bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of magnetic circular dichroism of matrix-isolated high temperature molecules
Authors: Brittain Robert , Powell David , Voigtman Edward , Vala Martin
Published: March 2003

An apparatus for the measurement of the absorption and magnetic circular dichroism (MCD) spectra of matrix-isolated high temperature molecules is described. A conventional electromagnet capable of producing fields up to 5500 gauss (0.55 T) is shown to produce high quality MCD spectra. A closed-cycle helium cryostat is used to provide the variable low temperatures required, while a commercial microcomputer furnishes the wavelength advance, the photoelastic modulator voltage control, and digital signal collection. A pseudodouble beam absorption apparatus provides an absorbance (log I0/I) measurement on the same matrix-isolated sample used for the MCD measurement, enabling straightforward comparison of the two and facilitating interpretation of any MCD 𝒜1 and 𝒞0 terms that are observed. The absorption and MCD spectra of the γ′ and α bands of the diatomic TiO in an argon matrix (14 K) are presented to illustrate the power of the combined absorption/MCD matrix isolation method for the assignment of the excited electronic states of high temperature molecules.
Fast high-resolution ion energy and momentum spectrometer
Authors: Krishnan M. , Hirshfield J. L.
Published: March 2003

A novel energy/momentum spectrometer consisting of a multigrid ion energy analyzer in tandem with an inflexion focusing magnetic sector momentum analyzer is described. The entire analyzer ion flight path may be negatively biased relative to the outer (grounded) instrument housing, enabling post acceleration (up to a few keV) of grid extracted ions from laser blow-off plasmas or laser-initiated vacuum arcs. Used as a time-of-flight momentum spectrometer, the instrument is shown capable of unraveling velocity distributions and relative abundances of ions of different charge in expanding laser blow-off plasmas, even for a few keV initial ion energy spread. Used as a discharge ion analyzer, the high mass resolution of the instrument, (m/Δm=110), enables ion isotopic species of carbon, iron and copper to be readily separated and energy analyzed. A channeltron collector provides wide dynamic range (∼105) and high time resolution (∼1.0 μs), enabling detection of low abundance species such as polymer ions in carbon discharges.
Shock loading and unloading behavior of carbon piezoresistive gauges up to 5 GPa
Authors: Perez M. , Chartagnac P.
Published: March 2003

The shock loading and the unloading behavior of piezoresistive carbon gauges was investigated by means of impact experiments performed with a smooth bore gas gun. Experiments in the range 0.291–5.485 GPa provided shock stress-time profiles. Up to about 2 GPa the shock loading data were fitted with a least square polynomial in good agreement with other published date. Over 2 GPa the carbon presents a strongly scattering behavior. The unloading response in the reliable loading behavior range (0–2 GPa), exhibits an important hysteresis phenomena which could be imputed to the presence of pores in the carbon strip.
Electronic instrumentation for heterodyne holographic interferometry
Authors: Mastner J. , Masek V.
Published: March 2003

An electronic instrumentation for heterodyne evaluation of holographic interferograms by accurate phase-measurements is described. It allows to achieve an overall interpolation accuracy of 1/1000 of a fringe. The specifications for the electronic circuitry are derived from the conditions in the optical experiment. To improve the SNR, a narrow-band signal-filtering is needed; an AGC circuit has to adapt the gain in the signal channel to various experimental conditions. Special measures for reduction of phase errors due to these circuits are discussed. The phase meter with an accuracy of 0.1 deg is described in detail. It counts continuously the multiples of π’s as obtained when the detectors are crossing fringes in the image plane of a reconstructed interferogram. The total measuring range for phase is given by the capacity of the up-down counter, and thus practically unlimited.
Modular multiplexed digital to analog conversion
Authors: Smith Owen I. , Rodgers Wayne E.
Published: March 2003

A design is provided for a 16 channel, multiplexed, digital to analog converter. Output channels are unipolar, zero to ten volts, with ten bit accuracy. Computer bus interfacing by means of a commercially available parallel interface results in a relatively low cost, easily assembled instrument to which digital to analog channels may be added as the need arises.
Fluorescent decay thermometer with biological applications
Authors: Sholes R. R. , Small J. G.
Published: March 2003

The time constant for fluorescent decay of the red R lines of Ruby has previously been shown to be a monotonic function of temperature over a range of more than 200 °C. An optical thermometer using this effect has been constructed and has a resolution of ±0.3 °C. Improvements in digital signal processing may increase this resolution another factor of 16.
High voltage SCR trigger circuit utilizing disc capacitors in a Marx array
Authors: Jacoby B. A. , York T. M.
Published: March 2003

An SCR Marx circuit which is characterized as inexpensive and reliable, with no warm-up or heater power has been constructed, tested, and utilized in a pulsed discharge experiment. The specific circuit design produced an output pulse of 13 kV with a risetime of 0.12 μs and a FWHM of 0.16 μs. With a 500 V self-enclosed battery power supply, the pulse generator was insensitive to triggering by stray signals, with an observed jitter of ±50 ns in triggering a spark gap of 18 kV.
Microcomputer-controlled digitizer and image analyzer
Authors: Lum R. M. , Jones R. P.
Published: March 2003

An automatic digitizer has been developed that employs a microcomputer-controlled photosensor to detect and digitize analog curves from strip-chart paper, drawings, photographs of oscilloscope traces, negatives, etc. The control and data acquisition programs are coded in BASIC enabling real-time interactive control of the system. Movement of the photosensor is accomplished under program control and is selectable in either a curve-follower or raster-scan mode. Use of visible-LED photodetectors permits curves drawn with different colored inks to be discriminated and separately digitized. The system is simple to use and highly versatile with capabilities that extended beyond curve digitization. In the raster-scan mode, operation of the apparatus as an optical densitometer is possible enabling detailed image analysis and digital image reconstruction to be performed (e.g., quantitative measurement of intensity distribution and mode structure from photographs of laser output beams.)
Asymmetrical friction in a piston-cylinder device and the effect on the melting curves of indium and bismuth
Authors: Richter P. W. , Clark J. B.
Published: March 2003

The melting curves of indium and bismuth were determined in a piston-cylinder device. A comparison of the results obtained by differential thermal analysis and volumetric techniques confirms the existence of an asymmetric friction component. Transition pressures are overestimated if allowance is not made for asymmetric friction. The application of Mirwald’s ’’zero friction’’ technique for talc and NaCl assemblies indicated that only symmetrical and not asymmetrical friction is eliminated.
New high pressure low temperature differential scanning calorimeter
Authors: Arntz H.
Published: March 2003

A high pressure differential scanning calorimeter for low temperature investigations is described. It allows the measurement of thermodynamic properties of substances over wide ranges of temperature and pressure, e.g., between 100 and 450 K at normal pressure and between 100 and 300 K at 4 kbar. Up to now the calorimeter has been used for the determination of transition enthalpies and transition temperatures of some plastic crystals up to 1500 bar from which other properties, e.g., transition entropies and transition volumes, can be calculated.
Automation of a popular monochromator
Authors: Look D. C. , Farmer J. W. , Ely R. N.
Published: March 2003

A wavelength-scan and intensity-control system for a widely-used, high-intensity monochromator is described. The wavelength scan is bidirectional and variable speed, and may be controlled manually or by TTL logic from a computer. The intensity control is effected by use of a programmable dc power supply and D–A converter. Various filters are described which allow an intensity of up to 2×1014 photons/cm2 s to be achieved in a 1 cm×3 cm area over a wavelength range 0.76–2.50 μm, at 0.07 μm bandwidth, with a single grating. (A lesser intensity is available to 3.4 μm.) This wide range is made possible by the use of second-order light from 0.76–1.00 μm. Photoconductivity data in GaAs:Cr and InP:Fe are presented, as an example.
Slow-positron apparatus for surface studies
Authors: Lynn K. G. , Lutz H.
Published: March 2003

We describe an apparatus for producing an intense low energy positron beam of well defined energy by moderating the decay positrons from a radioactive source using a clean single crystal convertor with high conversion efficiency (ε≃10−3). These positrons are used as a probe to study well characterized surfaces in an ultra-high vacuum system. The magnetically focussed beam can deliver a current on the order of 2×105 positrons/s to a target when a 300 mCi 58Co source is used. Characteristics of the apparatus are given and possible directions for future improvements are mentioned.
Compensated count rate circuit for portable Geiger-Mueller survey meter
Authors: Todd R. A.
Published: March 2003

A count rate circuit is described that better compensates for counting losses due to detector dead time than previously used techniques in Geiger–Mueller survey meters. Bench tests show the new design response to be within 1% of the ideal response even up to counting losses of 50%.
A method for measuring small rotational velocities for a couette-type viscometer
Authors: Berberian John G.
Published: March 2003

A parallel plate capacitor assembly is used to measure the angular rotation in viscosity measurements using a Couette-type viscometer. This measurement coupled with a time base permits extremely small angle velocities to be measured thus permitting large viscosities (ca. 1011 Pa s) to be determined. Sample data on supercooled isoamyl bromide at low temperatures obtained by this method are presented.
Mechanical aids for the alignment of four-circle single-crystal diffractometers
Authors: Guggenheim Stephen , Schreckeis Joseph
Published: March 2003

Two simple mechanical devices are described to aid in the alignment of x-ray four-circle single-crystal diffractometers. The first is a table mounted on the goniostat for use as a reference plane; the second a telescoping pointer for positioning the collimators. Suggestions for use are applied to a Picker system.
A focussing hog-horn antenna for microwave diagnostics in plasma machines
Authors: Moresco M. , Vendramin A. , Zilli E.
Published: March 2003

We describe the design of a type of millimeter wave antenna which is particularly suitable in plasma diagnostics applications. It is an all metal focussing hog-horn antenna. Its main advantages are high spatial resolution, capability of working at short distance, little space taken, wide band, ruggedness. Moreover it does not produce vacuum or plasma bombardment problems.
High sensitivity pulse-counting mass spectrometer system for noble gas analysis
Authors: Hohenberg C. M.
Published: March 2003

A pulse-counting mass spectrometer is described which is comprised of a new ion source of cylindrical geometry, with exceptional optical properties (the Baur source), a dual focal plane externally adjustable collector slits, and a 17-stage Allen-type electron multiplier, all housed in a metal 21 cm radius, 90° magnetic sector flight tube. Mass discrimination of the instrument is less than 1 per mil per mass unit; the optical transmission is more than 90%; the source sensitivity (Faraday collection) is 4 ma/torr at 250μm emission; and the abundance sensitivity is 3×104. A low blank extrction system is also described which routinely provides precedural blanks at 1600°C of approximately 10,000 atoms of 132Xe. The corresponding blanks for 84Kr, 36Ar, and 20Ne are 70,000, 4×106, and 5×107 atoms respectively.
Effect of linear drifts and low-frequency noise in phase shift measurements
Authors: Takemori M. T.
Published: March 2003

The presence of slowly varying signal drifts or low frequency (subharmonic) contributions can produce significant errors in the calculation of phase shifts using a correlation analysis. Under these conditions, the phase shift calculation becomes dependent on the reference signal phase angle. In this paper, we propose a modification to the correlation analysis to remove this dependency. We also present our analysis in discrete form to enable a digital implementation. Finally, we discuss the adverse effects that changes in the limits of integration can have on the phase shift calculation under the presence of linear signal drifts.
Curved-crystal (LiF) x-ray focussing array for fluorescence EXAFS in dilute samples
Authors: Marcus M. , Powers L. S. , Storm A. R. , Kincaid B. M. , Chance B
Published: March 2003

A focussing monochromator array for detection of fluorescence EXAFS (Extended X−ray Absorption Edge Fine Structure) is described. The array is made of LiF crystals, specially prepared for large mosaic spread. Design criteria, performance specifications, and details of fabrication and crystal preparation are given.
Improved pressure calibration system using the ruby R1 fluorescence
Authors: King Hubert E. , Prewitt Charles T.
Published: March 2003

When measuring pressures in the diamond anvil cell, undersirable line broadening and wavelength shifts result if small ruby crystals are used in a calibration system designed for large ones. These effects can be eliminated through the proper choice of objective lens, condensing lens, and slit system. Using such a system, we obtained excellent results with samples as small as 30 μm. In addition, we describe the use of the spectrum from a neon light to provide an internal wavelength standard during the measurement of the ruby spectrum. This eliminates the stripchart - wavelength drive synchronization error, a potential source of large errors. A calculation of the estimated error associated with a typical pressure measurement indicates that, for small ruby samples, the pressure can be determined with a precision of ±0.5 kbar.
Speer carbon resistors as pressure gauges
Authors: Wasim S. M. , Aldana R. , Cabrera F.
Published: March 2003

A study has been made of the resistance pressure characteristics of a number of Speer carbon resistors in the temperature range between 295 K and 76 K under hydrostatic pressure of up to 10.5 kbar. It is found that the resistance of the resistors decreases markedly with pressure. The results are quite reproducible and the effect of hysteresis is reduced after several pressure treatment.
Instrumentation for the size determination of submicron particulates systems by sideway light scattering method
Authors: Suda K.
Published: March 2003

A new submicron particle counter using a low output He–Ne laser (unpolarized, 8 mW) is proposed for in situ measurement of particulates. The design is based on calculations and experimental checks of factors governing the signal-to-noise ratio. Right angle scattering is found to be the most suitalbe optical system for eliminating miscellaneous noise and fundamental noise components derived from the carrier gas. The present version of the instrument with nine channels is constructed so as to minimized the noise level by reducing the sensing volume. This instrument can actually measure correct size distributions from 0.1 to 10 μm without detectable coincidence loss, at environmental particulate concentrations of up to 5×104/cm3.
A scanning laser probe for the direct observation of acoustic wave phenomena at liquid–solid interfaces
Authors: Davids Douglas A.
Published: March 2003

A novel system has been developed for the direct measurement of acoustic displacement at a liquid–solid interface which is useful in the observation of leaky wave and related beam-shift phenomena. Theory predicts that under certain conditions the acoustic field configuration is sensitive to material characteristics such as grain structure and hence assessment of this sensitivity is relevant to ultrasonic surface evaluation. The system utilizes a scanning laser probe together with knife-edge detection; it permits rapid data acquisition, is remarkedly stable and easy to align, and provides linear maps of field intensity with minimal corruption even with acoustic transducer electrical input levels in the submilliwatt range.
Nanosecond light pulser with Hg vapor: Determination of quenching rate constants for Hg(3P1) with H2, C2H4, CO, and NH3
Authors: Hikida T. , Santoku M. , Mori Y.
Published: March 2003

A pulsed discharge lamp containing Hg vapor suitable for kinetic spectroscopy in the nanosecond time range is described. The spectral output is practically the same as that from a conventional low pressure mercury resoance lamp. The light intensity of the 253.7 nm resonance line is about 1010 photon/pulse. The width of light pulses is about 10 ns, except at 253.7 nm, which pulse width is about 40 ns. The repetition rate is 5–10 kHz. Quenching rates of Hg(3P1) atoms by H2, C2H4, CO, and NH3 are obtained by measuring decay rates of the 253.7 nm resonance line.
High voltage capacitor charge control by low voltage cycle counting
Authors: de Brito Cruz Carlos H. , Gerck Edgardo
Published: March 2003

We describe a low voltage open loop control for high voltage capacitor charging circuits. The control is achieved by counting the number of halfcycles from the line supply that are allowed to excite the HV transformer primary. This number of half cycles determines the amount of charge stored in the capacitor, therby setting its voltage to the desired value. This open loop system avoids the use of HV sampling or switching. An implementation is presented for a RC charging circuit, together with graphs and formulas for design purposes. LC resonant charging is also discussed.
Direct measurement of internal friction with continuous variation of frequency
Authors: Lakkad S. C. , Karnik Y. P.
Published: March 2003

A method for the measurement of the internal friction in solids by measuring the instantaneous values of applied sinusoidal stress, the resulting strain and the phase difference between them is presented in this paper. The experimental setup utilizes the instruments normally used in the vibration analysis and the variation of internal friction with frequency can be recorded automatically on a level recorder. The values obtained by this method are compared with those by the amplitude repsonse method for two epoxy resin systems. The agreement is found to be satifactory. The method is very suitable for locating the relaxation peaks up to 2000 Hz.
Inexpensive timing circuit for a Q-switched solid-state laser using NE555 Timers
Authors: Subhash N. , Sathianandan K.
Published: March 2003

A simple circuit using NE555 Timers for controlling a low repetition rate (upto 10 pulses/min.) Q-switched solid-state laser is described. This circuit produces two pulses, one for firing the flashlamp and the other for driving the electro-optic Q-switch, whose delay can be continuously varied up to 700 μs.
Laser-beam attenuation for spatial profiling of small focal spots
Authors: Nichols D. B. , Hall R. B.
Published: March 2003

We describe an attenuation scheme for high-power laser beams which uses only two optical surfaces and is continuously variable over several orders of magnitude. We demonstrate its application to the spatial profiling of a pulsed DF laser focal spot with 10−2 cm diameter and ≳1010 W/cm2 peak irradiance.
Three-watt near-room-temperature CO waveguide laser
Authors: Hauck J. P. , Huffman E. H.
Published: March 2003

We report stable performance of a carbon monoxide waveguide laser which produces 3/4 W with the gas and base near zero °C, and 3 W with flowing chilled gas. Stable output power and frequency spectra are obtained by using low-thermal-expansion boron nitride as the waveguide material.
Electron distribution function measurement by harmonically driven electrostatic probes
Authors: Schoenberg Kurt F.
Published: March 2003

An electron distribution function measurement system, applicable to noisy plasma environments, is presented. The system is based on the harmonic differentiation technique, which utilizes the nonlinearity of the probe current-voltage characteristic to infer distribution function structure. Measurements couple low noise, phase sensitive detection with digital data acquisistion and analysis, resulting in fast and accurate measurement in noisy environments where active electronic differentiation may prove untenable. The accuracy of the experimental technique and measurement system is discussed. Using a high power arc plasma, an example demonstrating the experimental system is given.
State purification of a fast neon metastable beam by collinear optical pumping
Authors: Gaily T. D. , Coggiola M. J. , Peterson J. R. , Gillen K. T.
Published: March 2003

An apparatus has been constructed to produce well-characterized fast beams of rare gas metastable atoms for subsequent scattering experiments. Optical pumping by a collinear laser beam can be used to selectively remove either of the two metastable components from the beam. Laser-induced-fluorescence (LIF) techniques can be used to determine the original beam composition and to monitor composition changes resulting from optical absorption. These techniques have been successfully applied to a metastable neon beam produced by near-resonant charge transfer of Ne+ in Na. A simple model has been developed which accurately reproduces the observed LIF lineshape generated by tuning the laser throught the optical transition frequency.
Low temperature thermal conductivity measurements under uniaxial compression
Authors: Adolf Alain
Published: March 2003

A new technical method of thermal conductivity measurements of uniaxially compressed samples, at liquid helium temperatures, has been tested. This method allows rigorous guiding and alignment of the sample while the problems linked to the thermal insulation of the sample are also minimized. Good reproducibility of the results was obtained after the sample was taken off and mounted again.
Simple thermal conductivity cell using a miniature thin film printed circuit for analysis of binary gas mixtures
Authors: Devoret M. , Sullivan N. S. , Esteve D. , Deschamps P.
Published: March 2003

We describe a thermal conductivity cell for the measurements of the composition of binary gas mixtures. The main advantage of the cell is that its response is pressure independent in the range 20–100 Torr. The apparatus, of the parallel plate type, uses a very thin printed circuit film as the hot plate in order to achieve a fast response time. The cell was designed and operated to determine the ortho-para-composition of hydrogen gas samples but it also works reliably as an analyser of 3He–4He gas mixtures. In both cases the precision of the instrument is better than 10−2 for the mole fraction.
Design of partial dielectric cavities for wide-band microwave measurements
Authors: Amato J. C.
Published: March 2003

A novel microwave cavity is presented in which a conducting sample can be excited by a strong microwave field and, simultaneously, its response can be measured over a wide frequency range surrounding the excitation frequency.
Analog measurement of the autocorrelation function of Gaussian noise
Authors: Gabriel C. J.
Published: March 2003

A new method for measuring the autocorrelation function of stationary, Gaussian distributed, differentiable or nondifferentiable noise is presented. This method does not require real-time digitizing or analog multiplying and can be easily realized since it is based on the use of either a sampling oscilloscope or a boxcar averager. The method requires the measurement of the ensemble average of the multiple traces generated by internally triggering the oscilloscope or averager on the noise. Expressions for interpreting this average to obtain the autocorrelation function as well as examples of measurements made by this technique are given and discussed.
Microanalytical ultracentrifuge
Authors: Moroz Pavel E.
Published: March 2003

An ultracentrifuge based on the air turbine of a dental drill attains 400,000–600,000 rpm and a centrifugal force 2 to 3 million ×g. It is used for the examination of cell suspentions and homogenates and can be applied to macromolecular solutions. Microcuvettes with volumes ranging from less than 1 mm3 to 0.001 mm3 (suitable for single cells) are of disk and square capillary form and are made of polycarbonate or glass. A special microscope is used to obtain a stopped image of the rotating cuvette. A new method to preserve the centrifugal state of the contents is tested: deep freezing of a rotating cuvette for subsequent freeze-drying and microscopical examination. Experiments on cells include centrifugal intercellular movement of nuclei and cytoplasmic particles, cell fusion, and homogenization.
Low-drift optical-densitometer
Authors: Karkiewicz L. M. , Panitz J. A. , Fowler G. L.
Published: March 2003

A general purpose, optical densitometer has been constructed using inexpensive components. A drift rate of approximately 0.3% per hour, and a measurement accuracy of 0.1%, permit the instrument to detect small changes in the optical transmission of unknown samples.
Device for measuring positions in spherical coordinates
Authors: Villeneuve D. M.
Published: March 2003

A simple device is described which can determine the positions of objects in spherical coordinate systems by extending a pointer to touch the object. The coordinates are read directly from a digital display.
Fast preamplifier for low background infrared detectors
Authors: McDonald J. D.
Published: March 2003

A fast preamplifier for low background infrared detectors is described. It provides background limited performance for Ge:Hg detectors at 77 °K background up to almost 1 MHz.
Plasma density measurements using FM–CW millimeter wave radar techniques
Authors: Doane J. L. , Mazzucato E. , Schmidt G. L.
Published: March 2003

Modified FM–CW radar techniques using swept millimeter–wave oscillators are useful for determining when a particular density has been reached in a plasma. Narrowband measurements on the Princeton Large Torus (PLT) demonstrate the suitability of these techniques for controlling high-power auxiliary plasma heating systems. Broadband measurements using these same techniques are proposed, by which the density profile could be determined.
Magnetic levitation with thyristor control
Authors: Upton S. R. , Murgatroyd P. N.
Published: March 2003

A magnetic levitator is described in which the electromagnet is the load for a fully controlled thryistor bridge working at 50 Hz.
Temperature coefficient of the silica spring balance and estimation of errors in gravimetric adsorption measurements
Authors: Berkheiser V. E. , Rao P. V. , Pothier W. G.
Published: March 2003

Silica spring adsorption balances were calibrated and temperature coefficients of the spring sensitivities were determined by a novel method. The method allows direct measurement of the temperature coefficient of torsional modulus of silica, which may depend on the type of silica from which the spring is constructed. By use of a first-order Taylor series approximation, an approximate expression is derived for the variance of the quantity of vapor adsorbed per weight of solid (x/m). The expression points out certain experimental designs which may be altered to minimize the variance. Limitations in estimating the variance of x/m at low values of x/m are discussed.
On-line display used with cathode ray tube film measuring device
Authors: Fortney L. R. , Robertson W. J.
Published: March 2003

An improved display has been developed for use on our computer controlled measuring device (RIPPLE). The device features a television image of the film and a digital presentation on the same X, Y display. The television image is formed using a modified left and right raster scan which can cover 50% more area in the same time as the traditional raster.
Interface for a microcomputer-controlled digital display system
Authors: Lynk E. T. , Ludke Siegwalt
Published: March 2003

This report describes an interface device which permits a Ramtek GX-100B digital display system to be controlled by an Intel MDS-800 microcomputer system, using an Intel direct memory access controller card.
Photoselection spectrometer by a simple modification of a luminescence spectrometer
Authors: Carlin Clifford M. , DeArmond M. K. , Hanck K. W.
Published: March 2003

A microprocessor-controlled L-format photoselection spectrometer has been developed. A simple modification of a standard luminescence spectrometer by addition of a rotating chopper allows polarization values to be determined with a precision limited only by counting statistics.
Thin film photoconductor mounting schemes for picosecond optical detectors
Authors: Smith P. R. , Auston D. H. , Johnson A. M.
Published: March 2003

Three mounting schemes of thin film photoconductors for picosecond optical detectors are presented. All have risetimes (10%–90%) which approach the 25 ps limit for sampling oscilloscopes.
Simple, compact, and inexpensive light–dark attachment for scanning spectrophotometers
Authors: Kendall-Tobias M. , Takemoto Jon
Published: March 2003

A simple attachment has been constructed to allow the use of an actinic light source for cross illumination of samples in a UV/VIS spectrophotometer. Examples are given of how this unit can extend the use of the spectrophometer beyond its standard capabilities.
Measurement of impurities in a long-pulse, multiampere hydrogen beam
Authors: Okumura Y. , Mizutani Y. , Ohara Y. , Shibata T.
Published: March 2003

Impurity concentration in intense neutral beams extracted from both a 75 keV/6 A/10 s duoPIGatron ion source and a magnetic multipole line cusp ion source has been measured by magnetic deflection mass analyzer. After passage of 90% equilibrium neutralizer cell, the ion beam contains 1%–2% light impurities (such as C+, O+, H2O) and 0.02%–0.15% heavy impurities (such as Cu+, W+, Ag+). Taking into account the neutralization efficiency, the neutral beam is estimated to contain 3%–6% light impurities and 0.04%–0.3% heavy impurities. The impurities related to oxygen decrease with time during a 10 s pulse, while those related to carbon, copper, and tungsten increase slightly with time. The origin of these impurities is discussed and the source operation mode to reduce the impurity level is proposed for neutral beam injection.
Design of a hyperbolic microwave metallic lens
Authors: Uckan Taner
Published: March 2003

Due to problems caused by multiple reflections in the cavity walls of the EBT fusion research device, the use of a horn becomes important for the directivity of waves in the millimetric range. An ordinary dielectric lens cannot be used because of plasma–wall interactions. Microwave metallic lenses, designed to focus the energy into a plane wave, can improve the directivity considerably. By implementing a 70-GHz standard-gain horn with a delay-type hyperbolic lens, which consists of a solid metallic disk with a number of equal size small holes, a gain of 15 dB over the no lens case was realized.
Design and calibration of a Thomson ion analyzer for plasma focus studies
Authors: Herold H. , Mozer A. , Sadowski M. , Schmidt H.
Published: March 2003

The construction of a mass and energy analyzer applicable for studies of ion streams generated by plasma focus facilities is presented. An appropriate ion extractor (skimmer) system is described. A simple calibration method of the device is also given.
Simple apparatus for testing the line optical thinness in a free burning arc
Authors: Buchet G. , Castro A. , Haug R.
Published: March 2003

An optical system has been developed which allows measurement of light absorption at a given wavelength in the column of a free burning electric arc by comparison of the direct and back reflected light intensities. The difficulties arising from arc movements are avoided by using a corner cube reflector.
Fabry–Perot cavity pulsed Fourier transform microwave spectrometer with a pulsed nozzle particle source
Authors: Balle T. J. , Flygare W. H.
Published: March 2003

We describe the design, construction, and operation of a new type of microwave spectrograph which allows the measurement of the resonant transitions of transient or otherwise short-lived species. The spectrograph is composed of three parts: a Fabry–Perot cavity, a pulsed supersonic nozzle as a source for the sample, and the pulsed microwave Fourier transform method. Following a detailed discussion of the three above components in the spectrograph, the operation of the entire system is described and several examples are given.
Digital inelastic electron tunneling spectrometer
Authors: Dargis A. G.
Published: March 2003

A computerized inelastic electron tunneling spectrometer designed for use in practical analyses is described. Spectra are obtained by measuring the first derivative of current vs voltagg using a first harmonic detection technique and then calculating the second derivative using a linear least squares fit of the first derivative segments. This method provides convenient qualitative and quantitative comparisons with conventional infrared spectra.
Diamond anvil high-pressure cell for Raman spectroscopy
Authors: Hirsch K. R. , Holzapfel W. B.
Published: March 2003

A design of a diamond anvil cell is described where a single crystal of sapphire is used for the backing of one anvil with the advantage of an enlarged aperture at an extended pressure range. The selection of diamond anvils with low luminescence at excitation with the Argon Ion laser is discussed. Procedures to control the stresses in samples at very high pressures are given and illustrated by Raman spectra of D2O.
Improved technique in electron stimulated desorption ion angular distributions
Authors: Niehus H. , Krahl-Urban B.
Published: March 2003

An improved technique for the measurement of ion angular distributions of electron stimulated desorption (ESDIAD) has been developed. The use of a chopped electron beam in connection with a gated detector system significantly reduces the background in the ESDIAD patterns. A comparison of experimental data obtained with the improved scan and the conventional display technique is presented. The essential advantages of the new method are increased sensitivity, low background, high-angular resolution and ion energy determination at any desired point of the ESDIAD pattern.
New principle of contactless lifetime determination in semiconductor wafers
Authors: Hlávka J.
Published: March 2003

The principle of contactless determination of excess carrier lifetime or diffusion length in semiconductor wafers employs the magnetic flux created by the photomagnetoelectric (PME) current. Under certain conditions, the measured signal is nearly proportional to the lifetime according to a simple theory in which one-dimensional diffusion is considered. Experimental verification of the theory is presented. A sample region of a few square millimeters is sufficient for lifetime determination and lifetime up to 10−7 s or less is measurable by the method.
Externally quenched air counter for low-energy electron emission measurements
Authors: Kirihata H. , Uda M.
Published: March 2003

An air-filled counter with two grids serves to detect and measure low-energy electrons emitted into air from a solid surface. The grids are provided for quenching of a counter discharge caused by an incident electron, and for protection of a sample from positive ions produced during the discharge. The gridded counter operates well with the aid of electric equipments, e.g., amplifiers, pulse generators, and a scaling circuit. The air-filled counter was then successfully applied to the measurements of photoelectron emission and exoelectron emission.
Windows for x-ray diffraction experiments
Authors: Ewen D. A. , Wirth F. W. , Hallock R. B.
Published: March 2003

The scattering properties of a number of substances potentially suitable as windows for x-ray diffraction studies are measured. The study includes a variety of plastics, epoxies, and metal foils. Measurements are reported for a fixed target configuration such as is used in isotropic liquid studies over a range in scattering angles 2 °⩽Θ⩽75 ° for CuKα radiation.
Low-shear, small volume viscoelastometer
Authors: Zaner K. S. , Fotland R. , Stossel T. P.
Published: March 2003

A simple viscoelastometer is described which can measure dynamic moduli in shear of less than 0.01 dynes/cm2 and requires a sample volume of less than 0.5 ml. The principle of operation is to follow the motion of a probe, generated by the tilting of the table on which it is mounted. The probe is suspended from a knife edge and generates a shear stress in the material. Calibration data using 100% glycerol is presented.
Apparatus with nanosecond field transition times for field reversal studies of surface processes at high temperatures
Authors: Holmlid Leif , Lönn Benny , Olsson Jim O.
Published: March 2003

A new type of field-reversal apparatus is described. It is intended for desorption and surface reaction studies in systems with surface ionization. The problems of mechanically modulating the molecular beam are circumvented by instead reversing the electric field outside the surface and thus perturbing the steady-state desorption conditions. The short field reversal time of ⩽ 10 ns with a 90 V voltage step is reached by using VMOS transistors with optoisolated driving circuits. The ions from the ionizing surface are converted to electrons on a Cu–Be dynode. The electrons give photons in a scintillator, and the photons are detected by a photomultiplier outside the vacuum wall. The apparatus dependent signal rise time is around 40 ns, which means that surface processes with very short characteristic time constants can be measurable.
Intense subnanosecond nitrogen laser system for use in flash photolysis experiments
Authors: Rayner D. M. , Hackett P. A. , Willis C.
Published: March 2003

A simple oscillator–amplifier system has been constructed. The system allows the amplification of short (300 ps), intense (40 μJ) pulses from an atmospheric pressure nitrogen laser. Pulses of up to 0.5 mJ energy, ≊1.7 MW peak power, were routinely obtained.
LC oscillators using the operational amplifier pole
Authors: Mohan P. V. Ananda
Published: March 2003

It has been shown that Lambeck’s LC oscillator generates oscillations because of the finite Gain–Bandwidth Product of the operational amplifier. Conditions for oscillation and frequency of oscillation are derived assuming both a single-pole and two-pole model for the operational amplifier.
Computer-controlled timing for multilaser experiments
Authors: Muller D. F. , Egger H. , Yost B.
Published: March 2003

A computer-based system has been developed to control the timing sequence in multilaser experiments. In particular, it has been used to compensate for the long-term drift, ∼50 ns/4 h, associated with thyratron-switched excimer lasers.
Density and electrical conductivity measurements of conducting liquids at high temperatures and pressures—application to tellurium
Authors: Barrue R. , Perron J. C.
Published: March 2003

Experimental methods are presented for the measurement of mass density and electrical conductivity of liquids. Density is measured by a new thermometrical method using a resistive detector, and conductivity by a standard four probe method. An application is given to tellurium and density–conductivity data are obtained in the temperature range of 450°–800°C and the pressure range of 30–1500 bars.
Multichannel scanning radiometer for remote sensing cloud physical parameters
Authors: Curran R. J. , Kyle H. L. , Blaine L. R. , Smith J. , Clem T. D.
Published: March 2003

An instrument for remote observation of cloud physical properties was designed and fabricated. As part of a larger payload, it was tested in a series of aircraft flights on the NASA CV-990 in the summer of 1976 and the NASA WB-57F in the summer of 1979. The instrument is a scanning radiometer with six channels in the near infrared and one channel in the thermal infrared. The optical techniques employed, and the mechanical and electrical design implementation of the instrument, are described. Early results of the data gathered using this instrument are presented to indicate the instrument performance.
Rotating flume with uniformly flowing, linear stratified water
Authors: Gershenfeld Neil , Frazel Robert E. , Whitehead John A.
Published: March 2003

A new flume is described which contains a rotating laminar flow with a linearly varying temperature distribution from top to bottom, making it useful for a number of model experiments in geophysics. Some experimental results in selective withdrawal from this apparatus are presented as examples of the types of problems that can be addressed.
Automated analyzer for aircraft measurements of atmospheric methane and total hydrocarbons
Authors: Cofer W. R. , Purgold G. C.
Published: March 2003

An automated methane/total hydrocarbon analyzer was developed and flight tested that produced alternate methane/total hydrocarbon measurements every 7 s, providing the spatial resolution needed for regional hydrocarbon measurements at aircraft speeds. The sensitivity of the analyzer to oxygen and water vapor interference was characterized at appropriate concentrations. A technique to periodically measure atmospheric oxygen was determined to be necessary for accurate hydrocarbon measurements and incorporated into the analyzer. A data collection methodology was developed to minimize errors resulting from changes in flame ionization detector sensitivity at different altitudes (pressures). Selected aircraft data acquired during the 1979 Southeastern Virginia Urban Plume Study are presented to illustrate instrument performance.
Pulsed thermistor technique for measuring very low liquid flow rates
Authors: Briggs-Smith M. , Piscitelli S. , Livrea A.
Published: March 2003

In order to monitor perfusion during certain surgical operations a simple instrument for measuring the rate of flow of a liquid in the range 2–20 ml/min was developed and has proved useful in the laboratory. A miniature thermistor is used as the measuring probe and a pulse technique to reduce heat dissipation in the liquid. The circuit described is self-oscillating and its frequency is proportional to the liquid flow. A frequency-to-voltage converter allows a recorder to be driven directly but the response is not linear, the sensitivity being much higher for the lower rates of flow (i.e., recorder scale expanded at the lower end). The dimensions of the measuring cell and methods of temperature compensation are discussed. Calibration curves are shown as well as a typical flow recording. The same circuit may be adapted to measure flow in a gas.
Automated control and data acquisition for a small dilution refrigerator
Authors: Haase David G.
Published: March 2003

An automatic temperature controller and data acquisition system for use with a dilution refrigerator is described. The unit is controlled by a 16-bit home microcomputer and operates and reads a resistance bridge, capacitance bridge, and temperature controller. Interfacing is achieved with common components and minimum additional wiring. Flexibility is retained in the software to allow application to several types of measurements.
Capacitive measurement of high dc voltages
Authors: Wolzak G. G. , Bekkers J. A. G. , van der Laan P. C. T.
Published: March 2003

This paper describes a new technique for the capacitive measurement of high dc voltages, based on the principle of consecutive differentiation and integration. A measuring electrode acts as the differentiating high-voltage capacitor; the electric flux to the measuring electrode can be intercepted by a movable shield. The signal is integrated with a commerically available integrator. The method has excellent accuracy and linearity, while the long-term stability is determined by the drift of the integrator. Calibration is only necessary after a change in the high-voltage circuit. The system is sensitive to corona, but the onset of corona can easily be observed by the operator. The described principle can also be used to measure 60 Hz and impulse voltages.
Performance characteristics of a circular multicusp neutral beam source
Authors: Obiki T. , Sasaki A. , Sano F. , Uo K.
Published: March 2003

The performance of the Heliotron-E neutral beam system, composed of intense cylindrical magnetic multipole bucket sources and beam line facilities, has been investigated. The investigation of the influence of the filament shape on the arc discharge stability shows that a wide-hairpin shaped filament results in more stable arc discharge without increasing the arc voltage than does a narrow-hairpin filament. An electrolytic polishing process has been tested for surface treatment of the Molybdenum grid and found to be very effective in reducing the number of conditioning shots. Beam extraction experiments show that a single bucket source can deliver the total beam current of 35 A at the accelerating voltage of 30 kV with the corresponding power transmission efficiency of more than 85% at the focal point of the grid curvature, the minimum beam divergence is less than 1.15° and the proton yield of the source is above 85%. Measurements of the equivalent gas line density in the neutralizer cell suggest the existence of the gas flow process different from a standard vacuum model.
Hollow cathode discharge as a plasma source for H— production
Authors: Hershcovitch A. , Prelec K.
Published: March 2003

Experiments have been performed on a hollow cathode discharge to test the feasibility of an efficient H— production. When a negatively biased converter electrode was placed in the plasma column of the discharge, a current density of up to 2.7 A/cm2 was recorded. Strong evidence was found for an H— surface production with a lower limit of about 0.3 A/cm2 at the converter.
Subnanosecond time-correlated photon counting spectroscopy with atmospheric pressure nitrogen laser pumped dye lasers
Authors: Imasaka Totaro , Kawabata Yuji , Ishibashi Nobuhiko
Published: March 2003

Tunable dye lasers pumped by a transversely excited atmospheric pressure nitrogen laser have been constructed and operated at the repetition rate up to 1.2 kHz with spectral resolution of 0.2 nm. The high repetition rate of the nitrogen laser is made possible through the use of a closed-cycle transverse gas flow system. The tunable dye lasers are combined with a time-correlated single photon counting system for the purpose of measuring nanosecond fluorescence decay. The dye laser pulse, which has an intrinsic <400 ps FWHM, is 740 ps when measured by this laser fluorimeter. This value appears to be characteristic of the transit time spread in the photomultiplier tube. The fluorescence decay curve of fluorescein could be measured at a concentration of 3.2×10−11 M with a fluorescence spectral resolution of 0.5 nm. The fluorescence lifetimes of fluorescein and benzo(a)pyrene were determined to be 5.05±0.05 and 44.18±0.05 ns, respectively. Comparisons with cavity-dumped and mode-locked dye laser excitation systems are described, with emphasis on application to spectroscopic studies.