bluuebunny/crossref_metadata_2025 huggingface dataset:
Cavitation as Artifact in Stopped Flow Experiments
Authors: Wong Mo-Mui , Schelly Z. A.
Published: February 2004

The time resolution of stopped flow devices is limited by the time required for homogeneous, rapid mixing. At high enough flow velocities cavitation occurs in the liquid, which at high sensitivity obscures optical detection in the early history of the reaction mixture. In a Gibson-Milnes type stopped flow apparatus, in the flow rate range of 5–10 m sec−1, forced vortex or inertial breakdown is the major mechanism of bubble formation, depending on the way of stopping. The amplitude and lifetime of the effect are reported in pure water, methanol, and benzene as a function of mixer design, flow velocity, mixing ratio, temperature, way of stopping, as well as way of detection.
Helical Resonator for VHF SQUID Operation
Authors: Corruccini L. R.
Published: February 2004

A helical resonator for SQUID magnetometer operation in the 30 MHz-1 GHz frequency range is described. The device offers a convenient means of utilizing the expected linear increase in SQUID sensitivity with operating frequency throughout this range. Experimental results which demonstrate this effect at 460 MHz are presented.
A Study of the Ion Beam Intensity and Divergence Obtained from a Single Aperture Three Electrode Extraction System
Authors: Coupland J. R. , Green T. S. , Hammond D. P. , Riviere A. C.
Published: February 2004

Experimental results are given for the perveance and beam divergence of a single aperture three electrode extraction system using helium ions at energies between 10 and 30 keV. The aperture radii, the electrode thicknesses, and the spacings were varied and from the results a preferred design was obtained for use in a multiaperture array. The most critical parameter was the ratio (S) of the radius of the first aperture to the distance between the first and second electrodes, the highest current density being obtained at values of this ratio less than 0.5. The optimum beam divergence observed corresponded to a Gaussian beam profile with a width (ω) of ± 1.2° at 2 m from the source. The measured perveance at small values of S and at minimum ω lay between 75% and 90% of the value predicted on the basis of a simple model using the Langmuir-Blodgett formula for the spherical diode.
UHV-Compatible Collimator and Faraday Cup Assembly
Authors: Musket R. G. , Taatjes S. W.
Published: February 2004

A versatile UHV-compatible collimator and Faraday cup assembly has been designed for studies that utilize ion beams. The collimator structure consists of two solid copper gaskets with small diameter holes for ion beam collimation and an electron stripper for removel of low energy electrons from the ion beam. Highly accurate ion current measurements have been made possible by appropriate biasing of the demountable Faraday cup, which is supported from the collimator structure. The assembly should also be appropriate for many studies employing electrons
A Dynamic Mass Spectrometer for the Study of Laser-Produced Plasmas
Authors: Oron Moshe , Paiss Yehuda
Published: February 2004

A method of multichannel analysis of ions blown off laser-produced plasma is described. The ions are analyzed in a time-of-flight tube followed by a dynamic, capacitorlike, analyzer. This combination enables one to determine simultaneously the relative yield and energy distribution of all the ions created in one laser shot. Design considerations are presented together with some typical experimental results. The spectrometer is currently being used for the diagnostics of laser-produced plasmas.
A New Zero-Field Paramagnetic Resonance Spectrometer
Authors: Bernstein E. R. , Dobbs G. M.
Published: February 2004

The construction of a new zero-field paramagnetic resonance (ZFPMR) spectrometer is discussed. Spectrometer organization and construction details are presented for both resonant cavities and broadband traveling-wave helices as sample holders. A new circuit diagram for a square wave magnetic field modulator with fast rise time is given. The performance of each kind of spectrometer is discussed with particular emphasis on investigation of paramagnetic rare earth ions with zero-field splittings in diamagnetic host lattices.
Signal Conditioning Electronics for a Laser Vector Velocimeter
Authors: Crosswy F. L. , Hornkohl J. O.
Published: February 2004

A type of laser velocimeter termed a laser vector velocimeter (LVV) resolves the 180° directional ambiguity problem of the conventional laser velocimeter by exploiting optical frequency translation techniques and frequency division demultiplexing techniques. This paper defines some fundamental LVV system signal characteristics and signal conditioning and data acquisition problems. The signal conditioning electronics for a three velocity component LVV system are described. Data obtained from atmospheric wind velocity measurements using a two velocity component LVV system are presented to illustrate the vector velocity measurement capabilities of the system. The operational status LVV systems presently in use are two orthogonal velocity component units. However, a laboratory status LVV system has been used to make three-dimensional vector velocity measurements.
A Reciprocal Kelvin Temperature Sensor
Authors: Fowler L. , Trump W. N.
Published: February 2004

A simple bridge circuit using a platinum resistance thermometer is described which generates a signal proportional to 1/T. The error is less than 0.1% over wide ranges. Direct plotting of the temperature response of appropriate physical systems in a useful form is thus expedited. The superiority of platinum over other materials is discussed.
Specific Heat Measured at High Pressures by a Pulse Method
Authors: Loriers-Susse C. , Bastide J.-P. , Bäckström G.
Published: February 2004

The classical electric pulse technique has been adapted to measurements of specific heat at high pressure. A wire specimen is heated by a 100 μsec pulse, stabilized at I = 50 A. The resulting temperature rise is extracted from the voltage drop U over the sample by means of a bridge circuit. The specific heat is obtained from the formula cp = C(T,P)U I / m ė, where C(T,P) is a function to be experimentally determined for a given sample, m the mass of the sample, and ė the time derivative of the bridge output voltage. A procedure has been developed for in situ corrections of ė for heat loss to the medium surrounding the wire. Digital techniques are used for the pulse analysis. The method has been used to ascertain the pressure dependence of cp for Cu up to 100 kilobars at room temperature. The relative change in cp was found to be 2.8 × 10−4/kilobar.
A Pneumatic Sample Changer For Gamma-Ray Spectroscopy
Authors: Massoni C. J. , Fones R. V. , Simon F. O.
Published: February 2004

A gravity-feed, pneumatic-ejection sample changer has been developed. The changer is suitable for both flat and well-type detectors and permits the continuous use of gamma-ray spectroscopy equipment 24 h a day, 7 days a week. The electronic circuitry has a fail-safe feature which stops the operation of the changer if a malfunction occurs.
Influence of an Inhomogeneous Phase on the de Haas-van Alphen Effect
Authors: Paton B. E. , Slavin A. J.
Published: February 2004

The causes and results of inhomogeneous phase on oscillatory magnetization are considered and methods for determining experimentally whether phase inhomogeneity is producing significant deviations from the Lifshitz-Kosevich theory are discussed. General expressions are derived for (i) the reduction in oscillation amplitude and (ii) the relative phase shifts between harmonics which result from inhomogeneous phase. For the specific case of a parabolic field distribution, several universal curves are given for estimating the size of field inhomogeneity effects as a function of the magnetic field strength and of the sample position along the field axis. The effects on the measured values of the collision parameter and absolute amplitude are also considered and these effects are illustrated by experimental results from oscillatory magnetization and magnetostriction measurements.
Instantaneous Temperature Measurement
Authors: Praul Samuel H. , Hmurcik Lawrence V.
Published: February 2004

Measurement of temperature using a thermocouple or any other device requires a certain length of time. This time interval is of the order of magnitude of the thermal time constant of the measuring device. Here we describe an electronic circuit which makes the temperature measurement ``instantaneous.'' This is accomplished by combining the temperature at any instant with the rate of change of temperature. Thus the only limiting factor becomes the electronic time constant of the circuits involved. We have used our device in absolute measurement of optical power and have found that the typical time necessary for a temperature measurement can easily be 10–3 × the thermal time constant of the measuring device.
The Parallel Plate Condenser as a Relativistic Particle Analyzer
Authors: Proca Georges A.
Published: February 2004

A fully analytical study of the properties of the parallel plate electrostatic spectrograph in the relativistic region is presented. The formalism used allows for an exact tridimensional treatment whereby the coupling between the polar angles θ, φ appears through the quantity α = −dφ/dθ only while the explicit expression of α(θ, φ) remains unspecified. This freedom in the choice of the relationship φ = f (θ) may be used to improve on the properties of the instrument. The main consequence of the relativistic effect is to alter the shape of the focal surface in a way which reduces the versatility of the instrument when changes in energy range are considered. This stems from the dependence of θ, φ on β = v/c introduced by the second order focusing condition. It is shown that versatility is restored to a considerable extent for suitable choices of φ = f(θ). The relative merits of various choices are discussed. A numerical calculation of the basic parameters of a spectrograph suited for astrophysical research is given stressing the possibility of flying such an instrument aboard a Space Shuttle within the Post Apollo program.
Carbon and Case Depth Determination in Steel by Electron Microprobe
Authors: Swaroop B.
Published: February 2004

Using the high velocity helium jet and the cold finger simultaneously, the anticontamination of the sample in vacuum chamber of the probe can be achieved for at least the first 12 min. A limit of detection (LOD) of carbon of 0.03 wt % in steel samples has been achieved. Further, it has been shown that the anticontamination technique extends the general usefulness of the electron probe for obtaining the carbon concentration profile of carburized steel.
Velocity Filtering for Secondary Ion Quadrupole Mass Spectrometer
Authors: Šroubek Z.
Published: February 2004

A simple method of secondary ion velocity filtering for sputter ion mass spectroscopy is described. The experiments on Ni surfaces show that the method allows sorting of secondary ions according to their adsorption energies and thereby enhances the analytic capabilities of the spectrometer.
A Leak-Free Gas-Switching Valve for Isotope-Ratio Mass Spectrometry
Authors: James Alan T.
Published: February 2004

A simple gas-switching valve system for dual feed isotope-ratio mass spectrometry is described, for which no gas mixing exists.
Cleavage Device for Alkali Halides
Authors: Pelá C. A. , De Oliveira J. X. , De Arguello Z. P.
Published: February 2004

This Note describes a cleavage device for alkali halides. This device was used in our laboratories for crystals of NaCl, KCl, and LiF with very good results. For this last crystal special care should be taken due to its cleaving characteristics; this harder material is quite difficult to handle. Our success in cleaving LiF under vacuum makes perhaps of general interest a description of the cleaving device. The freshly vacuum cleaved surface offers the possibility of initial nucleation studies of evaporated single crystal thin films. In order to simultaneously meet the needs of heating and high vacuum, the device is made of stainless steel.
Removal of Evaporated Tungsten from Glassware
Authors: Burns Robert W.
Published: February 2004

Tungsten heaters often deposit opaque films on glassware. This Note describes the use of household bleach (hypochlorite solution) to completely remove these coatings. The process is accelerated by warming the bleach, and in all cases there is no attack on the glassware.
Apparatus for Contactless Measurement of the Photomagnetoelectric Effect
Authors: Hlávka Jan , Širůček Ivan
Published: February 2004

The new apparatus for contactless measurement of the photomagnetoelectric (PME) effect is described and its analysis is carried out. By this technique the contactless measurement of lifetime and surface recombination velocity in semiconductors is made possible.
Stroboscopic Observation of Magnetic Domain Wall Motion with a Light Emitting Diode
Authors: Ikuta Takashi , Shimizu Ryuichi
Published: February 2004

A simple stroboscopic apparatus using a light emitting diode as a light pulse source is described for the observation of dynamic response of domain walls under high speed magnetic pulse field.
A Safe Superfluid-Tight Pressure Cell
Authors: Rosso M. J. , Oversluizen T.
Published: February 2004

A safe superfluid-tight pressure cell in which crystals of helium are grown has been developed. Incorporated in the cell are three unique devices, two of which, a room temperature pump-out valve and a rupture disc, are described in this paper.
An Interpolator for Reading Plots in Technical Journals
Authors: Wolke Robert L.
Published: February 2004

A simple device is described by means of which one can read accurate numerical values from the minuscule data plots which are published in scientific journals.
Computer Differentiation of dc Soft X-Ray Appearance Potential Spectra
Authors: Baun W. L. , Chamberlain M. B. , Solomon J. S.
Published: February 2004

An alternative method of measuring soft x-ray appearance potential spectra is presented. In this method no modulation, tuned tank, or lock-in amplifier are used. Rather, the dc current induced in a simple Park-Houston type detector is measured and digitized, and the data are placed on paper tape for computer processing and differentiation. The computer differentiated spectra compare favorably with spectra obtained by modulation technique.
A Compensating Device for Parasitic Beat Signal in NMR Double Resonance Experiments
Authors: Bucci P. , Rolla P. A. , Veracini C. A.
Published: February 2004

A solid state device to compensate the NMR double resonance beat signal is described. A beat signal reduction of a factor greater than 102 has been reached by using a single coil NMR spectrometer. The compensating effect in a tickling experiment on the AB spectrum of 2-bromo-5-chlorothiophene is shown.
A Magnet Sweep Controller
Authors: Elliott M. T. , Blackstead H. A.
Published: February 2004

This paper describes a circuit which can be used to control the sweep of an electromagnet between preset field limits and provide sychronizing pulses for a signal averager. Two operating modes are provided: manual and automatic. In the automatic mode the field sweeps continue indefinitely between the two preset limits. In the manual mode, the sweep is terminated when a field limit is reached. The controller requires an input voltage proportional to the magnetic field which can be easily obtained from a Hall probe.
Electron Transmission Spectroscopy for Calibration of the Energy Scale in Optical Excitation Experiments
Authors: Kurzweg L. , Burns D. J.
Published: February 2004

Electron transmission resonances observed using a retarded energy modulation technique are used to calibrate the electron energy scale for an optical excitation apparatus.
Latching Solenoid Valve
Authors: Savoie R.
Published: February 2004

A latching solenoid valvue, designed for the protection of vacuum systems, is described. In case of power failure, the latching mechanism is released by the action of a charged capacitor and the valve seals off the main part of the system. An air vent is incorporated in the valve.
An Adjustable rf-Biased SQUID
Authors: Strayer D. M. , Catchings R. M. , Oversluizen T. , Kitchens T. A.
Published: February 2004

A symmetric rf-biased point-contact superconducting quantum interference device, which can be adjusted while in operation at low temperatures, is described. The device retains the inherent stability and other features of the symmetric rf-biased SQUID while increasing its flexibility, reliability, and even convenience with a simple adjustment feature.
Opening Time of Brittle Shock-Tube Diaphragms for Dense Fluids
Authors: Thompson P. A. , Loutrel W. F.
Published: February 2004

Metal diaphragms have proved unsuccessful for use with dense fluids. Thin mechanically fractured diffusion-strengthened glass diaphragms are successful and have opening times which correlate well with a simple theory.
Measurement of internal stress in thin films
Authors: Paesler M. A. , Fritzsche H.
Published: February 2004

A description is given of a device used to measure internal stresses in thin films vapor deposited on cantilevered beam substrates. The stress-induced deflection of a substrate used as the electrode of a capacitor causes a shift in the null of a capacitance bridge. A tuned amplifier is used to detect the shift in capacitance null indicating the value of the stress in the film. Our circuitry provides a resolution of 0.02 pF which results in a stress sensitivity for our apparatus of 5×107 dynes/cm2. This enabled us to determine the stress in a 103 Å film of amorphous germanium to within 5%. Inexpensive integrated circuits are used to generate and process the ac signal.
Velocity distributions in metastable atom beams produced by coaxial electron impact
Authors: Rundel R. D. , Dunning F. B. , Stebbings R. F.
Published: February 2004

A technique is described for producing a beam of metastable atoms utilizing coaxial electron impact excitation. Measured velocity distribution functions are presented for metastable helium, neon, and argon. Characteristics of the coaxial source are compared with those of a transverse excitation source.
A digital velocity transducer
Authors: Stone Roger R.
Published: February 2004

A new velocity gauge that allows use of as many as 64 gauges per signal cable has been developed and tested. The gauge, designated ``make-wire,'' uses moving wires contacting a printed circuit board to provide a digital signal consisting of a series of electrical offs and ons. The distance and the time between these discrete electrical changes are known; therefore, the velocity of the moving system can be determined. The gauge allows scaling up or down to obtain a sample exposure area as small as 0.6 cm2. The gauges have been used in an underground nuclear effects test. The minimum velocity measured with the present configuration was estimated to be 50 cm/sec.
Pyrgeometer measurements from aircraft
Authors: Albrecht Bruce , Poellot Michael , Cox Stephen K.
Published: February 2004

An Eppley Laboratory pyrgeometer was tested in several different modes of operation to determine its ability to measure infrared irradiance from an aircraft platform. During the initial tests, the instrument output varied by 30–40 W m−2 as the incident solar irradiance or air flow over the KRS-5 dome changed. The long pass filter (the KRS-5 dome) was found to be opaque to radiation of wavelengths shorter than 3.6 μ. Hence, the fluctuations described above may be attributed to changes in the temperature of the filter. The pyrgeometer output was studied as a function of the incident infrared irradiance and the temperature difference between the sensor surface and the KRS-5 dome. Laboratory tests verified this dependence and showed that by utilizing the thermopile cold junction and dome temperatures, infrared irradiances may be measured with a precision of ± 1.7 W m−2. Although not the original intent of this research, it is shown that the KRS-5 shielded pyranometer may be used to measure infrared irradiance with a precision of ± 2 W m−2 in a ground station installation. However, in order to realize the precision value mentioned above, two precautions must be taken. First, the temperature of the KRS-5 dome must be monitored; and second, the entire instrument should have sufficient air flow over it to minimize temperature differences between the KRS-5 dome and the thermopile cold junction. The pyrgeometer was also mounted in an upward-looking configuration on an aircraft platform and measurements were made at constant pressure levels under clear sky conditions to approximate a constant irradiance. It was found that the intense flow over the instrument minimized the effect of the solar heating of the dome. Infrared irradiances measured on a day/night flight comparison differed by an average difference of 3.5 W m−2. rms deviations about the mean value at any level were less than ± 2.5 W m−2. Observed downward irradiance divergences differed from values calculated using a radiative transfer model by less than 0.3 W m−2 mb−1. The ventilation, however, did not eliminate the sink-dome temperature differences because the temperature response of the thermopile heat sink is an order of magnitude slower than that of the KRS-5 dome; therefore, horizontal fluctuations of air temperature or abrupt changes of altitude result in erroneous output values. An attempt was made to determine an empirical correction for air temperature fluctuations from the aircraft air temperature data. No general correction factor relating temperature and output changes could be determined. However, individual applications of such an empirical relationship did reduce rms deviations of the output to less than 2 W m−2.
Laser-generated pulsed atomic beams
Authors: Friichtenicht J. F.
Published: February 2004

The irradiation of thin films of solid material by a moderate energy (0.5 J/pulse) Q-switched ruby laser beam has been used to produce intense pulses of neutral atoms and molecules in the 1 to 10 eV energy range. For a given total laser beam energy, both the flux and energy range of atoms within the pulse can be varied within limits by adjusting the energy density of the laser light at the target surface. As observed at a distance of 60 cm from a thin BiF3 compound target, the flux of 5 eV fluorine atoms from a typical burst was estimated to be about 1.3×107 atoms/cm2/sec. For the same burst, the flux integrated over the 1 to 10 eV range yields a value of ∼2×1013 atom/cm2. Similar results were obtained with aluminum and uranium thin films.
Low temperature thermometry in high magnetic fields. III. Carbon resistors (0.5–4.2 K); thermocouples.
Authors: Sample H. H. , Neuringer L. J. , Rubin L. G.
Published: February 2004

The magnetoresistance of 1/2 W, grade 1002, Speer carbon resistors with nominal room temperature resistances of 100, 200, and 470 Ω and of 1/8 W, 10 Ω, Allen-Bradley resistors was measured at various temperatures between 0.5 K and 4.2 K in static magnetic fields up to 140 kG. In this temperature range the maximum magnetic field induced temperature error of these thermometers amounts to 14%. The Allen-Bradley unit is to be preferred over the Speer resistors for use as a thermometer in a magnetic field for the following reasons: it has a more reproducible and regular magnetic field dependence, greater temperature sensitivity, and its much smaller physical size facilitates its incorporation in experimental apparatus where dimensions are restricted. One drawback of the 10 Ω Allen-Bradley resistor is its relatively high impedance at the lowest temperatures. In addition, the effects of magnetic fields up to 150 kG on the characteristics of Chromel P/Au+0.07 at.% Fe and Chromel P/constantan (type E) thermocouples were determined in the temperature range 4.2–45 K. A description is given of the measuring apparatus along with a discussion of possible measurement errors and the necessary precautions which must be observed. The magnetic field induced temperature errors for the Chromel P/Au+0.07 at.% Fe thermocouples are relatively large at temperatures below 20 K, and are nonreproducible between sections of gold-iron wire taken from the same lot. We do not recommend the use of these thermocouples below 20 K at fields greater than 50 kG. In contrast, Chromel P/constantan thermocouples have small, reproducible temperature errors up to 150 kG for 4.2≤T≤45 K. The data indicate that even in strong magnetic fields, at temperatures above 20 K, it is practical to correct for magnetic field induced temperature errors when using thermocouples. The reproducibility of the field induced errors in wires from different sources is still an open question and is worthy of further investigation.
A strain-modulated electron spin resonance spectrometer
Authors: Boef J. H. den , Henning J. C. M.
Published: February 2004

A new design for an ESR spectrometer, using strain modulation, is presented. The novel features are: (i) The sample is nonresonant, so that single crystals of any size and shape can be investigated; (ii) the loss in mechanical Q-factor, due to the nonresonant technique, is compensated for by using an electrostrictive ceramic (with high piezoelectric constants) instead of quartz; (iii) the whole transducer is kept outside the microwave cavity; (iv) the modulator can be used also at low temperatures (1.2 < T < 400 K). Some illustrative applications are given.
A small retarding field analyzer for Auger electron spectroscopy
Authors: Koch Jürgen
Published: February 2004

A small retarding field analyzer for Auger electron spectroscopy is described. The resolution and sensitivity for chemical investigations is tested with Pd/Ni alloys and adsorbed oxygen.
A detector for high frequency modulation in auroral particle fluxes
Authors: Spiger R. J. , Oehme D. , Loewenstein R. F. , Murphree J. , Anderson H. R. , Anderson R.
Published: February 2004

A high time resolution (HTR) electron detector has been developed for use in sounding rocket studies of the aurora. The detector is used to look for particle bunching in the range 50 kHz–10MHz. The design uses a Johnston Laboratory MM-1 electron multiplier and an onboard frequency spectrum analyzer. By using the onboard analyzer, the data can be transmitted back to ground on a single 93 kHz voltage-controlled oscillator. The detector covers the 50 kHz–10 MHz range six times per second and detects modulation on the order of a few percent of the total electron flux. Spectra are presented for a flight over an auroral arc.
Solid state power supply for high impedance NMR magnets
Authors: Holder Bert E. , Maddux Alvin S.
Published: February 2004

We present design and construction details of an all solid-state power supply suitable for dc electromagnets in the impedance range 500–1300 Ω. Current is limited to a conservative 2 A. Current control is implemented through a series element consisting of cascaded, water-cooled power transistors isolated and regulated to operate at equally spaced voltage intervals within the transistor voltage rating. Current regulation is estimated to be a few parts in 105 for a 10% voltage or load change. Conversion of existing tube-type power supplies to this configuration is detailed.
A fast, large aperture, electromechanical shutter
Authors: Van Hook A. R.
Published: February 2004

This paper describes a fast closing shutter which is capable of closing a 5 cm aperture within 40 μsec to be used to prevent rewrite on high speed drum and synchronous turbine-type cameras.
Target fabrication and positioning techniques for laser fusion experiments
Authors: Friedman W. D. , Halpern G. M. , Brinker B. A.
Published: February 2004

Solid targets of pure deuterium or deuterium-bearing compounds are required for experiments designed to explore the feasibility of laser fusion as a source of energy. This paper deals with three aspects of the targets used in this application, namely, (i) the selection of suitable compounds which provide optimum heating by the laser radiation, (ii) the fabrication of appropriately sized and shaped targets from these compounds, and (iii) the positioning of these targets in laser-irradiation experiments. Spherical targets of lithium deuteride, deuterated polyethylene, and paraffins with diameters of 50–200 μ are considered, as well as 400 μ cylindrical extrusions of deuterium ice. Detailed descriptions are given of the apparatus and techniques used to position these targets in the focal region of the laser radiation.
Computerized control and data acquisition system for quenching and annealing thin metal wires
Authors: Huang H.-C. W. , Berger A. S.
Published: February 2004

In the study of the thermal generation and the annealing of point defects, e.g., vacancies, in metal crystals, it is necessary to have accurate and reproducible control over the thermal history of the specimen. This paper describes a computer-controlled system for the rapid thermal pulsing, quenching and annealing (thermal cycling) of thin metal wires. The system features complete software control of the temperature vs time profile of the sample. Using programmable gain instrumentation amplifiers and a crystal-controlled programmable time base, both rapid and accurate (d T / d t ≤ 106 K/sec; Δ T ≤ ±5 K) control of the thermal cycle is obtained.
Quadrupole fields in circular concave electrodes and poles
Authors: Bosi G.
Published: February 2004

Two-dimensional equipotential models of circular concave quadrupole lenses are investigated. Exact solutions are carried out by the method of conformal mapping and expanded in series of multipoles. Conditions for approximating the ideal quadrupole field are obtained. Slight errors in an earlier, approximate treatment are detected.
A new microcell design for use with large volume NMR tubes. Application for low natural abundance isotopes studied by NMR
Authors: Cargioli J. D. , Williams E. A.
Published: February 2004

A new NMR microcell design for recording the NMR spectra of low natural abundance isotopes, such as 13C, 29Si, 15N, and 17O, when sample size is limited, is described. The new cell makes sample preparation and clean up an order of magnitude easier than with a conventional microcell. Nearly 100% recovery is also possible with the use of this cell design.
Sensitivity of a Mance configured Wheatstone bridge for the determination of internal resistance of a cell
Authors: Mathur S. S. , Bahuguna R. D.
Published: February 2004

Normally the sensitivity of the Wheatstone bridge in the conventional position is not much different from that in the conjugate position. In other words, the sensitivity in the two positions is of the same order. This is true for the case when all the four arms are pure resistances. In this paper we have shown that in Mance's configuration, when the unknown arm consists of a cell, the conjugate position is far more sensitive than the conventional one particularly for higher values of R1/R2, where R1 and R2 are the ratio arms of the bridge.
Mechanical analog calculator for laser gain measurements
Authors: Robinson A. M.
Published: February 2004

A simple mechanical device is described for calculating pulsed laser gain from oscilloscope traces.
Accurately measuring nuclear polarization using a phase sensitive detector
Authors: Potter W. H.
Published: February 2004

A method is presented in which the first Fourier component of the resonance absorption signal is obtained with a phase sensitive detector. This method has several advantages when compared to the usual method of detecting the derivative of the absorption signal with a phase sensitive detector.
Technique to examine surface features in profile using the SEM
Authors: Woods R. T.
Published: February 2004

A new folded replica technique has been developed to view in profile features at the surface of a solid using the scanning electron microscope (SEM). A thin plastic replica of the surface is made and folded over upon itself. Metal is evaporated onto the surface of the folded replica which is then viewed in the SEM in a direction tangent to the fold. With this technique a portion of a surface can effectively be viewed in a direction parallel to the plane of the surface.
An integration circuit for photodiode single-pulse energy measurements
Authors: Dymerski Paul P. , Dunbar Robert C.
Published: February 2004

A circuit was designed for automatic and repetitive measurement of the light energy (peak area) of submicrosecond laser pulses by direct time integration of the light intensity. DC amplification and sample-hold circuitry interface the laser output directly to a computer analog input.
An internal modification to extend the conductance ranges of the General Radio Company type 1615-A capacitance bridge
Authors: Addison J. R. , Stalinski P.
Published: February 2004

As supplied, the General Radio Co. type 1615-A capacitance bridge can accommodate materials having loss tangents only as high as 1.0. A method of extending this capability, which does not involve additional external standards, and their attendant uncertainties, is described. The modified bridge may operate either as originally designed, with no deterioration in original performance, or in one of two new conductance ranges, greater than the original ones by a factor of 100. Slightly more involved calculations, allowing for the increased effect of stray capacitances, are required when the modification is in use. The new ranges must be compared with external precision standards initially in order to determine certain parameters used in these calculations. The results were most satisfactory.
Measurement of plasma wave spectral density from the cross-power density spectrum
Authors: Harker K. J. , Ilić D. B.
Published: February 2004

Determination of the spectral density of plasma waves from the cross-power density spectrum is shown to be simpler than the alternative determination from the cross-correlation function. A device for measuring the cross-power spectral density is described in detail. A model with a bandwidth of 30 MHz has been constructed using integrated circuits, and applied to the study of ion acoustic wave propagation on a plasma positive column. Since it is an analog device, it should be possible to extend the bandwidth for operation into the gigahertz range. Only a fixed delay is required to measure the quadrature component of the cross-power spectral density. These features are in contrast to other correlators and cross-power spectrum analyzers described to date, which are either limited to the low megahertz range, or require a variable delay line.
Phase-sensitive pulse counting in modulated beam mass spectrometry
Authors: Calo J. M. , Bailey A. D.
Published: February 2004

A phase-sensitive pulse counting method, which shows considerable promise as a signal processing technique for modulated beam mass spectrometry, is presented. This method allows near-simultaneous monitoring of mass peaks of interest by fast mass spectrometer scanning, while retaining the advantages of phase-sensitive detection. The electronic system and the molecular beam apparatus are described, and mass spectrometric results for supersonic water vapor beams, obtained with the system, are presented and discussed.
Detection of low energy positrons using spiraled electron multipliers
Authors: Pendyala S. , McGowan J. Wm. , Orth P. H. R. , Zitzewitz P. W.
Published: February 2004

The positron detection efficiency of a Spiraltron is determined using a conventional two-gamma coincidence detection system as a reference. Under the experimental conditions described in this note, the efficiency of the Spiraltron is found to be nearly 90%, as compared to an ∼2% efficiency of the two-gamma system employed in our laboratory.
Simple, multiple arc, dielectric switch applied to a theta pinch
Authors: Nunnally W. C. , Kristiansen M. , Hagler M. O.
Published: February 2004

The construction and the operating details of a simple, field distortion, dielectric switch first used by Martin at A.W.R.E. and later extensively investigated by Dokopoulos at Jülich are presented. The switch, triggered by a small, fast Marx circuit, holds off approximately 110 kV and switches 70 kV at 500 kA with an inductance of 12 nH. The switch produces multiple arcs through the switch package without meticulous switch package preparation, with pitted and scarred switch electrodes, and with a relatively slow trigger system. The dielectric switch is used in a fast theta pinch system and is designed to facilitate ease of operation, switch package preparation, and repeatable performance.
A helium-cooled optical system for low-background measurements in the far infrared
Authors: Passenheim B. C. , Kitterer B. D. , Flanagan T. M. , Denson R.
Published: February 2004

This paper describes the construction and calibration of a complete optical system, built entirely within a standard helium cryostat, for making absolute measurements of radiation-induced luminescence and optical absorption in the infrared range out to 25 μ. Helium cooling the entire optical system reduced the thermal background radiation at the detector to approximately 1 × 109 photons/cm2-sec (λ<25 μ). Although helium Dewars for radiation effects have been described previously, to our knowledge no similar instrument for measuring radiation-induced optical effects has been reported.
An inexpensive automatic telescope dome controller
Authors: Brookes Michael
Published: February 2004

An automatic telescope dome controller which makes no use of computers has been developed and used. The device uses read-only memories to derive the correct dome position from a digital readout of the telescope position. Interpolation is used to reduce the amount of memory required. The controller works equally well on large or small domes and is considerably less expensive and less complicated than existing automatic dome controllers.
Factors influencing the relative frequency stabiltiy of He–Ne laser structures
Authors: Hochuli U. E. , Haldemann P. , Li H. A.
Published: February 2004

6328 Å He–Ne laser structures, made from ultralow expansion materials, suspended in temperature- and pressure-controlled chambers, have shown drift rates in excess of +5 MHz/day. The same structure, evacuated and used as passive Fabry-Perot resonators, suspended in the previous now evacuated chambers, still show a drift rate of the order of +2 MHz/day. Computer simulated mirror model aging shows that relatively large changes of the dielectric constants of the mirror coatings are needed to explain the measured drift. We feel that the dimensional stability of the materials and the properties of the optical contacts used, as well as the behavior of the dielectric mirrors, have to be more carefully investigated.
An analog technique for the measurement of Auger electron currents: Application to sulfur on Ni(110)
Authors: Isett L. C. , Blakely J. M.
Published: February 2004

The conventional potential modulation technique employed in Auger electron spectroscopy measures the derivative of the electron energy distribution (d N / d E). A technique is described for recovering the energy distribution itself and the area under an Auger feature via electronic integration of the measured signal. This integration is conveniently performed using operational amplifier technology. This technique is demonstrated in a retarding field analyzer in the particular case of sulphur in a c(2×2) structure on a Ni(110) surface. The measured area under the sulphur Auger peak follows the square law dependence on oscillator modulation amplitude predicted by Houston. A quantitative comparison is made between the sulphur Auger signal strength, as measured by the area under the Auger peak, and that predicted by the calibration performed by Perdereau for this system. The sulphur (L2,3VV) Auger peak shape in the N(E) spectrum, as obtained by integration, was found to be in good agreement with that observed by other workers.
Gated optical multichannel analyzer for ruby laser scattering from plasma
Authors: Offenberger A. A. , Burnett N. H. , Strilchuk A. R. , Way-Nee D. F.
Published: February 2004

An optical detection system is described which employs a commercial multichannel analyzer, augmented by a flat spectral response image intensifier and Kerr shutter, to provide time-resolved, sensitive detection of plasmascattered ruby laser light. Operating characteristics are discussed and scattered spectra from CO2 laser induced hydrogen plasma are shown.
A simple particle counter for complex detection systems
Authors: Conversi Marcello
Published: February 2004

A new type of particle counter, made sensitive by the application of a pulsed electric field, is described. The counter is comparatively slow, having a sensitive time in the 100 ns region and a recovery time of some 100 ms. Nevertheless, on account of its simplicity of construction, stability of operation and extemely low cost, the counter appears to be a useful tool, especially for complex experiments involving large detection systems. Examples of possible applications to particle physics experiments and to nuclear physics (ionization measurements) are given.
Application of electro-optical image intensification to liquid diffusion studies
Authors: Chiang S. H. , Hatters H. D.
Published: February 2004

This paper describes the development of a radioactive tracer system using an electro-optical image intensifier integrated with a low light level photographic system to permit recording of concentration profiles in liquid systems undergoing diffusion. Diffusivities of liquid components can be rapidly and accurately determined from the resultant concentration-position-time data. Results for the d-glucose-water system at 25°C are presented.
A stripline resonator for ESR
Authors: Johansson B. , Haraldson S. , Pettersson L. , Beckman O.
Published: February 2004

A stripline resonator for ESR is described. Spectra obtained show that the relatively low Q value, as compared with a standard cavity, is to a high degree compensated by the higher filling factor. The same resonator can be used for different frequencies. At low ESR frequencies the size of the resonator is much smaller than that of a cavity. A possibility of obtaining circularly polarized radiation is pointed out.
The use of the interbase resistance of the unijunction transistor as a thermometer in the 20–300 K range
Authors: Janik R. , Lechevet J. N. , Gregory W. D.
Published: February 2004

We have investigated the interbase resistances of 12 General Electric 2N2646 unijunction transistors between 20 and 300 K. Although the resistance is not a single-valued function of temperature, the heavily n-doped silicon chip is an inexpensive thermometer of high sensitivity that is free of thermal cycling or current dependent effects. Its small thermal mass makes it well suited for measurements such as specific heat.
Sealable sample holder for dielectric measurements on hygroscopic solids
Authors: Nanassy A. J.
Published: February 2004

Mating Teflon rings hermetically seal a disk-shaped sample between the plates of a three-electrode system to hold moisture content constant at various temperatures. The sealing joint of the Teflon rings is flexible enough to ensure contact between the electrodes and the sample in spite of variations in the sample thickness.
A simple and inexpensive fluorescein detector
Authors: Engler Peter E. , Calabrese Paul R. , Giori Francis A.
Published: February 2004

A simple and inexpensive fluorescein detector is described that is capable of detecting a solution of approximately one part fluorescein to five million parts of water. The device can be constructed in a laboratory or workshop equipped with the minimum tools and instrumentation. As conceived, the device is used as a leak detector and is designed to activate a relay when an aqueous fluorescein solution exceeding a concentration of one part per five million flows through a quartz tube.
Instrumental broadening of the parallel plate analyzer
Authors: Rayborn Grayson H. , Hsiao Ta-Lee
Published: February 2004

Broadening curves for the parallel plate energy analyzer are presented for Gaussian input kinetic energy distributions, for no angular broadening, and for a uniform angular distribution over ±30 for an analyzer of nominal resolution of forty. Use of the curves is demonstrated on a measured kinetic energy spectrum of Ar+ ions. The broadening curve for two Gaussian functions is given for comparison.
Simple bridge for detection of superconductivity
Authors: Claeson T. , Wingbro T.
Published: February 2004

A very simple instrumentation for superconductivity detection down to the millikelvin range is described.
High sensitivity creep tester
Authors: Raj R. , Chen Y. T. , Van Baren F.
Published: February 2004

A high-sensitivity creep tester has been built to measure creep rates of the order of 10−11 sec−1. The high sensitivity is achieved by measuring the differential displacement between a loaded sample and a reference sample, thus compensating for fluctuations caused by thermal expansion. Creep measurements at these low strain rates should be of importance in the fundamental and applied study of creep in metals, ceramics, and polymers.
An automatic sequential rainfall sampler
Authors: Gray J. , Hage K. D. , Mary H. W.
Published: February 2004

An automatic sequential rainfall sampler has been developed which is capable of operating unattended for periods of days. The pulse produced by a raindrop impacting with a loudspeaker actuates the collection and recording systems. The apparatus records the duration of rainfall and collects samples at a predetermined rate. The samples may be left for a period of weeks before collection. The equipment is battery powered and easily portable. Sample sizes vary between 1 and 20 ml but may be increased to any desired volume.
1000-A cryotrons for superconducting-magnet flux pumps
Authors: Atherton D. L. , Vilbikaitis R. J.
Published: February 2004

Cryotrons are being developed for a low temperature flux pump power supply to energize superconducting coils without the excessive helium boiloff characteristic of high current input leads. The cryotrons have been tested to 1200 A at frequencies up to 40 Hz. For 1000 A, the optimum operating frequency is presently 5 Hz (determined by the current transfer rate and the normal cryotron gate resistance). The cryotron gates are Pb-4% Sb and have a normal state resistance of 6 μΩ (resistivity 3.8×10−7 Ω-cm).
Heat capacity measurement method for bridgewires
Authors: Rosenthal Louis A.
Published: February 2004

A single, full-sine-wave current pulse, of zero average value, adiabatically heats a bridgewire. Due to the electrothermal nonlinearity of the temperature-sensitive wire, a dc voltage which can be related to lumped heat capacity appears across the bridgewire. This dc signal can be readily extracted and interpreted.
Versatile cryostat systems for low-temperature ion-implantation studies
Authors: Stein H. J. , Baxter R. H.
Published: February 2004

The design, use, and performance of cryostat systems for ion implantation at temperatures between 7 and 300 K are described. Special features of the cryostat systems are: (i) a trapped-gas heat exchanger; (ii) a sliding gate valve to allow separation from the implantation line vacuum; (iii) a rotatable tail section with optical windows; and (iv) ion-beam location plates. The systems have been used successfully to study the effects of ion implantation into solids at controlled temperatures between 7 and 300 K, and to study isothermal and isochronal annealing of solid materials following implantation at low temperatures.