bluuebunny/crossref_metadata_2025 huggingface dataset:
Precision grinding device for radioactive tracer diffusion studies in very hard ceramic materials
Authors: Hong J. D. , Griffin W. E. , Davis R. F.
Published: March 2003

Precision grinding equipment for the removal of very thin layers of hard materials containing slowly diffusing isotope tracers is described. The system is unique in the use of vacuum techniques to hold the sample in place and in the procedures used to insure maintenance of an optically flat sample with essentially parallel faces throughout the removal process.
Thomson parabola ion analyzer for laser-plasma studies
Authors: Slater D. C.
Published: March 2003

A compact, flexible design for a parallel-fields ion analyzer is presented. Accurate ion velocity and charge state measurements can be obtained over a wide range without the need for calibration sources. Etchable cellulose-nitrate foil is used to record individual ion tracks.
Magnetic stirrer with no external moving parts
Authors: Engel Paul S.
Published: March 2003

This note describes a variable speed stirrer which is based upon a rotating magnetic field produced electronically. Digital circuitry is used to generate two stepped functions which approximate sine waves differing in phase by 90°. The signals are amplified to drive sets of perpendicular coils such that a magnet situated between the coils rotates at the chosen speed.
Novel technique for dynamic surface tension and viscosity measurements at liquid–gas interfaces
Authors: Sohl C. H. , Miyano K. , Ketterson J. B.
Published: March 2003

A novel means of generating and detecting surface waves at liquid–gas interfaces has been successfully developed. Electrocapillarity is used to generate the waves which are detected via specular reflection of a laser beam from the fluid surface to a position sensitive photodiode. Such a scheme is compact, sensitive, and does not mechanically touch the fluid surface. A preliminary study of highly damped waves on the magnetically oriented liquid crystal MBBA is reported.
Gas discharge ion source III. Modified Berkeley multifilament ion source
Authors: Bickes R. W. , Bacon F. M. , O’Hagan J. B.
Published: March 2003

Total ion current, ion energy, mass and current density distributions, and the impurity content of the ion beams produced by a modified Berkeley multifilament ion source (MFIS) were measured as a function of source configuration, gas pressure, and operating conditions: the ’’best’’ configuration produced beams of 200 mA or more at pressures between 0.40 and 2.0 Pa. In comparison with earlier studies of duoplasmatron and duopigatron sources, the MFIS beams contained less D+, only ca. 33%, but the beams had much narrower energy distributions and flatter current density distributions. The beams contained 1%–2% impurities which consisted mainly of masses 18, 20, and 22.
UHV application of spring-loaded Teflon seals
Authors: Auerbach Daniel J. , Becker Charles A. , Cowin James P. , Wharton Lennard
Published: March 2003

Large, bakeable, rotatable ultrahigh vacuum seals capable of operation at 10−11 Torr are described. They employ doubly differentially pumped commercially available spring-loaded Teflon seals. A static version is very convenient for quick access as it requires nearly negligible sealing force other than atmospheric force.
Microcomputer-based high-voltage pulse controller and temperature monitor for Kerr effect investigations
Authors: Alameda G. K. , Mann R.
Published: March 2003

A microcomputer-based high-voltage pulse controller was developed for use in Kerr effect studies. The system allows the user to program pulse format and change pulse sequence by a simple entry from a keyboard. A silicon diode temperature probe which is interactive with the microcomputer is also discussed. Details of the necessary interface and a sample pulse format program are given.
Simple adjustable liquid sample holder for x-ray absorption studies
Authors: Moss S. C. , Metzger H. , Eisner M. , Huang H. W. , Hunter S. H.
Published: March 2003

A sample holder is described which permits the rapid optimization of liquid thickness for x-ray absorption fine structure studies. In particular it has been applied to the measurement of both Extended X-Ray Absortion Fine Structure (EXAFS) and near-edge structure in the vicinity of the K absorption edge of potassium ions (E0≃3605 eV) in a variety of solutions. The instrument basically consists of a pair of blocks—one fixed and one movable, both with transparent x-ray windows of stretched polypropylene which sandwich a thin sealed liquid sample bag of polyethylene or polypropylene and which, through squeezing via a micrometer drive, are experimentally adjusted to yield the desired sample thickness.
Optically coupled high-voltage isolation amplifier
Authors: Pearce James W.
Published: March 2003

A common and persistent problem in modern instrumentation is the observation and recording of small signal waveforms that are removed from ground by very high voltages. Examples of this are the instrumentation of neutral particle injectors used in controlled thermonuclear research and the construction of safety breaks for air core toroidal devices. To overcome this problem a very high voltage isolation amplifier was designed. It employs analog-to-digital conversion with serial data transmission on a fiber optic cable.
Instrumentation to measure the oil thickness on a wavy water surface
Authors: Kordyban E. , Cuker S.
Published: March 2003

The instrumentation developed to measure the thickness of an oil layer on water in the presence of waves is described. It consists of a probe which follows the surface of water; a light-sensitive gauge attached to the probe measures the extent to which it is submerged in opaque oil, thus determining the oil thickness. In transparent petroleum products motion pictures may be used for this purpose. The results of performance tests of components and the preliminary tests on actual waves are presented.
Capillary viscometer for use with crosslinking polymer melts
Authors: Shaw M. T. , Burkert S. , Sundstrom D. W.
Published: March 2003

A capillary viscometer is described which adapts a conventional capillary rheometer for use with crosslinking polymers. Illustrative data obtained with the viscometer using diallyl phthalate resin are included.
Dynamic power supplies for TEA lasers
Authors: Coïsson R. , Rancan E.
Published: March 2003

The purpose of this note is to suggest the use of simple dynamic charging methods for small fast-discharge transversely excited atmospheric pressure lasers.
GaAs junction field effect transitors for low-temperature environments
Authors: Forrest S. R. , Sanders T. M.
Published: March 2003

Thermal, electrical, and noise characteristics of a GaAs junction FET are described. Low voltage noise [1.5±0.2 nV/(Hz)1/2 at T =4.2 K] and insensitivity to temperature change in the range 1.3⩽T ⩽300 K make it suitable for low-temperature applications.
Sample modulated Raman spectroscopy and frequency modulated visible light—resonance Raman spectrum of a polydiacetylene fiber
Authors: Tzinis Costas , Bahl Surinder K. , Davidson Paula , Risen William M. , Baughman Ray H.
Published: March 2003

Methods for obtaining sample modulated Raman (SMR) spectra and frequency modulated visible light are described. The sample modulated Raman method is one in which the frequency of the Raman scattered light is modulated by the sample which is responding to an externally applied periodic stress. The Raman active modes of the sample which are due to the vibrational motion of those molecular-scale units that change in response to the external stress are modulated and appear in the frequency-locked phase sensitively detected Raman spectrum. Those modes due to units that do not respond significantly to the stress do not appear. In principle the SMR method permits determination of those molecular units of a complex substance that are responsible for the substance’s response to an external stress. The Raman scattered light is frequency modulated, has the wave form ν=ν0−νi−(δν)  sin(2πft), where ν0 is the incident monochromatic light, νi is the vibrational frequency of the statically stressed material, and (δν) is the magnitude of the frequency shift caused by the maximum stress applied at the frequency f.
Self-contained automatic recorder of the dc Josephson current
Authors: Simon R. W. , Landmeier P.
Published: March 2003

A circuit for the automatic recording of the dc Josephson current as a function of magnetic field or other variable has been designed and constructed. The apparatus requires no additional signal processing devices as have techniques for this measurement utilized in the past. Sensitivity to critical current amplitudes corresponding to the appearance of 5 mV across a sensing resistor is attained, as well as separate examination of the positive and negative halves of the zero-bias current.
Improved apparatus for trapped radical and other studies down to 1.5 K
Authors: Woollam John A. , Sugawara Kuzushi
Published: March 2003

This note describes a Dewar system and associated apparatus for trapped free radical and other studies at temperatures down to 1.5 K. Cylindrical and rectangular microwave cavaties can be used.
Semiautomatic liquid helium transfer controller
Authors: Vanderkooy J. , Kang C. S.
Published: March 2003

The controller described here allows liquid helium transfers of long duration into cryostats with minimum supervision. Dewar pressure is maintained by a controlled electrical heater that shuts off when the Dewar is empty.
Grazing incidence spectrograph–monochromator for xuv spectroscopy in the 5–900 Å region
Authors: Malvezzi A. M. , Tondello G.
Published: March 2003

A combination grazing incidence spectrograph for photographic recording and scanning monochromator has been realized. The instrument is of a modular concept and all the internal components like the grating, the plateholder, and the scanning exit slit are easily removable. The radius of curvature of the Rowland cylinder can also be easily changed. The entrance beam is always kept fixed in position and direction, allowing the instrument to be permanently aligned with fixed light sources. The vacuum case is mechanically independent from the optical components.
Multichannel audio monitor for detecting electrical signals
Authors: Friesen W. Otto , Stent Gunther S.
Published: March 2003

The multichannel audio monitor (MUCAM) permits the simultaneous auditory monitoring of concurrent trains of electrical signals generated by as many as eight different sources. The basic working principle of this device is the modulation of the amplitude of a given pure tone by the incoming signals of each input channel. The MUCAM thus converts a complex, multchannel, temporal signal sequence into a musical melody suitable for instant, subliminal pattern analysis by the human ear. Neurophysiological experiments requiring multi-electrode recordings have provided one useful application of the MUCAM.
Two-way ESR cavity for magnetic- and electric-dipole transitions
Authors: Suzuki Isao , Kaneko Yoshihisa , Yamamoto Takamitsu
Published: March 2003

A two-way ESR cavity for magnetic dipole transition (MDT) and electric dipole transition (EDT) was manufactured. There are two openings to fit the sample cell for MDT or EDT in the cylindrical TE011 mode. One opening is located on the axis of the cavity and the other is located away from the axis. The ESR spectra of the mixture of oxygen and nitrogen oxide obtained when the sample cell was inserted in each of the openings showed the selective transition of the MDT or of the EDT of the species.
Continuously recording refractive index spectrograph for transparent and opaque insulators and semiconductors
Authors: Enke K. , Tolksdorf W.
Published: March 2003

An apparatus is described which enables the user to measure continuous refractive index spectra of opaque and transparent optically flat samples. The method of measurement is based on finding the Brewster’s angle βB of the sample. By modulating the angle of light incidence, the output signal of a lock-in amplifier, tuned to the modulation frequency, changes sign abruptly at βB. The lock-in signal is applied to a dc motor which drives a goniometer in that way that the sample is continually held at βB. Provided that the sample extinction coefficient k≲0.5, the accuracy of the refractive index measurements is better than 1%, or even 0.1% where k≈0.
High-power, high-repetition rate pulser for photo-impulse ionized lasers
Authors: Merchant V. E. , Seguin H. J. J. , Dow J.
Published: March 2003

The design and operational parameters of a high-power pulser suitable for a photo-impulse ionized laser are presented. The relatively compact device utilizes a ceramic thyratron in a triggered resonant charging circuit. Efficient operation at repetition rates up to 40 kHz, with pulsed powers in excess of 2 MW and average powers of several kilowats has been achieved.
Logarithmic analog-to-digital converter using switched attenuators
Authors: Gottschalk B.
Published: March 2003

One can construct a successive-approximation analog-to-digital converter (ADC) whose output is proportional to the logarithm of the input voltage, by using independent electronically switched attenuators. The output step size of such an ADC corresponds to a constant relative change in the voltage being measured, rather than a constant absolute change as in a linear ADC. The principle described here is fully ’’digital’’ in that it depends only on the accuracy of resistors and not on the logarithmic I–V characteristic of any solid-state device. A practical ten-bit prototype conforms to the ideal logarithmic characteristic to about 1% over a four-decade input voltage range, 1 mV to 10 V; effectively, any input in that range is measured to about 1%. Complexity, cost, and speed are comparable to simple linear ADCs.
Versatile resonance-tracking circuit for acoustic levitation experiments
Authors: Baxter Keith , Apfel Robert E. , Marston Philip L.
Published: March 2003

Objects can be levitated by radiation pressure forces in an acoustic standing wave. In many circumstances it is important that the standing wave frequency remain locked on an acoustic resonance despite small changes in the resonance frequency. A self-locking oscillator circuit is described which tracks the resonance frequency by sensing the magnitude of the transducer current. The tracking principle could be applied to other resonant systems.
Subnanosecond pulsing of a 3-MV Van de Graaff electron accelerator by means of a passive coaxial pulse shaper
Authors: Luthjens L. H. , Hom M. L. , Vermeulen M. J. W.
Published: March 2003

A passive coaxial pulse shaper has been developed which produces a subnanosecond duration pulse with short rise and decay time from a long pulse with short rise time. The mechanical construction of the pulse shaper is a modified coaxial air line T-section. The pulse shaper has been incorporated in the pulsing circuit of a 3-MV Van de Graaff accelerator. The form of the resulting electron beam pulses was monitored both as the charge collected by a coaxial target and as the Čerenkov light emitted by a quartz plate. In both cases sequential sampling techniques were used. The electron beam pulses were found to have rise and decay tiems of approxiamtely 100 ps and a half-width as short as approximately 200 ps could be obtained. An advantage of this method of producing subnanosecond beam pulses is that it does not interfere with normal nanosecond pulsed operation of the Van de Graaff.
New instrument for continuous and simultaneous recording of changes in ultrasonic attenuation and velocity
Authors: Odru R. , Riou C. , Vacher J. , Deterre Ph. , Peguin P. , Vanoni F.
Published: March 2003

The study of microplasticity of pure single crystals at low temperatures (i.e., the study of the first movements of dislocations) implies the measurement of elastic and anelastic characteristics during tensile tests. Hence a new method has been developed for continuous and simultaneous recording of changes in ultrasonic attenuation and velocity. The attenuation measurement is obtained by the usual pulse–echo technique. The relative velocity measurement is obtained by automatic comparison between a reference square pulse and the attack front of a selected echo. The relative accuracy is 6×10−6 with a sensitivity of 30 mV ns−1 for frequencies up to 40 MHz. Application to dislocation studies in aluminium is reported.
Wire-packed heat exchangers for dilution refrigerators
Authors: Polturak E. , Rappaport M. , Rosenbaum R.
Published: March 2003

Very simple wire-packed step heat exchangers for dilution refrigerators are described. No sintering is used in fabrication. Flow impedances and thermal resistance between the liquid and the copper wires are low. A refrigerator with five wire-packed heat exchangers in addition to a countercurrent heat exchanger attains a temperature of 11.4 mK with a single mixing chamber and 6.1 mK with two mixing chambers. High cooling power is achieved at modest 3He circulation rates.
Point light source detection characteristics of a SEC vidicon digital TV camera
Authors: Dargis A. B.
Published: March 2003

Optimization of the point source detection properties of a Secondary Electron Conduction (SEC) vidicon TV camera tube as a detector of point light sources such as star fields or certain optical spectra requires the accurate determination of peak height, half-peak width, background, and location of the point image. Two perpendicular Gaussian curves have been used to define a point image, allowing changes in the parameters of these Gaussian curves to be used in the study of SEC vidicon point source properties as a function of electrical and optical parameters. Peak height was shown to depend on priming time and a method was developed to reduce the priming time by almost an order of magnitude by momentarily raising the target voltage during priming. Power supply specifications needed for 0.1 pixel (picture element) addressing accuracy were found to be ±0.03 V. Focus current was optimized to obtain the best sensitivity and resolution over the entire target. Peak height, background, and half-peak width were found to be strongly dependent on readout beam current. Target voltage, over the limited range examined, was found to affect only the gain without compromising other image parameters, so that any value could be used, consistent with gain and sensitivity required.
Photoconductivity null apparatus for the determination of minority carrier lifetime
Authors: Richardson W. F. , Meese J. M. , Westbrook R. D.
Published: March 2003

A variable time constant exponential pulse generator used to null exponential photoconductivity decay signals is described. Circuitry using this generator for the direct readout of minority carrier lifetime of semiconductors is also presented.
ir laser induced fluorescence cell for multiple photon processes
Authors: Manuccia T. J. , Frankel D. S.
Published: March 2003

An efficient, easy to construct, long-path laser-induced fluorescence cell is described which is useful in studies of multiple ir photon induced phenomena.
Optical fiber index profiling by video analysis of interference fringes
Authors: Presby H. M. , Astle H. W.
Published: March 2003

An electronic technique to make fringe displacement measurements on the output field of an interference microscope to 1/1000 of a fringe, not including systematic errors, is described. The method, based upon line-selected video signal analysis, is applied to the evaluation of the refractive index profile of a graded index optical fiber. The index difference at a given point between the core and cladding is determined to better than 1 part in 105, implying a precision in the profile parameter α of ±0.005, an order of magnitude better than existing techniques.
Very low temperature thermal conductivity and optical properties of Stycast 1266 epoxy
Authors: Armstrong G. , Greenberg A. S. , Sites J. R.
Published: March 2003

The thermal conductivity of Stycast 1266 epoxy has been measured between 0.045 and 0.45 K. The thermal conductivity closely follows a T2 behavior in this temperature range. In addition, some room temperature optical properties of this epoxy are reported.
Materials and techniques for pressure calibration by resistance-jump transitions up to 500 kilobars
Authors: Dunn K. J. , Bundy F. P.
Published: March 2003

The resistance jump of α→ε transitions for Fe–V alloys up to 20-wt. % V is observed by static compression. It is used along with α→ε transitions for Fe–Co alloys and some other transitions as the basis for pressure calibration up to 500 kilobar.
Li/Li2 supersonic nozzle beam
Authors: Wu Chung-Yung Robert , Crooks Jonathan B. , Yang Sze-Cheng , Way Kermit R. , Stwalley William C.
Published: March 2003

The characterization of a lithium supersonic nozzle beam has been made using spectroscopic techniques. It is found that at a stagnation pressure of 5.3 kPa (40 Torr) and a nozzle throat diameter of 0.4 mm the ground state vibrational population of Li2 can be described by a Boltzmann distribution with Tv= (195±30) K. The rotational temperature is found to be Tr= (70±20) K by band shape analysis. Measurements by quadrupole mass spectrometer indicate that ∼10-mol. % Li2 dimers are present far downstream for an oven body temperature of 1370 K in the supersonic nozzle expansion. This measured mole fraction is in agreement with the existing dimerization theory.
Automatic digital data collection for ion scattering depth profiles
Authors: McCune R. C. , Hoffman D. W. , Baird R. J.
Published: March 2003

A means for acquiring elemental depth profiles in digital form using ion scattering spectrometry for materials having well resolved binary elastic scattering peaks is described. The integrated counts for each elemental peak or background region are stored in consecutive channels of a multichannel scaler using the system sweep multiplexer to provide the time base necessary to advance the scaler address. A typical depth profile for a copper–chromium bi-layer sample collected in this manner is presented.
Continuously variable filter for iodine lasers
Authors: Ariga S. , Ahlborn B.
Published: March 2003

A water cell has been developed as an attenuator for 1.315-μm radiation, providing a variable transmission with a dynamic range of typically 103. The filter was used to determine the linear range of a photoresistor.
Josephson junction resonance detection circuit
Authors: Smith H. J. T.
Published: March 2003

An electronic circuit is described that enables all the resonances in a Josephson junction current–voltage characteristic to be observed.
Visible-infrared window assembly for ultrahigh vacuum systems
Authors: Wierenga P. E. , Mollenhorst G. J. , Wikkerink A. T. B.
Published: March 2003

A window assembly for ultrahigh vacuum systems is described which uses Irtran 4 visible-infrared transmitting optical material. The assembly is made in a standard ultrahigh vacuum flange. The window is sealed in place with Pyroceram. The assembly can be repeatedly heat-cycled up to 200°C without failure.
Improved charcoal trap for rare gas mass spectrometry
Authors: Reynolds J. H. , Jeffery P. M. , McCrory G. A. , Varga P. M.
Published: March 2003

A charcoal trap for progressive desorption of rare gases, including helium and neon, is described and performance data given. Cooling is by a commercial helium expansion refrigerator. Temperatures are readily controlled down to about 20 K. No cold, condensed gases are used.
Sensitive temperature gradiometer for use at low temperatures
Authors: Yarmchuk E. J. , Glaberson W. I.
Published: March 2003

A device capable of very sensitive temperature gradient measurements in the presence of relatively large ambient temperature fluctuations is described. The device uses a pair of ’’matched’’ superconducting thin films in a bridge arrangement, with a SQUID magnetometer probe as the null detector.
Influence of chromatic aberrations on space charge ion optics
Authors: Whealton J. H. , Tsai C. C.
Published: March 2003

By solution to the Poisson–Vlasov equation the influence of fluctuations (chromatic aberrations) on ion optics is shown for various accelerator designs : (1) cylindrical bore triode with various aspect ratios, (2) pseudo-Pierce shaped electrode triode at various aspect ratios, (3) insulated coating emission electrode triode for various preacceleration potentials, and (4) cylindrical bore tetrodes for various field distributions. Fluctuation levels of 20% can be very important in limiting the ion optics in certain cases.
High precision Mössbauer furnace for 1100 K
Authors: Kobeissi M. A. , Hohenemser C.
Published: March 2003

Detailed designs are given for a high precision Mössbauer furnace that may be used up to temperatures of 1100 K. With proper precautions the furnace designs described yield long-term temperature instability better than ∼0.02 K and temperature inhomogeneity of better than 0.05 K.
Balloon-borne ion sampling package
Authors: Olson J. R. , Amme R. C. , Brooks J. N. , Murcray D. G. , Steffen D. A. , Sturm R. E. , Keller G. E.
Published: March 2003

A mass filter package for atmospheric sampling in the stratosphere has been designed and constructed so that ambient positive ions can be detected in one mode of operation (PI) and ambient negative ions in a second mode of operation (NI). The range of the quadrupole mass filter is 1–150 amu. Any one of the 150 mass positions can be selected for a fixed peak operation, or the total range can be covered in a continuous sweep at the rate of 300 amu/s. Filtered ions are individually counted. The atmosphere is sampled through a valved 0.03-cm-diam orifice which has a conductance of about 9× (10−3) l/s and width-to-thickness ratio greater than 10. Ambient temperature, ambient pressure, atmospheric electrical conductivity, and cosmic ray ionization detectors are also part of the package. An on-board clock and logic circuitry control the gathering of data. However, the mass filter operations can also be preferentially controlled via telemetry. Data are concurrently recorded with an on-board digital tape recorder and telemetered to earth for real-time data analysis. The entire package has been designed and constructed to minimize contamination of the atmosphere being sampled. Preliminary results from a recent flight show evidence for the presence of hydrated protons in the stratosphere.
Streak camera measurement of subnanosecond plastic scintillator properties
Authors: Cheng J. C. , Tirsell K. G. , Tripp G. R. , Lent E. M. , Lerche R. A.
Published: March 2003

A streak camera technique with temporal resolution of 20 ps has been used to measure the fluorescence properties of several subnanosecond plastic scintillators. The method employs a vacuum light pipe coupled to an optical streak camera. The scintillators are excited by a 200-ps x-ray pulse generated by a 1.06-μm Nd:YAG laser focused onto an iron target. The time history of the low- energy x-ray pulse is measured with an x-ray streak camera. Results are given for NElll plastic scintillators doped with benzophenone or acetophenone, for PVT doped with butyl-PBD, and for a ZnO phosphor doped with Ga.
Inexpensive apparatus for the measurement of the temperature dependence of gas phase fluorescence spectra
Authors: Swords M. D. , Caplin M. , Phillips D.
Published: March 2003

An inexpensive and easily constructed cell is reported which allows the observation of gaseous fluorescence spectra over a wide temperature range.
Simple laser pulse energy monitor
Authors: Smirl Arthur L. , Shoemaker R. L. , Hambenne J. B. , Matter J. C.
Published: March 2003

A simple and inexpensive relative energy monitor for short laser pulses is described. The three basic units of this system are an integrating detector circuit, an amplifier, and a peak detector and hold circuit. With this device one can measure optical pulse energies (at 1.06 μm) as small as 1.0 nJ with an electronic accuracy of ∼1%.
Fluorescence polarimeter for flow cytometry
Authors: Pinkel D. , Epstein M. , Udkoff R. , Norman A.
Published: March 2003

We have added the ability to measure the fluorescence polarization of single cells to a flow fluorimeter cell sorter system. The fluorescence, which is excited by a vertically polarized laser beam, is split by a Glan–Thompson prism into vertical and horizontal components. These pass through beam diffusers and are measured by two photomultipliers. The signals from the photomultipliers are processed electronically on line by a PDP-11 computer based system. The ratio of the polarization components can be measured to 1% over a dynamic range of 10:1 in intensity, providing the fluorescence is bright enough. A Fresnel rhomb is used to rotate polarization of the exciting laser beam to the horizontal for calibration. Our system can display in real time the distributions of fluorescence polarization, fluorescence intensity, and cell volume either singly or in two-parameter correlations, and it can sort cells on the basis of preset limits on these distributions.
Dual laser interferometer for plasma density measurements on large tokamaks
Authors: Baker Dan R. , Lee Shu-Tso
Published: March 2003

A two-wavelength plasma density interferometer utilizing a CO2 laser and an HeNe laser is described. The interferometer is being designed for use on Doublet III, a large noncircular cross-section tokamak. The use of the two wavelengths allows the distinction between fringe shifts due to plasma density and fringe shifts due to mirror vibrations. Plasma density fringe shifts of 1/10 of a fringe shift can be measured in the presence of mirror vibrations which cause several fringe shifts. A simple digital phase comparing electronic system is used.
Miniature ELF electric field probe
Authors: Misakian Martin , Kotter F. Ralph , Kahler Richard L.
Published: March 2003

A miniature ac electric field probe having direct electrical connections with its battery-operated electronics is described. Because its small size introduces little field perturbation, fields generated by relatively small electrode structures in laboratory environments can readily be characterized.
Improved circuit for impedance measurement at very high frequency and its application in testing dielectric properties of insulating materials
Authors: Ogawa I. , Kakimoto A.
Published: March 2003

This paper describes improvements on an impedance measuring circuit for the measurement of very small conductance at very high frequency and one of its applications, viz., the accurate measurement of dielectric constant and loss angle of very low loss materials. In this circuit, a feedback loop for the stabilization of the output level of the high-frequency oscillator unit also provides compensation for the changes of the series resistance of resonance coil and the transfer characteristic of the detector that occur with their temperature drifts. This circuit has the sensitivity and stability to detect a 0.002 μmho change in a 16-pF specimen at 100, 150, or 200 MHz. It is capable of measuring a loss angle of several μrad with the electrode system developed for the varying gap immersion method. The warming-up time is also shortened to about 10 min even for measurements requiring the highest sensitivity.
Fast hydrogen gas injection system for plasma physics experiments
Authors: Burrell Keith H.
Published: March 2003

A system has been developed for fast injection of hydrogen gas into a vacuum system, which can produce feedback controlled flows in the range 0.1–10 Torr l/s. The unit uses a fast pressure transducer as a flow sensor. The flow will respond to an external programming voltage whose time variation is as short as several milliseconds.
’’Wonderstone’’ ENDOR cavity
Authors: Chacko V. P.
Published: March 2003

We report the design and construction of a high-quality ENDOR cavity from a naturally occurring rock, ’’Wonderstone.’’ It consists of a cylindrical cavity operated in the TE011 mode, with four vertical posts forming the ENDOR coil. 100 kHz field modulation is achieved by external coils mounted on the pole faces of the magnet. This cavity is especially suited for the insertion of a cold-finger Dewar. The merits of Wonderstone as a substrate material for microwave cavities and the details of obtaining a fine conducting layer of silver on the inner surface of the cavity are discussed.
Further stability studies on germanium resistance thermometers at 20 K
Authors: Besley L. M.
Published: March 2003

Thirty germanium resistance thermometers from three manufacturers have been thermally cycled 90 times between 20 and 300 K. Detailed results are presented on the stability of the thermometers at 20 K.
Description and characteristics of a ’’wave follower’’ system for energy exchange studies in the vicinity of an air–water interface
Authors: Baldy S. , Ramamonjiarisoa A. , Coantic M.
Published: March 2003

This paper describes the design, construction, and testing of an electromechanical servomechanism capable of responding to the vertical displacements of a wavy air–water interface. The device is to be used to maintain various probes at a fixed distance above or below the moving interface in a large wind-wave tank. The measurements so obtained will help to elucidate the mechanisms of mass, momentum, and energy transfer between air and water in the presence of waves. The dynamical characteristics of the wave follower are given. For frequencies below 9 Hz, it possesses a linear reponse characterized below 5 Hz by a 7.4 ms time lag. This is the sum of two time lags, 4.9 and 2.5 ms, which correspond, respectively, to the servomechanism itself and to the capacitance-type wave height measurement system. The maximum position error is found to be ±2 mm for typical wave amplification by wind studies (maximum wave height of about 6 cm).
Optical probe for local void fraction and interface velocity measurements
Authors: Abuaf N. , Jones O. C. , Zimmer G. A.
Published: March 2003

In view of the importance of obtaining unsteady local void fraction and interface velocities in liquid–vapor two-phase flows, an optical probe with a controlled tip geometry was developed and is described. In order to minimize the disturbances caused to the flow field by the presence of the probe, its dimensions have been miniaturized. The electronic and hydrodynamic responses of the probe were investigated experimentally. The probe was found to be sensitive to both the interface velocities and the phase present at the probe tip. A possible explanation for the behavior of the probe is presented. Within the velocity range checked and with proper calibration, the optical probe described can be used to determine both local void fractions and interface velocities.
Detection of lower hybrid waves within a plasma by microwave scattering
Authors: Motley R. W. , Paoloni F. J. , Bernabei S. , Hooke W. M.
Published: March 2003

The spatial distribution and intensity of electrostatic waves injected into a hot plasma may be inferred from the scattering of millimeter microwaves. We report measurements on the 30° scattering of 8.6-mm microwaves by a 500-W, 2.45-GHz slow wave excited in a linear plasma by a phased array of two waveguides. From the magnitude of the scattered signal and auxiliary measurements with probes, we infer that a large fraction of the injected power penetrates to the center of the overdense test plasma.
Resolving the positive, negative, and neutral fluxes of an expanding, laser-produced plasma
Authors: Sarraf S. , Woodall D. M.
Published: March 2003

The space-charge separation seen in an expanding, laser-produced plasma is a remnant of energetic electrons produced in anomalous laser absorption. In order to better understand this phenomenon, a Faraday cup collector has been devised which simultaneously records positive, negative, and neutral components of such an expanding plasma. The response of this detector to a laser-produced plasma is measured and compared to magnetically filtered ion collectors. This detector proves superior to the magnetic collector for energetic ions, but is limited to low plasma densities by collective effects.
Acoustic ringing effects in pulsed nuclear magnetic resonance probes
Authors: Buess M. L. , Petersen G. L.
Published: March 2003

The troublesome spurious ringing phenomenon found in pulsed nuclear magnetic resonance probes is explained in terms of the electromagnetic generation and detection of ultrasonic waves. A few techniques for eliminating this problem are discussed.
Narrow zone heating by a new radiation focusing technique—toroidal ellipsoid furnace
Authors: Davidson Mirt C. , Holland Lawrence Rozier
Published: March 2003

A new form of focused radiation furnace for narrow zone heating is described. Performance of a preliminary prototype is given, and some useful parameters for design are discussed.
Contactless Hall coefficient measurement in materials of small Hall angle in the skin depth regime
Authors: Vanderkooy J.
Published: March 2003

The Hall coefficient RH can be determined in materials of small Hall angle by observing the tilting of induced eddy currents by a transverse magnetic field. Two qualitatively different regimes exist depending on whether the skin depth is greater or smaller than the sample size. The higher frequency regime has some useful charactieristics.
Superconducting multicontact rotary switch
Authors: Kotowski T. , Lewandowski S. J. , Sobolewski R.
Published: March 2003

A compact mechanical multiposition superconducting switch, suitable for a wide variety of cryoelectronic applications, has been developed. The switch is easy to fabricate in laboratory conditions. Its design is based on principles used in normal rotary switches and offers the same ease in stacking together multiple sections.
Effects of a long entrance aperture upon the azimuthal response of spherical section electrostatic analyzers
Authors: Gosling J. T. , Asbridge J. R. , Bame S. J. , Feldman W. C.
Published: March 2003

The transmission characteristics of spherical section electrostatic analyzers with long entrance apertures have been studied. The presence of a long entrance aperture appreciably broadens the normally narrow azimuthal response of such analyzers at large incident polar angles. A technique for calculating the transmission at any polar angle is presented. Calculated azimuthal response curves at polar angles of 0°, 25°, and 50° agree well with laboratory measurements for a 90° section analyzer. In the limit of zero polar angle, our calculations reveal that a previously derived and widely used analytical expression for the integrated energy-angle response underestimates that response by 12%–25% depending upon the analyzer bending angle. An analytical expression that better approximates the true response is presented.
Microwave cavity for EPR at high hydrostatic pressures
Authors: Cevc P. , Srinivasan R.
Published: March 2003

The design of a simple pressure locked cavity for use in X-band EPR studies at high hydrostatic pressures and temperatures down to liquid nitrogen is described. A coaxial coupling arrangement which avoids the use of sapphire is used.
Interfacing a microcomputer with the Varian EM−360 NMR spectrometer
Authors: Wright John R.
Published: March 2003

Numerous NMR signal enhancement devices (CAT or Computers of Average Transients) are available commercially but at relatively high cost. These also have little or no flexibility of application, i.e., they are essentially signal averagers and nothing else. A far superior alternative, both in economy and range of application, is found in the new generation of computational devices based upon 8-bit LSI microprocessors. This paper reports the practical details of achieving a successful interface between one such microcomputer, the Altair 8800B, and the Varian EM-360 1H-NMR spectrometer. The resulting system is programmable in high level language (8k basic) and has sufficient memory to achieve 4096 point (12 bit) field resoltuion. The interface yields an intelligent instrument with multiple capabilities. Several operating modes have been developed using high level language programming, and these include conventional spectrum acquisition with variable field resolution, repetitive scan CAT, difference spectrometry, kinetic NMR spectrometry, progressive saturation analysis (for T1 and T2), and INDOR. The CAT program, for example, required 2 h to develop and debug, while a graphic output subroutine (shared by all modes) was written in 1 h. Correlation spectrometry is under development and requires user defined machine language routines. The system provides a graphic output of digitized data (using the existing recorder), magnetic storage of data files, and immediate data reduction capabilities.
Gigahertz stroboscopy with the scanning electron microscope
Authors: Hosokawa T. , Fujioka H. , Ura K.
Published: March 2003

The application of the stroboscopic scanning electron microscope to gigahertz Gunn effect devices is discussed. Two modes of operation, the deflection mode and the bunching mode, are considered. In the bunching mode, using 1.5 ps beam pulses, two-dimensional voltage contrast in a Gunn effect device triggered at 1 GHz has been observed. A powerful technique for a device in pulsed operation is also presented. With this technique, the nonuniform domain propagation in the three-dimensional-structure Gunn device in pulsed operation has been clearly observed. The duty cycle of the pulsed operation has been 4×10−3.
Spatial dose uniformity monitor for electrically scanned ion beam
Authors: Natsuaki N. , Ohyu K. , Tokuyama T.
Published: March 2003

A technique is described for direct and precise monitoring of the spatial dose uniformity of an electrically scanned ion beam. The method employs a two-dimensional 10×10 array of Faraday cups, individually connected to a current integrator, to measure local dose distribution. It also employs a microprocessor for rapid data processing and topographic data display. The technique is applicable to high quality ion implantation processes as a uniformity monitor with an accuracy of 1%. In addition, a new concept for uniform ion beam scanning is proposed.
Surface wave velocity measurement using reflections from laser scribed grooves
Authors: Gerhart G. R. , Kolb D.
Published: March 2003

The measurement of ultrasonic surface wave (USW) velocity is difficult using the pulse overlap method (POM) in the presence of an externally applied stress. Coupling variations between the sample and the transducer cause nonuniform distortions of the two received pulses which makes the overlap condition difficult to determine over an extended stress range. The adaptation in this paper of a single transducer configuration to generate and detect the USW eliminates coupling variations between two or more transducers. In addition, two parallel, precisely positioned and contoured grooves are laser scribed on the sample surface to provide the necessary overlap echoes. Since both echoes are reflected only once by identical grooves and are equally affected by the distortions due to coupling variations, the overlap condition is relatively unaffected by the external stress and the accuracy of the USW velocity measurement is increased significantly.
System for monitoring the thickness of transparent layered structures
Authors: Klyce S. D. , Russell S. R.
Published: March 2003

A system is described that will track light reflections from transparent lamellar structures and will provide a running time average of the thicknesses of the component layers. Thicknesses measured with the microprocessor-controlled system can be read to 0.2 μm (0.02% of the scan range). Its performance is demonstrated by the effect of a hypotonic shock on the thicknesses of the stroma and epithelium of a rabbit cornea.
Measurement of thermoelectric power of solids up to 10 GPa
Authors: Singh A. K. , Ramani Geetha
Published: March 2003

A method of measuring thermoelectric power of solids as a function of pressure up to nearly 10 GPa is described. A tungsten carbide opposed anvil setup is used to generate the pressure.
Digital technique for the simultaneous measurement of velocity and temperature
Authors: Keffer J. F. , Budny R. S. , Kawall J. G.
Published: March 2003

A computer-oriented, hot-wire anemometer technique for the simultaneous measurement of velocity and temperature in heated turbulent flows is described. This technique involves conversion of analogue anemometer voltage signals into digital forms and processing of these latter on a digital computer, in accordance with the anemometer response equations, to obtain instantaneous temperature and velocity. The technique was tested with a heated plane jet and found to be satisfactory.
Use of centrifugal disk atomizer to produce CdS films
Authors: Maa J. S. , Huang T. L. , Sung M. F. , Chang Y. , Chiue S. C.
Published: March 2003

The use of a centrifugal disk atomizer to produce chemically sprayed CdS films is described. The film growth rate has been found to depend on substrate temperature, solution concentration, and feed rate. The films grown on glass substrates have been studied by electron microscopy and x-ray diffraction. A fine-grained wurtzite structure has been obtained.
Time-of-flight electron velocity spectrometer using transverse electric field deflectors
Authors: Littlefield R. G. , Harmon G. S.
Published: March 2003

A time-of-flight electron velocity spectrometer using two transverse electric field deflectors as fast electronic shutters has been constructed. Square-wave voltage pulses applied to the two shutters limit the transmitted current to electrons in selected narrow velocity ranges. Analysis of the magnitude of this transmitted electron current as a function of the time delay between the two shutter openings leads to the electron velocity or energy spectrum in the incident charged particle beam. Time resolutions of 5 ns (FWHM) can be obtained with the present apparatus for electrons in the 5–100 eV range.
Measurement of water vapor in the stratosphere by photodissociation with Ly α (1216 Å) light
Authors: Kley Dieter , Stone Edward J.
Published: March 2003

Photodissociation of polyatomic molecules by vacuum-uv light often results in the formation of electronically excited diatomic molecular fragments. Based on this, instruments that measure mixing ratios or densities of selected polyatomic species in the stratosphere and higher troposphere can be constructed. This is demonstrated by an instrument to detect and measure stratospheric water mixing ratios utilizing H2O photodissociation by Ly α (1216 Å) light and detecting OH(A2𝒥+X2Π) emission. Also, detectors for H2O2, HNO3, and NO2 are discussed.
Differential thermoluminescence (DTL) —a new instrument for measurement of thermoluminescence with suppression of blackbody radiation
Authors: Manche Emanuel P.
Published: March 2003

A new instrumental technique for the determination of thermoluminescent glow curves, especially useful for investigation at high temperatures, is described. Two samples, identical in all respects except that one is preheated, are simultaneously heated. The light outputs from the samples are individually modulated at two different frequencies, fed to a single photomultiplier tube the output of which is amplified by two lock-in amplifiers. The selectively amplified signals are further fed to a differential amplifier which cancels out the undesirable blackbody radiation to give a signal due only to the luminophor. This technique conveniently extends the temperature range of thermoluminescence and further allows high-temperature investigation of emissions in the red region of the spectrum.
AlGaAs DH pump laser for photoluminescence lifetime measurements
Authors: Nelson R.J.
Published: March 2003

The use of GaAlAs double heterostructure lasers as a pulsed excitation source for photoluminescence time-decay measurements is described. Subnanosecond laser pulses easily allow the determination of luminescence decay times ⩾500 ps using a single photon counting system. In contrast to mode-locked gas or dye lasers, this new technique utilizes simple equipment (diode laser and pulse generator) and requires no special alignment or tuning procedures.
1/4-J discharge pumped KrF laser
Authors: Sze Robert C. , Scott Peter B.
Published: March 2003

Over 1/4-joule per pulse is obtained from a cable-fed uv preionized discharge device where a faster energy deposition rate compensates for a slower voltage rise time. These slower voltage rise-time devices may be scalable to high repetition rates using conventional thyratron switching techniques.