bluuebunny/crossref_metadata_2025 huggingface dataset:
Gravitational configuration effect upon precision mass measurements
Authors: Almer H. E. , Swift H. F.
Published: March 2003

Modern weighing practice consists of making comparisons between the gravitational attractive forces exerted on standard and unknown weights. An effect coupling the gravitational force exerted on a weight to the height of the weight’s center of gravity above its base has been found to be significant when weighings of the highest precision are attempted. This effect will cause systematic errors in mass measurements if not properly accounted for. The effect, called the ’’gravitational configuration effect,’’ arises because the centers of gravity of nominally equal weights above their bases, and hence the weights’ effective distances from the center of the Earth, are affected by the weights’ size and shape. Variations of 1 cm in the separation between the centers of gravity of weights and the center of the Earth produce differences in gravitational attractions of 3.14 parts in 109. Currently, mass comparisons at the 1-kg level can be carried out with standard deviations as small as 1.5 parts in 109. Thus, the gravitational configuration effect must be considered if weighing accuracies approaching weighing precisions are to be obtained when kilogram weights of significantly different sizes and/or shapes are compared. Corrections for the gravitational configuration effect can readily be combined with corrections for better-known effects, such as air buoyancy, to generate an overall equation to express the results of mass comparisons.
Thermal and electrical properties of Evanohm and other resistance alloys below 4 K
Authors: Cieloszyk G. S. , Cote P. J. , Salinger G. L. , Williams J. C.
Published: March 2003

The specific heat c of Evanohm resistance wire has been measured to be c=0.037+0.333 T J⋅kg−1⋅K−1 between 0.15 and 1.5 K. The thermal conductivity λ of Evanohm is given by λ=0.020 T+0.048 T2 W⋅m−1⋅K−1 in the same temperature range. These results are compared with similar measurements for constantan, manganin, Nichrome, and a platinum–tungsten alloy. The electrical and magnetic properties of these materials are also reviewed.
Beam focusing by aperture displacement in multiampere ion sources
Authors: Stewart L. D. , Kim J. , Matsuda S.
Published: March 2003

Results are given of an experimental study of beam focusing by aperture displacement (Δx) in duoPIGatron ion sources. Measurements with a single aperture, accel–decel electrode geometry show that the beam deflection angle is linear with Δx/z for the round aperture and with Δx/z*2 for the slit aperture, where z and z* are, respectively, the extraction gap distance and the effective gap distance. Applying the result of the single aperture study to the multiaperture duoPIGatron sources, it was possible to increase the neutral beam injection power to the Oak Ridge Tokamak (ORMAK) plasma by ?40%. Also presented are a discussion and comparison of other work on the effect of aperture displacement on beam deflection.
Programmed pulsing to initiation apparatus for electroexplosive testing
Authors: Rosenthal Louis A. , Menichelli Vincent J.
Published: March 2003

The sensitivity of an electroexplosive device can be determined by delivering pulses of increasing energy in a step-wise fashion. An energy-firing contour relating the energy required to the programmed step size describes the single-pulse firing energy and the possible sensitization or desensitization of the device under test.
Simple, low-noise uhf SQUID magnetometer
Authors: Clark T. D. , Jackel L. D.
Published: March 2003

We describe the development of a simple, rugged, low-noise SQUID magnetometer, biased in the uhf range, and constructed around the extensively used two-hole SQUID ring. This design is novel, both in the manner in which rf is coupled to the SQUID ring, and in the ability of the magnetometer system to couple strongly to an external signal or a flux transformer cell.
First x-ray diffraction photograph of a shaped charge jet
Authors: Green Robert E.
Published: March 2003

A flash x-ray diffraction system has been constructed which permits x-ray diffraction patterns to be recorded from shaped charge jets. The system was tested by recording an x-ray diffraction pattern from an aluminum jet 80 μsec after charge detonation with a single pulse of 70 nsec duration. This result represents the first successful recording of an x-ray diffraction pattern from a shaped charge jet and indicates that the system should be an important new device for determination of internal jet structure.
Easily constructed pure nuclear quadrupole resonance spectrometer
Authors: Sullivan E. P. A.
Published: March 2003

An easily constructed circuit for a nuclear quadrupole resonance spectrometer suitable for searching for resonances in solids is given. The oscillator of the spectrometer is operated in the self-quenching mode, and incorporates a simple ratemeter for the manifestation of detection. Graphs of signal intensity for differing quench frequencies, as the radio frequency is scanned through resonance, are given for paradichlorobenzene and sodium chlorate polycrystalline samples at room temperature. The dependence of the detection signal upon the quench frequency is quite noticeable in the graphs.
Channeltron entrance aperture gain variations for energetic heavy ions
Authors: Hird B. , Suk H. C. , Guilbaud A.
Published: March 2003

Considerable differences in the current gain have been found in a channel electron multiplier when used as a detector of 100 keV N1+ ions, depending on the point of impact at the channel entrance. These differences occur at high current gains which are usually considered near to saturation. In contrast to the current gain, the detection efficiency shows no significant variation with the point of impact, suggesting that at least one of the electrons from the primary interaction of the ion with the secondary surface is multiplied by the channel to provide a detectable pulse.
New laser-induced fluorescence method for molecular beam velocity analysis
Authors: Gaily T. D. , Rosner S. D. , Holt R. A.
Published: March 2003

We have measured the velocity distribution of a Na2 supersonic beam by a time of flight method in which a chopped beam from an argon ion laser depopulates a single vibration–rotation level of the Na2 ground electronic state, and a continuous laser beam further downstream is used to detect the arrival of the tagged molecules by observation of changes in the laser-induced fluorescence.
Investigation of microchannel plates as parallel-bore collimators for electron pulses
Authors: Webb Clinton B. , Lieber Albert J. , Sutphin H. Dean , Benjamin Robert F.
Published: March 2003

Microchannel plates have been investigated for use as parallel-bore collimators using a chopped electron beam. This note compares the collimation ability of plates with theory and gives transmission results. It is found that collimation ability approaches the ideal collimator when pulse duration does not allow charge buildup on tubule walls of the plate.
High voltage pulsed circuit for dichroic studies
Authors: Glick Harold A.
Published: March 2003

A high voltage pulse generator using stacks of silicon-controlled rectifiers (SCRs) is described. Pulses of 2 kV are easily produced and applied to solutions for dichroic studies. The system is easily adapted for higher voltage pulses.
Low temperature nanohm contacts to tungsten
Authors: VanHarlingen D. J. , Garland J. C.
Published: March 2003

Electroplated lead contacts have been found to exhibit contact resistances lower than 10−9 Ω/mm2 to tungsten below 7 K, and to withstand repeated thermal cycling between room temperature and liquid helium temperatures.
Successful operation of a scanning ion microscope with quadrupole mass filter
Authors: Wittmaack K.
Published: March 2003

An ion microprobe has been combined with a quadrupole equipped secondary ion mass spectrometer. Operating the microprobe in the raster scanning mode, ion images with a lateral resolution of about 10 μ could be obtained. Moreover, the system provides stereoscopic imaging. In-depth profiling capabilities of the instrument are also described briefly.
Simple method for measuring conductance changes to one part in 106 at MHz frequencies
Authors: Kanazawa K. , Schoenes J.
Published: March 2003

A phase lock technique for the measurement of small conductance changes at MHz frequencies is described. The method requires a stable Q meter having an analog output proportional to the Q and a lock-in detector. The sensitivity is excellent, with changes as small as one part in 106 having been easily observed.
Optical detection and electronic simulation of magnetic resonance in zero magnetic field of dihydroporphin free base
Authors: van der Bent Sievert J. , de Jager Adrie , Schaafsma Tjeerd J.
Published: March 2003

An apparatus for the measurement of optically detected magnetic resonance (ODMR) in zero magnetic field at 4.2 K using commercially available parts is described. A simple electronic analogue device is used to obtain kinetic data from ODMR transients in a fast and reliable way. From these data decay rates of the three spin levels of the lowest molecular triplet state can be obtained, whereas populating rates can be determined within defined limits. Since the apparatus is suited for unguarded operation during long periods of time, signal averaging of weak signals, e.g., from biological molecules, is particularly easy. Kinetic data have been obtained for dihydroporphin, which can be considered as the structural basis for chlorophyll: k1= 121±12 sec−1; k2=277±28 sec−1; k3=22±2 sec−1; 0.28<P1<0.43; P2=1; P3<0.08, where ki and Pi are the decay and populating rates of the ith spin level.
Modulated polarization measurement of structural phase transitions in KMnF3
Authors: Benard D. J. , Walker W. C.
Published: March 2003

A polarization modulated birefringence scheme allowing continuous measurements on single domains at phase transitions has been developed. Measurements on the 184 K transition in KMnF3 clearly revealed the initial first order nature of the transition and yielded improved values for the critical exponent and transition parameters.
Superconducting magnetometer for high resolution susceptibility measurements
Authors: Cerdonio M. , Cosmelli C. , Romani G. L. , Messana C. , Gramaccioni C.
Published: March 2003

A susceptometer, based on various properties of superconductors, has been developed. It makes possible the resolution of differences in magnetic susceptibility of less than 1% of the diamagnetism of water, in the whole temperature interval between liquid helium temperature and room temperature, on sample volumes of about 0.1 cm3. Two prototypes are presently in routine operation for measurements on solutions, suspensions, powders, and crystals.
Parabolic smoothing simplified
Authors: Giannelli G. , Altamura O.
Published: March 2003

Quantitative evaluations of the noise reduction and signal deformation that are produced in parabolic smoothing are obtained, and their utilization for the optimization of smoothing is discussed. These results ensue from a general method of analysis of smoothing procedures that was developed in a previous paper. As a by-product a new smoothing method is developed. It has practically the same properties as the parabolic one, but smoothing is achieved with a notable reduction in the number of operations required.
Design of experimental signal smoothing
Authors: Giannelli G. , Altamura O.
Published: March 2003

The object of this method of design is the determination of the smoothing weighting function wf. This approach makes it possible to base the design on minimum total error (signal deformation plus noise) evaluated at every or at any characteristic important point of the experimental signal. In a previous analysis classes of weighting function were defined. In the present paper the optimum wf of each class is calculated. These are universal functions and in the design only the width of the weighting function (the averaging interval) must be determined. The optimum width is calculated as a function of a priori information on the signal and the noise. Also, the precision with which this information is required is calculated. Examples of design of experimental signal smoothing are developed.
New method of measuring the shape of precise antenna reflectors
Authors: Payne J. M. , Hollis J. M. , Findlay J. W.
Published: March 2003

The shape of the paraboloidal reflector surface is determined by making a large number of measurements of the reflector curvature along several radii of the surface. These measures of curvature are then integrated twice to give the reflector profile along each radius; the results from several radii then allow the reflector surface shape to be mapped in three dimensions. The curvature measurements are made by a three-wheeled cart with a depth sensor resting on the surface at the midpoint of the wheels. Tests of the method on an 11 m diam antenna show an average repeatability of 0.037 mm in the measurement of the shape of the parabolic reflector.
Constant pulse energy power supply for a high repetition rate laser system
Authors: Lo C. C. , Fan B.
Published: March 2003

A pulsed power supply system with constant pulse energy has been developed to drive flashlamps in a 0.5–5 pulses per second Nd : glass laser. By using a stable, absolute reference voltage source to set the trigger level, the energy discharged through the flashlamps is kept constant despite pulsing frequency change, power line fluctuation, and minimum dc power supply regulation. The concept can be expanded or adapted to operate other similar systems.
Transition radiation for the diagnosis of low-energy electron beams
Authors: Mahan A. H. , Gallagher Alan
Published: March 2003

Electron bombardment of metallic silver is known to produce ’’transition radiation,’’ predominantly at 300–450 nm wavelengths. In reported measurements at 15–500 eV impact energies, transition radiation was used to diagnose the shape and time dependence of an rf modulated electron beam. It is suggested that this is a superior target, as opposed to phosphors or gases normally used, to determine instrumental time response functions and electron beam imaging.
Nanosecond x-ray pictures recorded with a pulsed channel plate
Authors: Nahrath B. , Shakhatre M. , Decker G.
Published: March 2003

A channel plate phosphor system has been electrically pulsed in order to obtain time and space resolved images of a fast varying x-ray source. Effective exposure times of about 3 nsec have been realized. Plasma focus x-ray pictures obtained by this method are presented.
Hold-time stage for intermittency detector
Authors: Tutu Narinder K. , Chevray Rene
Published: March 2003

A circuit which allows independent hold time for turbulent and nonturbulent states is presented and shown to provide a distortion-free intermittency signal.
Aerosol fractionator for large-scale sampling
Authors: Forney Larry J.
Published: March 2003

The design of a versatile instrument for aerosol assessment is described. The single stage device incorporates the principal of virtual impaction and a continuously variable slit width to provide for ease of calibration, low internal wall losses, and potential for large-scale sampling, as well as the option of either fractionating particles into two size classes for mass or chemical analysis or determining entire particle size distributions. Initial tests indicate the efficiency curve of the device is solely a function of particle Stokes number ψ for typical geometries and flowrates and is characterized by the cutoff value ψ1/250=0.36 ±0.04 and a steepness of ψ1/284/ψ1/250 =1.32±0.06. Moreover, wall losses are shown to peak at less than 15% at the critical Stokes number ψ1/250, which is an improvement over existing devices now used for large-scale sampling.
High pressure x-ray diffraction at liquid-helium temperature
Authors: Endo S. , Mitsui T.
Published: March 2003

An apparatus for high pressure x-ray diffraction at liquid-He temperature is described that consists of a vessel capable of holding pressure up to 100 kilobar between Bridgman anvils immersed in liquid He in a cryostat. A technique is described for attachment of vacuum-tight beryllium windows to the cryostat. With this apparatus, the superconducting transition temperature of Pb and its dependence on pressure were measured; the pressure was determined from the lattice parameter of NaCl on the basis of the equation of state for NaCl. The result can be used as a low temperature manometer.
High-voltage probe system with subnanosecond rise time
Authors: Sarjeant W. J. , Alcock A. J.
Published: March 2003

A high-voltage probe measuring system with an overall rise time of less than 50 psec and a peak voltage capability of 20 kV has been developed. Probe perturbations at the 50 Ω impedance level are minimized by maintaining a moderately high input impedance, in conjunction with the absorption of internal reflection waves by means of a lossy distributed transmission line. System long-term stability and constructional reproducibility have been investigated.
Display device for ion beam profile
Authors: Sakudo Noriyuki , Kanomata Ichiro , Tsuyama Hitoshi , Mitani Eisuke
Published: March 2003

A display device for ion beam profiles which permits the study of mass spectrometer ion source performance is presented. In this device the ion beam from the source is deflected by two pairs of plate electrodes, and a small portion of the beam’s cross section is directed through a 50-μm aperture. Thus, the sampling spot of the beam’s cross section is scanned as in a TV. The analog signal of the detected ion current is fed into an equistrength signal generator and converted into pulses, which are used to modify the brightness of a CRT. At the same time, the flying spot on the CRT is synchronized with the ion beam scanning. Thus, the intensity distribution of the beam’s cross section is displayed as equistrength lines on the CRT.
Frequency measurements with 10 MHz resolution in upper microwave bands
Authors: Jansen K. , Sperlich G.
Published: March 2003

Microwave lengths, especially in the millimeter range, can be measured quickly and exactly with highest resolution with the help of a spherical Fabry-Perot cavity.
Optical heterodyne interferometer with improved two-channel crosstalk signal-to-noise ratio
Authors: Lavan M. J. , Cadwallender W. K. , Van Damme G. E. , De Young T. F.
Published: March 2003

A modification to a previously reported optical heterodyne interferometer [Lavan et al., Rev. Sci. Instrum. 46, 525 (1975)] which greatly improves its signal stability and aids in alignment is described.
Simplified aerodynamically stabilized cathode for longitudinal discharge lasers
Authors: Cohn D. B. , Mendoza P. J. , Lim D. G.
Published: March 2003

A single cathode of arbitrary size and shape in conjunction with downstream, sonic radial gas injection has demonstrated significant enhancement in performance over much more complicated aerodynamically stabilized cathodes applicable to convective flow CO lasers at low temperatures.
Magnetic suspension densimeter for measurements on fluids of cryogenic interest
Authors: Haynes W. M. , Hiza M. J. , Frederick N. V.
Published: March 2003

An apparatus incorporating a magnetic suspension technique has been developed for density measurements on liquids and liquid mixtures, particularly at saturation, at temperatures between 90 and 300 K and at pressures to 5 MPa (approximately 50 atm). The feasibility of adapting this method, previously used at room temperature, for low temperature use had been demonstrated in an earlier study with a density measurement on saturated liquid nitrogen near its normal boiling point. The present apparatus, which is significantly improved, and in most respects different from the earlier model, is described in detail. It includes a cryostat for continuous wide-range temperature control, a windowed equilibrium cell particularly suited for studies of liquid mixtures, and a new electronic servocircuit with a linear differential transformer for position control of the magnetic buoy. Extensive tests and density measurements have been carried out to evaluate the performance of this apparatus. Densities of saturated liquid nitrogen between 95 and 120 K and saturated liquid methane between 105 and 160 K are reported. The estimated standard deviation of a single density measurement is less than 0.02%. The total systematic error in the measurement process from known sources is approximately 0.05%. The total uncertainty of a single density measurement, which is taken as three times the standard deviation plus the systematic error, is approximately 0.1%. Comprehensive comparisons of the present results with previous experimental data are presented.
Variable-frequency automatic capacitance/conductance system for impurity profile and deep level determination
Authors: Anderson C. Lawrence , Baron R. , Crowell C. R.
Published: March 2003

Development of new semiconductor technologies frequently requires impurity density analysis on material with high leakage currents or deep level contamination. Previously described impurity profilers provide minimal diagnostics for such cases. We have constructed a new variable-frequency capacitance/conductance analysis system applicable to impurity profile, Schottky barrier height, MOS interface state, and deep level analysis. The system, which consists almost entirely of commercial ’’building blocks,’’ uses phase-sensitive detection to provide better than 40-dB isolation between capacitance and conductance signals. For impurity profile measurements a two-frequency intermodulation technique avoids the stringent filtering requirements inherent in the Copeland plotter. In this mode the system can measure either capacitance, C, and dC/dV or conductance, G, and dG/dV over two decades in frequency. A small-scale analog computer integral with the unit allows presentation of the data as impurity profiles. A simple change of circuit parameters permits measurements of C or G with amplitude response flat within 1% over four decades of frequency. The computer may then be used to present the results in formats appropriate to Schottky barrier height or deep level determinations.
Digital stabilizer for scanning Fabry–Perot
Authors: Bechtle Daniel
Published: March 2003

An electronic unit for maintaining plate parallelism in a scanning Fabry–Perot is discussed. The unit is a digital version of an analog unit previously described. It offers significantly improved performance over the analog unit, and is capable of maintaining high finesse for many hours under low input light conditions. In a test using high-reflectance plates in a triple-passed system, the unit held a finesse of 84 over a period of 7 h with a Rayleigh peak height of 2100 counts/sec.
Compact magnetic mass separator with low stray fields
Authors: Köllmann K. , Grüter J.
Published: March 2003

A 90° magnetic sector field mass separator designed for low ion energies (≳1 eV) is described. The main features of the instrument are compact construction, small size, and low stray fields.
Flow calorimeter cell for measuring heats of solution of solids
Authors: Gill S. J. , Seibold M. L.
Published: March 2003

A novel flow calorimeter cell has been designed to allow insertion of soluble solids into the stream of the flowing solvent fluid. Only small amounts (∼1 mg) of solid material are required. A model of the flow cell has been constructed for use within a Tian–Calvet microcalorimeter. Effective thermal equilibrium of the flowing fluid is achieved by a counterflow technique developed by Gill, Nichols, and Wadsö in a similar system for study of heats of slightly soluble liquids. A precision of 1–2% is obtained by measurements of the heat of solution for diketopiperazine and several purine and pyrimidine compounds at 25 and 40 °C.
Electron spin resonance spectrometer with a new wideband resonator for aqueous samples
Authors: Giordano M. , Martinelli M. , Pardi L. , Santucci S.
Published: March 2003

We describe an electron spin resonance spectrometer operating in the full 1–2 GHz octave band which by the use of a new resonator with a filling factor ca. 1 reaches a very high measured sensitivity also at low power levels (1.3×1013 spins/cm3 G at 0.6 mW). A thorough discussion of the specific advantages of this spectrometer is given.
Molecular carbon vapor source for flowing systems
Authors: Mann David M.
Published: March 2003

A furnace for the production of molecular carbon species is described. The furnace generated equilibrium concentrations of carbon species (predominantly C3, C, and C2) by sublimation from a resistively heated graphite tube. Inert gas, admitted at the base of the furnace, provides a carrier for the carbon vapor. Furnace operating parameters and stability are also discussed.
Method for extending the range of low-frequency admittance measurements
Authors: Greve D. W.
Published: March 2003

An admittance bridge, using a lock-in amplifier as a null detector, is described for making low-frequency capacitance measurements when the device conductance is large. Improved convenience of operation has been obtained by operating the bridge in a self-balancing mode. Capacitance has been measured to ±0.2% accuracy when G=100ωC. It is suggested that a similar method would be useful for conductance measurements when ωC≳≳G.
Accurate method for the simultaneous determination of the thermal conductivity and specific heat of nonconducting solids
Authors: Bruce Richard H. , Cannell David S.
Published: March 2003

A relatively simple technique employing a two-dimensional form of the temperature wave method is described. With reasonable care, both the specific heat and the thermal conductivity may be measured with an accuracy of 1% and a precision of 0.1%. Samples as small as 5×7 mm may readily be studied. The region of the sample in which the measurements are made is quite small and may be maintained isothermal to better than 15 mK, making the method suitable for use near phase transitions. The method should also be useful in applied fields and at high pressures or temperatures.
Long-term operation of a sealed waveguide CO2 laser
Authors: Laughman L. M.
Published: March 2003

Procedures for constructing a BeO waveguide CO2 laser are discussed and life-test data for one such laser are presented. After an initial decrease, laser power is constant for at least 2500 h.
New modification of the diamond anvil press: A versatile apparatus for research at high pressure and high temperature
Authors: Sung Chien-Min
Published: March 2003

A new modification of the diamond anvil pressure that can achieve up to 300 kilobars and 1000°C is described. The new modification employs a new alignment technique and a new heating element and is aversatile apparatus for research at high pressure and high temperature.
Bragg cell heterodyne interferometry of fast plasma events
Authors: Kristal R. , Peterson R. W.
Published: March 2003

Plasma interferometry using the fringe shift technique has been extended to the 100-MHz range by the use of Bragg diffraction in a lead molybdate acousto-optic cell. The cell splits a 633-nm laser beam into zero and first-order beams, which are separated in frequency by 80 MHz. These beams are used in the scene and reference arms of a modified Michelson interferometer and are then recombined on a silicon photodetector. Phase changes are deduced from the variations in time separation of consecutive peaks in the beat signal. The technique has been used to make electron density measurements in a 1-m-long, shock heated theta pinch with 6-nsec time resolution. Density variations during the implosion produce a total phase shift of nearly 1 fringe in 150 nsec. Phase noise in vacuum shots (without plasma) is 1/40 fringe rms; the peak-to-peak noise is 1/10 fringe, thus corresponding to a maximum area density (ℱn dl) uncertainty of 2×1016 cm−2.
Novel short recovery time high-voltage switch
Authors: Dufour M. , Egger H. , Seelig W.
Published: March 2003

A novel sealed-off low-pressure quenching discharge gap capable of switching voltages up to 25 kV has been built. A recovery time of a few microseconds was measured, allowing switching rates in the 100 kHz range.
Blanking resistive heating circuit for Auger electron spectroscopy experiments
Authors: Tu Yung-Yi , Blakely J. M.
Published: March 2003

A blanking circuit is described that is suitable for resistively heated samples. The Auger spectrum is blanked synchronously with the pulsed heating current. This arrangement allows the detection of undistorted Auger spectra from a fixed point on the specimen surface.
Compact high-voltage vacuum feedthrough
Authors: Stein J. D.
Published: March 2003

A vacuum feedthrough has been designed at this laboratory to operate at 40 kV and 10−9 Torr. It is small in size, 3.81 cm in diameter and extending 4.45 cm into the vacuum chamber. A selection of commercial connectors is available. The re-entrant design fully shields the conductor for safety, prevention of noise pickup, and protection from environmental effects.
Device for stretching microscope specimens
Authors: Whitmore Robert A. , Calhoun Robert R. , Skasko Joseph
Published: March 2003

A device is described for holding and stretching thin unsupported sheets or fibers near the plane of a slide surface on the microscope stage. Photographs of the instrumental details are shown. Specimens can be not only stretched, observed, and photographed on the microscope stage, but the clamped material can, while in the device, be removed from the microscope, treated by heating (cooking), freezing, or fixing; and returned to the microscope for further observation or prepared for sectioning. Shop drawings are available.
Apparatus for studies of matrix-isolated sputtered products
Authors: Bates J. , Gruen D. M. , Varma R.
Published: March 2003

A system making use of matrix isolation techniques in the elucidation of the sputtering process has been developed and is described. A stable beam of positive ions produced with a commercially available sputter ion gun impinges on a target. The matrix-isolated back-sputtered products are collected on a cryogenically cooled optical plate for spectroscopic observation. The system can be used to identify atomic and molecular sputtered products and to measure sputtering yields. For demonstration purposes, the spectra of sputtered gold atoms in a deuterium matrix and sputtered molybdenum atoms in an argon matrix are shown.
Argon triple point realization cryostat for platinum resistance long stem thermometers
Authors: Ancsin J. , Phillips J.
Published: March 2003

A high-precision realization cryostat was developed for long stem type platinum resistance thermometers at the argon triple point. Six liters of argon gas (at room temperature) are sufficient for calibration and if ultrahigh purity grade is used one may expect the results to yield better than ±1 mK accuracy.
Digital detector for monitoring lidar output energy
Authors: Reagan J. A. , Spinhirne J. D. , Bruhns T. V. , Peck R. L.
Published: March 2003

A digital detector for monitoring laser output energy that has been used successfully for accurate collection of lidar data is presented. The detector includes both an optical system to sample laser pulses and electronic circuitry to provide a digitized electronic output proportional to the energy in the sampled light pulses. Test results show that the detector system is capable of monitoring lidar relative output energy to within 1%.
Picosecond trigger system useful in mode-locked laser pulse measurements
Authors: Cunin B. , Miehe J. A. , Sipp B. , Thebault J.
Published: March 2003

A highly sensitive tunnel diode trigger useful in temporal intensity buildup measurements of mode-locked lasers has been developed; the device reduces notably the time walk due to the lack of repeatability in intensity of the laser output. The performance of the trigger has been established by means of a 5-GHz wideband, 0.1 V/cm sensitive real-time oscilloscope and of an image converter camera of picosecond resolution. The experimental results show that a variation of the amplitude of the laser pulse train of a factor of 5 leads to a time jitter of less than 30 psec.
Flux gradient accelerometer: Tests on a working model
Authors: Hoffman Alan W. , Douglass D. H. , Gram R. Q. , Lam C.
Published: March 2003

A device to detect small vibrations, which we call a flux gradient accelerometer, has been constructed. We propose to use such a device as the transducer for a low-temperature gravitational wave detector. The accelerometer is found to respond as predicted by a simple harmonic oscillator model with a sensitivity nearly equal to the sensitivity calculated theoretically. If the accelerometer signal were amplified by a SQUID (superconducting quantum interference device) having a flux noise of 1.4×10−12 G cm2 Hz−1/2, the signal should just equal the noise when Δxrms =9×10−18 (Δf)−1/2 cm where Δxrms is the rms displacement, and Δf is the amplifier bandwidth.
Optical technique for measurement of random water wave surfaces
Authors: Sorrell F. Y. , Withers A. L.
Published: March 2003

An optical system for measuring the slope of random wind-generated water waves is described. The instrument employs the refraction of a vertical light ray, which is a technique that has been previously used. The present system, however, employs a large-area array of individual photovoltaic cells to measure the refraction angle of the beam. Because the array provides a much larger active area with no preferred direction, it is much better suited to the measurement of random water wave fields, typical of those generated by wind.
Combined optical and electron spin resonance kinetic spectrometer
Authors: Warden Joseph T. , Bolton James R.
Published: March 2003

A combined optical and electron spin resonance spectrometer is described. Construction details and typical kinetic data are presented.
Pressure-jump relaxation technique with optical detection
Authors: Knoche W. , Wiese G.
Published: March 2003

An autoclave is described which allows the measurement of chemical relaxation induced by a pressure jump and observed by the change in optical absorbance. The autoclave fits into the optical arrangement of conventional temperature-jump equipment. Relaxation times longer than 0.5 msec can be determined.
Thermal conduction of metals under pressure
Authors: Sundqvist B. , Bäckström G.
Published: March 2003

It is shown that the original Ångström method of determining the thermal diffusivity of metals is not valid in the case of a specimen surrounded by a solid medium, and an appropriate modification is described. Several simplifications of this method are also presented and criteria for their validity given. An electronic system has been developed for automatic sampling and analysis of the temperature data. The new method has been applied to Cu under pressure, and the results show that the thermal conductivity rises by 6.4% up to 2.5 GPa (25 kilobar).
Optimization of isolated electron pulses in the picosecond range from a linear accelerator using a streak camera–TV diagnostic system
Authors: Mavrogenes G. S. , Jonah C. , Schmidt K. H. , Gordon S. , Tripp G. R. , Coleman L. W.
Published: March 2003

We describe the technique and the results of a measurement of the width of a fine structure pulse from our L-band electron linear accelerator. The pulse width was measured by measuring the width of the C̊erenkov light pulse generated by the electron beam using a streak camera–TV camera–computer system. With very low beam currents, a pulse width of 20 psec (FWHM) was measured, while at higher beam currents a pulse width of 27 psec was measured showing a space-charge effect. In addition, a broad energy spectrum for the electrons or improper focusing into a 270° bending magnet was also shown to increase the pulse width of the beam after it had traversed the magnet.
Electronic liquid-in-glass thermometer
Authors: Saarimaa R. , Wallin P.
Published: March 2003

This project developed a device for measuring temperature in which the heat expansion of mercury is measured capacitively. Using this method, the step-like movement of the mercury restricting the performance of conventional mercury-in-glass thermometers can be reduced. In our new devices, the average step is less than 1 mK. The instability of the electronic part with time appears to limit the measuring range to 3–4 decades. The device is particularly suitable for highly accurate remote measurement of temperature. Compared with other accurate electronic devices for measuring temperature, the device constructed is extremely inexpensive.
Switching subreflector for millimeter wave radio astronomy
Authors: Payne J. M.
Published: March 2003

A method of beam switching a Cassegrain antenna used for radio astronomy by tilting the hyperbolic secondary reflector is described. The system described has been in use for over a year at the 11-m millimeter wave antenna operated by the National Radio Astronomy Observatory at Kitt Peak, Arizona.
Electrostatic energy analyzer using a nonuniform axial magnetic field
Authors: Hsu T. , Hirshfield J. L.
Published: March 2003

Electrostatic electron energy analysis in a strong magnetic field using conventional retarding-field methods may be inaccurate, because these devices discriminate against parallel momentum and not total energy. We show how a magnetic-field minimum at the point of minmum potential can remove this difficulty. Examples of elastic and inelastic electron–atom scattering, and of electron energy loss in a plasma, are given.
Measurement of circular and linear polarization of Raman-scattered radiation by differential techniques
Authors: McCaffery A. J. , Shatwell R. A.
Published: March 2003

We describe a Raman spectrometer in which the polarization of scattered radiation, both circular and linear, is measured by ac differential techniques. The essential element in this is a photoelastic polarization modulator. The advantages of using differential techniques, particularly circular differential methods, are illustrated and discussed.
High pressure low temperature ENDOR/EPR cavity
Authors: Wolbarst A. B.
Published: March 2003

We discuss an X-band TE011 cavity and bomb for use in performing ENDOR (electron nuclear double resonance) and EPR at 2 K and pressures to 5 kilobar, with gaseous and solid helium as pressure conducting media.
Compounds for use as optical attenuators for CO2 laser radiation
Authors: Roberts T. G.
Published: March 2003

The absorption coefficients and some of the physical and chemical properties of compounds which have been found to work well in a continuously variable attenuator for CO2 laser radiation are presented.
Neutron scattering at high pressure
Authors: Bloch D. , Paureau J. , Voiron J. , Parisot G.
Published: March 2003

Neutron scattering spectra at pressures up to 30 kilobar in the temperature range 300–4 K have been obtained with a compact clamped type apparatus. The pressure cell geometry, by allowing the detection of neutrons scattered in a plane, makes it compatible with operation on crystal spectrometers, both for elastic and inelastic scattering. The instrument is light (4.5 kg) and easy to move. An external diameter of 68 mm makes the pressure cell adaptable to standard cryostats or furnaces.
Compact calorimeter for measuring laser absorption coefficients of small samples
Authors: Magee T. J. , Johnson N. M. , Lehmann M. , Peng J. , Hannigan J.
Published: March 2003

A relatively simple calorimeter has been designed for measuring laser absorption coefficients on samples of small cross-sectional area. This instrument has proven useful in studies of absorption or scattering within samples by microscopic defects, where bulk samples of small volume are required.
Rapid determination of the overlap integral in a merging beams system
Authors: Nitz D. E. , Geis M. W. , Smith K. A. , Rundel R. D.
Published: March 2003

A method for determining the beam overlap integral semiautomatically in a merging beams experiment is presented. The apparatus consists of a driven beam scanner and an analog circuit which computes two-dimensional overlap integrals from the sampled beam currents. Only a simple additional computation is required to obtain the three-dimensional overlap integral. Results of qualitative and quantitative tests demonstrate the validity of the technique. The capability for rapid measurement of beam overlap is employed to investigate the stability of the overlap integral.
Versatile nanosecond fluorometer employing a boxcar averager
Authors: Badea M. G. , Georghiou S.
Published: March 2003

A nanosecond pulse fluorometer which employs a boxcar averager and has the following novel features is described: (a) It achieves a short data acquisition time with a noise reduction factor in excess of 103; (b) corrects for baseline drift and for exciting light intensity fluctuations; and (c) employs intense nanosecond optical pulses which cover the ultraviolet to the far visible wavelength range. Examples of the performance of the fluorometer, including the measurement of sub-nanosecond fluorescence decay times, are presented. The effect of the variation of the time profiles of the exciting light pulses with their wavelength on the accurate determination of fluorescence decay times has been investigated for a variety of flashing gases over a wide range of pressures.
Electrostatically driven apparatus for measuring work function differences
Authors: Fain S. C. , Corbin L. V. , McDavid J. M.
Published: March 2003

A tungsten ribbon and a grounded sample form two electrodes of a vibrating capacitor connected to a sensitive radio frequency capacitance bridge and to a source of dc and ac bias. The ac bias frequency is tuned to the fundamental resonance of the ribbon (f?2.5 kHz, Q≳500) and the work function difference between the ribbon and the sample is determined from the dc bias for which the ribbon capacitance variation at the ac driving frequency vanishes. Work function differences at different positions on a flat sample can be measured to millivolt precision. An example of the change in work function of evaporated Ag–Au alloys with oxygen exposure is given.
Refractive index profiling of graded index optical fibers
Authors: Presby H. M. , Mammel W. , Derosier R. M.
Published: March 2003

Details of a method of determining the refractive index distribution of graded-index optical fibers based on interference microscopy are discussed. Sample preparation techniques, observational methods, and data reduction and analysis by a computer fitting program are described. Representative data for optical fibers prepared by chemical vapor deposition are shown.
Emission and polarization spectrometer for biophysical spectroscopy
Authors: Sutherland John Clark , Cimino George D. , Lowe John T.
Published: March 2003

We have constructed a spectrometer which, using well established techniques, measures both fluorescence and circular dichroism (natural and magnetic) as well as several other parameters of interest in biophysical spectroscopy. This combination is feasible since the various measurements, aside from sharing many optical components, can all use a lock-in amplifier to process electronic signals. Although fluorescence and circular dichroism provide greatly different information about the material under investigation, from the standpoint of instrumentation they are very similar. Combining several functions in a single spectrometer has the advantages of economy and flexibility.
Measurement of all three mean velocity components by a single hot film anemometer
Authors: Favier Daniel , Pellerin Nicole
Published: March 2003

A convenient method for the measurement of all three mean velocity components by a single hot film anemometer is presented. Emphasis is placed on the simplicity of the measuring procedure and on the accuracy of the results obtained when the mean flow undergoes small deflections.
Versatile precision source ratioing system for fast kinetic spectroscopy
Authors: Anson Michael , Bayley Peter
Published: March 2003

A system is described for the reduction of source intensity fluctuation errors in rapid kinetic spectroscopy. The system provides ratioing of the observed signal by a reference of source intensity. This operation is performed by true division in real time with an accuracy of ±0.15% over a ten-fold source intensity range and with a rise time of 11 μsec. Silicon photodiodes, operational amplifiers, and an electronic analog divider are used. The frequency response was evaluated with a modulated LED source, showing ≳ 100-fold rejection of common mode sinusoidal modulation for frequencies dc through 10 kHz. Broad band noise reduction of 100-fold was achieved for a He–Cd laser, running with ∼20% peak-to-peak noise. While designed initially for stopped flow spectroscopy, these characteristics are suitable for a wide range of rapid kinetic techniques with microsecond time response (e.g., temperature jump, light scattering, Raman, flash photolysis, and fluorescence) using both laser and arc sources.
Time resolution of Ge avalanche photodiodes operating as photon counters in delayed coincidence
Authors: Fichtner Walter , Häcker Walter
Published: March 2003

The application of Ge avalanche photon counters for fast light detection in the energy range 0.7<hν<1.1 eV is investigated. Individual photons cause discrete self-sustaining avalanche pulses in alloyed Ge diodes, slightly biased above breakdown voltage at 77 K. The shape of short light pulses (τ=1 nsec) was determined by a delayed coincidence method, which accumulates the distribution of delay times between a light pulse and the following microplasma pulse. It is shown in a quantitative model that the time response of the detector is determined by minority carrier diffusion. Germanium avalanche diodes operating as photon counters with a delayed coincidence technique are suitable for detection of very short light pulses at low levels, and the shapes of fast signals can be detected despite relative long time constants of the detector. In order to reduce the necessary integration times, signal repetition rates up to ∼100 kHz can be used.
Fast rise-time calorimeter for relativistic electron beam diagnostics
Authors: Benson D. A. , Ouellette A. L.
Published: March 2003

A 10-μsec rise-time calorimeter using an infrared optical pyrometer for temperature measurement is described. The present equipment is suitable for pulsed high-energy electron beam diagnostics in graphite targets over the range from 100 to 4000 J/g and includes provisions for temperature calibration and optical alignment. Measurement procedures and applications of the equipment are described. These applications include high-speed energy absorption diagnostics and measurement of absorbed energy profiles versus target penetration. Improvements over conventional calorimetric dosimeter accuracy appear to be possible for some types of measurements with this approach. The present work demonstrates better than ±3% accuracy for measurement of absorbed energy in a series of experiments.
Some remarks on the determination of dead time by the two sources method
Authors: Picot A.
Published: March 2003

The condition n12τ≲0.1 usually prescribed in measuring the dead time τ of an electronic chain is too drastic. Indeed, if the recurrence is increased by a factor n, the measurement duration of τ is n3 times smaller. Even if n12τ=0.1, the exact formula giving τ, n12τ =1−(1−2n12τap)1/2, where τap= (n1+n2−n12)/2n1n2, is needed for an accuracy of 1%. These conclusions have been verified experimentally.
Magnetic field shielding by a superconducting cylindrical tube of finite length
Authors: Thomasson J. W. , Ginsberg D. M.
Published: March 2003

The shielding of the internal volume of a superconducting tube from an external magnetic field aligned parallel to the tube axis is incomplete since the ends of the tube are open. The magnetic field at the center of the tube is reduced from the external field by a factor of 1.13×10−ph/a, where p=5/3, for a tube length 2h which is at least as large as the diameter 2a.