading system makes 350 digital photocurrent readings across a 10 cm diam pattern in 25 min. The precision in density values is ±0.03% in favorable cases. An error discussion includes an analysis of the effect of finite slit, density error as a function of density, and error in density resulting from averaged transmission.
A High Resolution, Four-Terminal, ac Resistance Bridge for Low Temperature Use
Authors: Friedman Alan J. , Ody Michael R.
Published: February 2004

Using operational amplifiers in the follower configuration, a four-terminal, ac resistance bridge can be inexpensively constructed for use with low temperature resistance thermometers from 10 Ω to 10 kΩ (and higher if necessary). Operating the bridge with 1 mV across the thermometer (providing power dissipation of 1 nW at 1 kΩ), the resolution and stability over several hours are 0.003% of the resistance.
A Microsecond Pulse Generator Employing Series Coupled SCR's
Authors: Campbell James D. , Kasper Jerome V. V.
Published: February 2004

A pulse generator circuit is presented in which capacitive discharge through a high voltage switch incorporating a chain of series coupled SCR's produces pulses of microsecond durations with peak currents of 1 kA at 1 kV. The basic operation of the switch, limitations governing the choice and arrangement of components, extension to voltages higher than 1 kV, and the electrical performance of the circuit when used to initiate the firing of xenon flash tubes are discussed.
Compact Photomultiplier Housing with Controlled Cooling
Authors: Shardanand
Published: February 2004

A compact photomultiplier housing is described. The housing can provide controlled cooling to the photomultiplier tube down to −90°C. The cooling is accomplished by flowing liquid nitrogen cooled helium gas through a series of coils which envelope the photocathode portion of the tube. The temperature is controlled by controlling the flow of the gas with a fine adjustable needle valve. The temperature is measured near the photocathode of the photomultiplier by a calibrated thermistor.
Nuclear Magnetic Resonance Measurements at High Pressure
Authors: Jonas J.
Published: February 2004

Instrumentation for the measurement of spin lattice relaxation times in liquids at pressures up to 5 kilobar and temperatures from −50 to 350°C is described. The experimental setup allows the use of the Fourier transform technique to obtain high resolution spectra and/or relaxation of chemically shifted nuclei under these extreme conditions.
Improved ``Tuning'' of Ion Microprobes Using Scandium Thin Film Targets
Authors: Guthrie J. W. , Blewer R. S.
Published: February 2004

The optical sensitivity of thin film scandium metal to energetic ions is used to observe and record the position, shape, and size of the primary beam of an ion microprobe during the beam tuning process. The tuning sample is also useful as an in situ gauge of the relative sputtering rate for various beam types and energies.
Strain Gauge Measurements of Volume Changes in Polymorphic Transitions under Pressure
Authors: Cedergren M. , Bäckström G.
Published: February 2004

A strain gauge wire was wound around a sample of cylindrical shape. One part of the wire was wound around the belly, the other in a plane going through the axis. For a certain choice of the turn ratio and the length-to-diameter ratio the strain could be made proportional to ΔV. From tests performed on Bi, it appears that ΔV/V0≈2×10−4 may be detected with the present method. No volume discontinuity corresponding to the phase transition at 43 kilobar reported by Bridgman was observed.
Tinning Aluminum Wire
Authors: Diamond Joseph M. , Jensen B. Skytte
Published: February 2004

A one-step method of tinning aluminum wire, to prepare it for soldering, is described. The flux is a molten NaOH–KOH–ZnO mixture which dissolves the surface oxide and zincates the wire. The container is a stainless steel tube which permits the wire to be tinned immediately after zincating and before reexposure to air. Safety precautions are considered.
A Dilatometer for Volume-Temperature Determinations of Liquids
Authors: Rothman James E. , Melchior Donald L. , Morowitz Harold J.
Published: February 2004

An instrument is described for the continuous volume measurement of small (3.7 ml) samples of liquids as a function of temperature. The sample is sealed in a stainless steel bellows chamber. Volume changes are measured with a linear variable differential transformer while temperature is measured by means of a thermistor and associated circuitry. Volume changes of sample can be determined to better than 1.0×10−4 ml over a temperature range of 10–60°C. The maximum sample volume change is 7%.
A 1/H Drive for Use with Superconducting Solenoids
Authors: Everett P. M.
Published: February 2004

A circuit is presented that can be used with nearly all superconducting solenoid magnet systems to sweep the magnetic field such that equal intervals in the inverse of the field are progressed in each instant of time. The circuit produces a programming voltage that controls the total power supply current. The ideal situation of the resistanceless solenoid shunted by the virtually inductanceless persistent mode switch causes the programming voltage to assume a particularly simple form.
Vibrating Sample Magnetometer for Protein Research
Authors: Redfield Alfred G. , Moleski Charles
Published: February 2004

A simple magnetometer for use with weakly paramagnetic frozen solutions is described. It uses the same superconducting coil for generating the field and detecting the vibrating magnetization. A nearly translationally invariant sample holder and low frequency vibration of large amplitude are advantageous. In a sample volume of 0.7 ml, 2×10−7 moles of a species having a single g=2, s=½ spin produces a signal reproducibly different from that of pure water, when the temperature is varied from 77 to 2 K.
Pulsed-Current Control and Measurement System for Precision Microcalorimetry
Authors: Albert Harrison B.
Published: February 2004

Instrumentation for heat measurement in differential microcalorimetry is described in sufficient detail so the electronic apparatus can be built and used reliably with various calorimeters. Theory and calibration techniques are explained for calculating endothermic and exothermic heats from indicated digital data for reaction calorimetry and temperature scan calorimetry (including DTA). The cooler of twin calorimeter cells is heated electrically to counteract thermal effects of the system being measured. This heating is by pulses of current, all identical, whose rate of occurrence is controlled proportionally to the small residual intercell temperature gradient; counting pulses gives heat indication directly as numbers. The heat per pulse is known accurately, and the pulsed (indicated) heat is related to effects of the system under study; the relation is by a constant, near unity factor (such as 1.010) which can be calculated using easily measured calorimeter parameters. The factor is constant because heating is proportional to the residual temperature gradient, and differs from unity because of heat conduction through that gradient. Over-all accuracy, experimentally confirmed, exceeds 0.1% and depends on well-standardized electrical measurements, so calorimetric calibrations are not needed with calorimeters of known material capacity. Pulses, 16.666 msec long, occur at rates up to 30/sec and have switch-selected amplitudes from 0.02 to 640 μcal per pulse (60 Ω heater). Equipment design includes devices for routine tests to detect component deterioration before it has become serious.
Rotational Temperature Measurement in Nitrogen Using Raman Spectroscopy
Authors: Hickman R. S. , Liang L. H.
Published: February 2004

The rotational temperatures at pressures near 1 atm have been successfully measured in pure nitrogen. The precision available, even with unsophisticated instruments, is adequate to allow local temperatures to be measured in a flowing gas with virtually no disturbance of the flowfield. Using a double monochromator and including the flowfield within the laser cavity would increase the signal and decrease scattered light.
A Fast Electron Gun for Study of Atomic Decays
Authors: Sutton John F.
Published: February 2004

A fast electron gun with subnanosecond rise and decay times and 100 mA peak beam current has been developed for delayed coincidence studies of atomic decays. The gun is fabricated from an inexpensive tetrode Nuvistor, involving only slight modification.
Off-Axis Particles in Coulter Type Counters
Authors: Smythe W. R.
Published: February 2004

The resistance increase due to a centered sphere in a tube traversed by an ideal fluid or electric current is tabulated in Phys. Fluids 7, 633 (1964). A lower limit for off-axis spheres is also known. This note gives an off-axis upper limit theory and a numerical table which should be useful in sizing particles by the Coulter counter method.
A Robust High Vacuum Multipin Electrical Leadthrough
Authors: Mills J. C.
Published: February 2004

A simple multipin leadthrough is described. The seal has been tested to a pressure of 4×10−10 Torr.
Apparatus for Measurement of High Vapor Pressures and Densities at High Temperatures under Isothermal Conditions
Authors: Rau Hans
Published: February 2004

An apparatus is described by which vapor pressures and densities of sulfur were measured up to 800°C and 33 atm with a sensitivity of about ±5 Torr. The substance is in contact only with quartz glass.
A Versatile Laboratory Programmer
Authors: Schwender G. E. , Goosman D. R. , Jones K. W.
Published: February 2004

The logical design of a versatile laboratory programmer is described. The programmer can be used to control the operation of low and high power circuits over a wide range of time intervals.
Thermal Conductivity of Mylar between 0.05 and 0.5 K
Authors: Peterson R. E. , Anderson A. C.
Published: February 2004

The thermal conductivity of Mylar between 0.05 and 0.5 K is similar to that of Pyrex.
Data Acquisition System for Residual Gas Analyzer
Authors: Lomnes R. K.
Published: February 2004

A relatively simple data acquisition system is described for use with data having a spectral distribution. The paper deals specifically with problems encountered in performing both functions of visual monitoring and periodic recording of the mass spectrum from a residual gas analyzer. The ideas presented, however, are not necessarily restricted to mass spectral data and could be adapted to data collection from other forms of spectra.
Charge Exchange Cross Sections Measured at Low Energies in Q Machines
Authors: Andersen S. A. , Jensen V. O. , Michelsen P.
Published: February 2004

A new technique for measurements of charge exchange cross sections at low energies is described. The measurements are performed in a single-ended Q machine. The resonance charge exchange cross section for Cs at 2 eV was found to be 0.6×10−13 cm2±20%.
High Pressure, High Temperature Infrared-Ultraviolet-Visible Spectrophotometer Cell for in situ Catalyst Studies
Authors: Tinker H. Burnham , Morris Donald E.
Published: February 2004

An ir and uv-visible spectrophotometer cell for recording the spectra of solutions at elevated temperatures and pressures has been designed and fabricated. The cell is used for characterization of reactive catalyst species and reaction intermediates which exist only at conditions above ambient. The temperature and pressure maxima are limited by the window material which, in turn, is determined by the spectral range to be examined. Large windows, variable path length, and relatively compact design permit the use of the cell interchangeably among a variety of commerically available ir and uv-visible spectrophotometers without the need for special instrument modifications. The cell with CaF2 windows has been applied to studies of catalyst solutions at reaction conditions up to 100 atm at 200° C without any suggestion of window or cell failure. The design and construction of the cell are reported.
A Graphite Crystal Polarimeter for Stellar X-Ray Astronomy
Authors: Weisskopf M. C. , Berthelsdorf R. , Epstein G. , Linke R. , Mitchell D. , Novick R. , Wolff R. S.
Published: February 2004

The first crystal x-ray polarimeter to be used for x-ray astronomy is described. Polarization is measured by modulation of the x rays diffracted at an average 45° glancing angle from large, curved graphite crystal panels as these rotate about an axis parallel to the incident x-ray flux. Arrangement of the crystal panels, the design of the detector, and the signal-processing circuitry were optimized to minimize systematic effects produced by off-axis pointing of the rocket and cosmic ray induced events. The in-flight performance of the instrument in relation to the observed background signal is discussed.
A Capacitor-Type Rain Gauge with dc Output and Improved Flow Characteristics
Authors: Seibel R. R.
Published: February 2004

A rain gauge for continuously measuring rainfall rates in the range 0–800 mm/h is described. The collected rain water is channeled to flow through a capacitor which constitutes one arm of an RC bridge. The ac voltage across the bridge is processed to give a dc output which is nearly linearly proportional to rainfall rate. This gauge is an improved version of the one discussed by R. A. Semplak [Rev. Sci. Instrum. 37, 1554 (1966)]; low as well as high rain rates can be measured accurately. The output incorporates a time constant which can be switched in to smooth rapid fluctuations in rain rate. An example of an actual rain measurement is given.
In-Beam Mössbauer Spectroscopy in Scattering Geometry
Authors: Hicks J. A. , Owens W. R. , Wilenzick R. M.
Published: February 2004

An in-beam spectrometer system has been modified to allow Coulomb excitation Mössbauer measurements in a back scattering geometry, rather than the usual transmission arrangement. Mössbauer scattering measurements with the 122.6 keV γ rays of 186W are presented and compared with the results of conventional techniques.
A Depth Dose Calorimeter for High Intensity, Low Voltage Flash X-Ray Machines
Authors: Wood D. S.
Published: February 2004

A small tantalum foil depth dose calorimeter has been constructed for use with high intensity flash x-ray sources. Incident x-ray energy is deposited in an array of tantalum foils monitored by 25 μ iron-constantan thermocouples. Readout is made with a high speed scanning digital microvoltmeter. Comparison is made between the measured x-ray energy deposition in tantalum and the deposition calculated with a Monte Carlo computer code which takes account of the current and voltage waveforms on the diode.
An Electronic Partial Vacuum Regulator
Authors: Parker Donald L.
Published: February 2004

The design and performance of a servosystem for controlling pressures from a few mm Hg to atmospheric pressure is given. The technique used is applicable to maintaining a predetermined constant pressure for an indefinite period with high vapor pressure substances (i.e., liquid gases) in the system or for the automatic scan of pressure with a shaft rotation as the input. The fluctuation of the system pressure during cycling of the servomechanism is considerably less than 1% over most of the pressure range and is about 0.1% (±0.05%) for pressures near 30 cm Hg absolute.
Low Level Tracking Marginal Oscillator for in situ Magnetic Field Measurements at Low Temperatures
Authors: Anderson J. R. , Sandfort R. M. , Stone D. R.
Published: February 2004

A low level NMR spectrometer which operates satisfactorily over the frequency range between 1 and 100 MHz has been developed using standard integrated circuits and field effect transistors. The high gain automatic level control allows rf levels of less than 1 mV to be achieved without adjustment; the system has been used to make in situ magnetic field measurements in superconducting magnet systems with the narrow 1G NMR spectra observed in doped alkali halide specimens at 4.2 K. In conjunction with the marginal oscillator, an automatic tracking system which utilizes capacitor switching is described.
An Atomic Oxygen Beam System for the Investigation of Mass Spectrometer Response in the Upper Atmosphere
Authors: Niemann Hasso B.
Published: February 2004

An atomic oxygen beam system has been designed and tested for the laboratory evaluation of mass spectrometers used in upper atmospheric measurements. The atomic oxygen is generated by thermal dissociation of molecular oxygen on the surface of a tungsten filament heated to 2800 K. A symmetrical bidirectional beam is produced to permit simultaneous monitoring of the particle flux in the beam while target experiments are being conducted. Flux levels of 5×1014 particles cm−2 sec−1 over a cross-sectional area of 1 cm2 have been produced with a relative atomic oxygen concentration of 70%. At flux levels below 1013 particles cm−2 sec−1, relative atomic oxygen concentrations of more than 90% were obtained. The oxygen beam is of high purity and free from chemically active contaminants. Strong chemical and low temperature pumping are used to reduce background gas contributions to less than 1%. Measurements of the relative atomic concentration in the beam were made with a quadrupole spectrometer using an open flowthrough ion source. The absolute flux of molecular oxygen was determined with the aid of an enclosed omegatron mass spectrometer. The combined use of both instruments permitted a determination of the magnitude of the atomic oxygen flux in the beam.
A Fast Response Thin Film Wattmeter for Measurements of CO2 Laser Power
Authors: Stricker J. , Rom J.
Published: February 2004

A thin platinum film wattmeter for measurements of instantaneous power output from a pulsed CO2 laser is presented. Its design, operating characteristics, calibration, and use in the experimental investigation are described. The time response of this gauge is shorter than 1 μsec. The response of this gauge is linear for exposure duration of up to about 20 msec and up to total laser energy of about 100 J. The thin film wattmeter was used for measurements of the power output obtained in CO2 gasdynamic laser experiments in a shock tunnel. The laser radiation measurements of the thin film gauge are compared to those obtained with gold-doped germanium detector. The absolute power output values obtained from the calibrated thin film wattmeter are in agreement with theoretical calculations.
Small Combination X-Ray Calorimeters
Authors: Pellinen D. G.
Published: February 2004

An array of x-ray calorimeters reading absolute energy fluence and front surface dose in tantalum was developed for measuring the areal distribution of x rays from a pulsed source. The device functions in a high electrical noise environment and in pulsed magnetic fields in excess of 1 T. The fluence detector utilizes a shielded construction to allow accurate measurements to be made in inhomogeneous radiation fields.
A Simple Pulsed Nitrogen 3371 Å Laser with a Modified Blumlein Excitation Method
Authors: Small J. G. , Ashari R.
Published: February 2004

The Blumlein circuit used to excite pulsed discharge gas lasers is by now well known and has had several successful applications. This article describes a similar excitation method but with a modified electrode configuration which offers a uniform discharge over a larger cross section and which can be constructed with relative ease. The method is successfully demonstrated in a nitrogen 3371 Å pulsed laser.
A Simple Computer-Spectrophotometer Interface
Authors: Williams Rodney C. , Turner Thomas J.
Published: February 2004

A modification is described which enables one to interface a Cary 14 spectrophotometer or similar instrument to a computer.
A Simple Glass Dewar for High Resolution Microscopic Observations of Magneto-Optical Phenomena at Liquid Helium Temperatures
Authors: van Kempen H. , Mischgofsky F. H. , Wyder P.
Published: February 2004

A simple glass Dewar setup for high resolution microscopic observations of magneto-optical phenomena at liquid helium temperatures is described. The light is guided via a light pipe system into the Dewar. The observations are made using a microscope with objective lenses with a working distance of a few millimeters placed outside the Dewar. Resolutions of the order of 1 μ are obtained.
Controlled Sectioning Technique for Small Gallium Arsenide Samples
Authors: Magee T. J. , Comer J. J.
Published: February 2004

A technique has been developed for sectioning small gallium arsenide samples utilizing anodic oxidation and subsequent removal of the oxide layers. It differs from those previously reported in that only one surface of the wafer is exposed during anodization and total immersion in the electrolyte is not required. The use of an ammonium pentaborate solution as the electrolyte and a relatively simple anodization apparatus has yielded oxide layers of uniform thickness on the surfaces of gallium arsenide wafers. After removing the oxide layers, the surfaces of the wafers were found to be relatively free of pitting and macroscopic defects.
Versatile Power Supply for Electron Bombardment Heating
Authors: Hudson John B.
Published: February 2004

This note describes an electronic circuit developed to provide power and temperature control for electron bombardment heating applications in ultrahigh vacuum. Salient features of the design include closed-loop feedback control based on a temperature sensing element and a configuration which is fail safe with respect to both short and open circuits in the temperature sensing device. This circuit has been used for control of a Knudsen cell in molecular beam studies and for heating a single crystal substrate in LEED-Auger spectroscopy studies.
Spatial Spark Jitter Measurements of Highly Charged Nuclei for Optical Spark Chambers
Authors: Smoot G. F. , Buffington A. , Smith L. H.
Published: February 2004

The spatial jitter of sparks about the paths of relativistic nuclei of various charges z has been measured for optical spark chambers. For normal incidence the jitter measured was consistent with the 1/z dependence expected from diffusion of the ionization electrons.
A Versatile Microprobe Analyzer for Magnetic Thin Films
Authors: Wichner Ronald
Published: February 2004

The versatility of a cross wire rf magnetic microprobe tester is increased with the use of orthogonal 60 Hz and dc magnetic fields. Determination of magnetic thin film parameters such as coercivity, anisotropy field, magnitude and angular dispersion, skew, magnetostriction coefficient, and the general shape of the Stoner-Wohlfarth astroid is made possible with a single instrument. The new techniques described are quite sensitive and allow for easily obtainable results.
Spiral Electron Multiplier Operation Characteristics Using Positive Ions
Authors: Potter Wentworth E. , Mauersberger Konrad
Published: February 2004

Operational characteristics of a spiral electron multiplier are discussed, and measurements of gains and detection efficiencies using positive ions are presented. These parameters were observed during lifetime tests on two multipliers. Gains above 107 were found up to 1011 accumulated counts. The detection efficiencies for ions in the mass region from 4 to 40 amu varied between approximately 60% and 90% for incident energies of 3–4.5 keV.
High Voltage Sweep and Controlled Magnetic Lens Current Supplies for the Electron Microprobe
Authors: Kyser David F. , Horne Donald E.
Published: February 2004

Three electronic systems have been developed for the electron probe x-ray microanalyzer to provide (1) automatic sweep of the electron beam high voltage, (2) automatic control of the target current as the electron beam voltage is varied, and (3) automatic control of the electron beam focus as the beam voltage is varied. In addition to conventional applications in quantitative electron probe microanalysis, special applications of these components include measurement of absorption coefficients for soft x rays, voltage dependence of cathodoluminescence in semi-conductors and insulators, three dimensional microanalysis, and ditital computer control of the microprobe analyzer.
Temperature Dependence and Stabilization of Avalanche Photodiodes
Authors: Nishida Katsuhiko , Nakajima Masato
Published: February 2004

Temperature dependencies of avalanche photodiodes have been represented by two temperature coefficients, γ and β. γ is defined for the temperature variation of multiplication factor M under the bias condition of constant voltage, and β for the avalanche voltage sustaining constant multiplication. γ and β are related to physical parameters determined by materials and the diode parameters depending on junction profiles. These dependencies accounted for experimental results. The results of analyses were applied to the design of operating circuits to stabilize the performance of avalanche photodiodes. Multiplication was regulated within the experimental error of ±5% at M = 525 over a temperature range of ± 100°C using a bias circuit capable of self-adjustment of applied voltage. Constant current biasing is shown to be effective for stabilization. Circuit response speed is discussed.
A Versatile High Pressure Apparatus for Optical Spectroscopy at Temperatures between 77 and 500 K
Authors: Nicol Malcolm , Ebisuzaki Yukiko , Ellenson William D. , Karim Ahzez
Published: February 2004

Modifications of Drickamer's type I high pressure optical cell are described that permit operation of the cell at pressures as high as 50 kilobars at temperatures between 77 and 500 K. The cell has been calibrated at several fixed points in terms of the applied loads at which known phase transitions occur. The calibration at other pressures is related to these fixed points by measurements of the pressure dependence of the Raman frequency of the CN− stretch of the cyanide ion dissolved in NaCl.
A Transmission Line Circuit for Reliable Spark Gap Operation
Authors: Ireland C. L. M.
Published: February 2004

The common transmission line circuits employed to enable a fast laser triggered spark gap to switch an optical cell are discussed. A modification is suggested that leads to a more reliable operation of the gap.
Improved Electrical Leads for High Pressure Systems
Authors: Terry Robert E. , Ruoff Arthur L.
Published: February 2004

A convenient method is described for making plastic cone seals by heat shrinking for use in high pressure liquid and gas systems.
A Simple Circuit for cw NMR Measurements
Authors: Klever H. , Schlaak M.
Published: February 2004

A simple circuit for cw NMR measurements is discussed. The purpose of this circuit is similar to that of bridge arrangements: The rf at the input of the receiver is compensated by an additional branch within the circuit consisting of a potentiometer and a phase shifter. As shown by theoretical calculations, the sensitivity of the discussed arrangement is higher than similar uncompensated circuits and higher than bridge arrangements as well. The 203Tl and 205Tl resonances measured with this circuit show signal-to-noise ratios comparable to the signal-to-noise ratios of the resonances measured with a commercial wide-line NMR spectrometer.
A Capacitive Integration System for the Precise Measurement of Isotopic Ratios in a Mass Spectrometer
Authors: Jackson M. C. , Young W. A. P.
Published: February 2004

An automated data collection system has been developed and applied to the measurement of O16/O18 ratios with high precision. The design is based on the simultaneous capacitive integration of two ion beams from a mass spectrometer. The results obtained have shown a consistent precision of 10–20 parts per million.
A 0.3–40 Micron Wavelength Modulation Spectrometer
Authors: Hart G. P. , Neely John A. , Kearney R. J.
Published: February 2004

A 0.3–40 μ wavelength-modulation spectrometer, utilizing dual beam optics and a single detector, has been designed which is free of most of the difficulties present in previously reported instruments. Over the wavelength range of the photomultiplier tube this system, limited by photon noise, is capable of an optical resolution of 6 Å. For purposes of evaluating the performance of the system, the measured derivative spectra of a holmium oxide filter and of a single crystal gallium arsenide plate are reported. Measurements at liquid nitrogen temperatures, in gallium arsenide, produce spectral details that are substantially more pronounced than in electroreflectance or thermoreflectance spectra. The additional resolution permits new optical structures in gallium arsenide to be observed. The values of measured transition energies in this semiconductor confirm many of those earlier reported. New values for the temperature dependence of the band structure are reported.
New Large-Aperture Energy Analyzer
Authors: Marmet Paul
Published: February 2004

A new instrument is described which permits focusing and energy analysis of electrons on any other charged particle coming from a source having a large area. This instrument is specially convenient to measure an electron energy spectrum when a very large sensitivity is required, because the electron optics are such that the entrance slit is no longer required.
A Tunnel Diode NMR Spectrometer
Authors: Aslam J. , Weyhmann W.
Published: February 2004

A tunnel diode oscillator is presented which is useful for NMR studies in ferromagnets at VHF and UHF frequencies. The oscillator can be tuned electronically over octave ranges and can be operated at low temperatures. The sensitivity is comparable to standard cw oscillators, but it is much more compact and does not require long rf lines.
A Compact, Pulsed Nozzle Beam Source for Crossed Molecular Beam Experiments with Arbitrary Beam Intersection Angles
Authors: Köhler K.-A.
Published: February 2004

A source for condensible gases and vapors which allows for the production of a pulsed nozzle beam with a beam oven temperature of about 670 K is described. This source is especially suitable for providing the target beam at a beam intersection angle of between 20° and 160° needed for scattering experiments with crossed molecular beams.
Silver Chloride Infrared Windows Used Successfully in All-Metal Spectroscopic Absorption Cells
Authors: Kucerovsky Z. , Rumbold D. G. , Brannen E.
Published: February 2004

Decomposition and cold flow of silver chloride windows when used in an all-metal absorption cell have been eliminated by encapsulation of the window in a Lucite holder of simple design.
Low Temperature Nozzle Beam Source
Authors: Skofronick J. G. , Pope W. M.
Published: February 2004

A nozzle beam source that can be operated to 3 K with helium gas is described. At this lowest temperature the full width at half maximum in velocity is 9%, the gas flow rate is 3.3 atmospheric ml /min of room temperature helium, and the density is 4.6×1012 atoms/cm3 measured 2.5 cm from the source.
A Gas-Phase EPR Cavity
Authors: Brown I. M. , Richardson R. J.
Published: February 2004

The design of an X-band cylindrical TE011 cavity resonator with a 25 mm diam axial access hole for gas-phase EPR studies is described. The empty cavity is tunable over a frequency range of at least 8.0–10.0 GHz and critical coupling is attained over this range with a novel variable coupling device.
Digitized Magnetic-Field Sweeper for ESR Spectrometer
Authors: Hidaka Takehiko
Published: February 2004

A digitized magnetic-field sweeper is described that is designed for the signal-averaging digital computer aided ESR spectrometer.
Measurement of Velocity Distributions in Two-Phase Suspension Flows by the Laser-Doppler Technique
Authors: Einav S. , Lee S. L.
Published: February 2004

This paper describes the application of laser-Doppler anemometry to measurement of velocity distributions in two-phase suspensions. It is shown that two groups of scattering particles, members of each of which are different in size and move with distinct velocities, will produce separate signals in the frequency domain, different in both amplitude and frequency. Block diagrams of the electronics used in the measurement of suspension flow are shown.
Single Nanosecond Pulse Generation at 10.6 μ Using a Brewster Angle Modulator
Authors: Figueira J. F. , Reichelt W. H. , Singer S.
Published: February 2004

A method is described for generating single millijoule pulses of nanosecond duration through use of a CO2 laser mode-locked with a Brewster angle, acousto-optic modulator coupled with an electro-optic switch (extinction ratio of 50 000:1) driven by a laser-triggered spark gap. The Brewster angle geometry eliminates the damage problems associated with the use of AR-coated normal incidence modulators.
Determining the Time Dependence of Rapidly Responding Systems Using the Mössbauer Effect
Authors: Pfeiffer Loren , Lichtenwalner C. P.
Published: February 2004

The concept of Mössbauer spectroscopy on time dependent systems is explored. Several Mössbauer spectra are simultaneously generated, each with a different time relation to a pulsed perturbation. Obtainable resolving times span the range of hours to nanoseconds.
Simple Instrumentation for the Inductive Detection of Superconductivity
Authors: Soulen R. J. , Schooley J. F. , Evans G. A.
Published: February 2004

A circuit is described which can be used to detect the superconductive transitions of several elements used as thermometric fixed points. The circuit is found to perform as well as much more elaborate mutual inductance bridges previously used for this research. Details for construction and operation of the circuit are given.
A Simple High Vacuum Baffle
Authors: Hastings L. , Spenceley B. J.
Published: February 2004

A simple, water cooled, spiral high vacuum baffle is described.
Functional tests of a cryo-cooled mass spectrometer ion source in a supersonic wind tunnel
Authors: Offermann D. , Scholz T. G.
Published: February 2004

A modified helium cooled ion source was operated in supersonic gas flows simulating some conditions of a rocket flight through the upper mesosphere and lower thermosphere. It is shown that the shock in front of this ion source is removed due to the low temperature of the ion source front part and that the mass spectrometer measures the composition of the undisturbed gas flow. Stability and angular dependence of the ion source signal are analyzed. The light emission from the cold ion source in an arc heated supersonic flow is discussed.
A noise pollution level instrument
Authors: Hamburg James A.
Published: February 2004

Noise pollution level is an index of the annoyance and objectionability of noise which has recently been drawing increasing interest. It is based on two quantities, one relating to the equivalent continuous energy level and the other relating to the variations in level. This paper describes an instrument which has been designed and built for measuring and displaying noise pollution level directly. In addition, it displays the sound pressure level, the mean level, and the standard deviation of the level. The measurement is based on a 5 min interval, allowing 12 complete measurements per hour. The instrument has a dynamic range in excess of 60 dB and is automatic in operation, allowing its unattended use for long periods of time with a chart or digital recorder.
A linear oscillatory viscometer
Authors: Chung Ping L.
Published: February 2004

A new type of viscometer consisting of a steel tuning fork measures viscosity over a large range in a simple and convenient way. It requires only small quantity of specimen and offers hope to determine the anisotropic viscosities of ordered fluids such as liquid crystal.
A photoresist film applicator for long and fragile crystal substrates
Authors: Stiglitz Martin R. , Kearns William J.
Published: February 2004

Long and fragile crystal substrates can be processed in a drawing device that produces uniform photoresist coatings on them. The film thickness can be varied with the pulling speed, from 2500 to 4300 Å in a single pull. Thickness uniformities of ± 80 Å over the entire surface have been obtained.
Precise resistance ratio measurements using a superconducting dc ratio transformer
Authors: Harvey I. K. , Collins H. C.
Published: February 2004

The application of a superconducting dc ratio transformer to precise resistance ratio measurement at temperatures below 2.2 K is described. Resistors of Si–Cu alloy have been tested for stability under thermal cycling and their load coefficient has been measured. The load coefficient measurements lead to a determination of the combined thermal conductance of the wire insulation and Kapitza thermal boundary conductance.
The use and limitations of an electrostatic analyzer for time resolving an electron beam distribution function
Authors: Mix L. P. , Swain D. W. , Chang J.
Published: February 2004

A technique is described for time resolving, to nanosecond precision, the velocity distribution of a periodically varying electron beam and for generating a direct plot of the entire phase plane distribution function. Calculations are presented to indicate the maximum time rate-of-change of the distribution function which may be accurately observed with this technique. The high-frequency response obtainable with this technique makes it a powerful diagnostic tool for use in studying the interaction of an electron beam with plasmas and, in particular, the trapping phenomenon in beam-plasma interactions.
High intensity copper atom beam - preliminary results
Authors: Kelly Arnold J. , Santavicca Domenic
Published: February 2004

The development of a nozzle which gasdynamically accelerates neutral copper atoms at controlled energy levels, and flux rates suitable for the investigation of inelastic copper atom collision processes is reported. Preliminary test data demonstrate that vapor deposited rhenium nozzles do not degrade in the presence of copper vapor at high temperatures. Operation with high purity helium gas at nozzle stagnation temperatures in the range 2650–2700 K and total stagnation pressures from 1/4 to 2 atm with continuous copper atom flux rates of [inverted lazy s] 1018 sec−1 has been maintained, for a total time of 8 1/2 h to date.
The reuse of copper gaskets in demountable vacuum seals
Authors: Shen L. Y. L. , Rowe J. E. , Chaban E. E.
Published: February 2004

A simple method is described to reuse copper gaskets that seal the steel flanges of ultrahigh vacuum systems. A tapered-leaf thickness gauge is employed to measure the air gap between the steel flanges. The same copper gasket can be used many times by successively reducing the distance between the sealing flanges.
Dynamic measurement of optical fiber diameter
Authors: Cohen L. G. , Glynn P.
Published: February 2004

This paper describes a novel technique for monitoring the outside dimensions of clad or unclad optical fibers. An oscillating mirror is used to deflect a laser beam with constant velocity across a fiber in order to measure the time interval during which the fiber intercepts the beam and casts a shadow on a photodetector. For 110 μ fibers, individual measurements made every 1/60 sec are repeatable within a spread of ± 1% from the 330 μsec mean time interval (rms deviation ≈ ± 0.6%). Results are displayed in digital form, but can be converted to an analog signal for use in a servo loop to control the pulling rate of fiber drawing machines. An additional feature of the technique is that fibers with noncircular cross sections can be monitored by making sequential diameter measurements along orthogonal axes of the fiber.
A simple compact cavity-tuning arrangement for variable temperature EPR experiments
Authors: Sharp G. R. , Misra Sushil K.
Published: February 2004

A simple cavity-tuning arrangement, designed for use with a small sample area at variable temperatures, is described. It is easily and economically constructed.
Filling factor for two-coil nuclear magnetic resonance spectrometer
Authors: Ladjouze H. , Benoit H.
Published: February 2004

We present an extension of the filling factor for NMR spectrometers with two coils. We calculate the induced flux in the receiving coil and we show that it is possible to separate dimensionless factors which are filling factors.
32-msec scan of the NAD(P)H fluorescence spectrum in single living cells
Authors: Kohen Elli , Kohen Cahide , Thorell Bo , Salmon Jean-Marie
Published: February 2004

A multichannel microspectrofluorometer based on an electron bombardment silicon camera tube, a multiscaling computer, and a miniature Amici prism for spectrometer, allows the scanning of the NAD(P)H fluorescence emission spectrum from a 30 μ region in a single living EL2 ascites cancer cell, within 32 msec. Observations of changes in the relative maximum emission intensities of two fluorochromes within a same cell are quite possible (for emission maxima ∼ 10–20 nm apart). Thus, in the fluorescence emission spectrum of cells incubated with benzpyrene or dibenzanthracene, the 423 nm (polycyclic hydrocarbon)/443 nm [NAD(P)H] ratio is 1.25 or over, while it decreases to 1.0 or less upon microelectrophoretic addition of glucose-6-phosphate [NAD(P) reduction].
Automatic recording dilatometer
Authors: Bernatchez Pauline , Goutier Dominique
Published: February 2004

We present a dilatometer and an apparatus which automatically records the height of the mercury column as a function of time. The precision on changes of 30 cm in height may attain ± 0.007cm. The stability of the electrical circuitry is such that measurements may span over several weeks. The measurement is based on electrical conductivity. An application is reported.
A Dual rf Gate System with Adjustable Delays for NMR Double Resonance Experiments
Authors: Dorn Harry C. , Uurtamo Stephen J. , Maciel Gary E.
Published: February 2004

A dual gate system with adjustable delays is described; this system is ideally suited to a wide variety of double resonance experiments in nuclear magnetic resonance. The incorporation of the dual gate system into a typical pulse Fourier transform spectrometer is described, and the timing sequences of a typical double resonance experiment are outlined.