bluuebunny/crossref_metadata_2025 huggingface dataset:
Apparatus for alternating fields microelectrophoresis
Authors: Delatour Evelyne , Hanss Maxime
Published: March 2003

Based on principles which are outlined, an apparatus for alternating fields microelectrophoroesis is described. It uses a laternal orientation cell which is moved vertically at constant speed while a wave burst is applied to the cell. The resulting particles movements are photographed through dark-field illumination and a microscope. The mobility is deduced from the track amplitudes on the photographs. An easy temperature correction is given. The main advantage of the A. C. microelectroesis method is a higher precision in the determination of the mobility distribution curve.
Versatile x-ray spectrometer in the range 5–200 keV
Authors: Strachan J. D.
Published: March 2003

A spectrometer is described which provides time resolution down to a few nanoseconds and broad-band energy resolution in the range 5–200 keV along a single line of sight. The spectrometer consists of five channels arranged so that the x rays which are not absorbed in one plastic scintillator pass on to the next channel, but the scintillator emission is deflected onto a photomultiplier.
Continuous-wave source of highly excited atoms using Doppler-tuned ir laser radiation
Authors: Bayfield James E.
Published: March 2003

A 10-keV atomic beam source of hydrogen atoms in the n=44 or other selected state was based upon charge exchange production of the n=10 state followed by Doppler-tuned cw CO2 laser excitation to the desired highly excited state. In present operation the output atom flux of the source is 2.5×105 sec−1, a value that can be increased by as much as 105. The technique can be extended to considerably higher and lower atom energies, to a wide range of atom quantum numbers, and to atoms other than hydrogen.
Construction of an inexpensive platinum electrode
Authors: Simpson Raymond , Berberian John G.
Published: March 2003

A method for fabrication of an inexpensive platinum electrode is presented. The process is based on the thermal deposition of a Pt film upon a glass substrate yielding a chemically inert electrode; the electrode is amenable to Pt blacking. The measured polarization capacitance for this electrode as a function of frequency is presented for both the bare and Pt blacked states.
Thermal conductivity of solids under pressure by the transient hot wire method
Authors: Andersson P. , Bäckström G.
Published: March 2003

An electronic circuit has been constructed which delivers constant power to a nickel wire, also functioning as a resistance thermometer. The temperature increase versus time, t, is linear in ln t, and the coefficient of slope directly yields the thermal conductivity of the medium surrounding the wire. Systematic errors due to finite time, wire length, and lateral extension of the medium and due to plastic deformation of the wire are analyzed. Temperatures are sampled automatically, and the digital data are reduced by means of an on-line desk calculator. The thermal conductivities of AgCl and polytetrafluoroethylene have been measured up to 10 kilobar.
Time-domain measurement of dielectric dispersion as a response to pseudorandom noise
Authors: Husimi Yuzuru , Wada Akiyoshi
Published: March 2003

A new method of measuring the complex permittivity in the time domain is proposed. By taking responses of a sample solution to a binary pseudorandom noise, a simultaneous measurement of all the frequency components are performed. Due to its high efficiency, an extreme reduction in measuring time together with low power excitation becomes possible. The Fourier transform of the response is multiplied by the Fourier transform of the binary pseudorandom noise and normalized; from the transfer function thus obtained, the complex permittivity is calculated, and the dispersion profile is displayed. A measuring time of 28 msec is required to obtain the dielectric dispersion profile from 71 Hz to 36 kHz. This is demonstrated for a solution of poly-γ-benzyl L-glutamate.
Optical microspectroscopic system for use with a diamond anvil high pressure cell to 200 kilobar
Authors: Welber Benjamin
Published: March 2003

We describe an optical system which has been used in conjunction with a high pressure diamond anvil cell to obtain absorption, reflectance, and photoluminescence spectra. The system is shown to yield useful results to pressures at least as high as 200 kilobar.
Imaging electrometer capable of low temperature operation
Authors: Maynard Julian D. , Carver Thomas R.
Published: March 2003

A device is described which can produce images of small, low mobility (low energy) negative electric currents. The device can map the cross section of an impinging current density as small as −10−13 A⋅cm−2 with a spatial resolution of 102 points per mm2. The charge carriers need an electrostatic energy of only ∼1 eV to be detected. A device for room temperature operation is easily constructed. With some modifications the device can operate at temperatures as low as 1 K.
Analyzer of trace impurities in silane gas
Authors: Yusa A.
Published: March 2003

A compact analyzer for electrically active impurity hydrides such as phosphine, arsine, and diborane in silane gas was constructed and operated. It consisted of a stainless steel chamber for formation of silicon epitaxial films and an ultrahigh vacuum pumping system. The impurity content in silane was deduced from the resistivity value of film produced from the silane in question. Contamination from a heater to the silicon film was avoided by using direct electrical heating of the substrate. Special care was taken to prepare epitaxial films of good quality. Several silane gases containing known amounts of phosphine were analyzed by using the present analyzer. The epitaxial films with resistivities ranging from 10−2 to 104 Ω cm were grown on a substrate of 0.6 Ω cm p-type silicon bar.
New pressure calibration technique of manganin gauge by microthermal analysis of mercury
Authors: Nakafuku Chitoshi , Takamizawa Kan’ichiro , Takemura Tetuo
Published: March 2003

Methods of microdifferential thermal analysis (DTA), simple thermal analysis using one thermocouple, and the change of electrical resistance of mercury during melting under high pressure are used to calibrate the pressure coefficient of a manganin coil. It is shown that the methods of microthermal analysis under isobaric conditions yield satisfactory results and are easier to operate than the usual isothermal methods.
Ultralow noise preamplifier for high impedance infrared bolometer
Authors: Stefanovitch D.
Published: March 2003

An ultralow noise preamplifier has been designed for use with a high impedance infrared bolometer. The preamplifier makes use of an ultralow noise field effect transistor connected to an operational amplifier in a cascode configuration. A simple regulator circuit allows the unit to be powered by any laboratory dc power supply instead of using special low noise batteries. The equivalent input noise, measured at room temperature with the input short circuited, is 1.5 nV/Hz1/2 rms at 80 Hz.
Spark gap optical isolator for high power infrared lasers
Authors: Burnett N. H. , Richardson M. C.
Published: March 2003

A zero insertion loss optical isolator has been developed and tested in a short pulse CO2 laser oscillator–amplifier system. The device, which uses a narrow plasma column produced by a streamer discharge in air and situated at the common focus of two cylindrical mirrors, provides effective isolation of the oscillator and pulse forming system against retroreflected laser light. Using this arrangement a reflected 1 nsec CO2 laser pulse of ∼2 cm diam and energy density up to 1 J/cm2 has been completely blocked after an optical delay as short as 4 nsec. The device should also find application in other infrared laser systems for which no isolators at present exist.
Measurement of the complex permittivity of lossy fluids at 9 GHz
Authors: Kumar A.
Published: March 2003

A new technique is described to measure the complex permittivity of high loss fluids at 9 GHz. Measurements on methyl alcohol and ethylene glycol are reported. The permittivity and loss tangent are calculated from changes in the resonant frequency and Q-factor of a resonant cavity which is coupled to an evanescent waveguide which contains the fluid sample.
Demountable 4He film stopper for dilution refrigerators
Authors: Abraham B. M. , Falco Charles M.
Published: March 2003

We describe an easily assembled and demountable film stopper for use in either a pumped 4He pot or a 3He–4He dilution refrigerator. The orifice plate for the film stopper is fabricated from a Pyrex glass plate and is sealed to the metal body of the still with an indium O-ring. The advantage of glass over metal for the orifice plate is achieved without complicated construction.
Simple, fully isolated, high voltage trigger generator
Authors: Leopold K. E. , Alcock A. J.
Published: March 2003

Conducting spirals formed on standard printed circuit boards provide a simple approach to the construction of a fully isolated, high voltage trigger generator.
Compact purifier for silane gas
Authors: Takaishi T. , Gomi Y.
Published: March 2003

A purifier for silane was constructed for use in silicon film epitaxy and CVD processes. The purification is realized with 1 kg of a newly developed molecular sieve (K6Zn3) -A zeolite by selectively sorbing phosphine, which is a main impurity in commercially available tanked silane gas. The column of absorbent is continuously cooled to −20 °C, and the flow rate of gas treated ranges is between 0.1 and 3.0 l/min. The effectiveness of the purifier was investigated by using a test gas, a mixture of silane and hydrogen at a volume ratio of 5:95 containing 0.1 ppm of phosphine. An epitaxial film with a resistivity of 0.7 Ω-cm at room temperature was produced from untreated test gas, while one of 3000 Ω-cm was produced from gas treated with the purifier. An estimated life of the absorbent is about 10 000 h, under the condition that the above test gas is passed at a flow rate of 1 l/min. It is further expected that films with much higher resistivities can be produced, if carrier-free silane is used as a raw material gas in place of the present test gas.
Electrically strobed optical waveform sampling oscilloscope
Authors: Andrews James R. , Lawton Robert A.
Published: March 2003

A new instrument for measuring optical waveforms is described. It is an optical sampling oscilloscope employing a GaAs photoconductive sampling gate and an electrical sampling strobe. The basic theory of operation is derived. A 100-psec rise-time rudimentary prototype has been built and results of measurements of a GaAs laser diode pulse are presented.
X-band cavity for low-temperature electron spin resonance experiments
Authors: Casini G. , Graziani P. , Linari R. , Tronconi A.
Published: March 2003

We describe an X-band cavity for ESR experiments at low temperatures. The device allows us to modulate the magnetic field into the cavity at a frequency of 100 kHz, which makes it possible to obtain at low temperature the same advantages of improved sensitivity typical of this modulation frequency. We show the ESR spectra of a sample (CaWO4 doped with Ce) obtained at two different modulation frequencies (234 Hz and 100 kHz). The comparison shows an improvement in signal/noise ratio of about 40, in accordance with the theoretical analysis. It is possible also to examine monocrystalline samples at low temperatures owing to the particular structure of this cavity.
Measurement of solder–flux–vapor surface tension by a modified maximum bubble pressure technique
Authors: Goldmann Lewis S. , Krall Bogdon
Published: March 2003

While it is widely known that flux is needed to maintain an oxide-free surface during soldering, the fact that flux also reduces the surface tension between solder and ambient is neither widely recognized nor treated extensively in the literature. An apparatus is described which quantitatively evaluates the reduction of surface tension in the presence of flux. Representative data of eutectic lead–tin with water white rosin fluxes are presented.
Spatial separation of fringe fields in quadrupole mass filters
Authors: Fite Wade L.
Published: March 2003

The use of leaky dielectric materials which appear to radio-frequency fields as dielectrics but to dc fields as conductors is described in connection with achieving a delayed-dc-ramp effect in quadrupole mass filters. The criteria for the conductivity and dielectric constant of the materials are derived theoretically. Some theoretical considerations with regard to application to practical mass filters are also presented. Apparent experimental verification of the theory is briefly described and practical problems of available materials are discussed.
Transmission–resolution curves for a quadrupole mass spectrometer with separated rf and dc fields in the entrance aperture
Authors: Dylla H. Frederick , Jarrell Joseph A.
Published: March 2003

The use of an entrance aperture which spatially separates the rf and dc fringe fields in a quadrupole mass filter is shown to improve the transmission–resolution characteristics. We have measured transmission–resolution curves at 28 amu for a quadrupole mass spectrometer with and without a field separating entrance aperture as described by Fite. The aperture design improves the resolution at near unity transmission, the ultimate resolution, and the absolute transmission of the mass filter.
Transportable cryostat for charged particle irradiation and optical spectroscopy
Authors: Pross L. , Hemmerich J. , Rössler K.
Published: March 2003

A versatile, transportable cryostat system for irradiation at liquid helium temperature and measurements by optical spectroscopy in transmission and reflectance in the temperature range from 5 to 470 K is described. The optical window plug can be removed during irradiation in order to avoid coloring of the windows due to scattered particles or bremsstrahlung.
Improved TV-scanning method for recording time-resolved optical spectra of transients
Authors: Schmidt K. H. , Gordon S. , Mulac W. A.
Published: March 2003

An improved method of recording a time-resolved transient absorption or emission spectrum produced by a single pulse of radiation is described. A streak image of the spectrum is produced by an image converter camera. The image is scanned by a TV camera, stored in a video-disk recorder, and transferred line by line to a computer. The computer can produce three- dimensional plots of absorbance or emission versus time and wavelength containing 100×100 data points.
High Q ultrasonic liquid resonators with concave transducers
Authors: Eggers F. , Funck Th. , Richmann K. H.
Published: March 2003

Experience with cylindrical ultrasonic liquid resonators (volume 2–20 ml) in the 0.1–4 MHz range employing concave quartz transducers is reported. The static overpressure applied on the liquid cavity, which causes concave bending of the quartz, improves the Q factors of the liquid resonator (for a water-filled 15 ml cavity, up to Q∼1.1×105 near 0.4 MHz and for a 2 ml cavity up to Q∼3.4×104 near 1.8 MHz and also reduces absorption effects from gas inclusions. For illustration absorption measurements on aqueous 0.1 M MgSO4 are shown. Some analogies to characteristic properties of dielectric and optical resonators are drawn.
Demountable seal between an epoxy resin and copper for low-temperature applications
Authors: Utton D. B. , Bowers W. J.
Published: March 2003

We describe an indium O-ring seal between an epoxy resin and copper. It is simple, reliable, can withstand severe thermal shocks, and is leaktight to superfluid helium.
Decay time measurement for high-Q ultrasonic resonators
Authors: Eggers F. , Richmann K. H.
Published: March 2003

Decay time and half-power bandwidth of high-Q ultrasonic resonators can be determined with a calibrated RC network generating an exponential time base on a CRT.
Improvement in the interferometric measurement of subangstrom vibrations
Authors: Haesen W. M. J. , Kwaaitaal Th.
Published: March 2003

Improvements in the calibration of a condenser-microphone-stabilized Michelson interferometer for the measurement of subangstrom vibrations are described. They consist of the elimination of errors caused by the fact that the sensitivity of the microphone is dependent on its bias voltage, and a new design of the stabilizing circuit.
Three-dimensional measurements from scanning electron micrographs by electron scribing
Authors: Simon William , Eden Murray
Published: March 2003

A technique has been developed which facilitates three-dimensional measurements from scanning electron micrographs. The method makes use of the electron beam to draw reference lines on the surface of the sample, which can then be viewed at an angle to provide unequivocal measurements of the height of the sample. Conventional scanning electron microscopes, with at most very minor modifications, are used.
Pulsed microwave Fourier transform spectrometer
Authors: Ekkers Jan , Flygare W. H.
Published: March 2003

A pulsed microwave Fourier transform spectrograph is described in detail. The increase in sensitivity and resolution obtained in the time domain relative to standard spectroscopy in the frequency domain is described theoretically and experimentally. Fast switching microwave diodes with a large dynamic range for the generation of high-power microwave pulses are essential for the operation of the spectrograph. A 512-point analog–digital converter and averager with a repetition rate of up to 30 kHz is used for signal-to-noise improvement. The observed emission signals in the time domain are Fourier transformed to the frequency domain on-line by a small laboratory computer. The spectra obtained for 13CH2O and CD2O show a marked improvement in signal-to-noise ratio and resolution. A 50-MHz bandwidth can be covered by a single pulse train.
Some observations on resistance thermometry below 1 K
Authors: Anderson A. C. , Anderson J. H. , Zaitlin M. P.
Published: March 2003

Three aspects of low temperature resistance thermometry have been studied: (i) The measuring power for doped germanium resistance thermometers must be limited at low temperatures to avoid heating the thermometer above its environment. Measurements indicate that the major impediment to the removal of this heat is the weak carrier–lattice interaction. (ii) Data are provided which allow an estimate to be made of the importance of current noise in the use of carbon composition resistance thermometers. (iii) For at least some carbon composition resistance thermometers, the temperature dependence of the resistance is given by the relation R=R0 exp(AT−1/4) below ?0.3 K.
Sensor and suspensions for a low-temperature gravitational wave antenna
Authors: Richard Jean-Paul
Published: March 2003

A dc-biased resonant capacitor sensor for cylindrical gravitational antennas is discussed. For appropriate tuning and Q, its noise is found to be below the thermal noise of such antennas down to millidegree temperatures. ’’Ring’’ and ’’knife edge’’ suspensions of antennas are also discussed as possible alternates to wire and magnetic suspensions.
RESURX: A computer-assisted human intervention system for high-energy physics data reduction
Authors: Pewitt N. D. , Hagopian S. , Hagopian V. , Wind B.
Published: March 2003

A system, RESURX, which is inexpensive to implement, has been developed and used to increase the efficiency of an automatic data processing system of a large experiment in a bubble chamber. The system includes a storage display CRT either connected to a dedicated small computer or as a time-sharing terminal of a large computer. Human intervention is accomplished by commands entered via the CRT keyboard. The RESURX system computer codes, written almost completely in FORTRAN, are modular in nature, transportable, and easily modified as a diagnostic or production tool for other applications which involve digitized trajectories. The design of the system and processing results are presented.
Four-electrode, very-low-frequency impedance comparator for ionic solutions
Authors: Bernengo J. C. , Hanss M.
Published: March 2003

An apparatus designed to compare small differences between the impedance modulus of two identical cells when the measurement frequency is varied from 0.1 to 500 Hz is described. The resolution is typically about 105. The electrode polarization errors are eliminated by using two four-electrode cells. This apparatus is used to determine the very-low-frequency dielectric relaxation spectrum of DNA solutions.
Optical integration of the exciting laser pulse and ratio circuit for fast emission measurements
Authors: Castelli Francesco , Hefner R. Dale
Published: March 2003

An economical ratio circuit for the measurement of fast emission signals induced by laser pulses is described. The laser pulse is first integrated by the use of a long-lived phosphor, and a photodetector is employed to provide the reference signal. The apparatus is used in combination with a single-beam sampling oscilloscope and a computer of average transients or with a single-channel boxcar integrator. In either case the ratio circuit can be used to correct for laser pulse amplitude variations.
Double patterns in reflection high energy electron diffraction for thin film structure observations
Authors: Vitali G.
Published: March 2003

A new technique to obtain reflection high energy electron diffraction (RHEED) double patterns has been developed. This technique has allowed us to obtain simultaneously the RHEED patterns of a thin film and of the single crystal substrate on which the same thin film has been grown. It is possible to have an identification and a relative calibration, on the same exposure, of the crystalline parameters of the film under observation utilizing the simultaneous diffraction pattern of the substrate.
Logarithmic-spiral focusing monochromator
Authors: Webb N. G.
Published: March 2003

A crystal monochromator with a logarithmic-spiral curvature has been designed as part of a low-angle x-ray diffraction camera that uses synchrotron radiation emanating from the storage ring SPEAR at Stanford Linear Accelerator Center. The logarithmic-spiral curvature allows a greater demagnification of the source than is permitted by a cylindrical geometry. Independent bending couples are applied at both ends of a rectangular crystal plate via pairs of parallel rods which rotate under a linear push from differential micrometer screws. Stepping motors control the bending mechanism, theta motion, guard slits, and camera alignment. A tenfold demagnification of the source is readily obtained. Focusing is rapid and easy. The crystal monochromator is combined with a focusing mirror in order to eliminate harmonics and produce a point focus (Webb, Samson, Stroud, Gamble, and Baldeschwieler, 1975).
Comparison of pressures at 300 K and liquid helium temperatures using a clamp-type bomb
Authors: Becker W. M. , Hoo Kuong , Winchell P.G.
Published: March 2003

A series of measurements in a clamp-type bomb which relates the pressure at 300 K to the pressure at liquid helium temperatures is described. Below a minimum applied pressure P (300 K), the pressure falls to zero at low temperatures, in agreement with previous observations. Above this pressure, the pressure is found to be a linearly decreasing function of P (300 K). Differential thermal analysis results are given which indicate crystallization rather than a glass transformation for the pressure transmitting medium, a 1:1 mixture of kerosene and mineral oil. A calculation based on known thermodynamic properties of similar organic materials indicates that the observed pressure change is basically due to the pressure dependence of the thermal expansion of the organic fluid mixture.
Improved flow microcalorimeter for biophysical studies
Authors: Weber Klaus W. , Hinz Hans-Jürgen
Published: March 2003

The flow version of the Beckman model 190 microcalorimeter has been improved by replacing the original platinum tubes with Teflon tubing and a Kel-F mixing chamber, and introducing a physically identical reference system into the thermopile. This modification abolishes the occurrence of spontaneous and irreproducible heat effects probably due to catalytic reactions of the platinum with sulfhydryl groups of the biochemical systems, and permits operation of the instrument as a differential calorimeter. The time constant of the instrument is 50 sec and the useful sensitivity is 6 μcal/min as demonstrated by calibration experiments employing HCl-neutralization and sucrose dilution. The calibration constant has been shown to be independent of the magnitude of the heat effects, the flow rate, and the mode of operation by continuous flow or pulsed flow experiments. The accuracy of experiments on biophysical problems has been illustrated by the good agreement of the binding enthalpies for the association of NADH and pig skeletal-muscle lactate dehydrogenase, and the reaction between isoleucine and isoleucine:tRNA ligase from E. coli, obtained using the flow calorimeter with the ΔH values determined when employing an LKB batch microcalorimeter.
Surface contaminant detector
Authors: Cuthrell R. E. , Tipping D. W.
Published: March 2003

The construction and operation of a surface contaminant detector are described. The sensitivity of the solid-phase bonding of gold-to-gold to adsorbed organic matter is used in this instrument to indicate the contamination level in the environment or on the surfaces of metallic solids. The detection range appears to be unlimited. The behavior of the instrument under various conditions is described for over l05 tests with the same pair of gold contacts. Some of the applications for the portable detector are the testing of clean benches, clean rooms, storage containers, and the surfaces of metallic parts.
Multiple preionization discharge TEA CO2 laser
Authors: Girard André
Published: March 2003

A new concept in utilizing preionization in the TEA CO2 laser is presented. The variable adjustment of the delay between the preionization and the main discharge in a pin-grid double discharge TEA CO2 laser permits the use of low He concentrations (?60%), and different CO2/(CO2+N2) ratios (ranging from 1 to 0) at relatively high main discharge storage energy density (150 J/liter). The addition of a different preionization source (Lamberton–Pearson type) to this laser type leads to further increase in overall performance. This permits a completely variable TEA CO2 laser operation over the gas mixture [100–45% He, and CO2/(CO2+N2) ratio from 1 to 0] and the pump energy (to more than 200 J/liter) without the use of any sophisticated discharge circuit configuration or any seeded gas in the laser mixture. We propose a qualitative explanation based on the comprehension of the different electron production–electron loss processes in the laser discharge. This contribution opens up a new point of view in using more profitably the different preionization schemes proposed to date.
Minicomputer analysis of multidipole plasma Langmuir probe characteristics
Authors: Taylor G. R. , Leung K. N.
Published: March 2003

A simple method which can be programmed on a minicomputer to evaluate the Langmuir probe characteristics of multidipole plasma is discussed. Typical Langmuir probe traces of an argon plasma at high and low neutral pressures are analyzed. Computer plots of the technique are shown to be a very close fit to the corresponding experimental probe traces.
Oscillating-analyzer ellipsometer
Authors: Azzam R. M. A.
Published: March 2003

The state of polarization of a light beam can be dynamically measured by Fourier analysis of the periodic irradiance variations detected after the beam has passed through an electrooptically oscillating analyzer (OA) composed of an ac-driven optical rotator (Faraday cell) followed by a fixed analyzer. From the dc, fundamental, and second-harmonic components of the photodetector current we obtain the same cosine and sine Fourier coefficients (α and β) as would be measured by a rotating analyzer (RA). An ellipsometer based on this principle, called the oscillating-analyzer ellipsometer (OAE), is proposed with speed and precision comparable to that achieved by the polarization-modulated ellipsometer (PME) of Jasperson et al. Significantly, the OAE does not require a special polarization modulator but uses a Faraday cell instead. Also of importance is the fact that a comprehensive analysis of the effect of systematic errors recently developed for the rotating-analyzer ellipsometer (RAE) applies, in its entirety, to the OAE. Whenever appropriate, the OAE is compared with both the RAE and PME.
Rapid and precise measurement of flatband voltage
Authors: Li S. P. , Ryan M. , Bates E. T.
Published: March 2003

A simple circuit using commonly available IC’s for rapid, precise, and automatic measurement of the flatband voltage of MOS capacitors is described.
Method for accurate determination of threshold pulse energies for laser-induced gas breakdown
Authors: Hacker M. P. , Halverson W.
Published: March 2003

A system for accurate determination of breakdown thresholds is described. Automatic recording of individual laser pulse energies allows statistical analysis of the outcomes of many laser pulses and a consequent determination of relative threshold pulse energies with better than 1% accuracy, in spite of much larger variations in laser energy from pulse to pulse. Other statistical information such as the probability of breakdown as a function of pulse energy and pulse-to-pulse correlations can be measured with comparable accuracy.
Multiwavelength discriminator and display system for solid-state lasers
Authors: White Kenneth O. , Watkins Wendell R. , Schleusener Stuart A. , Johnson Ronald L.
Published: March 2003

A technique is described which converts a single-beam absorption measurement into a de facto dual-beam measurement affording real-time calibration. The technique utilizes the narrow wavelength relaxation oscillations from within the long-pulse emission of a solid-state laser. It is used to measure the absorption line profiles of atmospheric gases.
Dual-channel diffractometer utilizing linear image sensor charge-coupled devices
Authors: Paolini Paul J. , Baskin Ronald J. , Roos Kenneth P. , Cline James W.
Published: March 2003

A position-sensitive dual-channel light diffracometer has been developed to allow the real-time monitoring of light diffraction patterns produced by the myofibrillar sarcomeres of single skeletal muscle fibers and small bundles of fibers during contraction. The diffractometer utilizes two linear image devices to permit the analysis of two or more diffraction lines. The sensors are highly sensitive (1.67×10−4 lux sec), lag-free, self-scanning 256-element charge-coupled devices driven by Schottky and standard TTL logic circuitry at a data transfer rate/element of about 20–400 kHz. Video output from the diffractometer can be displayed directly on an oscilloscope screen or can be connected to an ADC and minicomputer system so that diffraction spectra can be corrected for dark signal and element nonuniformities and displayed on-line by the computer CRT. The computer-evaluated spacing between diffraction lines provides an accurate measure of mean sarcomere length within the muscle, while line shape and width are indicative of the length distribution among sarcomeres. Sarcomere length resolution attainable with the instrument ranges from about 10 to 100 Å at a nominal length of 2.5 μ, depending on muscle-to-sensor spacing and whether one or two channels of the instrument are operated.
Angle- and energy-resolved charged particle spectroscopies—a simple way
Authors: Stein R. J.
Published: March 2003

The acquisition of angular and energy distribution information is of growing importance in a number of charged particle spectroscopies used for surface studies. A simple, inexpensive method is outlined for obtaining a visual display of angular distributions containing energy distribution information in the form of color. In essence, a detector optical bandpass is varied synchronously with an energy-selecting element of a spectrometer having a visual display in order to convert the analyzed particle energy distribution to a corresponding chromatic map. The primary utility of the method would be to obtain qualitative information rapidly in those cases where the particle energy spectra have distinct and strong features or when features of interest lie at the higher-energy end. Examples of the latter are plasma loss structure in low-energy electron diffraction, electron-stimulated desorption ion angular distributions, and the higher-energy structure in ultraviolet photoelectron spectroscopy. Other applications are also considered. The practical sensitivity limit for the case of visual observation is 1.0% [I (ΔE)/Itotal]. This sensitivity is not sufficient for application of the method to Auger electron spectroscopy or electron spectroscopy for chemical analysis.
Extraction of quadrature phase information from multiple pulse NMR signals
Authors: Rhim W-K. , Burum D. P. , Vaughan R. W.
Published: March 2003

A multiple pulse sequence (8-pulse sequence) used for high-resolution solid state NMR is analyzed with regard to the information available from each of the four wide sampling windows. It is demonstrated that full quadrature phase information can be obtained using only a single phase detector and that, for the commonly encountered situation where the spectral width is much less than the folding frequency, the signals from the various windows can be combined easily using standard complex Fourier transform software. An improvement in the signal-to-noise ratio of √3 is obtained over either standard single of quadrature phase detection schemes. Procedures for correcting spectral distortions are presented.
Molecular beam apparatus with supersonic O2 beam (700–3000 m/sec) for reactive scattering experiments with metal atoms
Authors: Cosmovici C. B. , Michel K. W. , Dirscherl R. , Stanggassinger U.
Published: March 2003

Design and performance of a heatable, easily alignable Pt-nozzle source (pinhole) are described, providing sufficient O2 intensity in both pure gas and seeded beam operation for crossed beam experiments with metal atoms and mass spectrometric detection. At the chosen skimmer-nozzle distance, nozzle Knudsen numbers around Kn?10−2 gave optimum velocity ratio and intensity for all gas mixtures at nozzle temperatures from 300 to 1300 K. The oven design is particularly suited for effusive metal beams at T<1200 K.
Point-spread functions and optimum filters for position sensitive detectors that use pulse-shape modulation and zero-crossing demodulation
Authors: Nowlin C. H.
Published: March 2003

To enable the later determination of nearly optimum, realizable position decoding filters for position sensitive detectors as well as to enable valid comparisons of various position sensitive detectors, we introduce in this work a productive, high-quality approximation to the point-spread function for position sensitive detectors that use pulse-shape modulation and crossover-time demodulation. This approximation is the result of a theoretical calculation and is determined as a general function of the input signal and rms noise at the input to each of the two crossover detectors. It is precisely applicable to position sensitive detectors that use any type of transmission line encoding. The effects of random variables, such as charge collection time, are included in the calculation, but the effects of correlated noise in the two channels are not included. In addition, for the broad class of position sensitive detectors that have electronic and thermal noise as the dominant causes of position uncertainty, general equations, based on our approximate point-spread function, are given for the optimum filter impulse responses, the optimum pulse shapes at the inputs to the crossover detectors, and the associated minimum positional full-width half-maximum (FWHM). General equations are also given for positional FWHM of electronic-noise-limited detectors that use nonoptimum filters. Finally, for electronic-noise-limited detectors that use an RC-transmission line encoder that is terminated in its characteristic impedance, a plot is given of the optimum pulse shape at the input to the crossover detectors.
Isothermal high pressure flow calorimeter
Authors: Christensen J. J. , Hansen L. D. , Eatough D. J. , Izatt R. M. , Hart R. M.
Published: March 2003

An isothermal flow calorimeter suitable for measuring heats of reaction and heats of mixing at high pressure is described. With the calorimeter endothermic or exothermic processes can be studied from 0 to 70 °C and from 1 to 400 atm. Energy effects from 0.15 to 30 J/min are measured with a precision of ±0.4% at a constant temperature through the use of an automatic controlled variable heater and a constant cooling Peltier device. A complete heat-of-mixing curve can be generated from a single run. The calorimeter was tested by measuring the heats of neutralization of HClO4–NaOH and HClO4–TRIS and the heat of mixing of n-hexane-cyclohexane, and was found to produce data in very good agreement with published literature values.
Hydrogen in smoke detected by the Pd-gate field-effect transistor
Authors: Lundström I. , Shivaraman M. S. , Stiblert L. , Svensson C.
Published: March 2003

A recently developed hydrogen-sensitive Pd-gate MOS-transistor was used to detect small amounts of hydrogen in smoke. It is shown that the device can be used to detect a fire before it has really started and therefore has a potential application as a fire alarm.
Improved bell type micromanometer for measuring low air speeds
Authors: Araki Nobuyuki , Nakagawa Kogoro , Hakomori Kyojiro
Published: March 2003

An improved fast-response bell type micromanometer with Pitot tube has been developed for measuring low air speeds in the range of about 1 m/sec. Displacement of an inverted bell is picked up by an unbonded strain gauge which has a large spring constant compared to its sensitivity. A balance system is used to cancel the weight of the bell and decrease drifts.
Amplitude-normalized decay integral: A method for measuring low-level luminescence lifetimes
Authors: Arnold S. , Wotherspoon N.
Published: March 2003

A method which utilizes photon counting is developed for measuring low-level luminescence lifetimes. The technique requires two counters and a pulse sequence generator. The method is applied to the measurement of the delayed fluorescence lifetimes in anthracene and tetracene single crystals. The lifetime of triplet excitons in vapor-grown tetracene crystals is found to be 43 μsec.
Apparatus for chemical vapor deposition of silicon dioxide from silane gas
Authors: Mitra N. K. , Heynen C. J. H.
Published: March 2003

A description is given of an apparatus for the formation of oxide films of uniform thickness by a low temperature (300 °–500 °C) chemical vapor deposition process. The reaction gases enter at the top of a rotationally symmetric reaction chamber. By means of locating two fritted–glass disks in the path of the gas, good gas mixing and turbulent conditions are maintained inside the chamber. During the process the axis of this chamber is moved along a circle, the center of which coincides with that of a stationary substrate holder of circular form. This relative movement results in an averaging of conditions, giving a uniformity of the dielectric layer deposited. Constructing this apparatus is simple because no rotating joints are necessary for feeding in the gases, nor sliding contacts for the heater supply and temperature measuring equipment.
Tidal gravimeter employing magnetic suspension
Authors: Pankey Titus , Thorpe A. N. , Marsh F.
Published: March 2003

A magnetic suspension consisting of a small Kovar cylinder constrained to float in the fringing field of a permanent magnet was used to monitor the semidiurnal components of the earth’s gravity field caused by the sun and the moon. No methodical drift of the equilibrium level of the cylinder for nongravitational reasons was ever observed. It appears that this apparatus has considerable potential for long-term uninterrupted gravitational observations.
Oil mist precipitator
Authors: Ash W.
Published: March 2003

A simple, inexpensive electrostatic precipitator has been built and used to eliminate oil mist in vacuum pump exhaust.
Programmable low-cost calculator accepting five-digit, BCD-coded input information from external instrumentation
Authors: Olofsson A. , Edwall G.
Published: March 2003

A programmable, low-cost calculator for analytical processing of output data from digital instrumentation is described.
Gated scintillator-photomultiplier neutron detector for time-of-flight measurements in the presence of a strong x-ray background
Authors: Ramirez J. J. , Kruse L. W.
Published: March 2003

A highly sensitive, fast rise-time detector has been developed that is capable of neutron time-of-flight (TOF) measurements in the presence of an intense bremsstrahlung background such as that from a relativistic electron beam (REB) accelerator. This detector, used in conjunction with thermal neutron counters, forms an effective neutron detection system. Such a system was used to measure neutrons from the HYDRA REB accelerator. By using a fast-acting and reproducible gating circuit, the inherent sensitivity of the detector has been retained while suppressing all deleterious effects caused by the intense bremsstrahlung burst. At no time during the measurements were any spurious afterpulses observed in the TOF detectors. The timing resolution obtained was sufficient to distinguish between neutrons produced by thermal and fast deuterium ions.
Photodiode and holder with 60 psec response time
Authors: Beck G.
Published: March 2003

The parameters governing the response time of a biplanar vacuum photodiode are discussed and the construction of a matched holder is described which permits operation of an ITT F-4014 diode under optimum conditions at 6 kV anode voltage. The diode–holder combination is tested with fast light impulses and step function changes in light intensity. The values obtained are in agreement with theory: 60 psec for the rise-time and 68 psec for the fall-time with minimum signal distortion. Additional measurements cover linearity and fatigue of the photodiode.
Electrostatic optical device for high-resolution differential cross section measurements in scattering experiments
Authors: Lebehot A. , Campargue R.
Published: March 2003

A new electrostatic optical system designed for high angular and energy resolution in ion–molecule-scattering experiments is described. This device is based upon a theoretical lens model (’’zero gap electrostatic double-aperture lens’’) proposed by Read. A first pair of these lenses accelerates a low-energy ion beam, with a relatively wide angular spread, up to a chosen collision energy and makes the beam parallel in the scattering region, without any system of slits. A second pair of lenses, symmetrical to the first, decelerates the ions scattered at a given angle and focuses them on the entrance slit of a 127° electrostatic analyzer. This analyzer and the final lens are scanned in order to obtain energy loss spectra. A simple theoretical study of the system which allows the angular spread of the ion beam in the collision region to be predicted as a function of the initial energy and the chosen scattering energy (between about 100 and 3000 eV) is given, the respective positions of the lenses being adjustable parameters. These positions are chosen according to the theoretical results in order to achieve the best angular resolution. The first experimental data obtained are in very good agreement with the theoretical predictions. An example of application to elastic He+–He collisions is presented.
Microscope cold stage for the direct observation of vacuum etching and freeze drying
Authors: Hildebrandt W. H. , Cocks F. H.
Published: March 2003

A low-temperature microscope cold stage which allows frozen specimens to be etched by either vacuum desiccation or sublimation in an inert gas has been developed. The application of this device to frozen thin films of the NaCl–H2O binary system reveals that the additional information obtained by such etching is analogous to the added information obtained from normal metallurgical specimens by etching.
Time jitter in sampling and averaging
Authors: Janney Robert
Published: March 2003

Time jitter in a sampling and averaging system used for the analysis of pulses having similar shapes but varying amplitudes is discussed. An analytical treatment of the problem for a mathematically tractable special case is presented. For this special case, the analysis shows that the shape of the input pulse will be preserved by the averaging process despite the time jitter. The amplitude and time shift resulting from the averaging process are shown to be functions of the trigger level and the statistical distribution used for the amplitudes of the input pulses.
Electrical conductivity measurements on silicate melts using the loop technique
Authors: Waff Harve S.
Published: March 2003

A new method is described for measurement of the electrical conductivity of silicate melts under controlled oxygen partial pressure at temperatures to 1550 °C. The melt samples are suspended as droplets on platinum–rhodium loops, minimizing iron loss from the melt due to alloying with platinum, and providing maximum surface exposure of the melt to the oxygen-buffering gas atmosphere. The latter provides extremely rapid equilibration of the melt with the imposed oxygen partial pressure. The loop technique involves a minimum of setup time and cost, provides reproducible results to within ±5% and is well suited to electrical conductivity studies on silicate melts containing redox cations.
Procedure for drilling small holes in fragile crystals
Authors: Hunter Tom
Published: March 2003

A simple technique by which small (0.066 cm or less) diameter holes may be drilled in fragile molecular crystals is described. Crystals of Rochelle salt, triglycine sulphate, N-acetylglycine, and L-alanine have been successfully drilled in this way.
Polarization modulation for photon-counting Raman spectroscopy
Authors: Engstrom Herbert
Published: March 2003

A system combining polarization modulation with digital synchronous detection has been adapted for Raman spectroscopy. The apparatus permits an accurate determination of the polarization of scattered light and offers a number of other advantages over conventional measurements of Raman spectra. Brief derivations of formulas useful for analyzing data are given. The resolution of this apparatus is 87% of the theoretical maximum. The utility of the system is demonstrated by presenting the modulation Raman spectrum of sodium chlorate.
Emissionless power cathode
Authors: Stangeby P. C. , Shmayda W. T.
Published: March 2003

The combination of a weak rf discharge and a plasma current multiplier constitutes an effective dc power cathode which operates without electron emission, elevated materials temperature, or wall bombardment, etc. Such power cathodes may find application wherever filament cathode operation poses difficulties, as with reactive gases, or where filament replacement is undesirable.
Regulation of arc or emission current in hot cathode ion sources
Authors: Ollison W. M. , Peters William A. , Cross R. James
Published: March 2003

Ion currents extracted from hot cathode sources may be stabilized by a simple modification of the filament power supply to regulate the emission current. Simultaneous regulation of both current and voltage in an arc discharge is provided.