bluuebunny/crossref_metadata_2025 huggingface dataset:
High-resolution magnetic field measurement system for recording heads and disks
Authors: Lustig C. D. , Baird A. W. , Chaurette W. F. , Minden H. , Maloney W. T. , Kurtzig A. J.
Published: March 2003

A high-resolution system for measuring the magnetic fields near recording heads and disks has been built. The perpendicular field components close to the head and disk surfaces are measured with an InSb Hall probe which is moved point-by-point under computer control. The computer also records the magnetic field strength as a function of position in a plane parallel to the head or disk surface. The active area of the probe is 2×2 μm and a roughly 1-μm separation between the probe and the surfaces being measured can be obtained. Measurements of the fields near transitions on a particulate disk and near the gap in in a ferrite recording head are presented and compared with calculated field distributions.
Soft x-ray appearance potential spectroscopy with a channelplate detector
Authors: Withers Richard S. , Lee R. N.
Published: March 2003

A soft x-ray appearance potential spectrometer using a channelplate detector is described and evaluated. This detector is much more sensitive than the metal photocathode in common usage and provides useful SXAPS spectra at primary electron currents of less than 10 μA. Operation of the detector at high x-ray fluxes is limited by saturation effects which can be minimized by the proper choice of channelplate and geometry.
Improvement of pyroanalyzer sensitivity for infrared and far-infrared studies
Authors: Debrie J. , de Martino A. , Lequime M. , Frey R. , Pradère F.
Published: March 2003

By using a [(signal) + (noise)] − (noise) digital averaging technique in order to reduce the offset drift, an improvement of about a factor 100 has been obtained in the sensitivity of a pyroelectric detector array (PDA). Different applications of the apparatus for measurement of infrared and far-infrared beam characteristics are also presented.
Fabrication and properties of rf niobium-on-sapphire superconducting resonators
Authors: Blair David G. , Hamilton W. O.
Published: March 2003

Niobium-on-sapphire resonators have been constructed as sensor elements for accelerometers in gravitational wave antennae. In their present form the resonators constitute small simple sensor elements for a wide range of applications where displacements take place, such as seismometry, gravimetry, thermal expansion measurements, as well as gravitational wave antennae. Radio-frequency losses in the niobium-sapphire interface have been observed. These limit the resonator Q to less than 105 and show a strong power dependence. Several methods of fabrication of the niobium-on-sapphire circuits have been investigated. Complete details for construction are given. An accelerometer based on these resonators is described in an accompanying paper.
Time correlation method for measuring fluorescence decays with a cw laser
Authors: Dorsey C. C. , Pelletier M. J. , Harris J. M.
Published: March 2003

A simple experimental approach to measuring fluorescence decay by time correlation signal analysis is described. The approach allows the use of continuous wave excitation and inexpensive detection-signal processing apparatus. The technique is demonstrated using a cw He–Cd laser. The transient response of the instrument is 0.88 ns, limited by the photomultipliers. The fluorescence lifetime of rose bengal in ethanol is determined, in absence of reorientation relaxation, to be 0.66±0.04 ns.
Nearly on-line picosecond streak camera diagnostics of the cw mode-locked YAG laser radiation
Authors: Hamal K. , Krajicek V. , Kubecek V. , Novotny A. , Vrbova M. , Schelev M. Ya. , Serduchenko J. N. , Vorobjov N. S.
Published: March 2003

An image-converter streak camera incorporating a TV video-recording system interfaced to a computer HP 2100 was used to record and instantly display the processed shape of a picosecond laser pulse. The output versus input exposure response curve linearity of the whole system was verified over a dynamic range of at least 10. Performance testing of the system was done using a cw mode-locked YAG laser.
Modified SCR for optically actuated triggering
Authors: Rice W. W. , Oldenborg R. C. , Wampler F. B. , Milligan D. F.
Published: March 2003

A simple inexpensive, optically actuated triggering device (optical trigger) has been developed for synchronizing pulsed lasers with signal gathering instrumentation. The heart of this device is a commercially available SCR that has been modified for light activated operation. The optical trigger delivers, into a 50-Ω load, a pulse of either 84 V with a 8.3-ns rise time and 3.5-μs width, or 42 V with a 6.2-ns rise time and 7-μs width. The device is sensitive throughout the visible and near-visible spectrum. It has a transit time of only 2.2 ns and less than 1-ns jitter. The performance of this optical trigger is examined in terms of the criteria of an ’’ideal’’ optical trigger and the effects of circuit and input parameters on output pulse characteristics are discussed.
Measurement of gradient index profiles by Babinet fringe analysis
Authors: Pandya T. P. , Saxena A. K.
Published: March 2003

A theory for determining one-dimensional ray deflections with the help of distorted Babinet fringes has been developed. An approach for investigating two-dimensional ray deflections has been presented. Applications of the techniques for the study of gradient index glass have been described.
Computer automation of data acquisition from a Knudsen, torsion-effusion pendulum
Authors: Edwards Jimmie G. , Heckler Mark K. , Thompson H. Bradford
Published: March 2003

A computer-automated data acquistion system has been developed for a dynamic torsion pendulum applied to measurement of vapor pressures at high temperatures by the torsion-effusion method. Laser beams reflected from mirrors on the pendulum are detected by a bank of photodetectors which, in turn, transmit signals representing pendulum positions through an encoder and interface to a laboratory computer with an internal clock. The computer uses pendulum position and time data with stored information to solve the equation of motion of the pendulum and to calculate vapor pressures. The physical parts, electronic circuits, and software are described and discussed. The rest point of a dynamic torsion pendulum has been reproduced within 1 min of arc.
Simple method of modulating Q-band microwaves
Authors: Cazaja W. , Graber N. , Schwerdtfeger C. F.
Published: March 2003

In this note a novel method of modulating microwave power at Q-band is presented.
High temperature 1H NMR probe
Authors: Webster D. S. , Cross L. F. , Lynch L. J.
Published: March 2003

A furnace is described which is suitable for single coil proton magnetic resonance experiments from room temperature to 1100 K, and which will fit a 30 mm magnet gap. The temperature variation is less than ± K at 800 K over a 27 mm-long sample.
Explosively triggered gas-dielectric crowbar switch
Authors: Higgins P. B. , Mathews F. H.
Published: March 2003

A gas-insulated gap switch with an unusually high standoff-to-trigger voltage ratio is described. Designed to standoff 500 kV when pressurized with SF6 at 1.5 MPa (212 psi), the switch was triggered with as little as 19.3 kV across the gap by firing a shaped charge from one electrode toward the opposite electrode. Similar air-insulated and SF6-insulated gaps pressurized to 83 kPa (12 psi) and designed to standoff 50 and 150 kV, respectively, were triggered with 15.4 kV across the gap by firing an ordinary RP-2 detonator from one electrode toward the other.
Simple apparatus for measuring the dynamic shear modulus of cylindrical specimens
Authors: Simpson H. M. , Pearson J.
Published: March 2003

An apparatus is decribed which has been used to determine the shear modulus of cylindrical specimens vibrating in the torsional mode. The specimens are maintained in self-excited vibration by an eddy-current driver, an eddy-current pickup, and a feed back circuit consisting of a phase-locked-loop and an amplitude control module. The system has a frequency stability of 1 part in 106 for high-Q materials (a few thousand) in the audio range. In addition, it can automatically track frequency changes of a few percent with negligible error in phase or frequency.
ESR dual sample cavities for Q-band and for spectrometers with small magnets
Authors: Froncisz W.
Published: March 2003

Dual sample cavities are described in which the standard sample sees both the primary modulation field and also an opposing secondary modulation field from a very small adjacent compensation coil. Both primary and secondary fields are at the same modulation frequency. The geometry permits solution of dual sample cavity design problems at Q-band, where the microwave cavity is small relative to the volume of space occupied by the primary modulation field and at X-band when magnets with a small volume of homogeneous field are employed.
Programmable digital pulse generator for proton enhanced 13C high resolution NMR in solids
Authors: van Os J. W. M. , Veeman W. S.
Published: March 2003

A programmable pulse generator is described for NMR spectrometers. The pulse generator can operate either in a single cycle mode where up to 16 pulses can be given sequentially or, in the double cycle mode, a programmable number (⩽15) of these pulses can be repeated n times (n⩽99) before the rest of the 16 pulses are completed. The length of all these pulses can be programmed, manually or by computer. As an example the programming of the pulse generator for a multiple contact proton enhanced 13C NMR experiment is given.
Simple method to measure the thermal conductivity of technical superconductors, e.g., NbTi
Authors: Schmidt Curt
Published: March 2003

A technique is described which allows the measurement of the thermal conductivity κ of superconductors below Tc without the use of a thermometer, if Tc is known. The method is particularly adapted to technical superconductors of poor thermal conductivity. It is convenient to use as sample a superconducting wire or band provided with a high conductivity matrix of a normal metal, which has to be removed from the test length. The stabilized ends of the sample are thermally anchored to a heat sink of variable temperature T. A current I flowing through the conductor holds the middle part of the test length in the normal state due to Joule heating. The length of the normal section and hence the voltage appearing on the sample are a functions of I and ℱκdT. The variation of the temperature of the heat sink then allows the determination of κ (T). Results for two NbTi samples are included.
Rapid investigation of sedimentation phenomena by vibrational force field
Authors: Wada Akiyoshi , Nishio Izumi , Soda Kunitsugu
Published: March 2003

A new method for the rapid investigation of sedimentation phenomena of fine particles is developed by using the force due to a vibrational acceleration. The small displacement of the particle with respect to the wall of the container, which is produced by the vibration, is measured by the interference between the light scattered by the particle and that of the cell wall. The interference is detected as a beat note in the scattered-light intensity, and displayed as a time-autocorrelation of the photocurrent, the analysis of which gives the sedimentation coefficient and the dispersion.
New magnetic command system for a 200-kA circuit breaker with 10-μs current transfer time
Authors: Baget R. , Rioux-Damidau F.
Published: March 2003

We present improvements of the previously described command system of a 200-kA circuit breaker with 10-μs current transfer time. It uses the magnetic pressure produced by a high-current pulse sent through two flat conductors instead of a coaxial circuit. The necessary command current is cut in half and the standoff voltage is higher.
Use of variable pH interface to a mass spectrometer for the measurement of dissolved volatile compounds
Authors: Weaver James C. , Abrams Jerome H.
Published: March 2003

A wide variety of dissolved chemicals can be measured continuously with some specificity by directly interfacing a relatively inexpensive mass spectrometer to a solution. Specifically, we describe the construction and initial use of a membrane interace to a mass spectrometer which allows the continuous measurement of the concentration of dissolved volatile compounds in buffered aqueous solution. In addition to volatile compounds that do not dissociate appreciably at pH 7 (e.g., ethanol, ethylene glycol), volatile acids and bases, such as acetic acid or ammonia, can be measured with the interface is operated within the range 1⩽pH⩽12. We also discuss the sensitivity of the system to variations in flow rate and describe a satisfactory method for providing sufficiently constant flow rates.
100-MHz noise spectrometer
Authors: Rzemien R. , Iddings C. K. , Love W. F.
Published: March 2003

The design, construction, and performance of a 100-MHz noise spectrometer are described. Basically a 100-MHz bridge, this system uses the properties of a double balanced mixer to enable the experimenter to determine spectral densities of fluctuations in the real or imaginary parts of a sample impedance, as well as the real part of the cross-spectral density. Calibration circuits and techniques are described. The results of measurements on commercial 50-Ω terminators demonstrate fluctuations of both the real and the imaginary parts of the impedance and partial correlation between them.
Versatile electron spectrometer for surface studies
Authors: Thomas G. E. , Weinberg W. H.
Published: March 2003

An electron spectrometer is described which is designed to measure a variety of electron spectra of solid surfaces in ultrahigh vacuum. The instrument is capable of the high-energy resolution (10–15 meV) required for vibrational inelastic electron scattering from atoms and molecules on surfaces. It has also been designed to carry out angle-resolved photoemission measurements, Auger electron spectroscopy, and energy-loss measurements of electronic excitations. The performance of the instrument in these modes of operation is discussed.
Thermal expansion of a fused quartz tube in a dimensional stability test facility
Authors: Wolff E. G. , Eselun S. A.
Published: March 2003

A facility to monitor the dimensional stability of structures of arbitrary size or shape under varying temperature and pressure conditions is described. Real-time linear displacements are measured with a modified Michelson laser interferometer to a resolution of less than one part in 107 and an accuracy of ∼2 parts in 107 for ∼1 m gauge lengths. Verification of the system accuracy with a quartz tube required considerations of its fabrication and compositional characteristics.
Simple, reliable, and sensitive interferometer for the measurement of the refractive index of liquids as a function of temperature
Authors: Beysens D.
Published: March 2003

We describe a very simple and inexpensive interferometer setup which provides high accuracy measurements of the refractive index (n) of liquids with temperature. A standard deviation σ (n) =5.4×10−7 has been observed in isooctane liquid when fitting n to a linear temperature variation.
Noninvasive beam-wave spectrometric instrumentation for measuring dielectric constant at microwave frequencies
Authors: Neelakantaswamy P. S. , Govindarajan R.
Published: March 2003

From the characteristics of the reflected Gaussian beam-wave for oblique incidence, measured with a spectrometer arrangement, the dielectric properties of a selectively exposed region of a dielectric slab are ascertained at microwave frequencies. For this purpose, a focused (Gaussian) microwave beam is launched from a suitable applicator to irradiate obliquely a selected protion of the test dielectric and the complex reflection coefficient is measured and analyzed. Further, the magnitude of the angular shift involved in the direction of the reflected beam is also used to calculate the dielectric constant. Application of this method to noninvasive measurements of dielectric properties of selective partial-bodies of commercial dielectrics and biological substances is discussed.
Addition of a polarizing microscope to the Weissenberg Rheogoniometer
Authors: Horn R. G.
Published: March 2003

This article describes modifications to a sophisticated commercial rheometer, the Weissenberg Rheogoniometer, to allow a sample in the cone and plate or parallel-plate geometries to be observed with a high-quality polarizing microscope. The addition of the microscope does not interfere with the measuring system in any way, so that samples can be observed in the course of rheological experiments.
Simple helium cryostat for Raman spectroscopy
Authors: Kirby R. D. , Duffey J. R.
Published: March 2003

We describe a simple and inexpensive flowing gas helium cryostat which efficiently cools the surface of a sample and eliminates the need for good thermal contact between the sample and a substrate.
Optimum designs of circular coil system for generating nonuniform axial magnetic fields
Authors: Murgatroyd P. N.
Published: March 2003

Optimum shapes are derived for coaxial circular coil systems to produce, for a given wire current density, the greatest d2B/dx2 and dB/dx.
Apparatus for sectioning diffusion specimens in liquid nitrogen
Authors: Weil Raoul , Lazarus David , Witt Frank
Published: March 2003

Details are given on the design and operation of an apparatus which enables sectioning of samples in a liquid nitrogen bath. The sectioning of samples, in which a radioactive tracer has been diffused, is made by abrasion.
20-kilobar pressure system
Authors: Wu R. K. , Dutton T. F. , Doyle W. T.
Published: March 2003

A reciprocating hand pump capable of generating hydrostatic pressure to 20 kilobars has been constructed for high-pressure magnetic resonance studies. The pump body and the high-pressure cell are two separate units, which are connected by a high-pressure tubing using connectors modified from a design of an unsupported area seal due to Warschauer and Paul. This makes high-pressure magnetic resonance work possible by reducing the required work space between the gap of the magnet pole faces.
K-band high-pressure cell for ENDOR studies
Authors: Wu R. K. , Dutton T. F. , Doyle W. T.
Published: March 2003

This article describes a versatile high-pressure K-band EPR–ENDOR system, designed for the examination of the effects of hydrostatic pressure on F-center hyperfine interactions. Dielectric filling is used to minimize the inner dimensions of the pressure cell. Cavity mode and coil geometry permit the same system to be used either for high-frequency field modulation EPR or for ENDOR by rotating the magnetic field. The pressure seal is also part of a rotatable microwave joint permitting the microwave coupling to be varied by rotating the cavity-pressure cell assembly. The beryllium–copper high-pressure vessel is separated from the pressure generating device by high-pressure transmitting tubing. It has been tested to 18 kilobars.
Automated system for electrical field-polarization studies in ferroelectrics
Authors: Yarberry V. R. , Fritz I. J.
Published: March 2003

An automated system for measuring dielectric polarization as a function of applied electric field and time has been developed. This system, which is based on the Sawyer–Tower technique for obtaining ferroelectric hysteresis loops, is built around a programmable high-voltage power supply and an automatic data acquisition system, both commercially available. The system can be used for obtaining well-resolved hysteresis loops at rates approaching 10 Hz, and also for measuring the time dependent response to steps in electric field with resolution on the order of 2 ms. Examples of data obtained on a ferroelectric ceramic material are presented.
Contactless technique for the measurement of electrical resistivity in anisotropic materials
Authors: Zeller C. , Denenstein A. , Foley G. M. T.
Published: March 2003

Measurement of basal plane electrical resistivities in quasi-two-dimensional materials by conventional four-point bridge techniques is extremely difficult. In making measurements of room temperature basal plane resistivities in highly conducting highly anisotropic synthetic metals we have developed an rf inductive technique which is both simple to use and provides accurate results. At the frequency we employ (100 kHz) the method is appropriate for resistivities in the range 10 −3–10−7Ω cm. Samples are thin square plates 5 mm on a side. The system is calibrated by fitting data from a series of samples of known resistivity to semi-empirical formulae. The theoretical motivation leading to these expressions is discussed and extensive calibration data are presented. The advantages of rf techniques in general have already been discussed. Two advantages commend the particular technique we describe here. First, it is simple in design and easily constructed. Second, with careful calibration, highly accurate resistivity measurements can be made in a very straightforward manner
Hall measurements to 40 kilobars under hydrostatic pressure in a piston-cylinder device
Authors: Lifshitz N. , Maines R. G.
Published: March 2003

A technique for Hall measurements under truly hydrostatic pressures to 40 kilobars is described. The method employs the piston-cylinder apparatus with a Teflon cell to contain a suitable fluid. The necessary magnetic field is generated by a coil placed inside the cell. Hall data can be obtained over the full pressure range, at temperatures from 150 to 300 K. Results for an AlxGa1−xAs sample are presented as an example.
PdPtAu alloys for low-temperature precision resistors
Authors: March J. F. , Thurley F.
Published: March 2003

Palladium-rich PdPt and PdAu alloys exhibit a resistance–temperature behavior characterized by flat minima even after eliminating the Kondo effect by oxidation of the impurities. The opposite signs of their thermoelectric potentials against a superconductor permit the preparation of ternary PdPtAu alloys free of a thermoelectric power. The measurements resulted in a nomogram suitable for determining the composition of the alloy necessary for a resistivity minimum at a given temperature between 1.5 and 4.2 K. Alloys manufactured in this way have a temperature coefficient of resistivity of less than 10−6/K within a temperature interval of 0.5 K and a thermoelectric power against a superconductor of less than 1 nV/K.
High-pressure apparatus for dielectric measurements in high frequency
Authors: Ai Bui , Lebarbier D. , The Giam Hoang , Bapt J. C. , Farzaneh M.
Published: March 2003

The present article describes an experimental apparatus for the measurement of low-loss dielectric material under conditions of high pressures (maximum pressure 1500 bars) and high frequencies (1–15 MHz.) The measurements of these losses are based on the classical method of the Q-meter with a general Radio type 1690-A sample holder, located in a high-pressure bomb. All the manual operations made on the holder during the measurements are controlled by dc motors. The first results have shown that the dielectric losses of polyethylene (PE) vary with the pressure. This apparatus will later be used in the measurement of the dielectric losses of the insulating materials used for submarine telecommunication cables.
Procedure for symmetric orientation of hot-wire probes
Authors: Gilbert Barry
Published: March 2003

A quick and simple procedure was developed for setting the sensing elements of an X-hot wire probe to be symmetric to the mean flow direction. The angle that the probe axis makes with the mean flow direction is changed until a properly conditioned voltage is maximized. This procedure does not require the rather restrictive assumptions of matched linear wire sensitivities, symmetric were orientations to the probe’s axis, wire mutual perpendicularity, or known mean flow direction. After the mean flow direction is determined, the linear sensitivities are matched and the probe is calibrated.
Construction of an inexpensive hydraulic microdrive for recording single nerve cell activity
Authors: Rieke Garl Kalman
Published: March 2003

A hydraulic microdrive that can be constructed for less than thirty dollars is described. The microdrive is assembled from stock hardware and two glass syringes. It consists of three sections: (1) a base section, (2) a driver section, and (3) a carriage section. The master cylinder is a 5 cm3 syringe, while the slave cylinder is a 50 cm3 syringe. The piston of the slave cylinder moves 10 μm for each 10° arc through which the drive wheel passes. The microdrive is effective in that it serves as the vehicle by which metal or glass electrodes are brought next to single nerve cells in order to record the electrical activity of the cells.
Device for the measurement of small liquid flow rates
Authors: Vilker Vincent L. , Dileo Anthony J. , Colton Clark K. , Smith Kenneth A.
Published: March 2003

A device has been developed for continuously monitoring liquid flow rates as low as 10−5 cm3/min. This is achieved by using a sensitive displacement transducer to follow the motion of a low-density float.
Properties of an intense 40-kV neutral beam injector
Authors: Stirling W. L. , Tsai C. C. , Haselton H. H. , Schechter D. E. , Whealton J. H. , Dagenhart W. K. , Davis R. C. , Gardner W. L. , Kim J. , Menon M. M. , Ryan P. M.
Published: March 2003

The properties of an intense neutral beam injector, the modified duoPIGatron ion source, are discussed and compared with other injectors. For this source (a) beam composition for hydrogen is ∼ (85±5) % monatomic, (b) nucleon gas efficiency is 50%, (c) the electrical efficiency of ion generation is 1.1 A/kW, and (d) up to 52% of the input power is delivered in the ion and neutral beam to a target subtending a half angle of 1.8°×1.4°.
Calibration of SQUID magnetometer for dilute alloy studies
Authors: Steelhammer T. J. , Symko O. G.
Published: March 2003

A SQUID magnetometer used in the study of dilute magnetic alloys or other weak magnetic systems can be calibrated by using the nuclear paramagnetism of aluminum metal. This material is useful as a calibration standard since magnetic impurities such as Fe and Mn form no local moment. This calibration is compared to others obtained with CMN powder and indium metal.
Linear induction accelerators made from pulse-line cavities with external pulse injection
Authors: Smith Ian
Published: March 2003

Two types of linear induction accelerator have been reported previously. In one, unidirectional voltage pulses are generated outside the accelerator and injected into the accelerator cavity modules, which contain ferromagnetic material to reduce energy losses in the form of currents induced, in parallel with the beam, in the cavity structure. In the other type, the accelerator cavity modules are themselves pulse-forming lines with energy storage and switches; parallel current losses are made zero by the use of circuits that generate bidirectional acceleration waveforms with a zero voltage-time integral. In a third type of design described here, the cavities are externally driven, and 100% efficient coupling of energy to the beam is obtained by designing the external pulse generators to produce bidirectional voltage waveforms with zero voltage-time integral. A design for such a pulse generator is described that is itself one hundred percent efficient and which is well suited to existing pulse power techniques. Two accelerator cavity designs are described that can couple the pulse from such a generator to the beam; one of these designs provides voltage doubling. Comparison is made between the accelerating gradients that can be obtained with this and the preceding types of induction accelerator.
Scanning multiple collector electrostatic analyzer with application to plasma potential measurement
Authors: Boedeker Laurence R.
Published: March 2003

Three collector electrodes have been located accurately on the focal plane of a parallel-plate electrostatic energy analyzer to form an exit slit matched to a large inlet slit by the design magnification ratio. In bench tests with a nearly uniform, monoenergetic K+ beam at 5 kV these collectors have been found to provide a scanning capability for measurement of the energy of such a large beam with sufficient precision, ΔV/V∼±10−3, to resolve plasma potential in heavy ion probe diagnostic studies of magnetically confined plasmas. In such studies a wide entrance slit is needed because of low signal levels. The method provides enhanced resolution with greater facility than obtainable with a feedback approach used in prior investigations. A nearly triangular sharply peaked profile was observed on the center collector providing the desired resolution. Scans at various entrance angle settings have been made and beam size and peak location results compared with predictions based on the existing model for an ideal instrument.
Lexan coating to eliminate the UV sensitivity of soft x-ray proportional counters with a polypropylene window
Authors: Fabricant D. G. , Goddard R. E. , Harnden F. R. , Gorenstein P.
Published: March 2003

Lexan coatings on polypropylene windows can eliminate the UV sensitivity of soft x-ray proportional counters. A method is described for coating thin polypropylene films by dipping into and withdrawing from a volatile solution containing Lexan. The x-ray absorption of a typical Lexan coating was only 7% at 44 Å which is small compared to that of 2 μm of polypropylene. The Lexan coatings are stable against vacuum cycling in an environment of UV irradiation. As an external, far-UV filter up to wavelengths of 2400 Å, Lexan-coated polypropylene is an interesting alternative to metallic films, particularly when large area, high x-ray transmission, and strength are important.
Noise in large-aperture self-scanned diode arrays
Authors: Simpson Raymond W.
Published: March 2003

An equation for the random noise of self-scanned silicon photodiode arrays is developed which includes significant terms not previously considered. It is shown that, including these terms, the new 2.5-mm-high self-scanned arrays are only slightly noisier than older arrays; but because of their much greater aperture, they can detect much smaller light fluxes than the older arrays even when used with simple, inexpensive amplifiers.
Hall-effect hysteresigraph for amorphous bubble-domain materials
Authors: Smith A. B. , Burilla C. T.
Published: March 2003

A hysteresigraph is described which provides a much more rapid measurement of the coercivity of amorphous bubble films than any previously used method. This device utilizes the Hall effect to sense the film magnetization and has sufficient sensitivity and stability that coercivities as low as ∼1 Oe can be readily measured. Although this device cannot provide an absolute measurement of saturation magnetization, approximate values of this quantity can be inferred from the saturation field indicated by the hysteresis loop. A probe-contact arrangement is employed which permits measurements to be made even on films having an insulating passivation layer.
Method for numerically enhancing the resolution of certain types of detection systems
Authors: Wickham Michael , Fornaca S.
Published: March 2003

We present a method for increasing the resolution of detection systems in which the desired information has been convolved with the system instrumental response function and further distorted by the presence of noise. We have written a computer program which can deconvolve the detected signal while treating the noise in a self-consistent manner, allowing to a good degree the reconstruction of the desired signal. We apply this method to reconstruct one component of the ion velocity distribution of a barium plasma. The information is in the form of Doppler-shifted resonance light which is detected and broadened by a Fabry–Perot interferometer. Results are presented and limitations to this method are discussed.
New type of stepping motor control for fast beam scraper
Authors: Ishimaru H. , Igarashi Z.
Published: March 2003

A stepping motor control for a fast beam scraper in high vacuum is described. High speed (5°/ms) and smooth angular velocity are obtained by using inertia motion within 270° in one revolution.
Influence of the flow velocity on a Kovasznay type vorticity probe
Authors: Kastrinakis E. G. , Eckelmann H. , Willmarth W. W.
Published: March 2003

The output signal of a Kovasznay type vorticity probe is in first-order approximation proportional to the longitudinal component of the vorticity ωx=∂w/∂y−∂v/∂z and does not depend on the two transverse components of the flow velocity v, w. An experimental investigation of the influence of all three fluctuating velocity components on the longitudinal vorticity signal showed that their influence may not be neglected. The error in the probe response caused by the longitudinal component of the flow velocity was easily corrected using the instantaneous longitudinal velocity component and digital measuring techniques. On the other hand, the error caused by the two transverse velocity components could not be corrected. The contamination of the vorticity signal produced by the two transverse velocity components has been calculated by considering first- and second-order terms. The agreement between the calculations and experimental measurements is good. It is concluded that in a turbulent flow field this probe cannot be used without the simultaneous knowledge of the instantaneous transverse velocity components.
Phase measurement using an interferometer having a filamentary spatial filter and an extended source of polychromatic light
Authors: Mori Sadahiko
Published: March 2003

The theory of phase measurement by means of the interferometer using a filamentary spatial filter (IFSF) is extended to the case in which the source has finite width. Experimental results satisfactorily coincide with theoretically obtained characteristics. The examination of accuracy suggests that the error in φ/2π can be easily restricted to within 0.01. It is hoped that the IFSF will improve efficiencies in the measurement of dispersive power of a fluid and the method of coincidence being used in the measurement of a distance between reflecting surfaces, because it can simultaneously measure phases in various wavelengths if a polychrometer is set in the rear of the image plane.
Digital, synchronously timed control system for pulsed ion cyclotron resonance mass spectrometry
Authors: Dugan R. J. , Morgenthaler L. N. , Daubach R. O. , Eyler J. R.
Published: March 2003

An integrated control system for a pulsed ion cyclotron resonance (ICR) mass spectrometer has been designed, constructed, and put into operation. It utilizes a crystal clock oscillator to accurately control the delay and width of the various pulses necessary for pulsed ICR operation. A switched integrator, sample/hold postdetection system is also described which improves aquisition, display, and signal-to-noise characteristics of the detected ion signal obtained from a gated marginal oscillator detector.
Qualitative and quantitative flow visualization technique using ozone
Authors: Dickerson R. R. , Stedman D. H.
Published: March 2003

We have developed a new flow-visualization technique based on the absorption of ultraviolet light by ozone. Ozone is an excellent tracer, because as a gas it has the same effective physical properties as air. Ozone strongly absorbs the principal line (253.7 nm) of a mercury lamp, ε=310 (atm cm)−1, where I/Io=exp(-εcl) such that when an ozone-traced flow passes between a mercury lamp and a fluorescent screen, a sharp, shadow-like image of the ozone tracer is cast on the screen. Quantitative photometry can be carried out by replacing the screen with ultraviolet detectors that yield the path-integrated column density of ozone in the flow. High-speed quantitative point monitoring (10 Hz at 10 ppb O3) is possible with capillary probes and chemiluminescent analysis.
Design of a compact cw chemical HF/DF laser using a microwave discharge
Authors: Bertrand L. , Monchalin J.-P. , Pitre R. , Meyer M. L. , Gagné J. M.
Published: March 2003

A compact cw chemical HF/DF laser is described. The laser system consists of a microwave discharge using a surfatron to dissociate SF6 molecules mixed with He, a reaction chamber engineered to provide a fast mixing of reacting atoms and molecules, and an optical resonator which includes a concave mirror and a blazed grating for line selection, both mounted on a rigid Invar frame. The laser oscillates on a single line single TEM00 mode over many P transitions of HF and DF with a typical intensity fluctuation of 5% and a frequency jitter of about 30 MHz.
Thermal conductivity comparison method based on silicon diode thermometry
Authors: Lawless W. N. , Clark C. F.
Published: March 2003

A room-temperature thermal conductivity comparison method is described which does not required calibrated thermometers and which involves temperature rises <1 K. The method is based on silicon diode thermometry, and the results obtained on three unknowns measured against alumina are presented. For the short samples measured, the uncertainty is ∼±5%. Methods for applying the technique at other temperatures and for improving the accuracy are discussed.
Use of synchrotron radiation for the measurement of fluorescence lifetimes with subpicosecond resolution
Authors: Gratton E. , Delgado R. Lopez
Published: March 2003

A method for the measurement of fluorescence lifetimes with subpicosecond resolution is described. The temporal resolution is achieved by using the high harmonic content of the synchrotron radiation produced by an electron storage ring.
Simple partial pressure measurement of SF6 in mixtures with nitrogen
Authors: Marks J. M.
Published: March 2003

A simple but accurate method for the measurement of the partial pressure of SF6 gas in mixtures with nitrogen is described. It is based on the ease with which the gases can be separated by freezing the SF6.
Design, construction, and analysis of a continuous-temperature infrared calibrator for temperature measurement using an infrared scanner
Authors: Hsieh C. K. , Su K. C.
Published: March 2003

A continuous-temperature infrared calibrator is designed and constructed for providing reference video signals in temperature measurement using an infrared scanner. The calibrator can be controlled for a wide range of temperature settings and to present a continuous span of reference signals for calibration purposes. Both analytical and experimental methods are used to evaluate the performance of the calibrator. Results show that the calibrator has a normal total emissivity of at least 0.984, which is about 1% lower than the predicted value. Methods to improve the emissivity of the calibrator are also discussed. The paper provides for analytical equations useful for parameters estimation in the future design of the calibrator.
High accuracy quartz crystal thin film monitor
Authors: Ramadan B. , Piyakis K. , Kos J. F.
Published: March 2003

A quartz resonator thin film monitor of exceptionally high accuracy and resolution has been developed. It is capable of providing measurements with an effective resolution of 0.001 nm and a corresponding relative accuracy of about 1% for a 0.100-nm-thick film of gold. A novel dual oscillator and mixer using integrated circuits is also described.
Analysis and design of helical capacitance sensors for volume fraction determination
Authors: Albouelwafa M. S. A. , Kendall E. J. M.
Published: March 2003

A theoretical and experimental study of the helical capacitor sensor for determining the in situ component ratios in two-phase systems is described. There is excellent agreement between the initial experimental data, the improved design data, and the theoretical analysis.
Differential automatic zero-adjusting amplifier
Authors: Broersen B. , Van Krevelen F. , van Heusden J. T. , van Heukelom J. Siegenbeek
Published: March 2003

A method is described for building a low-voltage-drift differential dc amplifier featuring automatic zero adjustment, a high input impedance, and a bandwidth of 10 kHz. This is achieved by an asymmetric two-step process between the input signal and ground. Bandwidth can be extended by the use of a second amplifier during the ground-sampling time. The amplifier can be made with standard electronic components. A major advantage of this method is that an existing amplifier can easily be converted into a low-voltage-drift amplifier by adding the essential elements of the described automatic zero-adjusting amplifier to its input stage. To illustrate the method a practical example is constructed featuring a drift of 0.2 μV/ °C.
Apparatus for dry stress corrosion kinetic studies
Authors: Pourantru Y. , Toesca S. , Colson J. C.
Published: March 2003

An apparatus for carrying out kinetic studies on the dry stress corrosion of threadlike metal specimens in well-determined conditions of uniaxial stress is described. The results obtained by electrical conductivity measurements can easily be related to those obtained by thermogravimetry.
Nondestructive method for reconnecting aluminum metallization on integrated circuits
Authors: Zubatkin A. D.
Published: March 2003

A failure analysis technique for reconnecting aluminum metallization on planar IC devices is described. The technique, utilizing a conductive paint deposited on the device surface, is nondestructive and easily removable.
Production of centrifugal fields greater than 100 million times gravity
Authors: Katano Rintaro , Shimizu Sakae
Published: March 2003

A high-speed rotation instrument to produce centrifugal fields greater than 100 million times gravity has been constructed. Small, solid, spherical high-carbon chromium steel rotors are suspended magnetically in high vacuum and spun by a rotating magnetic field. It is found that the spinning rotor explodes when the calculated average value of stress in the meridian plane reaches about 1.2 times the tensile strength of the material. The maximum speed of rotation so far achieved for more than a few days without bursting was obtained with a rotor of 1.50 mm diameter. The speed of 2.11×105 rev/s corresponded to a centrifugal field of 1.34×108 times gravity. Our instrument will find application in the study of nuclear atomic phenomena.
Reduction of spurious baseline effects in NMR
Authors: Abbas Daniel C.
Published: March 2003

The practical limitation on sensitivity in broad-line NMR is frequently spurious effects on the baseline rather than the masking of the signal by thermal noise. I discuss some of the causes of spurious baseline effects and describe a simple circuit used to reduce them by a factor of 300.
Absolute pressure measurements and analysis of diamonds subjected to maximum static pressures of 1.3–1.7 Mbar
Authors: Mao H. K. , Bell P. M. , Dunn K. J. , Chrenko R. M. , DeVries R. C.
Published: March 2003

Force per unit area measurements made in the megabar pressure cell, independently of other pressure calibration systems, are consistent with the ruby R1 scale of Mao, Bell, Shaner, and Steinberg and its extrapolation to 1.4 Mbar. Physical analysis of diamond anvils removed after experiments to maximum pressures of 1.3–1.7 Mbar suggests that the nitrogen platelet concentration may be related to the strength of the diamonds. The pressure face of one of the diamonds from the 1.7-Mbar experiment was deformed plastically by a macroscopic amount.
Magnetic shielding in a low-temperature torsion pendulum experiment
Authors: Phillips Peter R.
Published: March 2003

A new type of ether drift experiment searches for anomalous torques on a permanent magnet. A torsion pendulum is used at liquid- helium temperature so that superconducting cylinders can be used to shield magnetic fields. Lead shields attenuate the earth’s field, while Nb–Sn shields fastened to the pendulum contain the fields of the magnet. The paper describes the technique by which the earth’s field can be reduced below 10−4 G while simultaneously the moment of the magnet can be reduced by a factor of 7×104.
LED source for determining optical detector time response at 1.06 μm
Authors: Franzen Douglas L. , Day G. W.
Published: March 2003

A gallium indium arsenide light emitting diode (LED) is investigated as a source for determining optical detector time response at 1.06 μm. To obtain either impulse or step-shaped waveforms, the diode is driven by a charged transmission line switched by a transistor operating in the avalanche mode. A pulse with a 2.5-ns full width at half-maximum and a step with a 3–4-ns transition time are produced at repetition rates to 1 kHz. The effects of wavelength change during the pulse (chirping) are discussed and evaluated.
Neutron diagnostics for pulsed high-density thermonuclear plasmas
Authors: Ekdahl C. A.
Published: March 2003

Time-resolved measurements of the neutron flux from the Scylla IV–P linear theta-pinch experiment have been made with scintillator-photomultiplier combinations. Calibration of the detectors is accomplished by a comparison of their time-integrated output with the total neutron yield measured using a foil-activation technique for which an accurate calibration has been established. The temperature of the Maxwellian ion velocity distribution that would produce the observed flux is obtained from the Maxwellian reactivity <σv≳DD for D (d,n)He3 and measurements of the temporal evolution of the plasma column density and dimensions. This determination of the time history of the ion temperature is in good agreement with the plasma energy measured using other techniques.
High-energy optically pumped molecular lasers in the 13- and 16-μm regions
Authors: Tiee J. J. , Fischer T. A. , Wittig C.
Published: March 2003

This paper describes the construction of an optically pumped laser device. The device utilizes a line-tunable CO2 TEA laser as a source to optically pump a cell which is capable of cooling candidate laser gases down to ∼150 °K. Laser outputs of 750 mJ in the 13-μm region and 100 mJ in the 16-μm region are obtained by pumping NH3 and CF4 respectively with 10 J of CO2 laser radiation. The measured conversion efficiencies are 15% for NH3 and 3% for CF4. These lasers can be used to photodissociate polyatomic molecules and are attractive sources for practical laser isotope separation.
Novel variable-temperature chuck for use in the detection of deep levels in processed semiconductor wafers
Authors: Koyama R. Y. , Buehler M. G.
Published: March 2003

This paper describes the design, construction, and characterization of a variable-temperature wafer apparatus for use in the detection of electrically active defects which produce deep levels in the band gap of silicon. In its present form, the wafer chuck can heat and cool wafers as large as 51 mm in diameter over the temperature range from −196° to 350°C. Heating rates as high as 7°C/s have been achieved. Sensitivity for electrical measurements is sufficient to allow current measurements as low as 0.2 pA or capacitance changes (1 MHz) as small as 5 fF. The use of this apparatus is illustrated by wafer mapping the gold defect density in diodes fabricated across a silicon wafer.
Precise diode method for recording contact potential changes caused by gas adsorption
Authors: Christmann K. , Herz H.
Published: March 2003

A low-temperature recording diode is described which allows the determination of adsorption-induced contact potential differences with an accuracy of better than 0.5 mV. Some experimental work function results of the hydrogen adsorption on platinum (111) and (997) single-crystal faces are presented which demonstrate the usefulness of the method.
High-intensity carbon ion injector
Authors: Humphries S. , Mendel C. W. , Kuswa G. W. , Goldstein S. A.
Published: March 2003

An injector of intense beams of carbon ions is described. The device uses an array of carbon plasma guns to inject ions directly into a magnetically insulated acceleration gap. Ion currents exceed 3 kA with beam energies between 100 and 300 keV (for C+) and 200 and 600 keV (for C++) over a 700-ns pulselength.