bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical interferometry in liquids at high pressures to 14 kilobars
Authors: Vedam K. , Limsuwan Pichet
Published: March 2003

A high-pressure liquid cell interferometer to measure the variation of refractive index of liquids with pressure to 14 kilobars is described. The amount of liquid needed is only 3 cm3. Data obtained on n-hexane and n-pentane are presented.
DFVLR mobile lidar system
Authors: Werner Christian , Herrmann Hartmut
Published: March 2003

A mobile lidar was constructed for smokestack emission measurements. The containerizing of the ruby lidar is described, as well as the data acquisition system and the lidar itself.
Field ionization device used for measuring the pulse height defect of He+ in silicon
Authors: Curtis C. C. , Hsieh K. C.
Published: March 2003

A neutral particle detector using field ionization and cooled solid state detectors provides a means to study the pulse height defect of low energy He+ ions in silicon.
Medium pressure diffusion plasma column in a coaxial cold cathode discharge
Authors: Chen Sin-Li , Kamitsuma M.
Published: March 2003

A quiet homogeneous cylindrical plasma column is produced by using a coaxial diffusion discharge tube at medium pressure (0.1–10 Torr) with a cold cathode dc discharge. The basic characteristics of this plasma are checked by an electrostatic probe. By varying the gas pressure and input power, electron densities can be obtained from 106 to 1011 cm−3, and electron temperatures from 0.1 to a few eV. Using this plasma source, the advantage to the probe experiment is shown, and the possibility for time-independent measurements of the volume recombination coefficient is suggested.
Gas phase electrochromism studies in the vacuum ultraviolet
Authors: Causley G. C. , Scott John D. , Russell B. R.
Published: March 2003

An instrument and technique have been developed for the measurement of medium-resolution electrochromism spectra of gas phase samples in the ultraviolet spectral region from 300.0 to 165.0 nm. The primary result of studies utilizing this method is the difference in dipole moment between the ground state and an excited state of a molecule. The electrochromism spectrum of aniline is presented for the B2←A1 (π*←π) transition at 293.84 nm. The absolute value of the change in dipole moment for this transition is ‖1.25±0.30‖ D, which compares favorably with the value of ‖0.92±0.10‖ D reported from Stark field studies of a high-resolution spectrum. The primary advantage of of the technique is that it allows the determination of dipole moment changes associated with excited states, even when resolved rotational structure cannot be obtained.
Conversion of an E−3 ESR spectrometer to 1-MHz field modulation
Authors: Smith G. E. , Blankenship R. E. , Klein M. P.
Published: March 2003

Conversion of Varian E−3 spectrometer to 1−MHz magnetic field modulation is described. The Normal 100−kHz mode of operation of the instrument is not affected by the modifications. The system has an overall response time jof approximately 2 μsec, and has senstivity comparable to the 100−kHz receiver under similar conditions.
Laboratory instrument for measuring electrical conductivity in stratified NaCl solutions
Authors: Sheppard D. M. , Doddington H. W.
Published: March 2003

A high-resolution instrument for measuring electrical conductivity in NaCl solutions with concentration gradients is presented. The output from this instrument along with local temperature measurements allow the determination of local NaCl concentratin and mass density. This instrument is presently being used for laboratory investigations of density-stratified fluids.
Moderate-accuracy interferometer for speed of sound measurement in liquids
Authors: McCartney Michael L. , Drouin Gilbert
Published: March 2003

Inexpensive, integrated-circuit phase-locked loops are used in the design of an acoustic interferometer for speed of sound measurement in 1 liter quantities of liquids. At atmospheric pressure and within a temperature range of 20–40 °C an error band of 0.03% is predicted and achieved with distilled water.
Preliminary results with microchannel array plates employing curved microchannels to inhibit ion feedback
Authors: Timothy J. G. , Bybee R. L.
Published: March 2003

Microchannel array plates employing curved microchannels to inhibit ion feedback have been obtained for the first time. These plates with J- and C-configuration microchannels have demonstrated performances comparable to those of conventional channel electron multipliers with saturated output pulse-height distributions and modal gain values in excess of 106 electrons/pulse. The present limitations of the plates are discussed and the improvements required to optimize the performance for photon-counting detection systems are described.
Oscillating sample superconducting magnetometer
Authors: Cerdonio M. , Mogno F. , Romani G. L. , Messana C. , Gramaccioni C.
Published: March 2003

An oscillating sample version of the superconducting magnetometer has been developed which measures the volume susceptibility of water solutions. Changes in susceptibility as small as 0.3% of the diamagnetism of water, or 2×10−9 cgs, have been resolved in the same run over the temperature range between 30 K and room temperature on magnetically dilute solution samples of 0.1 cm3 volume. The reproducibility of the instrument between different runs in measuring the absolute value of the magnetic susceptibility is 2% of the diamagnetism of water, or 1.5×10−8 cgs. By the combined use of the present method and the previous version it has been possible to measure the temperature dependence of the molar density of ice between 150 K and the melting point.
Cryostat for accurate x-ray diffractometry of crystalline helium to 60 mK and 25 MPa
Authors: Heald S. M. , Simmons R. O.
Published: March 2003

A cryostat designed for accurate x-ray diffractometry of crystalline helium and other solidified gases is described and its performance characterized. The cryostat is a rigid tail design. It holds the crystal, grown at pressures up to 25 MPa, in fixed orientation and position independent of the levels of the cryogenic fluids. Such stability is necessary for crystal growth, orientation, characterization, and measurements of x-ray reflection intensities and x-ray scattering. A combination of beryllium and aluminized Mylar x-ray windows permits x-ray access to the specimen crystal over broad angular ranges, essentially 360° in polar angle and ±40° in inclination. At the same time, thermal radiation is small enough to permit temperatures as low as 60 mK to be achieved with a simple dilution refrigerator.
Inexpensive linear displacement transducer using a low power lock-in amplifier
Authors: Dratler Jay
Published: March 2003

Differential capacitance displacement transducers (DCDTs) using audo frequency excitation and phase-sensitive detection are discussed, and their sensitivities are calculated. An inexpensive, low-power DCDT using a miniature lock-in amplifier made of integrated circuits is described. The lock-in amplifier has a digitally controlled phase shift between drive and reference signals, a full-scale output of ±10 V, and total noise and drift of about 1 mV peak to peak. The DCDT system has a detection limit of 0.01 nm/√H√z, a dynamic range between 60 and 80 dB, and a power consumption of less than 0.75 W. Parts cost for the system is about $200. A simplified DCDT not requiring the full lock-in amplifier is outlined, and improvements possible in the DCDT design are mentioned where appropriate.
Role of image currents on the performance of Anderson-type electrical current shims for correcting magnetic fields
Authors: Rieger B. , Kummer J.
Published: March 2003

Anderson’s calculations of current shims for the homogenization of magnetic fields are extended by taking into account the influence of the mirror images of the currents. The results, which are compared with special cases treated by other authors, indicate that the zero values of only the linear and quadratic gradients are shifted towards higher wire distance-to-pole separation ratios. By allowing for these shifts, the observed slight coupling between certain gradient shims can be avoided.
Improved voltage measurement system using the scanning electron microscope
Authors: Tee W. J. , Gopinath A.
Published: March 2003

A method of voltage measurement in the scanning electron microscope (SEM) uses a hemispherical retarding field electron energy analyzer and a feedback control loop. This paper describes improvements made both to the analyzer and the control loop to overcome some of the disadvantages of this system. A compensation technique allows for changes in the incident beam current, and this also reduces the signal caused by specimen topography. Some changes are made to the analyzer geometry which improve the spherical field symmetry of the system, and allow semiconductor devices on circular headers to be examined. The present system is now capable of measuring voltages between 50 mV and 30 V in the presence of beam current fluctuations by a factor of 3 either way. A large loop gain of 100 can now be maintained without difficulty during the voltage measurement line scans across the surface of semiconductor devices, and this ensures lower error in the measurement.
Leak telescope
Authors: Ensberg E. S. , Wesley J. C. , Jensen T. H.
Published: March 2003

A device which senses the direction of molecular flow inside a large vacuum chamber can detect leaks. Such a device becomes useful when the usual helium leak detection methods cannot be used, as when local application of helium to the outside of the vacuum system is not possible. A theoretical analysis of the detector sensitivity is given, together with experimental measurements of sensitivity, angular resolution, and noise levels in a prototype device.
One-point calibration of Allen–Bradley resistor thermometers, 2–20 K
Authors: Lawless W. N.
Published: March 2003

Calibration studies of 25 Allen–Bradley BB resistors (220 Ω, 1/8 W) between 2 and 20 K according to logR=A+BT−P indicate that A, B, and P vary linearly with the resistance at 4.2 K.
Apparatus for detecting rate and direction of rotation of tethered bacterial cells
Authors: Kobayasi Syoyu , Maeda Kayo , Imae Yasuo
Published: March 2003

A simple apparatus was constructed for detecting the rate and the direction of rotation of tethered bacterial cells. Images of the tethered cells from a dark-field optical microscope were recorded by a TV camera and VTR. The playback image of a rotating cell was passed through an optical system consisting of an image splitter and two graded filters and then transformed into two electrically sinusoidal signals having a phase difference of 90°. Rotation rate of the cell image was determined from the frequency of the signal and the direction of rotation was detected from the phase shift between two signals. The range of the rate of rotation measurable was from 1.3 to 17 rps in the steady state and the change of the rate of rotation could be followed within 1 sec. For the detection of the direction of rotation the rate had to be less than 15 rps. The change of the direction of rotation could be detected within one or two cycles of the bacterial rotation.
Add–subtract digital correlator
Authors: Jen S. , Shook J. , Chu B.
Published: March 2003

We have designed and constructed an extremely simple, low-cost add–subtract digital correlator by combining a multichannel scaler with a simple control circuit. Using a single-start, multistop data processing technique, we have demonstrated successfully the essential feature of the add–subtract correlation function. A proposed extension of the add–subtract concept with multistart, multistop data processing should yield, in principle, a digital correlator that is more efficient than a single-clipped digital correlator; specifically, a gain by a factor of two, as compared with the Malvern type correlator, can be achieved.
Portable flash x-ray diffraction system
Authors: Green Robert E.
Published: March 2003

A flash x-ray diffraction system is described which weighs less than 27.2 kg and which permits Laue transmission x-ray diffraction patterns to be obtained with exposure times as short as several microseconds using multiple pulses of 60 nsec duration each. The system consists of a pulsed x-ray generator incorporating a tungsten target beryllium window x-ray tube and a specially designed collimator. Diffraction photographs are presented which permit comparison of the pattern obtained with the portable flash x-ray diffraction system with that obtained using a conventional x-ray diffraction system incorporating a heated filament tube.
Diagnostics for intense pulsed ion beams
Authors: Young F. C. , Golden J. , Kapetanakos C. A.
Published: March 2003

Diagnostic methods pertinent to the probing of intense pulsed ion beams are described. Special emphasis is given to the measurement of delayed radioactivity from nuclear reactions induced in a target by the ions. This nuclear activation analysis provides the most precise, unambiguous means of determining the number of ions per pulse that is presently available. A compilation of yields and cross sections for several nuclear reactions is given. Included among the nuclear techniques is the measurement of prompt radiation such as γ rays and neutrons from ion-induced reactions. In addition, a scintillator–photodiode detector is described which has proven to be useful for the measurement of time of flight and which may be used to observe the relative pulse shape. Biased ion collectors and difficulties associated with their use are also discussed.
Use of a hot wire anemometer as a particle velocity detector in standing sound waves
Authors: Nall B. H.
Published: March 2003

It has been determined experimentally that the hot wire anemometer can, with restrictions, be used as a linear-amplitude response particle velocity detector in a longitudinal mode standing sound wave. In the case of a straight filament proper orientation of both the hot wire and the velocity field are important. Maximum sensitivity is obtained for a horizontal hot wire in a vertically oriented particle velocity field, but the output of a hot wire inclined 45°/135° to vertical in a horizontal standing wave tube is phase sensitive to the sense of the particle velocity vector. High-pass filtering is required to remove low frequency nonlinear components of the repetitive driveup–free-decay amplitude modulation. Traverses of the particle velocity field near a 0.9525 cm diam sphere in a 5.08 cm i.d. cylindrical cavity are presented for both straight and curved hot wires.
LN2-cooled refractory metal elements as current limiters
Authors: Gilmour A. S. , Marshall J. D.
Published: March 2003

While designing a high-power current-limiting device which utilizes the large change of resistivity with temperature of certain metals, it was discovered that some metals, when immersed in liquid nitrogen, may form a jacket of gaseous nitrogen around them and can be heated electrically to any temperature up to their melting point without oxidation. Due to this effect, herein called the vapor lock effect, the resistivity of the metal has been observed to increase by a factor of 91 (for tungsten), and power dissipations of up to 550 W/cm2 have been attained.
Low-noise preamplifier for photoconductive detectors
Authors: Dereniak E. L. , Joyce R. R. , Capps R. W.
Published: March 2003

High-performance infrared detectors such as arsenic-doped silicon (Si:As) and bismuth-doped silicon (Si:Bi) have been successfully used in ground-based infrared telescope systems in the 2–20 μm range. Optimum performance (BLIP operation) of these detectors is obtained by using a special feedback amplifier. The advantages of such a system are discussed in conjunction with preliminary data on Si:As and Si:Bi detectors.
Micro-optic system for reflectance measurements at pressures to 70 kilobar
Authors: Welber Benjamin
Published: March 2003

An optical system which makes it possible to obtain reflectance spectra of solids in the range of hydrostatic pressures 0–70 kilobar and higher is described. The system is used in conjunction with a diamond anvil pressure cell, and has a spectral range of 0.6–4.5 eV. An example is furnished illustrating its use in an investigation of the shift with pressure of the plasma reflectance edge of TTF-TCNQ.
Simple two-axes sample positioning mechanism
Authors: Tommet Thomas N. , Bernasek Steven L.
Published: March 2003

A simple manipulator is described which allows rotation of a target crystal about two mutually perpendicular axes, independent of translational motion. The design is such that the mechanism can easily be added to a commercial offset manipulator.
Laboratory scale pulverized char feeder
Authors: Kriegbaum R. A. , Vogt R. A. , Laurendeau N. M.
Published: March 2003

A laboratory scale mechanical pulverized char feeder that is competitive with, yet inherently simpler than, fluidized bed designs has been developed. Performance evaluation of the feeder using 100% through 140-mesh char indicates a feed range of 7–18 g/min with short-term flow stability within 3% throughout 90 min of continuous operation. Independent control over the char and carrier gas flowrates allows for precise adjustment of the char/air feed ratio, the tested range being 0.07–0.10 by mass. The prototype incorporates a carrier gas preheater (673 K maximum) and is designed to feed at atmospheric pressure.
Electronic circuit for floating Langmuir double probe used in pulsed plasma diagnostics
Authors: Schneider H. , Szubert J.
Published: March 2003

An electronic circuit used with floating Langmuir double probes in pulsed plasma measurements is described. Current fluctuations of the double probe are transformed by means of a special transformer into voltage fluctuations. The signal is then integrated to give a voltage wave proportional to the measured current wave. A bridge circuit has been used to neutralize the influence of current-source stray capacitance.
Design of an acousto-optic modulator and driver
Authors: Spears Kenneth G. , Larsen James
Published: March 2003

We report a design for an acousto-optic mode locker suitable for use in cw or pulsed dye lasers. A circuit for a stable frequency source is shown and the system performance is briefly discussed with reference to mode-locker operating parameters.
Interferometric method for the determination of binary gas mass diffusivities
Authors: Black W. Z. , Somers R. L.
Published: March 2003

A new method has been developed for measurement of the mass diffusivity of gas pairs. The method utilizes fringe shift data produced by a differential interferometer. A test cell was constructed that modeled the transient one-dimensional evaporation of volatile liquids into stagnant air. The equations which describe this process were adapted to a relative time solution and modified to make use of interferometrically generated data. The method was used to determine the mass diffusivity of eight substances: five reference substances with well documented values of mass diffusivity and three unknown substances whose diffusivity has previously been unreported. The method is relatively simple and can be carried out in a relatively short time. The method was applied to liquids with vapor pressures in the range 23–230 mm Hg. The accuracy of the method proved to be strongly dependent upon the initial conditions within the test cell. The initial conditions were more accurately simulated with less volatile substances. As a result, values for the low-volatility substances were within 4% of published values while those for the higher-volatility materials differed by as much as 26%.
Portable visible-infrared reflectometer
Authors: Melsheimer F. M. , Rank D. M.
Published: March 2003

A simple reflectometer has been developed for measuring the conditions of aluminum coatings on large astronomical telescope mirrors.
Digital NMR frequency to magnetic field converter
Authors: Vanwelsenaers A. , Schoemaker D.
Published: March 2003

A simple inexpensive circuit is described which digitally converts the frequency of an NMR gaussmeter to gauss. The circuit uses synchronous binary rate multipliers and performs the conversion immediately and with arbitrarily high precision.
Microelectrode puller with high temperature heating element
Authors: Plowright M. , Barrs H. D. , Bleijie J. J.
Published: March 2003

A novel inexpensive microelectrode puller with a carbon rod heating element is described. Sufficiently high temperatures can be attained to fabricate glass microelectrodes from Pyrex and silica or micropobes from most high melting point metals.
Direct density display with a resonance cone rf probe
Authors: Ickovic J. , Stenzel R. L. , Gekelman W.
Published: March 2003

An rf technique is described for a direct oscilloscope display of the electron density in a magnetized plasma. The transmission between a point rf probe and a ring rf probe exhibits a maximum when the ring intersects the resonance cone of the point source. The ring is in the plane perpendicular to the magnetic field and the point is coaxial with the ring. For a given probe geometry and magnetic field, the frequency of the transmission peak is a simple function of the plasma density. A swept frequency display of the transmission curve on an oscilloscope gives an instantaneous, direct measure of the plasma density.
Large thermocouple thermometry errors caused by magnetic fields
Authors: Kollie T. G. , Anderson R. L. , Horton J. L. , Roberts M. J.
Published: March 2003

Chromel/Alumel thermocouples used in a magnetic field indicated temperatures in error by about ±150% at 100 °C. Diagnostic tests showed that the errors were caused by the Ettingshausen–Nernst (EN) effect. The EN effect produces an emf in a conductor, such as a thermocouple, placed in a magnetic field and temperature gradient which are both transverse to the length of the conductor. The heat transfer experiment at the Oak Ridge National Laboratory in which the temperature measurement errors were encountered is described, and the results of diagnostic tests performed in this experimental apparatus and in auxiliary lab-bench experiments to identify the EN effect are presented. Sources of error, other than the EN effect, for thermocouples used in a magnetic field are discussed.
Diamond anvil device for x-ray diffraction on single crystals under pressures up to 100 kilobar
Authors: Keller R. , Holzapfel W. B.
Published: March 2003

A new high-pressure diamond anvil device is described which allows for x-ray diffraction intensity measurements on single crystals up to hydrostatic pressures of about 100 kilobar. The present device fits into commercial x-ray diffractometers such as precession cameras and four-circle diffractometers. The pressure is determined by measuring the ruby R1-line shift with a Fabry–Pérot interferometer which is coupled to a microscope system. First measurements on Se carried out on a precession camera indicate that atomic position parameters and pressures can be determined with standard deviations of ±0.002 and ±0.7 kilobar.
Automatic recording of quantum yields in photoemission
Authors: Schmidt-Ott A. , Meier F.
Published: March 2003

A simple automated system designed to monitor quantum efficiency as a function of photon energy is described. Photocurrents ranging from 10−6 to 10−12 A can be measured continuously as a function of radiation energy and the corresponding logarithmic yield is plotted directly on a recorder. The main advantages are a drastic reduction of the measuring time and higher resolution compared to conventional point-by-point methods.
Gas cell for photochemical studies
Authors: Ledford A. E. , Braun W.
Published: March 2003

A cell design suitable for chromatographic sampling of products is integrated into an apparatus suitable for performing ir, visible, and photochemical studies. The design of the cell and a schematic of the apparatus are presented and described.
cw ruby laser pumped by a 5145 Å argon laser
Authors: Venkatesan T. N. C. , McCall S. L.
Published: March 2003

We describe an argon laser pumped ruby laser system which provides 300 mW in several modes using 2 W of single mode 5145 Å argon laser pump power. By filtering the output with a stabilized Fabry–Perot cavity, single mode outputs of 75 mW or more were obtained. The laser is tunable over a frequency width of 60 GHz about the R1 line at LN2 temperatures, with single mode powers between 10 and 100 mW.
Simple longitudinally pulsed CO2 laser and its application in single-mode operation of TEA lasers
Authors: Loy M. M. T. , Roland P. A.
Published: March 2003

We describe a simple longitudinally pulsed, low-pressure CO2 laser with peak power up to 1 kW and pulse duration about 100 μsec. Its relatively high gain allows lasing operation with output mirror reflectivity as low as 35%. It is especially useful as an intracavity gain section inside a high-power TEA laser for single-longitudinal-mode operation.
Thermal diffusivity measurement of Armco iron by a novel method
Authors: Mirkovich V. V.
Published: March 2003

A novel thermal diffusivity apparatus is described. It is based on the concept of an infinite cylinder and the measurements can be performed in transient and periodic temperature modes. Its ability to perform measurements on electrically conductive, medium range thermal diffusivity solids, as well as its accuracy of measurement, was established by measuring thermal diffusivity of an Armco iron specimen.
Measuring the position of a Josephson junction
Authors: Magerlein J. H. , Eick R. H. , Dunkleberger L. N. , Fulton T. A.
Published: March 2003

We describe a method for measuring the position of a Josephson junction from outside the cryostat. An inhomogeneous ac magnetic field from two opposed coils modulates the critical current of the junction unless it is in the central region where the field is small. We use the technique to measure the critical current of individual junctions in a series-connected array, using electrical contacts across the entire string.
Design of a friction-activated semi-demountable feedthrough seal
Authors: Hannemann R.
Published: March 2003

The design of a conical, pressed-in hermetic feedthrough seal is briefly reported in this note. The considerations discussed are applicable to gasket-type seals in general.
Extraction of an ion beam from a diverter-type plasma source
Authors: Yatsu K. , Nozaki Y. , Hagiwara S. , Miyoshi S.
Published: March 2003

A multiple-aperture ion source using a diverter-type plasma source has been developed. The density profile of the source plasma is uniform to ±7% across a diameter of 5.6 cm. An ion beam of 4 keV, 0.2 A has been extracted from the ion source. The experimentally obtained perveance is about half of the theoretical value. The ion source has the potential to be a high-current ion source.
Elimination of oscillator coupling effects in ion cyclotron double resonance experiments
Authors: DeFrees Douglas J. , McIver Robert T.
Published: March 2003

In ion cyclotron double resonance experiments, massive interference results when the frequency of the double resonance oscillator is close to the resonant frequency of the marginal oscillator detector. A compensator circuit has been developed which totally eliminates the interference and permits double resonance experiments to be performed for ions which are only 1 amu apart. TP E #YR 77 #XN 0758+g #XN 8430Wp #XN 7640+b #XN 8230Fi OSCILLATOR DETECTOR. A COMPENSATOR CIRCUIT HAS BEEN DEVELOPED WHICH TOTALLY ELIMINATES THE INTERFERENCE AND PERMITS DOUBLE RESONANCE EXPERIMENTS TO BE PERFORMED FOR IONS WHICH ARE ONLY 1 AMU APART.
Single ion counting in high-resolution mass spectrometry
Authors: Wachi F. M. , Gilmartin D. E.
Published: March 2003

A modification that permits the utilization of an air-stable, continuous-dynode electron multiplier that can be used either as an ion-counting or as an ion current measuring device without jeopardizing the photoplate ion detection capability of the high-resolution mass spectrometer is described.
Resistance welding of metals with high electrical and thermal conductivity
Authors: Ekern R. , Czanderna A. W.
Published: March 2003

A simple device for welding metals with high electrical and thermal conductivity is described. The use of the device, which was adapted from a commercially available carbon deposition unit, for welding 0.0127 and 0.0507-cm-diam Ag, Au, and Pt wires is discussed.
Linear unbalanced dc bridge
Authors: Rostocki A. J. , Wiśniewski R.
Published: March 2003

A modification of the classic Wheatstone bridge is presented in which the output voltage is exactly proportional to the increase in measured resistance. This modification is based on a special system of connection with the power supply. In its original version the circuit was successfully applied to high-pressure measurement by the manganin sensor method.
Effect of dynamic stress on commercial superconductors: a test facility
Authors: Schmidt Curt
Published: March 2003

A test facility was built for the investigation of commercial superconducting wires subjected to dynamic mechanical load. The apparatus permits measurement of stress–strain curves while the sample is exposed to a transverse or longitudinal magnetic field and a transport current is applied. The variation of cooling conditions is possible with the sample placed in vacuum, helium gas, and liquid helium, respectively. With this apparatus the ’’training’’ behavior of superconducting magnets was simulated in short sample tests. Other results obtained are stress–strain curves of NbTi showing serrated yielding, and the temperature measurement of superconducting composite wires during deformation with a response time in the millisecond range.
A noninterferometric optical probe
Authors: Chapman G. D. , Green E.
Published: March 2003

A noninterferometric optical probe has been designed and built on the basis of simple geometric principles. It may be used to sense the motion of unprepared and/or inaccessible targets of virtually any material with an accuracy of ±0.1 mm at a distance of 1550 mm. Experimental results are presented, which include the determination of the distortion of a target object in an electric furnance operating at 800°C.
Single particle aerodynamic relaxation time analyzer
Authors: Mazumder M. K. , Kirsch K. J.
Published: March 2003

An instrument employing a laser Doppler velocimeter and a microphone to measure the phase lag of the motion of aerosol particulates relative to the motion of the fluid medium within an acoustic field is described. The relaxation times and aerodynamic diameters of the particles or droplets are determined in real time from the measured values of phase lag; thus, the size analysis is independent of the electrostatic charges and refractive indices of the particulates. The instrument is suitable for analyzing the aerodynamic size spectrum of atmospheric particulate pollutants with aerodynamic diameters ranging from 0.1 to 10.0 μm.
Apparatus for producing uniform solid spheres of hydrogen
Authors: Foster C. A. , Kim K. , Turnbull R. J. , Hendricks C. D.
Published: March 2003

An apparatus has been constructed which produces uniform spheres of solid hydrogen for experiments testing the feasibility of using the solid hydrogen pellets for refueling fusion reactors. Two versions of the apparatus were developed, one which produced 70-μm-diam pellets at the rate of 105/sec and another which produced 210-μm pellets at the rate of 2.6×104/sec. The first step in the pellet production is to liquefy the hydrogen by flowing it through a liquid-helium-cooled heat exchanger. Then, a liquid hydrogen jet is formed by flowing the hydrogen through a nozzle. The jet is broken up into uniform drops by an acoustical excitation. The drops are frozen by evaporation in a pressure less than the triple point pressure of hydrogen. Finally, the drops are injected into vacuum for the experiments.
Device for stroboscopic extraction of atmospheric pressure species into regions of high vacuum
Authors: Watters Robert L. , Walters J. P.
Published: March 2003

An extraction nozzle and shutter device are described, which enable a short burst of species, created by a repetitive train of atmospheric pressure spark discharges (or similar excitation sources), to be inserted directly into a chamber at low pressure.
Differential ultrasonic velocimeter for measurements of dilute suspensions
Authors: Mitaku S. , Sakanishi A.
Published: March 2003

A differential ultrasonic velocimeter has been developed for the direct measurement of the difference in the ultrasonic velocity between a dilute suspension and the medium. The most suitable application of this system is for the type of experiment where a small change in suspended materials is masked by a large change in the medium, such as in the case of dilute suspension of biological materials. The difference in the ultrasonic velocity in a sample and the medium is directly measured to cancel not only the change in the medium but also the electronic drift with an accuracy of about 5 ppm and a long-term stability of about 5 ppm/day.
Circuit for a digital pulse programmer
Authors: Conway John L. , Cotts R. M.
Published: March 2003

A versatile digital pulse probrammer circuit is described which is capable of generating all of the major sequences for pulsed NMR spectroscopy involving up to four independently phased rf channels. The system provides control over the applied transverse magnetic field, H1, with a sufficiently varied range of timing intervals that it can be, and has been, applied to both liquid and solid systems. While the programmer has been designed specifically to meet the needs of pulsed NMR, the design could be applied to other systems requiring flexibile control of experimental parameters. Modular in format, the programmer consists of a main clock unit and four identical channel units. The main clock module controls the time between repetitions of the sequence, while the channel modules specify the time placement and duration of the rf bursts through each gating channel within a sequence. Complex pulse sequences are constructed with control pulses sent from module to module down a sequential hierarchy: the ability of each channel to loop a predetermined number of repetitions at a set rate, while producing resetting and initiating pulses to the next channel allows the production of repetitive sequences, such as the Carr–Purcell and the saturation burst. Automatic advance of delay times is also achieved through this sequential initiating technique. The output of trigger pulses from each channel module provides additional flexibility when using peripheral equipment such as signal averagers. Small and medium scale TTL integrated circuits are used throughout as the circuit elements for the device. A 10-MHz crystal clock oscillator provides highly stable timing signals for the entire programmer.
Direct soft x-ray response of a charge-coupled image sensor
Authors: Koppel Louis N.
Published: March 2003

To determine the feasibility of actively recovering data from x-ray imaging instruments used in the laser fusion program of Lawrence Livermore Laboratory, we have used a commercial, silicon video sensor to detect patterns of soft x rays (1–8 keV). The sensor is a two-dimensional, frame transfer, charge-coupled device (CCD), modified to allow direct access of x rays to the sensitive silicon. We discuss the x-ray sensitivity, linearity, and dynamic range of the CCD.
Adaptation of Cahn electrobalance for solid–gas reactions at elevated temperatures
Authors: Ray S. P.
Published: March 2003

A Cahn electrobalance model RG was adapted for reduction and oxidation studies of CeO2−x(0<x<0.3). Symmetrical design eliminated the disturbing effects like thermomolecular flow, buoyancy, and gas flow. The electrostatic effect was eliminated with a Pt coating. A sliding double furnace allowed reduction, quenching, and oxidation to be carried out in situ.
Programmed command unit for pulsed light source
Authors: Meyer J. J. , Aubard J.
Published: March 2003

A low-cost xenon light pulsing unit is described which provides light pulses of 10- to 990-μsec widths in 10-μsec increments.
Correct application of beam splitters with laser beams of fluctuating polarization
Authors: Neufeld C. R. , Saint-Hilaire G. , Noël P. , Robert A. , Szili Z. , Gagné M.
Published: March 2003

Measurements are presented which indicate that the polarization of a multimode CO2 laser beam produced in an unstable cavity varies considerably from shot to shot. This effect must be taken into account when using a dielectric beam splitter to monitor the laser beam.
Infrared opaque heat shield with high thermal conductance for use in changing magnetic fields
Authors: Tanner D. B. , Ihas G. G. , Muething K. A.
Published: March 2003

Spectral data on the transmittance, reflectance, and absorption of far-infrared radiation are presented for ’’coil foil,’’ Stycast 1266 epoxy, a Stycast 1266/charcoal powder composite, Stycast 2850 GT epoxy, Epibond 100 A adhesive, an Epibond 100 A/copper powder composite, silicone vacuum grease, and a vacuum grease/charcoal composite. These data show that a superior heat shield for low-temperature applications can be constructed with coil foil coated with a Stycast 1266/charcoal powder composite. This shield is opaque to all thermal radiation, has a high thermal conductivity to a heat sink, is not susceptible to eddy current heating, is light, strong, rigid, and yet easy to construct.
Submillimeter detector calibration with a low-temperature reference for space applications
Authors: Nolt I. G. , Radostitz J. V. , Kittel P. , Donnelly R. J.
Published: March 2003

Infrared observations from space will involve low levels of background radiation incident on the detector. We describe a detector calibration method which uses a cold blackbody source having low background. The effective wavelength of the modulated power is determined by the mean temperature of the source since no filters are employed. Direct temperature modulation of the source eliminates the need for any chopping mechanism. Such a low-temperature modulated source can be viewed as a low-resolution temperature-tuned absolute spectrometer.
Measurement of ion acoustic test waves in a magnetized plasma by means of a 30-GHz Lecher wire interferometer of high spatial resolution
Authors: Paris P. J. , Bitter M. , Hollenstein Ch.
Published: March 2003

A 30-GHz Lecher wire interferometer of high sensitivity and spatial resolution is used for the detection of ion acoustic test waves in a magnetized plasma. Coherent density fluctuations of 0.1% for electron densities of 1010 cm−3 can be detected by means of a phase-lock technique. The spatial resolution (minimum measurable wavelength) is given by the 1.5-mm spacing of the Lecher wires, which is large compared to the Debye length.
Moderate pressure, low-temperature microwave spectrometer
Authors: Rupp L. W. , Peercy P. S. , Walsh W. M.
Published: March 2003

An apparatus for generating up to ∼3.5 kilobars of hydrostatic pressure from ambient down to liquid helium temperatures has been developed at 35 and 17 GHz. The design incorporates a conical sapphire cavity pressure seal in a piston-and-cylinder loaded by a small commercial ram. The use of silicone grease as a hydrostatic working fluid to low temperatures is emphasized. The equipment has been used for several ESR experiments.
Variable temperature pressure cell for polycrystalline x-ray studies down to 2 K—application to Bi
Authors: Skelton E. F. , Spain I. L. , Yu S. C. , Liu C. Y. , Carpenter E. R.
Published: March 2003

A variable pressure diamond anvil cell is described for operation at temperatures continuously variable from 300 down to 2 K and controllable within 10 mK. Polycrystalline x-ray data are collected from the pressure cavity by means of either (1) standard photographic techniques, (2) diffractometer measurements, or (3) energy dispersive diffractometry. The facility has been used to examine parts of the phase diagram of Bi. Results from this study indicate that the Bi-I and Bi-III structures are retained to low temperatures; however, there is no evidence to support a structural transition from Bi-V to Bi-VIII.
Feedback-controlled particle suspension system for LITE magnetic mirror fusion facility
Authors: Tomlinson R. G. , Polk D. H. , Weise A. P. , Bar-Tal G. S. , McHugh T. M. , Hasselmark E. D. , Gagnon E. P. , McClurg W. C. , Wisner G. R. , Jong R. A. , Haught A. F.
Published: March 2003

A feedback-controlled particle suspension system has been developed for laser target plasma production in the LITE experiment. Suspension voltages derived from position and velocity (position derivative) feedback signals serve to capture an injected particle in high vacuum, damp the particle motion, and stably position the particle at the system null. In typical operations, LiH particles of ∼100-μm diameter, projected by a spring plunger into the suspension region, are captured and positioned at the system center in ⩽0.25 sec with a jitter of ⩽20 μm, less than 1/5 the particle diameter. With this system the precise particle positioning required for spherically symmetric plasma generation is obtained even with large particle sizes, and the feedback particle suspension system is incorporated as an integral part of the LITE experimental facility for studies of neutral injection buildup on a dense, mirror-confined, laser-produced target plasma.
Recycling molecular beam reactor
Authors: Prada-Silva G. , Kester K. , Löffler D. , Haller G. L. , Fenn J. B.
Published: March 2003

A novel recycling molecular beam reactor (RMBR) is described which has proved useful in the study of reactive molecule–surface collisions. A beam of reactant gas molecules is formed from a supersonic free jet. After collision with a target surface the molecules pass through the vacuum pumps and are returned to the nozzle source. Continuous recycling permits the integration of very small reaction probabilities into measurable conversions which can be analyzed by gas chromatography. Some successful experiments have been carried out on the isomerization of cyclopropane to propylene.
Double-pulse comparison ultrasonic spectrometer
Authors: Franz Judy R. , Gujral R.
Published: March 2003

A new technique, the double-pulse comparison technique, for measuring very small changes in ultrasonic velocity is described. With this technique, velocity shifts of less than 1 part in 109 can be detected. The application of the double-pulse comparison ultrasonic spectrometer to the measurement of the nonresonant Alpher–Rubin effect in vanadium is discussed.
Metallic thermal connectors for use in nuclear refrigeration
Authors: Muething K. , Ihas G. G. , Landau J.
Published: March 2003

Measurements of the electrical resistance at 4.2 K are used to infer the thermal conductance at ultralow temperatures of (1) copper magnet wires with Formvar and Allex insulations, (2) inert gas welded and silver-soldered joints, and (3) various demountable metallic connectors. The purpose of this study is to determine a wire suitable for use as the refrigerant in a nuclear adiabatic demagnetization refrigerator and an appropriate method of joining the wire to a heat exchanger in a 3He cell. It was found that ordinary magnet wire insulated with Allex can easily be annealed to have a very low resistance at low temperatures. Further, annealed copper-to-copper welds are indistinguishable from bulk OFHC copper, while alloying makes the resistance of silver-soldered joints somewhat larger than would be calculated from the bulk resistivity of the silver solder. An improved version of the ’’squeeze’’ connector and a simple pressure contact using a stainless steel screw are described. These have too high a resistance for nuclear refrigeration but are good enough for most other low-temperature applications. Finally, a large copper tapered screw joint was found to make relatively poor thermal contact.
Surface-acoustic-wave film thickness monitor
Authors: Kovnovich S. , Harnik E.
Published: March 2003

The construction and performance of a new type of quartz crystal film thickness monitor which operates on the principles of the surface-acoustic-wave oscillator is discussed. It is shown that this monitor has a number of advantages over the conventional quartz crystal thickness monitor: it has high sensitivity and resolution, the sensor can be reconditioned, and it needs no water cooling. There remain, however, some calibration problems.
Direct display of gas-gun projectile velocity
Authors: Hutchings I. M.
Published: March 2003

An analog circuit, triggered photoelectrically, provides a direct display, in meters per second, of the velocity of the projectile from a small laboratory gas gun. Signals from two phototransistors on the gun are combined by a gating circuit, which controls a ramp generator to produce a voltage proportional to the time interval. The reciprocal of this voltage, corresponding to the velocity of the projectile, is then displayed on a digital meter.
Single-bellows, hydraulic valve for use at low temperatures
Authors: Bischoff G. C. , Piskorski L. I.
Published: March 2003

A hydraulically actuated, superfluid-tight, liquid helium valve suitable for sealing a pumped 1-K pot in a dilution refrigeration is described. Details for construction of the valve components and formulas for design of the bellows are given.
Picosecond optical gate
Authors: Ripin B. H. , Feldman U. , Doschek G. A.
Published: March 2003

An optical shutter is described which opens on a few picoseconds time scale. The shutter consists of a thin foil irradiated by a laser.
High-temperature atomic beam source
Authors: Stockdale J. A. , Schumann L. , Brown H. H. , Bederson B.
Published: March 2003

A novel atomic beam source which employs radiant heating is described. It is capable of stable continuous operation for many hundreds of hours at temperatures up to 3000 K. Rapid recharging of source materials and temperature recycling may be carried out.
Crystal heater supply utilizing controlled electron bombardment
Authors: Chapman R. , Blair D. L.
Published: March 2003

Metallic crystalline samples used in gas/surface interaction studies are often very difficult to heat by direct ohmic connections. Electron bombardment of the sample accomplishes the desired heating but needs great care and constant monitoring if a nonregulated system is used. A power supply regulating system is described which provides up to 250 W to heat the sample. The power is fully adjustable and programmable.
Low noise preamplifier for gravitational research
Authors: Bordoni F. , Pallottino G. V.
Published: March 2003

The sensitivity of the new generation of gravitational wave antennas to be cooled to the temperature of liquid helium is limited by the noise performance of the preamplifier. Two circuits are described that have been realized to measure the Brownian motion of a small low temperature antenna. They use a parallel arrangement of four low noise FETs (2N6550) followed by an operational amplifier to obtain an input noise that is characterized by a voltage of 0.33 nV/√Hz and a current of 24 fA/√Hz plus a correlated current contribution of 8 fA/√Hz at 10 kHz.
Closed system gas circulating pump without moving parts
Authors: Schumacher Ernst
Published: March 2003

A closed system gas circulating pump is described. It consists of a gas volume enclosed between two unidirectional liquid valves. The volume is periodically heated and cooled, which creates gas circulation. A full-wave continuous pump has four valves and two volumes which are alternately heated and cooled. A half-wave pulsating pump has two valves and one volume. The pump can be used for pressures ≳0.2 Torr and circulation rates from <1 ml/h to 20 ml/min. It can be made by glass blowing and is very cheap.
Plasma position detector using a segmented photodiode
Authors: Gribble R. , Miller G.
Published: March 2003

A one-dimensional position sensing device is described which produces an electrical signal proportional to the position of maximum light intensity imaged upon its light detecting element. The device uses a segmented photodiode but the position resolution is significantly better than the segment width, which is the resolution that would be obtained using a purely digital circuit. The device is also quite fast with a delay plus rise time of about 50 nsec.