bluuebunny/crossref_metadata_2025 huggingface dataset:
Stable ultrashort laser diode pulse generator
Authors: Tsuchiya Y. , Takeshima A. , Hosoda M.
Published: March 2003

The design and operation of a stable ultrashort light pulse generator using a GaAlAs single heterostructure laser diode is presented. The unit is capable of generating optical pulses at a wavelength of 820 nm as narrow as 60 ps full width at half maximum (FWHM) at pulse repetition rates up to 10 kHz with a peak power of 3 W. The light pulses are emitted from a flexible light pipe with relatively small jitter of less than ±10 ps. Single pulses without any subpulses were confirmed by direct measurements using a streak camera system having a temporal resolution of better than 10 ps. This generator will find applications in the study and evaluation of time characteristics of fast photodetectors, optoelectronic devices, etc.
X-ray monochromator system for use with synchrotron radiation sources
Authors: Golovchenko J. A. , Levesque R. A. , Cowan P. L.
Published: March 2003

A double crystal x-ray monochromator system has been developed for use on synchrotron radiation sources. The system consists of two separate Bragg reflecting crystals constrained by a mechanical linkage system enabling it to tune continuously in x-ray energy, always maintaining an exit beam of constant offset and direction relative to the incident beam. Accurate parallelism between the two crystals is maintained by a piezoelectrically-controlled analog feedback circuit.
Field-frequency locked X-band Overhauser effect spectrometer
Authors: Chandrakumar N. , Narasimhan P. T.
Published: March 2003

The design and construction of an Overhauser Effect Spectrometer operating at X band is described. The ESR section is a Varian V-4502 spectrometer equipped with a 9-in. electromagnet and a shim coil assembly. NMR detection is based on a broadband rf hybrid juction feeding a coil in an X-band quartz dielectric cavity. Signal processing is carried out at a constant intermediate frequency of 25.1 MHz with a Varian V-4311 fixed frequency rf unit. The mixing scheme employed to translate the NMR information to 25.1 MHz is described. Medium resolution performance (resolution ∼10−6) for the NMR is achieved under field-frequency locked conditions. The lock is based on a Super-Regenerative Oscillator (SRO) housing a control sample, and operating as a field-tracking frequency source. This SRO injects into an oscillator which excites the analytical sample resonance and also serves as a local oscillator, thereby making the locked spectrometer multinuclear in capability. Typical Overhauser effect recordings of protons and fluorines are presented.
Apparatus for the direct measurement of the internal energy of heterogeneous reaction products
Authors: Thorman R. P. , Bernasek S. L.
Published: March 2003

An instrument to measure the rotational and vibrational energies of heterogeneous reaction products has been constructed. Reactant atoms pass through a membrane made of the material being studied. After recombination and desorption occurs, the product gas is analyzed via either electron beam or laser-induced fluorescence. Surface composition is monitored by soft x-ray appearance potential spectroscopy. Results for nitrogen molecule desorption from clean, polycrystalline iron are presented in order to illustrate the capabilities of the apparatus.
Liquid metal source of gold ions
Authors: Prewett P. D. , Jefferies D. K. , Cockhill T. D.
Published: March 2003

A fully engineered liquid metal field emission source of gold ions has been developed, operating with low heater power (<30 W) and without forced cooling. The design and performance of the source are described in detail. The present design can also be used to produce sources of a variety of elements, other than gold, including tin, bismuth, and lead. It provides a versatile and reliable research tool which is fully compatible with ultrahigh vacuum installations. Potential fields of application include materials development and surface analysis.
Computer-automated ratio transformer bridge
Authors: Lucas P. , Donnelly J. A.
Published: March 2003

A continuously balanced impedance bridge under computer control constructed for a cryogenic thermometry application provides a few ppm resolution in resistance ratio measurements. The use of IEEE-488 computer bus-compatible commercial equipment reduces the design mainly to that of software and permits flexibility in the balancing procedure.
Particle–velocity gauge system for nanosecond sampling rate of shock and detonation waves
Authors: Hayes Bernard
Published: March 2003

A high-resolution, particle-velocity gauge system was developed to obtain a hydrodynamic streamline in the flow field associated with shock waves or detonation products. The system is composed of a passive current loop (stirrup probe) embedded in the host material, a magnetic field generator to establish a Lorentz force, and a computer-controlled, analog-to-digital transient recorder to monitor the gauge response. The operation principle is that the motion of one side of a rectangular loop in a magnetic field produces a current proportional to the velocity of that leg. System tests were conducted with 50-mm diam. by 50-mm long cylinders of 1,3,5-triamino–2,4,6-trinitrobenzene (TATB) explosive and explosive-driven polytetrafluoroethylene (PTFE). The velocity profiles obtained have a time resolution of a few nanoseconds with an amplitude uncertainty of approximately 2% based on a system error analysis. Detailed descriptions of the gauge system components are included.
Device for emptying liquid nitrogen dewars
Authors: Miller W. M. , Terris B. D. , Ginsberg D. M.
Published: March 2003

We have invented a device for quickly emptying a dewar of liquid nitrogen without having to invert the dewar. The liquid is forced out by compressed nitrogen gas, using a type of pump which does not require the dewar to be sealed.
Variable power microwave discharge and cavity
Authors: Bozzelli Joseph W. , Barat Robert
Published: March 2003

The construction of a variable power electrodeless microwave discharge and cavity using a microwave oven magnetron and power supply is demonstrated. The apparatus is convenient to use, durable, and inexpensive.
Useful method for observing input face and focused beam launch conditions for optical waveguides
Authors: Persechini David L.
Published: March 2003

Light that is reflected from the input and output faces of an optical waveguide may be used to form an image of the input face and the focused input beam.
Energy spectrum diagnostics for collectively accelerated proton beams
Authors: Adler R. J. , Nation J. A. , Serlin V.
Published: March 2003

An account is presented of the proton energy spectrum diagnostic techniques employed in a Collective Ion Accelerator study. The emphasis is on a newly developed neutron time of flight diagnostic which yields the complete (E≳2 ⋅ 5 MeV) proton spectrum on every shot. A brief account is also presented of the stacked foil activation technique employed, and results from the two measurements are compared. Finally, we describe a stacked foil Faraday cup which provides temporal resolution of the proton acceleration.
Modeling of tunnel diode oscillators
Authors: Van Degrift Craig T. , Love David P.
Published: March 2003

The detailed behavior of tunnel diode LC oscillators is calculated by three different methods and compared with experiment. We present both analytic formulas and numerical methods which give corrections to the oscillator frequency calculated using the expression 1/(LC)1/2 and show that these corrections are often not negligible. The calculations also yield rf amplitude, bias current dependence, and other details necessary for the full realization of the performance of LC oscillators as transducers of pressure, temperature, and other physical quantities.
Wide band multiplier correlator
Authors: Gough Russell G. , Frater Robert H.
Published: March 2003

A transconductance multiplier correlator with a bandwidth in excess of 1 GHz is described. Computer modelling techniques were utilized in the circuit design. A balun is used to provide a balanced drive to the bases of the transistors in the multiplier differential pair and thereby reduce the self-detection of input signals. For frequencies below 1 GHz, the self-detection of signals at either input contributes less than 1.5% to the corresponding detected output.
High-resolution concave grating grazing incidence spectrometer for the spectral region of ultrasoft x rays
Authors: Gilberg E. , Hanus M. J. , Foltz B.
Published: March 2003

A concave grating grazing incidence spectrometer with a new type scanning device has been built for high-resolution spectroscopy in the ultrasoft x-ray region. The radiation source used consists of a high power x-ray tube with rotating anode permitting one to study emission spectra in fluorescence as well as absorption spectra. The spectometer is equipped with curved slits to achieve optimum performance with respect to resolving power and luminosity. Entrance slit and grating are kept fixed under operation, the exit slit and detector assembly is mounted on cross-stacked carriages driven by computer-controlled stepper motors. By appropriate computer programming the exit slit can be made to follow any focal curve. The system thus permits the use of gratings with different radii. Absolute wavelength determination capability is also provided. First results concerning emission as well as absorption spectra are presented.
Beam source for moderately fast neutral alkali atoms
Authors: Kita S. , Hübner H. , Kracht W. , Düren R.
Published: March 2003

In certain applications the linear arrangement of ion source and charge exchange chamber in standard charge exchange sources for neutral atomic beams leads to undesirable stray light. To avoid this problem a new design has been developed and tested. The maximum beam flux emerging from this source is 2.0 ⋅ 1010 atoms/s ⋅ mm2 at the energy E = 100 eV. The energy spread ΔE/E ≲0.5%. The angular spread is about 0.47 deg FWHM. Adjusting the ion optics every 100 hours the intensity of the neutral beam has been measured to be stable within 10% over a period of 400 hours.
Preliminary experiment on the Lambdatron ion source for the JT-60 neutral beam injector
Authors: Sakuraba Junji , Akiba Masato , Arakawa Yoshihiro , Horiike Hiroshi , Kawai Mikito , Ohara Yoshihiro , Tanaka Shigeru
Published: March 2003

As a candidate for an ion source to be used in the JT-60 neutral beam injectors, a magnetic multicusp ion source with a Λ-shaped backstream electron beam dump (Lambdatron ion source) has been proposed at JAERI. To make a preliminary investigation on this type of source, a circular shaped Lambdatron ion source has been fabricated and tested. This source has achieved extraction beam currents of 30 A at 30 kV, ion current densities of 0.27 A/cm2 at the plasma grid, and a proton yield exceeding 70%. The arc power necessary to produce unit beam current does not depend much on whether the plasma grid and the beam dump were electrically floated or they were connected to the negative cathode. The arc efficiencies of the Lambdatron source were found to be 60% of those of the conventional bucket ion source.
Pulsed high-voltage and high-current outputs from homopolar energy storage system
Authors: Ford R. D. , Jenkins D. , Lupton W. H. , Vitkovitsky I. M.
Published: March 2003

Pulsed energy source with a versatile output, using self-excited homopolar generator for the initial storage of energy, has been developed. Large energy storage of this inertial–inductive system provides an attractive option for satisfying pulse power requirements associated with such applications as plasma confinement and heating, electromagnetic acceleration of projectiles, and with production of intense radiation. These applications require high rate of energy delivery to the load at specific current and voltage levels. Megajoule output pulses, alternatively, at hundreds of kilovolts or at megampere levels, have been obtained by incorporating unique current interrupting system. The overall pulser efficiency, which depends sensitively on the load characteristics was measured over a range from 10% to more than 90% for different pulser-load circuit arrangements.
Thermal properties of carbon-impregnated porous glass at low temperatures
Authors: Lawless W. N.
Published: March 2003

Specific heat and thermal conductivity measurements 2–30 K are reported on a carbon-impregnated porous glass (35–45 Å pore size, ρ4.2∼9 Ω cm) which is used to make carbon–glass thermometers. The specific heat is considerably larger than that of fused silica due to the T2 surface-area contribution, and good agreement with literature estimates of the T2 term is obtained. A small Einstein term is seen at 2.2 K due possibly either to the surface-bound hydroxyl groups or to the impregnated carbon filaments. The thermal conductivity data do not display the plateau around 10 K characteristic of amorphous materials due to the diffraction of thermal phonons by the small pores. It is found that the carbon plays a negligible role in the thermal properties of carbon-impregnated porous glass in this temperature range.
Pyrolysis mass spectrometer for direct sampling of primary products of thermolysis reactions
Authors: Wells Gregory , Futrell Jean H. , Voorhees Kent J.
Published: March 2003

A pyrolysis mass spectrometer is described which allows direct sampling into the ion source of pyrolysis products generated under collision-free conditions. Scan rates up to 20,000 amu/s allow the mass spectra to be obtained for small sample sizes (∼2 μg) and for selected time intervals (100–200 ms) during the pyrolysis experiment. A liquid nitrogen shield surrounding an open source minimizes the possiblity of reactive encounters with the source and other molecular fragments, which may occur when pyrolyzing in a confined region. Some initial results for the pyrolysis of polystyrene are reported.
Measurements of high-frequency dielectric properties of liquids by the solid plate displacement method
Authors: Kakimoto Akira , Ogawa Kōichi
Published: March 2003

This paper describes a rapid precise method for measurements of the dielectric constant and dissipation factor of liquid specimens in a wide frequency range. Using a two-terminal micrometer-controlled electrode system with a conventional Q meter, a whole measurement of a specimen having a dielectric constant of 2–10 can be done with an accuracy of ±0.2%–0.5% for the dielectric constant and ±4–11 μrad or ±10% for the dissipation factor up to the highest frequency of the Q meter. Once the dielectric constant, dissipation factor, and the mean thickness of a reference solid plate are determined, it takes only a few minutes for the measurements regardless of the gap length and area of the electrodes.
Digital thickness monitor using only one crystal oscillator
Authors: Balasubramanian G. , Riesz R. P.
Published: March 2003

A digital thickness monitor which measures the thickness of a film deposited on a quartz crystal by measuring the change of frequency of a single oscillator controlled by the resonance of the crystal is described. Conventional beat-frequency techniques involving two precision oscillators are avoided by means of circuits including a presettable memory and an up-down counter. The monitor is easily reset at the start of a deposition, can display either frequency change or frequency, and can be easily modified to display film thickness directly. Film thickness determined by the monitor is compared favorably to thickness values determined interferometrically.
Power stabilization method for a synchronously-pumped dye laser system
Authors: Russo R. E. , Withnell R. , Hieftje G. M.
Published: March 2003

The average power stability of the synchronously-pumped dye laser can be improved by a factor of more than 5 by altering the optical feedback stabilization circuitry of the conventional laser system. Noise fluctuations in dye laser output power which normally occur are largely eliminated by changes in the pumping power of the ion laser. The slight loss in dye laser output power which is incurred by the beam splitter is largely offset by an increase in available ion laser power.
Statistical analysis of the noise in fluorescence measurements by the sampling technique
Authors: Andreoni A. , Cubeddu R. , De Silvestri S. , Laporta P.
Published: March 2003

Analysis of the statistical distribution of the noise in fluorescence measurements by the sampling technique is presented. The experimental results indicate that Poisson statistics are predominant. Least squares analysis of a fluorescence decay is performed by using correct standard deviations of the experimental points. The χ2 test is applied to evaluate the goodness of the fit for two interpolating functions.
Influence of velocity gradients on measurements of velocity and streamwise vorticity with hot-wire X-array probes
Authors: Vukoslavĉević P. , Wallace J. M.
Published: March 2003

An analysis and measurement of the effects of the streamwise velocity gradients, ∂U/∂y and ∂U/∂z, on the velocity components, U, v, and w, and the streamwise vorticity component, ωx, measured in turbulent flow with a pair of orthogonal hot-wire X arrays, is presented. It is shown that these gradients, which can have the same order of magnitude instantaneously as the mean shear stress at the wall, cause extremely large errors in the measured instantaneous cross-stream velocity and streamwise vorticity components.
New capacitive micromanometer
Authors: Rehman Mahfoozur , Murti V. G. K.
Published: March 2003

The theory, design, and preliminary test results of a new capacitive micromanometer for differential pressure measurement are presented. A U-tube manometer and two cylindrical cross capacitors are used to transduct pressure variation to capacitance variation linearly. The change in capacitance is measured with the help of a 2-winding transformer ratio bridge employing an 8-decade Inductive Voltage Divider (IVD). The value of differential pressure is obtained with a resolution of 60 m Pa in terms of the IVD ratio readings. The unit constructed can measure pressures from very low values to 10 k Pa. It is considered that the proposed system can be developed as a primary standard for the measurement of low range differential pressures.
Measurement and simulation of thermistor response time in the millisecond range
Authors: Balko Bohdan , Berger Robert L. , Anderson Karen
Published: March 2003

The Finite Element Simulation Technique (FEST) has been applied to the design of hermetically-sealed thermistors with millisecond response times. These thermistors are used in stopped-flow calorimeters developed especially for investigations of biological reactions. FEST is also used to reconstruct the reaction kinetics obtained with these thermistors by correcting for their finite sensor response times and temperature loss.
Large signal testing of fusible links
Authors: Rosenthal L. A. , Beck P. M.
Published: March 2003

Large signal testing of fusible links is accomplished by passing a destructive constant current level through the item and terminating the heating at a preset voltage level or pulse duration. Testing at currents typical of functioning levels provides insight as to performance and quality.
Bulk conductivity measurement of paper by a new i
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u pressure cell
Authors: Josefowicz Jack Y. , Anczurowski Edward , Jones Arthur Y. , Deslandes Yves
Published: March 2003

In this report a new bulk conductivity cell design is described which can be used to characterize both conductivized and nonconductive paper. By the use of optically flat stainless steel electrodes under a pressure of 115 bars during the conductivity measurement, it is shown that the contact resistance between the paper sample and the electrodes is reduced to negligible proportions. The effect of paper surface morphology on the contact resistance during the measurement of bulk conductivity was studied by a comparison between the polished stainless steel electrodes and electrodes composed of liquid Galium Indium, which make intimate contact with the paper surface. Bulk conductivity measurements were determined for paper samples having different basis weights and different degrees of calendering. The results obtained with the pressurized stainless steel electrodes for these paper samples indicate that the contact resistance is essentially eliminated for all the papers studied by using an applied pressure of 115 bars.
Large solid angle Lyman-α detector
Authors: Bollinger J. J. , Pipkin F. M.
Published: March 2003

A large solid angle Lyman-α (121.5 nm) detector designed for atomic beam experiments is described. The detector consists of 6 NO photoionization chambers which surround the beam and provide an average detection efficiency for Lyman-α photons of approximately 20% over the 3.5 cm length of the detector.
Data-smoothing digital interface between a high-speed transient recorder and a slow signal averager
Authors: Spencer P. A. , Ott A. H. , Hughes D. G.
Published: March 2003

A digital interface coupling a high-speed Biomation 805 transient recorder to a Fabritek 1062 signal averager is described. The combination extends the capability of the Fabritek so that fast transients, in particular NMR free induction decays in solids, can be averaged. The interface allows blocks of successive data words to be averaged before being transferred to the Fabritek. This form of data smoothing and compression facilitates the analysis of noisy signals.
Double-reflection x-ray spectrometer for pulsed-source diagnostics
Authors: Stoering J. P. , Crabb R. , McGee M. E. , Burginyon G. A.
Published: March 2003

The mirror technique provides a promising new soft x-ray, energy-resolving capability. Mirrors have the uncommon but very useful characteristic of behaving as low-pass filters. If x-ray absorption is low, then the change in reflection across the critical cutoff energy at a particular mirror angle is quite sharp and can be used to resolve x-ray spectra with energy resolution comparable to solid-state detectors. The properties of mirrors that enable them to resolve x-ray spectra have been incorporated into a two-mirror intermediate-resolution x-ray spectrometer, which is described here. The instrument is capable of measuring pulsed-source x-ray spectra between a few tenths and about 8 keV.
Copper activation counter calibration using solid state track detectors
Authors: Kacenjar Steve , Goldman Leonard , Entenberg Alan
Published: March 2003

A simple procedure has been developed in laser fusion diagnostics to calibrate, in situ, a copper-activation detector for 14.1 MeV DT neutrons. By mounting thin solid state track detectors in front of the copper-activation detector, one can measure the fluence of DT alpha particles and thus also determine the neutron fluence. An inferred alpha particle yield from this measurement can then be utilized to calibrate the copper-activation detector.
Capacitive transient detector of high sensitivity
Authors: Ellis F. M. , Brooks J. S. , Hallock R. B.
Published: March 2003

A capacitive detector is described which displays high sensitivity and accuracy in the measurement of transients. The device has been used in an LC circuit for studies of third sound in thin helium films. When operated in a phase-lock mode at 21 MHz its observed sensitivity is 15 Hz per angstrom of helium film thickness; changes in average film thickness as small as 0.01 Å have been detected.
Thermal diffusivity measurements under hydrostatic pressure
Authors: Sundqvist B.
Published: March 2003

The original Ångström method has been modified to allow, for the first time, measurements of the thermal diffusivity of metals and other very good conductors under high hydrostatic pressure. The method can also be used to obtain at the same time the pressure dependence of the thermal properties of the pressure transmitting medium, although with reduced accuracy. Some other modifications of the Ångström method are commented on and improved.
Wedge-and-strip anodes for centroid-finding position-sensitive photon and particle detectors
Authors: Martin C. , Jelinsky P. , Lampton M. , Malina R. F. , Anger H. O.
Published: March 2003

We discuss new anode geometries, employing position-dependent charge partitioning, which can be used with microchannel plates, planar proportional counters, and mesh dynode electron multipliers to obtain a two-dimensional position signal from each detected photon or particle. Only three or four anode electrodes and signal paths are required, yet images comprised of a number of detected events have little geometric distortion and the resolution is not limited by thermal noise inherent in resistive sheet anodes. We present an analysis of the geometrical image nonlinearity in the relationship between event centroid location and the charge partition ratios. Fabrication and testing of two wedge-and-strip anode systems are discussed. Images obtained with EUV radiation and microchannel plates that verify the predicted performance of this readout system are shown. We emphasize that the spatial resolution of the wedge-and-strip anode is in no way limited by the coarseness of the anode conductor pattern. The resolution is of the order of 0.4% of the image field size, and could be further improved by adopting low noise signal circuitry. Tradeoffs encountered in the design of practical x-ray, EUV, and charge particle image systems are discussed.
Low temperature magnetic cores and a preamp for low impedance cryogenic sources
Authors: Hannah Eric Cabot
Published: March 2003

The permeabilities at 10 KHz of a number of commercial magnetic materials have been measured at 293, 77, and 4.2 K. Supermalloy and Metglas 2826 (a metallic glass) were measured from 100 Hz to 5 MHz at these temperatures, and the complex permeability vs frequency of Matglas at 4.2 K is presented. These measurements show that Metglas has very little temperature variation in its permeability, but possesses slightly less permeability at 4.2 K than Supermalloy, at all frequencies, in spite of annealing and careful handling. Using Metglas, a matching transformer was fabricated to couple low impedance, cryogenic sources to a low noise JFET. This resulted in a 5-dB noise figure from 20 to 60 KHz for a 10-Ω source at 4.2 K.
Design data for a triple square coil system
Authors: Grisenti R. , Zecca A.
Published: March 2003

A system of three square coils was studied with computational methods. Design data are given which allow one to optimize the field uniformity for both the radial and the axial components, within a given volume of the coil system. By use of these data, it is possible to get a field of a given uniformity in a volume much larger than in a two-coil system.
Simple low-temperature press for diamond-anvil high pressure cells
Authors: Shaw Robert W. , Nicol Malcolm
Published: March 2003

A simple press for optical spectroscopy in diamond-anvil high pressure cells at 2 K and variable pressure to 10 GPa and higher is described.
Lloyd’s mirror as an optical beam splitter
Authors: Lyman Ona R.
Published: March 2003

The use of a front surface mirror at grazing incidence to provide two optical beams, suitable for broad band, infrared radiometric temperature measurements, from a single narrow pencil of rays is described. The difficulties of wavelength dependence and fragility of infrared beam splitters are avoided.
Simple wide temperature range ac susceptometer
Authors: Owers-Bradley J. R. , Zhou Wen-Sheng , Halperin W. P.
Published: March 2003

The design of an ac susceptometer that operates in the temperature range 0.5–500 K with a sensitivity of 10−7 emu is presented. The susceptibility is measured using a simple mutual inductance bridge with the pick-up coils kept at fixed temperature. The signals induced by the sample under investigation and a reference sample are compared and enable both the temperature and absolute susceptibility to be determined.
Real-time observation of x-ray diffraction patterns with the Lixiscope
Authors: Chung David Y. , Tsang Tung , Yin Lo I , Anderson J. Robert
Published: March 2003

We report on the use of a recently developed, very compact, totally portable x-ray imaging device, the Lixiscope, for the purpose of real-time observation of transmission Laue diffraction patterns. Such a device is also potentially useful in real-time dynamic studies of structural changes.
Reflectometer for precise measurement of absolute specular reflectance at normal incidence
Authors: Boivin Germain , Theriault Jean-Marc
Published: March 2003

In this paper we describe a simple and useful apparatus used to measure the absolute reflectance of a surface at normal incidence. A rotating beam splitter provides measurement of the intensity reflected by the sample and the intensity of the direct beam which has been previously compensated by a plate identical to the beam splitter, so that no correction for the transmittance of the beam splitter is necessary, which may even be unknown. The instrument can be used with or without a standard plate.
High-speed image processor for picosecond time-resolved spectroscopy
Authors: Takagi Y. , Sumitani M. , Yoshihara K.
Published: March 2003

A microcomputer-based image processor has been developed for picosecond time-resolved spectroscopy of single events. The instrument is used with a monochromator, a streak camera, and a TV camera. Video signals of a spectrum-resolved streak image are divided into up to 32 channels and their intensity profiles are quickly displayed on a TV screen or drawn on a recorder. The design of the hardware and the function of the software are described in detail. Time-resolved emission spectra of dimethylaminobenzonitrile excited by a mode-locked YAG laser have been obtained and a remarkable spectral change in the picosecond domain has been found.
Calibration of a mass spectrometer experiment for ozone
Authors: Anderson Stuart , Mauersberger Konrad
Published: March 2003

A system to calibrate a stratospheric mass spectrometer experiment for ozone has been developed and evaluated. The stability of ozone and the formation of impurities within the calibration volume were measured. The half-life of ozone is about 12 hours, its purity ranges from 95% to 99% and is known to within 1%. The total calibration accuracy of the mass spectrometer experiment for ozone is about ±2%.
X-ray diffractometer for use with cryogenic fluid targets
Authors: Robkoff H. N. , Weiss B. L. , Hallock R. B.
Published: March 2003

An x-ray diffractometer has been constructed so as to allow the study of cyrogenic fluids, in particular liquid helium, at temperatures below 4.2 K. The design and operating characteristics of the diffractometer are presented. Data acquisition is automatic. The x-ray beam is almost exclusively in vacuum and the slits which define the beam are adjustable while the vacuum integrity is maintained. Monochromatization of the x-ray beam is accomplished without use of crystal diffraction.
Automated system for the characterization of high resistivity semiconductors by the van der Pauw method
Authors: Forbes L. , Tillinghast J. , Hughes B. , Li C.
Published: March 2003

An automated system for dark conductivity and Hall measurements and photoconductivity and photo-Hall characterization of high resistivity semiconductors is described. This system has been applied to commercially available semi-insulating GaAs substrates.
New high-brightness multiple beam linear accelerator
Authors: Gammel G. M. , Maschke A. W. , Mobley R. M.
Published: March 2003

A new concept for the linear acceleration of high brightness particle beams, and a description of one working model, are presented. The idea involves the simultaneous acceleration of a large number of low current beamlets in individual, small bore, electrostatic quadrupole focussing channels. Large total current can be reached.
Molecular beam levitator for sputter coating of microspheres
Authors: Varon J. , Goldstein I. S.
Published: March 2003

A molecular beam levitation system is described which is presently being used to sputter deposit coatings on hollow glass microspheres for use as laser fusion targets. Stable levitation of the microspheres has been achieved down to 1×10−4 Torr and levitated microspheres have been coated successfully using both dc and rf magnetron sputter guns in a pressure range from 1 to 10 μm. The system has proven to be highly dependable in both levitation and recovery of the coated microspheres. The levitating gas flow does not appear to interfere with the deposition process, and the rotation of the microsphere, which is produced by the gas flow, ensures that uniform coatings are obtained. Microradiography has shown the coatings to have a high degree of uniformity and the SEM reveals local surface finishes, under specific deposition conditions, of better than 250 Å. Due to the excellent stability of the levitated microspheres, simultaneous deposition using multiple heads may be possible.
Closed-cycle annular-flow-return laser
Authors: Olson Robert A. , Sarka Benjamin , Garscadden Alan , Bletzinger Peter
Published: March 2003

A compact, high repetition rate, closed-cycle rare-gas laser has been achieved in a novel design utilizing an annular flow return surrounding the laser flow channel. The 112-cm long by 30.5-cm-diam. laser head is compact and attractive for portable applications. High repetition rate (to 15 kHz) multiline laser operation has been achieved in high-pressure (to 2 atm) mixtures of Ne–Xe (6 lines), Ar–Xe (7 lines), He–Xe (9 lines), He–Kr (4 lines), and He–Ar (3 lines). Reliable long lifetime performance has been demonstrated by operating a He–Xe laser continuously for 100 hours at a pulse-repetition rate of 5 kHz (1.8×109 pulses) with no degradation of the 1.1-W average laser output power.
Nanosecond risetime avalanche transistor circuit for triggering a nitrogen laser
Authors: Jethwa J. , Marinero E. E. , Müller Alexander
Published: March 2003

Using avalanche transistors, a trigger unit capable of producing several kilovolts in 25 nanoseconds—total risetime—has been constructed. We have used such a circuit to drive a nitrogen laser, resulting in a substantial decrement of the delay time between trigger signal input and the attainment of lasing which is common in commercial lasers. The minimum delay obtained is only limited by the switching time of the thyratron employed. In addition, the ±2 ns jitter of the commercial laser has been reduced to ±0.4 ns using the circuits here described. In order to effect a high degree of reliability, special attention was given to ’’burn-in’’ and selection of the avalanche transistors.
Pulse selection system with electro-optic modulators applied to mode-locked cw lasers and time-resolved single photon counting
Authors: van Hoek A. , Visser A. J. W. G.
Published: March 2003

An electro-optical pulse selection system for mode-locked cw lasers is described. The repetition rate of the exciting pulses can be chosen by electronically dividing the mode locker drive frequency. The shortest repetition time for pulse picking is 3 μs. The optics, electronics, alignment procedure, and adaptation to the detection system are outlined. We use this equipment for measuring the decay of fluorescence and of emission anisotropy of biological molecules.
Coaxial nanosecond flashlamp
Authors: Birch D. J. S. , Imhof R. E.
Published: March 2003

We have developed a coaxial thyratron-gated flashlamp capable of being operated with high stability over a much wider range of conditions than previous flashlamps. Novel methods for continuously monitoring discharge stability are described. We present comprehensive data on the dependence of pulse width and intensity on operating parameters. Using the single photon detection technique an overall instrumental profile of 950 ps FWHM and 630 ps rise time has been obtained using hydrogen as a filler gas. An instrumental width of 1.2 ns FWHM can be routinely obtained in nitrogen even at a repetition rate of 100 kHz. Intensities of ≳109 photons per pulse in nitrogen and ≳108 in hydrogen can be obtained at the minimum pulse duration. The maximum intensity per pulse without added capacitance is ≳1010 photons. This performance is considerably better than that reported for conventional flashlamps.
Images of single x-ray photons from x-ray phosphor screens
Authors: Fishman G. J.
Published: March 2003

Photographs show efficiency and resolution characteristics of single x-ray photons converted to optical photons in a variety of commercial x-ray phosphor screens. The recording system uses a cooled, two-stage image intensifier system with fiber optics coupling to the phosphor screen. High efficiencies in the energy range 20–100 keV with position resolution of the order ∼200 μ are readily achievable, although the sensitive area is presently limited. Potential applications include x-ray astronomy, high-speed x-ray diffractometry, and extremely low dose radiography.
Design and performance of an energy- and angle-resolved secondary ion mass spectrometer
Authors: Gibbs R. A. , Winograd N.
Published: March 2003

The design and performance of an energy- and angle-resolved secondary ion mass spectrometer are described. The instrument incorporates a quadrupole mass filter mounted on a flange which can be rotated under ultrahigh vacuum conditions, allowing variation of the polar collection angle of secondary ions, while rotation of the sample crystal about an axis parallel to the primary ion beam provides azimuthal angle section. Energy analyses are performed in the 0–100 eV range using a 90° spherical electrostatic sector combined with an accelerating/decelerating lens system which provides a variable 1–15 eV bandpass. Low energy electron diffraction provides complementary information on surface and adsorbate geometry. The determination of energy and angular distributions of secondary ions ejected from an ion-bombarded Ni(001)c(2×2)–CO surface illustrates the capabilities of the system.
Ultrahigh vacuum multipurpose offset manipulator for surface and thin film reaction studies
Authors: Crider C. A.
Published: March 2003

A novel ultrahigh vacuum (UHV) manipulator has been constructed which allows positioning of a sample on any point of an 11.5-cm radius main circle and provides two orthogonal off-axis rotations at the selected point. The motions are a 0 °–90 ° tilt of the sample face and a ±180 ° rotation normal to the sample face. The main circle position may be varied by ±1 cm in X and Y directions and ±0.7 cm in the Z direction, which is orthogonal to the plane of the main circle. Additionally, at any position the sample is electrically isolated, fitted with a thermocouple, and may be heated resistively to 1200 °C. The manipulator is UHV compatible and may be baked to 200 °C.
Hydroplane polishing of semiconductor crystals
Authors: Gormley J. V. , Manfra M. J. , Calawa A. R.
Published: March 2003

A new technique for obtaining optically flat, damage-free surfaces on semiconductor crystals has been developed. The polishing is very fast, being capable of removing over 30 μm of materials per minute in the case of GaAs and InP. Initial results indicate that the technique can also be used in the polishing of HgCdTe.
Influence of a dc magnetic field on proximity measurements with eddy-current gauges
Authors: Rajotte R. J. , Drouet M. G.
Published: March 2003

The influence of an external dc magnetic field on proximity measurements with an eddy-current gauge was studied with iron, stainless steel, and copper samples. The magnetic flux density was varied from 0 to 1 T and the direction of the external field was either perpendicular or parallel to the probe axis. Measurements show that with an iron sample, a magnetic field perpendicular to the axis has a tremendous influence on the gauge’s response, but practically no influence at all when parallel to the axis.
Electromagnet for nuclear magnetic resonance imaging
Authors: Hoult D. I. , Goldstein S. , Caponiti J.
Published: March 2003

The design and construction of a novel high-homogeneity magnet for use in nuclear magnetic resonance imaging experiments is described. The magnet consumes 7 kW to produce a field of 0.117 T (Larmor frequency of protons 5 MHz) with a homogeneity of about 3 ppm over a spherical volume of diameter 10 cm. The magnet is constructed on two hemispherical formers cast from aluminum, and large linear field gradients in any direction may be generated by manipulation of the magnet power supply and the orientations of the two hemispheres. The adverse effects on the field homogeneity of the environment are discussed and annulment of the effects is described. Power supply design is briefly considered and the use of a flux stabilizer advocated for obtaining excellent (0.1 ppm) short term stability.
Single crystal electron paramagnetic resonance studies: A computer-assisted two-circle goniometer
Authors: Morton J. R. , Preston K. F. , Strach S. J.
Published: March 2003

A two-circle goniometer is described which, used in conjunction with a computer, enables a crystal to be oriented for single crystal electron paramagnetic resonance (EPR) studies. Crystallographic planes can be explored in order to determine off-diagonal tensor elements.
Simple lock-in amplifier using a four-quadrant analog multiplier and a phase lock loop
Authors: Ramani K. , Ganapathy S.
Published: March 2003

A linear monolithic four-quadrant analog multiplier has been used for the detection of Nuclear Magnetic Resonance signals, in conjunction with a phase lock loop. The detection system employs an audio frequency modulation of the magnetic field, followed by a phase-sensitive detector, wherein an analog multiplier is used.
Electrometer preamplifier for measurement of voltage, current, and resistance on high resistivity materials
Authors: Barthwal S. K. , Subramanian S. , Majhi J. , Majhee P. C.
Published: March 2003

An electrometer preamplifier for the measurement of dc voltage, current, and resistance in high resistivity materials has been developed. The ranges of measurement for voltage, current, and resistance are from 30 μV to 10 V, 10−2 to 10−13 A and 103 to 1013 Ω, respectively. Charge measurements can also be made by connecting a suitable capacitor in the feedback loop. It uses commerically available operational amplifiers. The preamplifier is small in size and is used in conjunction with a commerical voltmeter or recorder. It is ideally suited for in situ measurement of electrical properties of amorphous semiconductor films.
Fully programmable microprocessor-controlled Mössbauer spectrometer
Authors: Benedetti M. , Fernandez D. R.
Published: March 2003

A description of the construction details and operation of a spectrometer controlled with a microprocessor of 8 bits is given. It contains 1024 channels with a storage capacity of 16×106 counts per channel. The design has no bearing on the kind of microprocessor selected and can be used for experiments requiring collection of data in real time along with off-line processing of the information. The programing was carried out so that the device operates as a Mössbauer spectrometer. Owing to the fact that the system is totally programmable, it is possible to select waveforms and frequencies of the drive function as well as the number of channels to be used. Furthermore, when an ADC is added, the spectrometer can operate as a pulse-height analyzer. Special attention has been paid to the minimization of dead time.
Frequency-selective amplifier
Authors: Kiess E. M.
Published: March 2003

A frequency-selective amplifier is described which has a Q in excess of 300. The circuit has a modified Twin-T feedback circuit which uses inductors.
Hyper-filter–fluorescer spectrometer for x rays above 120 keV
Authors: Wang C. L.
Published: March 2003

We present a new method of utilizing a filter–fluorescer system for measuring high fluence x-rays above 120 keV, where there are no practical absorption edges available for conventional filter–fluorescer techniques. The absorption edge (Ep keV) of the prefilter is chosen to be less than that of the fluorescer (Ef keV), i.e., Ep<Ef, contrary to the conventional technique, Ep≳Ef. In this way the response function is rendered virtually zero between Ep and Ef, while a broad peak at higher energy is enhanced for measurement above 120 keV. An application of the method for x-ray measurement between 150 and 350 keV from laser-driven nuclear fusion is described.
High efficiency ion beam accelerator system
Authors: Aston Graeme
Published: March 2003

An ion accelerator system that successfully combines geometrical and electrostatic focusing principles is described. This accelerator system uses thin, concave, multiple-hole, closely-spaced graphite screen and focusing grids, coupled to single slot accelerator and decelerator grids to provide high ion extraction efficiency with good focusing. Operating characteristics for this type of accelerator system and possible applications are discussed.
Novel finite pulse-width correction in flash thermal diffusivity measurement
Authors: Azumi Tadahiko , Takahashi Yoichi
Published: March 2003

A new method for obtaining correct thermal diffusivity values in flash measurement has been developed. This consists of two steps: (1) adjustment for an ’’effective’’ irradiation time using the center of gravity of pulse, and (2) the correction for the deviation in the parameter K from the ideal value, 0.1388. We have found that after the adjustment for the ’’effective’’ irradiation time, no further correction is needed for any form of pulse, even for very short t1/2 such as t1/2 = 2 τ.
Device for i
n s
i
t
u casting and tensile testing of materials freezing at cryogenic temperatures
Authors: Purushothaman S.
Published: March 2003

Tensile testing of materials that freeze at subambient temperatures usually requires casting of the material in a mold, transferring the cast specimen into precooled test fixtures held in a moisture-free environment to avoid frosting, followed by performing the test at the desired cryogenic temperature. In this report we describe a device that allows the casting as well as testing to be completed in one assembly and cool-down cycle, eliminating the cumbersome intermediate steps.
Simple and sensitive strain gauge displacement transducer
Authors: Ramana Y. V. , Sarma L. P.
Published: March 2003

We describe a simple and sensitive strain gauge displacement transducer. It is based on the linear movement of a shaft (with two cantilevers and four strain gauges) in a tapered chamber, resulting in a change in resistance proportional to the cantilever deformation. The transducer with its Wheatstone full bridge configuration is calibrated against a mechanical dial indicator of 0.002 mm accuracy for both ac and dc voltage excitations. Its output is linear for measurements of full range displacement up to 25 mm. It has a sensitivity of ±0.0082 mm for ac excitation with a strain indicator whose resolution is ±1 με. It has a dc full range sensitivity of 1.5 mV/V for excitation levels up to 5 V. It can have varied field and laboratory applications wherever displacements are precisely read, recorded, or monitored.
Compact analyzer and goniometer for angle-resolved electron spectroscopy
Authors: Stoffel N. G. , Margaritondo G.
Published: March 2003

We discuss the design and construction of a modified electrostatic plane mirror electron energy analyzer mounted on a novel dual axis goniometer. The system is compact, bakable, and well suited for ultrahigh vacuum angle-resolved photoelectron spectroscopy. The device is relatively inexpensive and simple to construct, yet provides ample performance and versatility. In particular, preaccelerating electron optics have been developed which allow operation of the analyzer in the constant pass energy mode with uniform sensitivity over an increased energy range. A differentially driven goniometer allows the polar and azimuthal directions of detection to be varied independently and read directly. Test results are presented and angular and energy resolutions of 3° and 3% are reported.
Thermal contact to dielectric materials at low temperature
Authors: Ackerman D. A. , Anderson A. C.
Published: March 2003

Vibrational heating is often troublesome at temperatures ≲0.1 K. This heating can be reduced by clamping samples rigidly. Measurements indicate that clamped joints to dielectric materials can be designed to have thermal impedances ranging from a minimum, determined by the thermal boundary resistance, to values that are a factor of ≊104 larger.