bluuebunny/crossref_metadata_2025 huggingface dataset:
Portable 3He detector cryostat for the far infrared
Authors: Radostitz J. V. , Nolt I. G. , Kittel P. , Donnelly R. J.
Published: March 2003

A portable 3He cryostat for far infrared detection applications is described. The cryostat has been used for a number of years in aircraft- , observatory- , and laboratory-based research. Some related studies of various bolometric materials are also reported.
Optical technique for the study of convective diffusion from falling drops
Authors: Pandya T. P. , Saxena A. K. , Srivastava B.C.
Published: March 2003

A recently developed deflection mapping technique has been exploited for measurement of rate of mass transfer from a liquid drop falling freely in another liquid medium. Results have been found to be in good agreement with theory. Simultaneously, measurement of the diffusion coefficient is also reported.
Appartus for high-resolution surface tension measurement
Authors: Magerlein J. H. , Sanders T. M.
Published: March 2003

We describe an apparatus for measuring surface tension of insulating liquids by capacitive sensing of capillary rise. Two guarded coaxial capacitors with different gap widths are connected to permit liquid to flow between them. The higher capillary rise in the narrow-gap capacitor is balanced by a dc voltage applied to the wide capacitor by a servosystem. In a measurements of the surface tension of liquid helium we obtain a resolution of 1 part in 105. The technique is well suited for automated measurements of small changes in surface tension.
Measurement of the position and displacement of a light beam with a spiral scanner
Authors: Ahlborn Boye , Dean Doug , Bressler Bernard H.
Published: March 2003

A rotating spiral scanner interrups an incident light beam for time intervals which are proportional to the position of the beam. This produces an electrical signal via a photodector system which is independent of beam intensity. The device was used to measure the relative change in sarcomere spacing during the initial development of tension in a contracting frog sartorius muscle.
Inexpensive, pulsed, tunable ir dye laser pumped by a flashlamp-driven dye laser
Authors: Passner A. , Venkatesan T.
Published: March 2003

A flashlamp-driven dye laser with a 250-ns, 10-mrad divergence, 2-mm-diam beam at 620 nm is used to pump an ir dye laser. The ir laser pulses are tunable from 700 to 900 nm with spectral widths of less than 1 Å. Peak ir powers of 100W have been obtained with a 5-kW pump power.
Laboratory systems for measuring short-term changes in water levels
Authors: Villeneuve J. P. , Ouellet Y.
Published: March 2003

In hydraulics, one is often involved with measurements of small amplitude and relatively fast changing water levels. Different types of instruments are now being used, among which the resistance types are of common usage. However, the nonlinearity of the output signal and the variation in the conductivity of the fluid are two types of problems commonly encountered with these systems. In a first step, the linear variation of the resistivity as a function of the immersion depth of the probes is verified. Then, the shape of electrodes is determined in order to make the output voltage a linear function of the immersion depth. Also a system is proposed to obtain a linear output voltage for parallel electrodes. In a second step, an electronic system has been developped and tested in order to compensate for the variation in conductivity of the fluid being measured. The use of a reference probe in such a system gives a linear output voltage which is constant even through the conductivity of the fluid is changed during testing.
New magnetic electron spectrometer with directional sensitivity for a satellite application
Authors: Korth A. , Wilken B.
Published: March 2003

Design and test of a new magnetic electron spectrometer with excellent angular and rather small energy resolution is described. The system is specifically designed for a space flight application to analyze the angular distribution of energetic electrons. Incident electrons with energies between 15 and 270 keV are focused with respect to the direction of incidence. Reasonable directional focusing is obtained over an angular range of 60° with a resolution of 5°. This magnetic electron spectrometer is part of the energetic particle instrument (EPI) developed for the European Space Agency (ESA) GEOS program. GEOS-1 was launched on April 20, 1977, and injected into a 12-h orbit. The instrument has worked successfully since the switch-on-phase in the beginning of May 1977.
Fabrication techniques for microdevices in soft superconductors
Authors: Berchier Jean-Luc , Sanchez Daniel H.
Published: March 2003

Fabrication techniques for devices having dimensions of about a micrometer are presented. A versatile low cost photolithographic microscope projection technique and chemical etching are used as part of the fabrication process. The whole procedure is proposed as an alternative to razor blade or diamond scratching techniques in laboratory research at low temperatures. A detailed description of the equipment and methods is given. Specific examples of one material devices and two material devices are described in connection with physical problems of recent interest. The broad field of application of the techniques shown make them appropriate for creating structures that might have defined and reproducible forms from millimeter dimensions down to 0.5 μm.
Measurement of the properties of liquids and gases using a transient hot-wire technique
Authors: Parsons J. R. , Mulligan J. C.
Published: March 2003

A transient method of making simultaneous, in situ measurements of the thermal conductivity, volumetric specific heat, and kinematic viscosity of liquids and gases is presented. The technique utilizes the temperature response record of a fine horizontal wire, functioning as a resistance thermometer, when subjected to a sudden and constant electrical heating. It is shown that a formulation of the transient mechanisms governing the transition from pure conductive to free convective heat transfer from the wire can be used to produce simultaneous determinations of fluid properties from a single wire temperature versus time record. A simple apparatus is presented, along with the results of its use in determining the properties of air.
Some properties and applications of thin self-supporting polymer membranes
Authors: Korn U. , Rav-Noy Z. , Shtrikman S.
Published: March 2003

Membranes as thin as 500 Å were produced from many plastic materials and transferred to frames with dimensions of several centimeters. The self-supporting membranes were obtained using simple-dip-coating techniques. In some cases additional plasma polymerized layers were applied. These membranes can withstand several procedures of photolithography and chemical processing. The mechanical properties of the membranes are similar to that of the bulk material. Some typical applications are described. These applications include the use of the membranes as substrates for thermoelectric detectors and also as beamsplitters and windows for cells employed in CO2 laser spectroscopy.
Superconducting silver brazing alloy (silver solder)
Authors: Thompson J. R. , Thomson J. O.
Published: March 2003

A superconducting transition has been observed in a type BAg-3 silver brazing alloy (silver solder) with Tc=96.6 mK and Hc=4.7 Oe. The associated diamagnetism indicates that approximately 1/3 of the sample volume displays the Meissner effect. This property dictates caution in its use at very low temperatures, particularly near sensitive magnetic devices such as ac and SQUID magnetometers.
Device for microparticle array preparation
Authors: Campbell Marilyn J.
Published: March 2003

A simple device is described for preparing arrays of microballoons to be characterized by radiography for use as laser fusion fuel containers.
Modification of an oxygen bomb calorimeter to measure enthalpies of reaction of liquid metals
Authors: Carling R. W.
Published: March 2003

Modification of a commercially available oxygen bomb calorimeter is described. This modification permits direct determination of the enthalpies of reaction of liquid metals that have melting points below about 310 K.
Apparatus for low-temperature inert atmosphere chemical reactions
Authors: Newell Joseph J.
Published: March 2003

An apparatus for carrying out chemical reactions at low temperature is presented. The apparatus is fully automatic and allows for large scale preparations.
Sampled photon counting with multilevel discrimination
Authors: Gustafson T. L. , Lytle F. E. , Tobias R. S.
Published: March 2003

Circuitry is described which provides increased data throughput by multilevel discrimination for time-resolved studies employing sampled photon counting. Linearity of response to within 5% for photon acceptance rates at 145% the repetition rate are obtainable.
New method for measuring electrical conductivities of solids in a diamond anvil cell
Authors: Walling Priscilla La Bonville , Ferraro John R.
Published: March 2003

A new method of measuring electrical conductivities of solids in a diamond anvil cell (DAC) has been developed. The dc method involves a four-point probe measurement. The method is suitable for measuring the electrical conductance of bulk (polycrystalline) solids or single crystals, as a function of temperature and/or pressure.
Coaxial fast metal-to-metal switch for high current
Authors: Boissady C. , Rioux-Damidau F.
Published: March 2003

A fast mechanical switch of coaxial configuration, driven by a magnetic field, is described. It presents a low inductance (6 nH), a low resistance (3 μΩ) and delay-times of 25 μs with a jitter of 0.08 μs.
Small mass spectrometer with extended measurement capabilities at high pressures
Authors: von Zahn U. , Mauersberger K.
Published: March 2003

For the in situ investigation of planetary atmospheres a small Mattauch-Herzog mass spectrometer has been developed. Its high-pressure performance has been improved by incorporating differential pumping between the ion source and the analyzing fields, shortening the path-length as well as increasing the extraction field in the ion source. In addition doubly ionized and dissociated ions are used for mass analysis. These measures make possible operation up to 10−2 millibars. Results of laboratory tests related to linearity, dynamic range, and mass resolution are presented, in particular for CO2.
Measurement of ac cataphoresis
Authors: Sery George E. , Chanin L. M.
Published: March 2003

An apparatus and techniques are described for measurements of ac cataphoresis. The system uses a fiber optics light pipe driven along the discharge tube axis by a synchronous clock drive system. The collimated light signal is directed to a spectrometer whose output is processed using various methods to obtain desired types of information, including longitudinal time averaged scans of the discharge tube, longitudinal gated scans, and gated single cycle observations. Using these techniques one is able to study the time development of the ac effect as well as the presence of ionization waves. Examples are shown using noble gas mixtures of the various sampling procedures.
Instantaneous laser Doppler velocimeter using a fast wavelength tracking Michelson interferometer
Authors: Smeets G. , George A.
Published: March 2003

A new species of laser Doppler velocimeter is presented based on wavelength detection with a two-beam interferometer. A finite optical path difference, Δφ, of the interferometer creates a sensitivity of the interference to wavelength changes. By means of a fast feedback system, the phase, Δφ/λ is kept constant. Wavelength changes are immediately answered by changes of Δφ generated with a Pockels cell. The Pockels cell voltage represents a continuous signal proportional to the instantaneous velocity component of the scattering object. A time resolution of 1 μs or lower can be obtained. The field of applications includes velocity recordings in gas flows containing tracer particles as well as velocity recordings of moving surfaces. A number of experiments are described demonstrating the performance of the system.
Interferometric method for measuring high velocities of diffuse surfaces
Authors: Maron Y.
Published: March 2003

An interferometric method for measuring the displacement of diffuse surfaces moving with velocities of a few millimeters per microsecond is presented. The method utilizes the interference between two light beams reflected from a constant area of the moving surface at two different angles. It enables the detection of the high-rate velocity variations. A light source with modest temporal coherence and power around 100 mW is needed.
New hydrostatic pressure cell to 90 kilobars for precise electrical and magnetic measurements at low temperatures
Authors: Fasol G. , Schilling J. S.
Published: March 2003

A new type of hydrostatic pressure cell is discussed. It is suitable for precise electrical and magnetic measurements on several samples simultaneously over a wide range of temperature and pressure. Pressures as high as 90 kilobars have thus far been reached in a four-point electrical resistivity measurement. These studies indicate minimal pressure changes upon cooling from 300 to 1 K, good pressure homogeneity, and absence of significant shear stresses.
Quasi-optical diplexer for millimeter wavelengths
Authors: Payne J. M. , Wordeman M. R.
Published: March 2003

A quasi-optical diplexer for injection of signal and local oscillator frequencies into a mixer at millimeter wave-lengths is described. The diplexer accepts both image and signal bands, presents low loss at both the signal and local oscillator frequencies and rejects local oscillator noise at the signal frequency. The configuration of the device makes it particularly useful for Cassegrain receivers using a cooled mixer and a lens corrected feed system. The diplexer has been tested at 150 GHz on the 11-m radio telescope operated by The National Radio Astronomy Observatory in Tucson, Arizona.
Integrator for use in bombardment experiments
Authors: Takeda Michihiko , Yasuda Kyoichiro , Ikuta Shiro , Masuda Haruho
Published: March 2003

A convenient integrator was developed for use in bombardment experiments with a charged particle accelerator such as a linac. In this device an irradiation dose is digitally displayed in the number of electrons per cm2. Furthermore, a linac is controlled to deliver a preset dose by this integrator.
Development of a laboratory EXAFS facility
Authors: Knapp G. S. , Chen Haydn , Klippert T. E.
Published: March 2003

The EXAFS technique is a powerful new structural tool, particularly useful for studies of disordered or otherwise complex materials for which x-ray diffraction techniques are difficult or unfeasible. At the present time, most EXAFS experiments are carried out at a synchrotron facility because of the larger fluxes available. We have developed an in-laboratory apparatus utilizing a focusing crystal technique which increases available fluxes two to three orders of magnitude over previous laboratory facilities, so that EXAFS measurements can be carried out quickly and accurately in the laboratory. We will discuss the principles of the focusing monochromator and we will also illustrate the experimental method with examples, including studies of chemical solutions, defect crystalline solids, and high-temperature superconductors.
Prism beamswitch for radio telescopes
Authors: Payne J. M. , Ulich B. L.
Published: March 2003

A dielectric prism and switching mechanism have been constructed for beamswitching a Cassegrain radio telescope. Spatially extended radio sources may be mapped without significant confusion utilizing the sensitivity and stability inherent in the conventional Dicke radiometer.
Improved resolution in fixed-wavelength photoelectron–photoion coincidence spectroscopy
Authors: Eland J. H. D.
Published: March 2003

The paper describes a technique of extraction-field pulsing, whereby the energy resolution in fixed-wavelength photoelectron–photoion coincidence spectroscopy can be substantially improved and extended light sources can be used.
Real-time phase microscopy using a phase-lock interferometer
Authors: Leiner Dennis C. , Moore Duncan T.
Published: March 2003

A phase-lock interference microscope (PLIM) has been designed and constructed. The instrument measures optical phase in real time with analog output voltages proportional to phase and position. The PLIM has been used to measure gradient index profiles in optical fibers, wall thicknesses of microballoons for laser induced fusion, the phase of biological specimens, and the surface finish of optical surfaces. The peak-to-peak noise of the instrument is λ/50.
Broadband and low insertion loss Stark cell for microwave spectroscopy
Authors: Thiebaut Jean-Marie , Roussy Georges
Published: March 2003

A groove guide cell for Stark modulation spectroscopy has been constructed and tested. This structure with quasi-unique mode propagation between two isolated plates is well adaped to application of a modulation voltage. The insertion losses are low (0.6 dB for a 3-m-long cell, and R band) and the cell is free of internal reflection. A metallic casing inclosing the plates acts as a shield against electrical interference, prevents low-voltage breakdown, and reduces wall adsorption of the gas. The performance of the cell is not affected by temperature variation (−80 ° to 25 °C). A high sensitivity has been obtained by converting the cell into a 3-m-long, high-Q cavity. This type of cell appears to particularly recommend itself for use in intensity measurements, broadband spectroscopy, analytical studies, and high frequency range work.
Nanosecond gating of an optical multichannel analyzer
Authors: Albrecht G. F. , Källne E. , Meyer J.
Published: March 2003

An optical gating pulse of 30 ns width combined with an electronic gating pulse of 50 ns width has been found to give a near perfect performance of a gated silicon intensified vidicon detector. The magnification as well as the focusing properties are found to be close to the real-time behavior and the small changes that do occur in the gated mode can be corrected for in the data analysis.
Microparticle dispenser
Authors: Miller John R. , Butler Susannah , Feuerherd Jurgen K.
Published: March 2003

A simple device suitable for dispensing laser fusion target fuel cores is described. These fuel cores are typically 100-μm-diam glass or metal microballoons having a wall thickness of 1 μm. The microparticle dispenser mechanically acquires a single microballoon and dispenses it at a given position, eliminating the previously difficult and time-consuming hand process. Dispensing rates of 1/s have been achieved. A repetition rate of 1000/s should be possible using the described modifications.
Intensity dependent time-resolution and dynamic range of Photochron picosecond streak-cameras
Authors: Bradley D. J. , Bryant S. F. , Taylor J. R. , Sibbett W.
Published: March 2003

The dynamic range of operation of Photochron I and Photochron II picosecond streak cameras is shown to depend upon the time-resolution employed. For events ∼2 ps a useful dynamic range of 30 is obtainable, and this increases to a value of 180 for 30-ps events. No accumulative saturation effects occur at a time resolution as short as 2 ps.
Accurate measurement of NMR amplitudes using a computer-controlled wide line cw nuclear double resonance spectrometer
Authors: Spencer P. A. , Boyd W. R. T. , Hughes D. G.
Published: March 2003

A computer-controlled cw nuclear magnetic double-resonance spectrometer, designed for studying the spin-lattice relaxation of quadrupolar nuclei in single crystals, is described. Resonances are detected by a Robinson spectrometer using a technique involving sinusoidal field modulation in conjunction with first and second harmonic phase-sensitive detection. The output of the first harmonic detector provides an error signal, which is used to ’’lock’’ the spectrometer to the center of the resonance. The output of the second harmonic detector is used as the measure of NMR amplitude. Comprehensive tests have shown that the amplitudes of weak NMR signals can be compared with an accuracy of better than ±0.1%. Numerous precautions to obtain such accuracy are discussed.
Savart plate interferometry for isothermal diffusion measurements
Authors: Becsey Julius G. , Bierlein James A.
Published: March 2003

Savart plate wavefront shearing interferometry has been applied to make accurate determinations of diffusivity in an electrolyte (KCl) solution, at low concentrations generally considered inaccessible to optical measurement. The necessary improvement in sensitivity is achieved by operating at high shear and using appropriate methods of analyzing the interferograms. The technique is equally applicable to dilute nonelectrolytes. Hydrodynamic stability of the diffusion column, rather than the sensitivity of the interferometer, is probably the ultimate limitation on the capability of the method as concentration is progressively decreased.
Reversing rectangular pulse generator applicable to transient electric birefringence
Authors: Asai Hiroshi , Watanabe Nozomu , Okuyama Tetsuya
Published: March 2003

An electronic reversing rectangular pulse generator, which can be used for experiments on electric birefringence in macromolecular solutions, was constructed. The performance was very satisfactory when four thyratron tubes of 2D21 or 1G50 type were used. The switching time for pulse reversing was less than 50 ns even without very careful wiring of the circuit. Transient electric birefringence for the common strain and HR strain of tobacco mosaic virus was demonstrated as a preliminary experiment.
Transient gas density measurement using neutron radiography
Authors: Johnston Sheridan C. , Dahlke Lutz W.
Published: March 2003

Neutron radiography is discussed as a line-of-sight gasdynamic diagnostic technique for studying internal flows in opaque, complicated geometry flow systems which are not optically accessible. Because neutron attenuation is very sensitive to nuclear structure, many material combinations that are difficult or impossible to image with optical techniques or x rays can be imaged by means of neutron radiography. The problem presented to demonstrate the neutron radiographic technique is the determination of the time-resolved gas–gas interface location inside a gas transfer system composed of three pressure vessels connected by opaque, thick-walled tubing.
The biology instrument for the Viking Mars mission
Authors: Brown F. S. , Adelson H. E. , Chapman M. C. , Clausen O. W. , Cole A. J. , Cragin J. T. , Day R. J. , Debenham C. H. , Fortney R. E. , Gilje R. I. , Harvey D. W. , Kropp J. L. , Loer S. J. , Logan J. L. , Potter W. D. , Rosiak G. T.
Published: March 2003

Two Viking spacecraft have successfully soft landed on the surface of Mars. Each carries, along with other scientific instruments, one biology laboratory with three different experiments designed to search for evidence of living microorganisms in material sampled from the Martian surface. This 15.5-kg biology instrument which occupies a volume of almost 28.3 dm3 is the first to carry out an in situ search for extraterrestrial life on a planet. The three experiments are called the pyrolytic release, labeled release, and gas exchange. The pyrolytic release experiment has the capability to measure the fixation of carbon dioxide or carbon monoxide into organic matter. The labeled release experiment detects metabolic processes by monitoring the production of volatile carbon compounds from a radioactively labeled nutrient mixture. The gas exchange experiment monitors the gas changes in the head space above a soil sample which is either incubated in a humid environment or supplied with a rich organic nutrient solution. Each experiment can analyze a soil sample as it is received from the surface or, as a control, analyze a soil which has been heated to above 160°C. Each instrument has the capability to receive four different soils dug from the Martian surface and perform a number of analysis cycles depending on the particular experiment. This paper describes in detail the design and operation of the three experiments and the supporting subsystems.
Subnanosecond time-correlated photon counting with tunable lasers
Authors: Spears Kenneth G. , Cramer Laurence E. , Hoffland Lynn D.
Published: March 2003

We present several laser based methods to improve the technique of time-correlated photon counting. Our Ar+ laser pumped tunable dye laser can be operated in three timing configurations: acousto-optically mode locked, cavity dumped, and cavity dumped–mode locked. Performance characteristics of the laser system in various operational modes are described along with measurement techniques for both gas and liquid phase. The subnanosecond pulses generated by mode locking are extremely stable and they maintain identical pulse shapes over a 6-h period, as shown via photon counting measurements at a 15-psec channel resolution. Our RCA C31034 photomultiplier with a red sensitive GaAs photocathode provides wavelength-independent response to detected fluorescence in both the visible and ultraviolet. The present limit of our apparatus is controlled by the accuracy of deconvoluting fluorescence decay from the finite response width caused by photomultiplier transit time dispersion (0.8 nsec FWHM). Our system stability is sufficient to accurately determine exponential decays as short as 50 psec. Furthermore, we can successfully analyze dual exponential decays such as those arising from solution reorientation times of 390 psec competing with a fluorescence lifetime of 725 psec. Examples of the laser performance are selected from a variety of measurements in the gas phase and from the fluorescent dye rose bengal in the liquid phase.
Evidence of hydrogen embrittlement of tungsten carbide
Authors: Kennedy George C.
Published: March 2003

Tungsten carbide vessels containing materials at high temperature and high pressure are used in many laboratories. We note that any oils at medium to high temperature which can break down and liberate hydrogen cause rapid failure of the pressure vessel, whereas perfluorated kerosenes used as lubricants inside a pressure vessel give sharply increased life of the vessel.
Simple logarithmic time base generator
Authors: Denby E. F. , Wills L. J.
Published: March 2003

A digital device containing only three inexpensive CMOS chips is described that can generate the log-time function over seven decades of time. Simple modifications that can increase the range and the accuracy are also described.
Characteristics of a multidipole ion source
Authors: Leung K. N. , Collier R. D. , Marshall L. B. , Gallaher T. N. , Ingham W. H. , Kribel R. E. , Taylor G. R.
Published: March 2003

The properties of a steady-state, dc discharge multidipole ion source have been investigated. The plasma density in the source depends on the magnet geometries, the discharge voltage, and the bias voltage on the first extraction grid. Different schemes to reduce the loss of ions to the chamber wall are described. Hydrogen ion species in the extracted beam are studied by a mass analyzer.
Apparatus for semi-automatic grain-size separation of small samples
Authors: Meyer G. , Grütter A. , von Gunten H. R. , Krähenbühl U. , Rössler E.
Published: March 2003

A semi-automatic sieving apparatus for separation of small samples (50–500 mg) of granular material into several uniform grain-size fractions is described. The achieved separations are reproducible, yielding more than 95% of the initial sample. Such separations are needed for investigations of surface phenomena in very fine powders. It is demonstrated that the apparatus is very suitable to handle highly radioactive materials, keeping the radiation doses very low for the operator. The separations into several fractions are faster, cleaner, and more reproducible than those obtained in ordinary hand-sieving techniques.
Methods for drift stabilization and photomultiplier linearization for photometric ellipsometers and polarimeters
Authors: Aspnes D. E. , Studna A. A.
Published: March 2003

We describe simple modifications to photometric polarimeter and ellipsometer systems that greatly reduce nonlinearity, component drift, and digital noise effects. A photomultiplier feedback circuit is described and analyzed that varies the effective system linearity by means of a single control. Linearity to 5×10−4 over more than three orders of magnitude of incident light intensity is obtained. Effective double-beam stability to 5×10−5 is achieved by blocking the source intensity over part of an extended measurement cycle. These refinements permit photometric instruments to approach accuracy capabilities compatible with their precision capabilities, and also allow measurements to be made in the presence of ambient scattered light, at high sample temperatures, or using solid-state detectors for which the zero reference is not well defined. As an example, we give the dielectric function of Ge measured from 1.5 to 5.8 eV at a sample temperature of 800° C.
High-precision measurement and control facility for electrical-resistivity experiments in an He i
i environment
Authors: Berger A. S. , Ockers S. T.
Published: March 2003

A control and measurement system is described that provides direct digital output of the electrical resistance of a metal sample with an uncertainty of ⩽5×10−9 Ω at 1.7 K with a linearity of ±0.04%. In addition, the system allows in situ isochronal and isothermal annealing experiments to be performed with ΔT⩽0.1°C and Δt⩽3 s between any two temperatures. With the exception of two commerical instruments, all devices were made with readily available components.
Determination of ion temperature by two-probe method
Authors: Makita Hideharu , Kuriki Kyoichi
Published: March 2003

A simple method is proposed to estimate the ion temperature of collision-free plasma using a cylindrical and a spherical Langmuir probe. This method is based on the difference in the ion-temperature dependence of the ion-current collection between these probes as predicted theoretically by Laframboise. Curves necessary for the ion-temperature determination are given and are applied to a low-density xenon plasma. Agreement of the probe characteristics with Laframboise’s theory was also demonstrated.
Method of measuring loaded Q-factor of single-ended cavity resonators using reflection bridge
Authors: Ghosh G. , Sen Susanta , Dasgupta D. , Saha P. K.
Published: March 2003

A bridge method of determining the loaded Q-factor and coupling coefficient of single-ended cavity resonators is described. The measuring system consists of a hybrid-T or ’’magic T’’ bridge with one of the collinear arms terminated by the cavity and the other by a precision attenuator followed by a variable precision short. The experimental procedure essentially measures the reflection coefficient of a cavity resonator as a function of frequency by balancing the bridge, using an oscillator with variable frequency amplitude modulation as the source.
Superconducting switch for large heat flow below 50 mK
Authors: Krusius M. , Paulson D. N. , Wheatley J. C.
Published: March 2003

We describe both the method of fabrication and the performance of a zinc superconducting heat switch used to couple thermally the mixing chamber of a dilution refrigerator and a nuclear demagnetization refrigerator.
Multichannel, high-energy railgap switch
Authors: Neil George R. , Post Richard S.
Published: March 2003

A low-inductance, multichannel railgap switch has been developed which is capable of switching 20 kJ at 500 kA. The switch has low jitter, a wide operating voltage range and low electrode erosion rate.
Technique for bonding gold and silver metals on sapphire
Authors: Varmazis C. , Viswanathan R. , Caton R.
Published: March 2003

A technique is described for bonding gold and silver metals onto sapphire. This technique has been successfully used in ac calorimetry for heat capacity of films.
EPR cavity matching device for use at low temperatures
Authors: Whitehouse J. E.
Published: March 2003

A variable-insertion pin matching device is described. It provides a simple solution to the matching of an ERP cavity at low temperatures.
Lanthanum hexaboride hollow cathode for dense plasma production
Authors: Goebel D. M. , Crow J. T. , Forrester A. T.
Published: March 2003

A hollow tube cathode using lanthanum hexaboride as the electron emitter has been designed and constructed. Tests in both argon and hydrogen indicate that this cathode is capable of producing over 800 A of electron current continuously, corresponding to over 25 A/cm2 from the LaB6. The cathode has been operated for over 300 h and exposed to air more than 100 times with no deterioration in emission. Projected lifetime is in excess of 3500 h for the sintered LaB6 piece tested in this configuration. Construction details, performance characteristics, and discussions of space charge limits on emission are described.
Secondary ion quadrupole mass spectrometer for depth profiling—design and performance evaluation
Authors: Magee Charles W. , Harrington William L. , Honig Richard E.
Published: March 2003

A quadrupole-based secondary ion mass spectrometer designed for depth profiling is described which combines ultrahigh vacuum construction with high sputtering rate, detection sensitivity, depth resolution, mass spectral purity, and abundance sensitivity. Impurities such as B and Al implanted in Si can be profiled to levels below one part per million atomic (ppma), at a depth resolution equal to that obtained by commercial ion microprobes. The primary beam consists of 5-keV, mass-analyzed 40Ar+ ions, focused to about 70 μm in diameter. Its high current density (≳25mA/cm2) permits adequate beam rastering and electronic signal-gating to optimize depth resolution. A secondary ion extraction lens and spherical energy filter are responsible for achieving abundance sensitivities of five to six orders of magnitude on the low mass side of a matrix peak. The ultrahigh vacuum environment of the sample dramatically reduces molecular peaks containing H, C, and O, allowing even hydrogen to be profiled to concentrations below 10 ppma. Because large amounts of data are generated by multi-element depth profiling, means for automated instrument control and data acquisition have been developed.
Plasma enclosed in a magnetic field produced by flexible surface magnets
Authors: Schott L.
Published: March 2003

A homogeneous steady state plasma with a usable volume of approximately 200 l and with an electron temperature of 1–2 eV and a plasma density of ∼109–1010 cm−3 is produced in a discharge chamber the outside of whose walls is covered with flexible magnetic strips. This magnet arrangement can be built at a fraction of the cost of a conventional system using rigid surface magnets. The magnetic multipole field leads to an increase of the plasma density by one to two orders of magnitude and it is also found to cause trapping of high energy electrons originating from the discharge region.
Gas discharge ion source. II. Duopigatron
Authors: Bacon F. M. , Bickes R. W. , O’Hagan J. B.
Published: March 2003

Ion source performance characteristics consisting of total ion current, ion energy distribution, mass distribution, and ion current density distribution have been measured for several models of a duopigatron. Variations on the duopigatron design involved plasma expansion cup material and dimensions, secondary cathode material, and interelectrode spacings. Of the designs tested, the one with a copper and molybdenum secondary cathode, and a mild steel plasma expansion cup proved to give the best results. The ion current density distribution was peaked at the center of the plasma expansion cup and fell off to 80% of the peak value at the cup wall for a cup 15.2 mm deep. A total ion current of 180 mA consisting of 60%–70% atomic ions was produced with an arc current of 20 A and source pressure of 9.3 Pa. More shallow cups produced a larger beam current and a more sharply peaked ion current density distribution. Typical ion energy distributions were bellshaped curves with a peak 10–20 V below anode potential and with ion energies extending 30–40 V on either side of the peak.
Radiometer system to map the cosmic background radiation
Authors: Gorenstein Marc V. , Muller Richard A. , Smoot George F. , Tyson J. Anthony
Published: March 2003

We have developed a 33-GHz airborne radiometer system to map large angular scale variations in the temperature of the 3 K cosmic background radiation. A ferrite circulator switches a room-temperature mixer between two antennas pointing 60° apart in the sky. In 40 min of observing, the radiometer can measure the anisotropy of the microwave background with an accuracy of ±1 mK rms, or about 1 part in 3000 of 3 K. The apparatus is flown in a U-2 jet to 20 km altitude where 33-GHz thermal microwave emission from the atmosphere is at a low level. A second radiometer, tuned to 54 GHz near oxygen emission lines, monitors spurious signals from residual atmospheric radiation. The antennas, which have an extremely low side-lobe response of less than -65 dB past 60°, reject anisotropic radiation from the earth’s surface. Periodic interchange of the antenna positions and reversal of the aircraft’s flight direction cancel equipment-based imbalances. The system has been operated successfully in U-2 aircraft flown from NASA-Ames at Moffett Field, CA.
Ultradense reproducible Z-pinch suitable for CO2 laser-pellet simulation experiments
Authors: Steel Duncan G. , Rockett Paul D. , Bach David R. , Colestock Patrick L.
Published: March 2003

The design and operating characteristics of a unique reproducible linear, high-density (≳1019 e−/cm3), low-temperature (17<Te<30 eV) helium Z-pinch are presented in this paper. It is shown that the temperature and critical density scale length (70–200 μm) of the pinched plasma are favorable for simulating CO2 laser-pellet experiments. Focused CO2 laser intensities of 1012 W/cm2 result in v0/vth≃2.8 at the critical layer, where v0 is the quiver velocity of an electron in the laser electric field and vth is the electron thermal velocity.
Superconducting aluminum heat switch and plated press-contacts for use at ultralow temperatures
Authors: Mueller R. M. , Buchal C. , Oversluizen T. , Pobell F.
Published: March 2003

We have measured the thermal conductivity of a 0.1-mm-thick Al foil in the normal and superconducting state down to 58 mK. At this temperature, our data give a ratio for the conductivities of kn/ks=1600 T−2. They show that Al is a better material for a heat switch than the usually used superconductors because of its large kn and large Debye temperature (reducing the lattice conductivity ks). In addition, we describe the design of a heat switch and an excellent performing demountable press-contact between Al and Cu, both gold plated, as joint to the switch.
Double induction method for electrodeless determination of Hall mobility
Authors: Swenumson R. D. , Even U. , Thompson J. C.
Published: March 2003

An electrodeless (double induction) technique has been developed for the determination of Hall mobility. Measurements were performed on seven solid or liquid metallic samples and the results compared to reported mobilities. With a current of 1 A and magnetic field of 100 G, signals of 100 nV were measured for Cu, Ag, or Au samples, while signals as low as 50 pV can be measured. Hall angles as small as 2×10−6 rad have been determined. The usefulness of this technique in Hall mobility measurements on systems in which electrode dependent results occur or in corrosive materials on which no electrode is stable is emphasized.
Resonant holography of plasma flow phenomena
Authors: Koopman David K. , Siebeneck H.-J. , Jellison G. , Niessen W.G.
Published: March 2003

A dye laser, tuned near the Ba ii ion resonance line at 4554 Å and used as a light source for a holographic interferometer, allows ion densities as low as 5×1013 cm−3 to be measured in flowing barium plasmas.
Microwave spectrometer for saturated absorption experiments
Authors: Legrand J. , Ségard B. , Krosta A. , Macke B.
Published: March 2003

A spectrometer has been built to perform Doppler-free saturated absorption experiments in the millimeter range (30–300 GHz); a plane-cylindrical resonator between Stark plates has been used. With that device, inverted Lamb-dips have been observed at 115 GHz with a width 25 times below the Doppler width. However, the essential feature of this apparatus is to allow the application of Stark field typically of 2500 V/cm, leading to such specific uses as the Stark tuned Lamb-dip, level-crossing, and mode-crossing experiments. Typical examples are given and other applications are proposed.
Fiberglas insert to liquid helium Dewar
Authors: Shen S. Y. , Halperin W. P. , Ketterson J. B.
Published: March 2003

We present the design of a simple Fiberglas insert to the liquid helium space of a conventional metal Dewar that results in a considerable reduction in the liquid helium evaporation rate. The original purpose of this simple modification was to minimize the volume of liquid helium that is used for experiments not requiring the full volume available at low temperature.
New technique applied to the ring method for determining surface tension of molten salts
Authors: Uchiyama Yohji , Kawamura Kazutaka
Published: March 2003

A new simple technique applied to the ring method for determining surface tension of molten salts is described. A small-sized motor which is operated by a light-sensitive phototransistor and is suspended from a balance pan is used for lowering and rising the ring. The present method was tested by determinating the surface tension of molten NaNO3, KNO3, and HTS (molten NaNO3–KNO3–NaNO2; 7−44−49 mol%). Published values for molten NaNO3 and KNO3 are convenient for checking whether our obtained data are adequate or not. No data, to our knowledge, are available for the surface tension of HTS. In these experiments, it was shown that the new method performed well.
Thin film thickness monitor shutter
Authors: Bailey W. E. , Hatfield L. L. , Marshall B. J.
Published: March 2003

This article describes a simple electronic dual-activated shutter which is designed to interface with the Sloan digital thickness monitor model DTM-200 or a set of double-pole double-throw switches which can be operated manually.
Application of a dc Fano effect polarized electron source to low-energy electron–atom scattering
Authors: Wainwright P. F. , Alguard M. J. , Baum G. , Lubell M. S.
Published: March 2003

A polarized electron source based upon the photoionization of unpolarized Cs atoms by circularly polarized light (Fano effect) has been developed and applied to the study of spin dependence in low-energy electron–atom scattering. Electron intensities of 10 nA with polarizations of 0.63±0.03 have been obtained routinely during continuous runs of up to 75 h. Frequent optical reversal of the direction of the longitudinal electron polarization minimizes systematic effects so that helicity dependent electron-scattering asymmetries smaller than 4×10−4 can be measured.
Construction and performance of a 20-pps unstable Nd:YAG oscillator
Authors: Andreou D.
Published: March 2003

A positive branch Nd:YAG unstable oscillator has been constructed using a small reflecting spot centered on an antireflection coated substrate as the output mirror. The confocal condition is achieved by taking account of the lens effect of the rod as well as the back mirror curvature. Q-switched output energies of 180 mJ in 10 ns have been obtained in a diffraction limited beam with a divergence of less than 0.25 mrad, at an overall efficiency of 1.3%.
Improved electromagnetic velocity drive for Mössbauer experiments
Authors: Genand-Riondet N. , Imbert P. , Lericque J. F.
Published: March 2003

We describe a velocity drive for Mössbauer spectroscopy, which uses a velocity transducer with a moving magnet core positioned between two symmetrically arranged drive coils. Among other advantages this device improves the feedback performance by suppressing the fundamental resonance frequency in the moving rod.
Apparatus for extruding wires of soft metals under vacuum or inert atmospheres
Authors: Kayser F. X. , Rashid M. S.
Published: March 2003

A bakeable apparatus is described that was constructed for extruding wires from small ingots of soft metals like the alkalis, the alkaline earths, and the divalent rare earths, while at the same time safeguarding the purity of the sample material. The unit is completely enclosed yet small enough to be hand transferred into and out of an inert atmosphere glove box where load/unload operations are performed. Extrusions are effected with the apparatus outside the glove box but with the sample material under the captured atmosphere of the box or under a vacuum. Given an external heating source it is possible to carry out extrusions at temperatures above room temperature as well as in situ recrystallizations of extruded materials.
Heat capacity of Matsushita carbon resistance thermometers below 1 K
Authors: Steinback M. , Anthony P. J. , Anderson A. C.
Published: March 2003

Matsushita resistors have a much smaller heat capacity than Speer resistors, and thus are preferable in some thermometry applications at temperatures below 1 K.
Automatic 300–4 K temperature cycling apparatus
Authors: Hamilton C. A.
Published: March 2003

The apparatus described here automatically cycles small samples between 300 and 4 K by alternately raising and lowering the sample through the neck of a commerical liquid helium storage Dewar. A bellows, which is pressurized by the helium boil-off gas, provides all of the required mechanical motion. By utilizing the cooling available from the boil-off gas, liquid helium helium consumption is limited to 0.03 l/cyc for a 12-g sample. Cycle times can be as short as 5 min.
Unwanted birefringence in low-temperature windows
Authors: Baldacchini G. , Grassano U. M. , Tanga A.
Published: March 2003

A small residual birefringence producing a retardation of 0.05 rad has been measured in silica windows mounted in a liquid helium cryostat. The effect is due to a uniaxial stress on the windows induced by the pressure difference between the helium reservoir and the vacuum jacket.
High resolution ac calorimeter for organic liquids
Authors: Smaardyk J. E. , Mochel J. M.
Published: March 2003

A calorimeter has been developed for organic liquids which utilizes the ac heat capacity technique. It can measure heat capacity changes of 1 part in 104 with a temperature resolution better than 1 mK from room temperature to 200°C. This calorimeter has been used to study the smectic A to nematic phase transition in a series of homologous liquid crystals.
Digital modulator and synchronous demodulator system: an alternative to the analog phase detector
Authors: Renkes Gordon D. , Thorne Lawrence R. , Gwinn William D.
Published: March 2003

A digital modulator and synchronous demodulator system has been developed which more effectively recovers signals buried in noise than does its analog counterpart. Circuitry of integrated design is described for controlling the modulation in physical measurements and the simultaneous, synchronous demodulation and conversion of the signal into a binary number. This system is especially useful when interfaced with a laboratory computer. The square wave which produces the modulation has purposely lengthened transition times to minimize modulation transients. Demodulation is accomplished by feeding the amplified AM signal into a voltage-controlled oscillator and counting the resulting pulses with counters gated, by the modulation reference circuitry, to count up and down on alternate half-cycles. The number accumulated by the counters is proportional to the true integral of the demodulated signal over a preset number of modulation cycles. The period of the modulation cycle is, in turn, determined by a quartz crystal oscillator. The demodulator can be gated to ignore excessively noisy portions of the modulated signal. Four demodulators with relative gains in ratios of eight operate simultaneously to provide a large dynamic range of more than 106. Application of this system to a computer-controlled microwave spectrometer is described. A sample spectrum is given to illustrate the wide dynamic range.