bluuebunny/crossref_metadata_2025 huggingface dataset:
Doppler velocimeter for laser accelerated targets
Authors: Obenschain S. P. , McLean E. A. , Gold S. H.
Published: March 2003

A doppler velocimeter utilizing a spectrograph and a short-pulse laser probe is described which provides good spatial (20 μm) and subnanosecond temporal resolution. This system has been used to measure the velocity profiles of targets ablatively accelerated to very high velocities by a high-power laser beam. In comparison to systems employing interferometric techniques, this velocimeter significantly relaxes requirements on the target surface being examined and the time resolution needed to measure velocities of rapidly accelerating surfaces.
Stabilizing feedback system for synchrotron radiation monochromators
Authors: Mills D. , Pollock V.
Published: March 2003

We have designed and constructed a feedback system that will maintain the angle between two x-ray diffracting crystals. The system was designed for use in conjunction with a double crystal synchrotron radiation monochromator at CHESS and will preserve the relative angle between crystals during energy scans and as a function of time for a fixed wavelength. A voltage proportional to the slope of the rocking curve is used as the feedback signal. This signal is normalized in such a way that the time dependence of the incident beam intensity is removed. The feedback system allows one to sit not only at the peak of the rocking curve, but also on the flanks, an aspect crucial when utilizing the harmonic rejection properties of the double crystal monochromator.
Variable-temperature ion–implantation cryostat
Authors: Sekula S. T. , Thompson J. R.
Published: March 2003

A versatile low-temperature apparatus for studies using ion beams in an ultrahigh vacuum environment is described. By providing variable-temperature operation from ∼2–300 K, the facility can be used for a variety of studies. These have included low-temperature ion implantations for the production of metastable superconducting systems, thermal-annealing studies, and ion-mixing experiments. The cryostat combines economical use of liquid helium, long-holding time (several days) at liquid–helium temperatures as required for some studies, and ion–beam accessibility with the capability of absorbing high power (∼∼6 W at 5 K) for short periods. To allow adjustment of the target position relative to implanting or analyzing ion beams, the entire cryostat is mounted on a separate assembly providing vertical motion and rotation about the vertical axis.
Fast multichannel time correlator for coincidence experiments in atomic physics
Authors: Brenot J. C. , Fayeton J. A. , Houver J. C.
Published: March 2003

Use of multichannel plate detectors has considerably extended the experimental techniques in atomic physics. In this context, a coincidence circuitry able to determine 64 simultaneous coincidence spectra is described. Use of fast electronic devices and separated amplifiers allows a high counting rate capability (5×105 events per second) with a time resolution of 3.1 ns. UV photon-scattered particle coincidence in He–He collisions is given as an example of the application of the present apparatus.
Regular and asymmetric negative ion magnetron sources with grooved cathodes
Authors: Alessi J. G. , Sluyters Th.
Published: March 2003

A significant improvement in the performance of the BNL Mark III magnetron negative ion sources has been achieved by putting cylindrical grooves on the cathode to geometrically focus surface produced H− and D− ions into the emission slit in the anode. The addition of these grooves has allowed us to reach desired negative ion emission current densities with an order of magnitude lower arc current than was previously required. An additional improvement in the operation of the magnetron has resulted from increasing the anode-to-cathode spacing in the back of the source, which facilitates ignition of the discharge at low pressures. The net result of these modifications has been an improvement in the gas and power efficiencies by at least a factor of three, and a reduction in the emittance of the beam.
Electric gun: a versatile tool for high-pressure shock-wave research
Authors: Chau H. H. , Dittbenner G. , Hofer W. W. , Honodel C. A. , Steinberg D. J. , Stroud J. R. , Weingart R. C. , Lee R. S.
Published: March 2003

We have developed a versatile tool for generating planar shock waves. This system, which we call the electric gun, is capable of projecting thin flyer plates with velocities in the range 1–20 km/s. It is presently being used in high-explosives-initiation experiments and is being developed for equation-of-state measurements in the 1–5 TPa range. We describe the electric gun facilities that are operational at Lawerence Livermore Laboratory and discuss applications of electric gun technology to problems of interest to shock-wave researchers.
Novel high-temperature, Na vapor cell
Authors: Zajonc Arthur G.
Published: March 2003

A novel Na vapor cell has been constructed for use at temperatures up to 500 °C. High-vacuum sapphire-to-metal seals have been made without brazing by use of copper gaskets placed between the sapphire windows and kovar compression rings. Careful design of cell dimensions allows for matched thermal expansion rates and thus the vacuum seal maintains its integrity over a very large temperature range (0°–750 °C).
Signal averager interface between a Biomation 6500 transient recorder and an LSI-11 microcomputer
Authors: Specht L. T.
Published: March 2003

This paper describes the design and implementation of a versatile and compact signal averager interface between a Biomation 6500 transient recorder and an LSI-11 microcomputer. The design allows for fast signal averaging in excess of 1 kHz and is also easily software configurable and controllable. This permits the rapid recovery of high-speed waveforms at a minimum sampling time of 2 ns (500 MHz sampling rate). The interface has been incorporated into an LSI-11 system using the RT-11 V3B operating system and found to perform very satisfactorily.
General purpose talking laboratory instrument for the visually handicapped
Authors: Salt Alger , Lunney David , Hartness Richard
Published: March 2003

The instrument described here was designed as a laboratory aid for the visually handicapped. It is basically a 3 1/2-digit multimeter with speech output; however, it has added functions which extend its usefulness beyond the ability to measure the usual ranges of ac and dc voltage and current. The device can function as a thermometer, a pH meter, a 6-digit timer, and an events counter. Two voltage-to-frequency (V/F) converters make it useful as an audible comparator and peak detector. An integrator is realized by using the counter to count the pulse train from a V/F converter which monitors the input signal. A low-level differential channel is provided for interfacing to instruments with recorder outputs, such as gas chromatographs. Spoken values of measured quantities are accompanied by sign, decimal point, and units. The instrument can also interface with other digital devices through 42 lines of parallel digital input–output. It can convert seven parallel BCD digits into speech or it can output BCD data from its counter or converter to a microcomputer.
Crossed TM110 bimodal cavity for measurement of dispersion electron paramagnetic resonance and saturation transfer electron paramagnetic resonance signals for biological materials
Authors: Mailer C. , Thomann H. , Robinson B. H. , Dalton L. R.
Published: March 2003

When commercial reflection cavities are utilized for electron paramagnetic resonance (EPR) experiments at high-microwave field intensities or for saturation transfer–electron paramagnetic resonance (ST–EPR) measurements, dispersion signals exhibit substantially worse signal-to-noise than absorption signals due to the increased sensitivity of the former to source frequency modulation noise. The development and testing of a TM110×TM110 bimodal cavity which completely eliminates the source noise problem is described. This cavity is used to obtain EPR and ST–EPR spectra of a variety of commonly encountered spin-labeled biological samples. When samples are contained in capillary tubes, this TM110×TM110 cavity often permits the realization of better signal-to-noise than can be obtained with commercial reflection cavities.
Modified signal-averaging technique to reduce measurement time
Authors: Neelakantan K. , Rajappan K. P.
Published: March 2003

A simple method of reducing the total measurement time in signal averaging is described. The method uses averaging over autocorrelation estimates rather than over the signal directly. The method may be useful in certain cases where the repetition rate is small.
High pressure pressure-jump apparatus
Authors: Heremans K. , Ceuterick F. , Rijkenberg J.
Published: March 2003

A pressure jump relaxation technique is described to study fast reactions in solution under pressure up to 1.5 kbar. The mechanical relaxation time of the instrument is 0.5 ms.
Development of a supersonic O(3PJ), O(1D2) atomic oxygen nozzle beam source
Authors: Sibener Steven J. , Buss Richard J. , Ng Cheuk Yiu , Lee Yuan T.
Published: March 2003

A high pressure, radio frequency discharge nozzle beam source has been developed for the production of very intense (⩾1018 atoms sr−1  s−1) supersonic beams of oxygen atoms. An efficient impedance matching scheme has been devised for coupling the radio frequency power to oxygen–rare gas mixtures as a function of gas pressure, temperature, and composition. Techniques for localizing the discharge directly behind the orifice of a specially designed quartz nozzle have also been developed. The above combine to yield a beam source which reliably produces a high degree of molecular dissociation in oxygen–rare gas mixtures at pressures up to 350 Torr. Atomic oxygen mean translational energies from 0.14–0.50 eV have been achieved using the seeded beams technique with Mach numbers up to 10 being realized. When helium is used as the carrier gas both O(3PJ) and O(1D2) atoms are present in the beam, while only ground state atoms appear to be present in argon seeded mixtures. This paper describes the design, construction, and operation of this beam source and provides a characterization of the atomic oxygen beams it has reproducibly generated in our laboratory.
High-temperature photochemistry reactor for kinetic studies of isolated elementary gas-phase reactions
Authors: Felder William , Fontijn Arthur , Volltrauer Hermannn N. , Voorhees David R.
Published: March 2003

A reactor suitable for kinetic measurements on photolytically initiated elementary free-radical reactions over approximately the 300–1900 K temperature range is described. Performance data are given for the O+CH4→OH+CH3 reaction.
Highly flexible pulse programmer for NMR applications
Authors: Dart J. , Burum D. P. , Rhim W. K.
Published: March 2003

A pulse generator for NMR application is described. Eighteen output channels are provided to allow use in both single and double resonance experiments. Complex pulse sequences may be generated by loading instructions into a 256-word by 16-bit program memory. Features of the pulse generator include programmable time delays from 0.5 μs to 1000 s, branching and looping instructions, and the ability to be loaded and operated either manually or from a PDP-11/10 computer.
Fluid insulator used in the investigation of gas phase ions with an electrometer
Authors: Auerbach A.
Published: March 2003

We describe a simple design modification which will solve the spurious surface charging effects associated with the use of sweep plates to investigate gaseous ions. The procedure involves using a fluid insulator to electrically isolate the electrometer electrode.
Retractable, rear viewing low energy electron diffraction/Auger spectroscopy system
Authors: Wendelken J. F. , Withrow S. P. , Herrell P. S.
Published: March 2003

The design of a rear viewing, retractable low energy electron diffraction assembly is described.
Inserting thermocouples directly through infrared windows
Authors: Draper Clifton W. , Pessel William O.
Published: March 2003

Small holes, approximately 0.25 mm diameter, are drilled through IR windows (NaCl, KCl, CsBr) 3.2 mm thick. Thermocouples wires (0.13 mm diam) are inserted and sealed with ’’Vacseal,’’ a silicone resin. After curing, a reasonably durable-vacuum proof seal exits. The method provides a very simple, inexpensive procedure for installing thermocouples in IR spectroscopy and reaction cells.
Measurement of the plasma potential with ion acoustic waves
Authors: Schott L.
Published: March 2003

Plasma potentials are determined from the bias of a Langmuir probe at which the ac probe current due to an externally excited ion wave vanishes.
Sample cell for EXAFS measurements on molten materials at elevated temperatures
Authors: Mikkelsen J. C. , Boyce J. B. , Allen R.
Published: March 2003

We describe the design, fabrication, and utilization of a simple sample cell for extended x-ray absorption fine structure (EXAFS) measurements at elevated temperature. The cell is rigid, inert, easy to fabricate, cheap and effective in maintaining the critical specimen dimensions of both solid and liquid samples up to 1000 °C.
New design for a microwave discharge lamp
Authors: Glangetas Alain
Published: March 2003

A simple discharge lamp with a microwave cavity fitting inside provides an intense source of VUV resonance radiation for photochemical work inside a vacuum chamber. Good coupling and minimum reabsorption result in better efficiency (≳1%) and more intense output power (up to 2.5×1016 quanta s−1) than have been achieved previously.
Some modifications of electric circuitry for internal friction measurements of U-shape specimens
Authors: Yoshinari O. , Koiwa M. , Sugawara H. , Satoh I.
Published: March 2003

Some modifications of the electric circuitry are described for the apparatus of the internal friction measurement of thin wire specimens; the apparatus has been developed by Franklin et al. The improved apparatus has been successfully used in the internal friction measurements of cold-worked vanadium specimens.
On-line data acquisition system for acoustic emission signals
Authors: Duncan Hibbert A. , Anderson Albert L.
Published: March 2003

An electronic system for processing and recording some very important parameters of acoustic emission signals at a relatively high speed is described. The system is applicable to almost any process in which acoustic emission is implemented for quality control. Data processing is done in real time. The processed data are ring-down count (threshold crossing), energy, duration, and time of occurrence of each acoustic emission burst.
Small barium rail gun for plasma injection
Authors: Kiwamoto Y.
Published: March 2003

A small rail gun with a barium electrode can be operated at higher than one shot per second to produce more than 2×1016 barium ions with energy 10–20 eV. The operation of the gun takes advantage of the external magnetic field for cross-field plasma injection into a trap. Up to 7 kG of the magnetic field examined, the gun performance improves with the increased magnetic field strength.
Five-frame, x-ray camera for charged particle, inertial confinement fusion studies
Authors: Fehl D. L. , Chang J. , Kuswa G. W. , Mendel C. W.
Published: March 2003

A prototype framing x-ray camera has been developed for photographic studies of inertial confinement fusion (ICF) targets irradiated by charged particle beams. Electron images from five, independently gated, microchannel plates are transported out of the radiation field by means of a toroidal magnetic field and are permanently recorded on film. The calculated, effective exposure time is ⩽5 ns (FWHM), and the resolution at the object is presently limited by the x-ray pinhole optics to ∼0.5 mm. Time-resolved photographic studies have been made of luminous targets irradiated by pulsed electron and ion beams. The camera has also been adapted for single frame, x-radiographic studies of nonluminous imploding targets.
Multiscaler-microcomputer interface
Authors: Wolpert Leo
Published: March 2003

An interface which enables data transfer to or from a microcomputer is described. Data transfer from an analyser uses the printer output under interface control. To put the processed data into a form acceptable to the analyser, the output of the microcomputer is converted by the interface into pulses the number of which is proportional to the binary-coded data.
Automatic, tracking, peak timer
Authors: Holcomb D. J. , Koczynski T.
Published: March 2003

We have designed an inexpensive instrument for automatically measuring time of flight for repetitive signals. It is stable in the presence of noise resembling the real signal. Specific peaks in a multipeak signal can be timed to an accuracy of about 10 ns with the present design. The output is either a digital word or an analog voltage. Computer control is simple and would make it possible to time several signals with the same instrument.
Visualization of standing vortices behind a cylinder in glycerin–water solutions
Authors: Matsunaga N. , Honji H.
Published: March 2003

The standing vortices behind a circular cylinder have been visualized by means of direct shadows produced in glycerin–water solutions, and the length of the vortices has been measured. It has been thereby confirmed that the method is applicable to visualize the closed regions of standing vortices correctly. The shadow pattern over the whole flow field, however, seems to correspond to none of the patterns of common hydrodynamic lines.
Electronic device for compensating for pen displacement in a multiple channel strip-chart recorder
Authors: Nylén Per
Published: March 2003

In multiple channel strip-chart recorders the different graphs are always displaced due to mechanical shortcomings. An electronic device which compensates for that displacement has been developed and tested. This displacement correction unit is a necessity in applications where the information in the different channels are strongly correlated, which is the case in our work in high resolution laser spectroscopy. The use of highly integrated electronic components makes the circuit design straightforward and compact.
Shape correction technique for stabilizing and linearizing a constant acceleration Mössbauer velocity drive
Authors: Corson M. R.
Published: March 2003

In a Mössbauer effect spectrometer employing a large vibrating mass or stiff drive centering springs, it is sometimes difficult to achieve satisfactory velocity tracking. In such situations, the linearity and stability of a constant acceleration Mössbauer velocity drive can be improved significantly by inserting a correction signal into the feedback loop. A simple physical interpretation of a shape correction technique is discussed, and a drive amplifier using this principle is described. This system has less than 0.1% tracking error over the velocity range ±2 cm/s, yet the feedback gain is reduced by a factor of 60 as compared to a conventional drive.
Simple low-cost digital events analyzer
Authors: Yangos John P. , Chen S.-H.
Published: March 2003

We present the design and applications of a simple and very low-cost digital events analyzer, suitable for use in a student laboratory as well as in research applications. The pulse analyzer can perform five functions: sampling measurement; pulse interval distribution measurement; simple triggered multichannel scaling; scaled triggered multichannel scaling; and auto- and cross-correlation function measurement. The memory capacity is limited to 100 channels with 11 bits or more word length. The basic cycle time of the analyzer is 500 ns as limited by the speed of MOS circuit used. We demonstrate the utility of it with counting statistics experiments of radiations from radioactive decay, neutron time of flight analysis, and also the photon correlations measurements of light scattered from particles in fluids.
Device for improving ultrasonic transit time measurements with standard pulse echo equipment
Authors: Reider Georg A. , Kittinger Erwin
Published: March 2003

A simple and inexpensive device is described which in conjunction with conventional pulse echo equipment allows the direct measurement of the time interval between the zeros of selected individual cycles in different echoes with an accuracy better than 0.2 ns.
Effect of heat leaks in platinum resistance thermometry
Authors: Goldratt E. , Yeshurun Y. , Greenfield A. J.
Published: March 2003

The effect of heat leaks in platinum resistance thermometry is analyzed. An experimental method is proposed for estimating the magnitude of this effect. Results are reported for the measurement of the temperature of a hot, solid body under different heat-leak configurations. Design criteria for thermometers are presented which minimize the effect of such heat leaks.
Narrow energy distribution of output electrons from a modified single channel electron multiplier
Authors: Koshida Nobuyoshi , Kunii Makoto , Yoshida Shigetomo
Published: March 2003

New methods which reduce the unfavorable energy spread of output electrons from a single channel electron multiplier are presented. A modified output electrode produces a pronounced narrowing effect on the energy distribution without much affect on the gain. A simplified analysis of the field inside the channel shows that the fixed channel wall potential near the output end is responsible for the narrow energy distributions obtainable.
Bifurcated fiber luminometer
Authors: Grojean R. E. , Sousa J. A.
Published: March 2003

Measurements of luminescence in turbid media or in situ at inaccessible or hazardous locations is facilitated through the use of a random, bifurcated optical fiber bundle.
Mechanical properties of Stycast-1266 at low temperatures
Authors: Hashimoto Tatsuo , Ikushima Akira
Published: March 2003

Young’s modulus, the critical tensile stress, and the fracture stress of Stycast-1266 have been determined by the tension test as functions of temperature between room temperature and 2.2 K.
Gravity fed Hg heat pipe: Its use in the production of a high purity, fixed density of Hg atoms
Authors: Schlie L. A. , Jusinski L. E. , Rathge R. D.
Published: March 2003

A modified heat pipe employing Hg as the working fluid and utilizing gravity to return the liquid Hg from the condensative to the evaporative zone is described. This device provides an easy and rapid means of producing a fixed density of Hg atoms of high purity for any test cell configuration without employing elaborate Hg distillation techniques. Densities from 1016 to 1020/cm3 can be easily acquired with a variable inert gas density.
Simple, fast rise time, high repetition rate Pockels cell driver
Authors: Plourde B. , Mack M. E. , Verro E.
Published: March 2003

A thyratron Pockels cell driver capable of optically switching Pockels cells of up to 2.5 cm aperture in 6 ns at repetition rates of up to 1000 Hz is described. The circuit is based on a modified HY-2 thyratron.
Butterfly-valve inductive orientation detector
Authors: Garrett Steven
Published: March 2003

Relative changes of inductance ΔL/L of a single layer coil surrounding a thin electrically conducting disk which can rotate about an axis perpendicular to the coil axis are studied experimentally as a means of measuring angular displacements. ΔL/L is found to be a strong function of disk diameter and is weakly dependent on the ratio of disk thickness to electromagnetic skin depth when this ratio is of the order unity. Values of ΔL/L as a function of disk diameter are given for lead, brass and copper. Detection sensitivities using a resonant tank circuit or an astatic transformer are given in terms of ΔL/L and it is shown that sensitivities of the order of 10−3 to 10−4 deg are practical. Application of this system to the Rayleigh disk and cryogenic environments are emphasized and an expression for the magnetic torque due to detection currents is given.
Quasiquadrature interferometer for plasma density radial profile measurements: Achieving ten channel operation
Authors: Lowenthal D. D.
Published: March 2003

A quadrature interferometer designed to measure radial electron density profiles in a long (3 m) small bore (2.8 cm) plasma tube, and described previously in this journal, has been further developed to have ten simultaneously operating channels. Achieving multichannel operation was essential to the accurate measurement of radial electron density profiles and required the design, fabrication, and implementation of two closely matched optical polished quartz tube sections. The first polished cylinder forms the cross tube scene beam window and is used as a sleeve to join ceramic tube sections that comprise the bulk of the 3-m plasma tube. The second matched cylindrical section is placed in the interferometer reference beam to compensate for the strong negative lens affects of the cylindrical scene beam window. Design criteria for the cylindrical tube sections is discussed, the plasma tube assembly technique is given, and typical ten channel data is presented for a laser heated 3-m-long theta-pinch.
Waveguide propagation in frozen gas matrices
Authors: Rossetti R. , Brus L. E.
Published: March 2003

Laser beam waveguide propagation in frozen gaseous layers at 4.2 K has been investigated. Propagation lengths of ∼1 cm are observed on metallic mirror substrates. Structures enabling efficient laser injection have been devised. A scattering enhancement factor of 34 in a neon matrix is observed in the waveguide mode, as compared with normal front surface illumination.
Experimental study of ion beamlet steering by aperture displacement in two-stage accelerator
Authors: Okumura Y. , Mizutani Y. , Ohara Y.
Published: March 2003

The steering of ion beamlets in a two-stage accelerator has been measured as functions of both aperture displacement and field intensity ratio between extraction and acceleration regions. Three different types of displacement have been investigated; i.e., displacement of (1) plasma grid, (2) gradient grid, or (3) suppressor grid with respect to the other three grids. In each case, the steering angle is found to be linear with the aperture displacement, and independent of final beam energy and beam current. The variation of steering angle with displacement distance is compared with the value predicted by linear theory using thin lens approximation. It is confirmed that they agree well in the case of (3), while they show appreciable differences in the cases of (1) and (2). This is because the lens effect of the gradient grid is weaker than is predicted by the linear theory. The deterioration of beam optics due to steering has not been observed.
The GaAs spin polarized electron source
Authors: Pierce D. T. , Celotta R. J. , Wang G.-C. , Unertl W. N. , Galejs A. , Kuyatt C. E. , Mielczarek S. R.
Published: March 2003

The design, construction, operation, and performance of a spin polarized electron source utilizing photoemission from negative electron affinity (NEA) GaAs are presented in detail. A polarization of 43±2% is produced using NEA GaAs (100). The polarization can be easily modulated without affecting other characteristics of the electron beam. The electron beam intensity depends on the intensity of the exciting radiation at 1.6 eV; beam currents of 20 μA/mW are obtained. The source is electron optically bright; the emittance phase space (energy-area-solid angle product) is 0.043 eV mm2 sr. The light optics, electron optics, and cathode preparation including the GaAs cleaning and activation to NEA are discussed in depth. The origin of the spin polarization in the photoexcitation process is reviewed and new equations describing the depolarization of photoelectrons in the emission process are derived. Quantum yield and polarization measurements for both NEA and positive electron affinity surfaces are reported. The important considerations for interfacing he polarized electron source to an experiment are illustrated by its application to polarized low energy electron diffraction (PLEED). The advantages of this spin polarization modulated electron gun for PLEED are clearly demonstrated by sample PLEED results for W(100) and ferromagnetic Ni(110). A comparison with other polarized electron sources shows that the GaAs spin polarized electron source offers many advantages for a wide range of applications.
High precision 3He-vapor-pressure gauge for use to 0.3 K
Authors: Greywall D. S. , Busch P. A.
Published: March 2003

The design and performance of a compact, high precision, capacitive, vapor-pressure gauge is described. The gauge was constructed using a thin electrodeposited copper diaphragm.
Analysis of a dual beam laser velocimeter applied to microcirculation studies
Authors: Le-Cong Phung , Lovberg Ralph H.
Published: March 2003

A laser crossed-beam anemometer has been applied to the study of capillary blood flow. Analysis of the various contributions to the S/N ratio of this system is presented, in which the effect of finite detector area is taken into account. Experimental data, taken in vivo from a rabbit omentum, using a coherent frequency tracker, are included. The frequency tracker also serves as a particularly effective phase-lock detection system, based upon the rotation of the relative polarization of the two incident beams. The data processing circuits are gated synchronously with the cardiac pulse, thus allowing measurement of flow velocity as a function of phase in the cardiac cycle. In spite of the considerable optical phase distortion incurred upon passage of the laser beams through the tissue covering the blood vessels, the autocorrelation of the fringe field (’’fringe visibility’’) remained high enough to permit useful velocity measurements. Rotation of the fringe direction allows measurement, with a one-dimensional velocimeter, of randomly oriented flows.
Soft x-ray imaging instrument for the Alcator A tokamak
Authors: Petrasso R. , Gerassimenko M. , Seguin F. H. , Ting J. , Krogstad R. , Gauthier P. , Hamilton W. , Ramsey A.T. , Burstein P. , Granetz R.
Published: March 2003

We describe an instrument that images the Alcator A tokamak plasma in the soft x-ray energy range with high temporal resolution. Radiation from a cross section of the plasma column is detected by an array of seventeen surface barrier detectors which provides 1 cm poloidal spatial resolution over a 16 cm field of view. The instrument’s nominal sensitivity lies in the spectral range from 0.27 to 25 keV; this range includes much of the radiation emitted by the Alcator A plasma, whose core temperature is typically in the 0.6 to 1.1 keV range. The frequency response of the detector-electronics system extends from dc to 170 kHz. We discuss: (1) some design considerations and instrument calibrations, including the instrument’s measured response to 0.28, 1.5, 8.0, and 17.5 keV x-rays and its theoretical response to a bremsstrahlung spectrum; (2) the detector-electronics noise levels under various conditions; (3) the instrument’s response to an electrically modulated x-ray source; (4) the detector x-ray response as a function of bias voltage and temperature; (5) the detector linearity of response to 1.5 keV x-rays; and (6) the stability of the detector x-ray response despite numerous and prolonged vacuum breaks. Sample data, obtained from Alcator A discharges, are presented.
Micromagnetic susceptometer
Authors: Nave Stanley E. , Huray Paul G.
Published: March 2003

A variable temperature (4.2 K to 300 K) micromagnetic susceptometer has been designed to maximize sensitivity to the magnetic flux produced by small samples. The susceptometer is based upon a superconductive flux sensor which measures the magnetic flux through a set of coils due to a sample magnetized in a uniform field. A minimum measurable volume susceptibility of 7.5 ×10−8 (emu) for a 1 microgram sample of curium has been achieved giving an increase in sensitivity of two orders of magnitude over Faraday devices designed for microgram metallic samples.
Observation of soft x-ray transition radiation from medium energy electrons
Authors: Chu A. N. , Piestrup M. A. , Barbee T. W. , Pantell R. H. , Buskirk F. R.
Published: March 2003

Soft x-rays (2 to 6 keV) have been observed from transition radiators using electrons at energies of 104 and 66 MeV. The observed spectra agree well with theory. Various stacks of mylar of 2.5, 3.5 and 6.35 μm thickness were used to produce the radiation. Optimum foil thicknesses and number were calculated and found experimentally to be correct.
Apparatus for trapping and thermal detection of atomic hydrogen in high magnetic fields at low temperatures
Authors: Woollam John A.
Published: March 2003

An apparatus is described in which hydrogen atoms were trapped at temperatures down to 1.1 K in the 11 T field of a large volume superconducting magnet. A high sensitivity thermal detector was used to study trapping and recombination of atoms on the detector surface. The apparatus permits the application of extremely high steady state magnetic fields to study the potential effects of electron spin polarization on the stabilization of hydrogen atoms.
Laser beam alignment fixtures
Authors: Gamble W. L. , Halford C. E.
Published: March 2003

Simple alignment fixtures to aid in maintaining the alignment of laser beams are described. The fixtures consist of four thermocouples arranged in horizontal and vertical pairs and bonded to an aperture. An analysis is presented to show that more sensitivity is achieved by using a position fixture and an angle fixture with focusing at the angle fixture as opposed to simply passing the beam through two separated fixtures. A measurement of the angular sensitivity using a focused beam at the angle fixture indicates that angular changes on the order of 10 microradians can be detected.
In situ tensile fracture device for Auger electron spectroscopy
Authors: Kobayashi H. , Omata H.
Published: March 2003

A new tensile device that would permit the in situ fracture and Auger electron spectroscopy (AES) examination of samples under well-controlled, measurable test condition, was developed. Using this device, a sample can be fractured in ultrahigh vacuum AES chamber at a temperature between room and melting point temperature of the sample and at any cross-heat speed (that is, tensile speed) between 3 cm/min and 300 cm/min. A sample is resistance heated by passing a current and therefore, heating rate is changed at any rate. The maximum heating rate is about 1000°C/s. In this system, an air pressure piston as the tensile device, is used, and then the tensile speed is easy to control by changing the flow of oil from the air pressure piston to the air changer. And also the system is designed so that the mechanical shock is absorbed when a specimen is fractured. It is very easy how to set a sample in this fracture device and to fracture it. It is possible to set three samples at one time. We can apply this device to the study of many metal failures which are controlled by time and temperature dependent mechanisms, such as creep rupture, temper embrittlement, weldability, and hot workability. In this paper, the new fracture device and its application to nickel-base superalloy are described.
Simple laboratory computer interface system
Authors: Black Jerry G.
Published: March 2003

A highly versatile and cost effective general purpose laboratory interface system is described. Used with a mini or microcomputer, it accepts data and issues commands to many laboratory instruments having digital inputs and outputs. This system can be constructed by a novice in electronics at minimal expense. Details of the hardware construction and software device handling are given. Also described is an application of this system towards performing several common laboratory tasks: collecting both rapidly and slowly varying analog data, and simultaneously plotting the data. An implementation that is directly applicable to the LSI-11 minicomputer is described in detail.
Measurements of high surface velocities using K-band microwave interferometry
Authors: Maron Y. , Blaugrund A. E.
Published: March 2003

A new technique for a continuous monitoring of the displacement of a surface moving at velocities up to several millimeters per microsecond was developed. The method is based on microwave (24 GHz) interferometry. The technique enables precise measurements of the free surface velocity as well as covenient observation of small velocity step increases. The measured velocity is averaged over a surface area of the order of 10 cm2. Various effects which may influence the measurements are discussed. Preliminary measurements of free surface velocities of shocked metals are presented.
Ultraviolet fluorescence water vapor instrument for aircraft
Authors: Stone Edward J.
Published: March 2003

A water vapor sensor for stratospheric aircraft based on the principle of ultraviolet fluorescence has been built and flown successfully. The instrument exhibits high sensitivity, rapid response, and good resistance to contamination. It is available for use in NCAR-associated research.
Microprocessor-controlled time domain reflectometer for dynamic shock position measurements
Authors: Virchow C. F. , Conrad G. E. , Holt D. M. , Hodson E. K.
Published: March 2003

Time-domain reflectometry is used in a novel way to dynamically measure shock propagation in various media. The primary component in this measurement system is a digital time domain reflectometer, which uses local intelligence, a Motorola 6800 microprocessor, to make the unit adaptable and versatile. The recorder, its operating theory and its method of implementation are described and typical data are reviewed. Applications include nuclear explosion yield estimates, and explosive energy flow measurements.
Design and performance of a UHV fatigue drive
Authors: Swami T. K. G. , Chung Y. W.
Published: March 2003

A simple fatigue drive that permits fatiguing of specimens in the flexural mode at rates up to 30 Hz under ultrahigh vacuum conditions has been built and successfully tested in fatigue-enhanced photoemission studies.
High isolation duplexing switch for a pulsed NMR spectrometer
Authors: Britt Chester O. , Moore Tony C. , Wade Chas. G.
Published: March 2003

A duplexing switch for a pulsed NMR spectrometer is described which produces high isolation and low loss when used as the series switch.
Microcomputer controlled boxcar integrator with subnanosecond rise time
Authors: Taylor D. G. , Turley T. J. , Rodgers M. L. , Peterson Steven H. , Demas J. N.
Published: March 2003

A low-cost 8-bit microcomputer interfaced with a sampling oscilloscope yields a versatile <0.35 ns rise time digital boxcar integrator. Firmware provides signal averaging, oscilloscope display of one or two transients, baseline stripping and restoration, X−Y plotting, tape punching and listing of data, and BASIC language data reduction.
Stopped-flow apparatus for the study of fast reactions in solution under high pressure.
Authors: Heremans K. , Snauwaert J. , Rijkenberg J.
Published: March 2003

A stopped flow apparatus is described to study fast reactions in solution up to 1.2 kbar. The reaction course is followed optically. The apparatus is capable of measuring reactions with a half life of 20 ms.
Method for the measurement of temperature in shock compression of solids
Authors: Sugiura Hiroshi , Kondo Ken-ichi , Sawaoka Akira
Published: March 2003

A new optical measurement method for obtaining the temperature of solids during shock compression has been developed. Spectral measurements of thermal radiation produced during shock compression of fused silica have been made, and the shock temperature estimated from the spectrum. This method is less sensitive to variations in emissivity, and has an accuracy of about 3%.
Application of sintered diamond tipped ultra high pressure apparatus to cryogenic experiments
Authors: Bundy F. P. , Dunn K. J.
Published: March 2003

The sintered diamond tipped, opposed piston, ultra high pressure apparatus developed in this laboratory in 1975 has been adapted to cryogenic experimentation by replacing the steel binding rings with nonbrittle stainless steel ones, and by providing it with a special stainless steel, squirrel-cage type, clamp press capable of locking the apparatus at desired loadings and making it possible to insert the loaded assembly in a cryostat and be cooled to liquid helium temperatures. Experiments to pressures over 500 kbar and to temperatures down to 2.7 K have been carried out. The high pressure metallic forms of Te, Se, S, Si and I have been investigated, particularly in respect to superconduction phenomena.
System for combined SIMS-AES-XPS studies of solids
Authors: Frisch M. A. , Reuter W. , Wittmaack K.
Published: March 2003

We have have assembled a system for combined surface and thin film studies by SIMS, AES and XPS. The SIMS and AES investigations are performed in the same UHV chamber, while for XPS measurements the sample is transfered into the XPS system via an isolation valve. The SIMS-AES and XPS units can be operated independently, thus increasing the versatility of the entire instrumentation. The primary ion gun, used for sample erosion, supplies velocity-analyzed ions of either nonreactive or reactive gases at an acceleratiang potential of up to 15 kV. The ion source is differentially pumped. The base pressure in the target chamber after bakeout is in the mid 10−8 Pa. The unique feature of the primary ion column is a movable Einzel lens, which allows the width of the square shaped rastered area to be increased to about 5 mm at 12 keV. The large area scanning capability is required for XPS measurements. The SIMS instrumentation comprises a quadrupole mass spectrometer, a secondary ion energy filter and electronic gating in conjunction with rastering. By use of a capillary the sample can be exposed to a directed flow of oxygen gas (oxygen jet). AES studies are performed by use of a cylindrical mirror analyzer with a coaxial electron gun which is also employed for primary ion charge compensation in SIMS studies of insulators. Both the SIMS systems and the XPS unit can be operated under computer control. The performance characteristics of the complete SIMS-AES-XPS system are described in detail and are illustrated by several examples.
Compact coaxial diode electron beam system: Carbon cathodes and anode fabrication techniques
Authors: Eden J. G. , Epp D.
Published: March 2003

A coaxial electron beam generator has been developed which produces current densities of 1–3 A cm−2 at the anode foil, is compact (Marx ∼0.2 m3) and yet utilizes an anode of 50 cm length and 250 cm3 volume. Carbon cathodes (carbon fibers and graphite felt) tested on this system have been found to be superior to metal foil blades for current risetime and peak current. Techniques for readily fabricating cylindrical anodes of arbitrarily large volume and length are also described. The use of this system in exciting Ar/5% N2 gas mixtures has resulted in intense laser emission (Emax∼2 mJ) on the (0,3) transition of the N2 (C→B) band at 405.9 nm. Also, coaxial photolytic experiments involving XeF2 and a buffer gas have yielded strong XeF emission on the B→X (ultraviolet) and C→A (blue-green) bands.
Method for simultaneous measuring diffusion coefficients and refractive index dependence on concentration at different wavelengths
Authors: Karawacki Ernest
Published: March 2003

An experimental procedure is described making it possible to determine from one diffusion experiment both the diffusion coefficient D and the dependence of the refractive index on concentrations ∂μ/∂c for many wavelengths of light. The results from the measurements of D and ∂μ/∂c at 6 wavelengths (6328Å, 5145Å, 4965Å, 4880Å, 4765Å and 4579Å) for LiNO3, NaNO3, KNO3, RbNO3, and CsNO3 in water are presented.
Holographic methods for the fabrication of various types of mirrors
Authors: Rao S. Ananda , Pappu S. V.
Published: March 2003

A comprehensive set of new configurations for the holographic simulation of a wide variety of mirrors is described. These holographically simulated mirrors (HSMs) have been experimentally realized and their imaging performance has been studied.
New distillation apparatus
Authors: Lunelli Bruno
Published: March 2003

A novel design for a vaporizer which induces a vapor flow pattern producing a centrifugal field is described. This design completely avoids contamination of the vapor, and hence of the distillate, by splashes of liquid, which is a severe problem in small scale, reduced pressure distillations. Other factors which give distillates of superior purity are the separation of very fine liquid particles dispersed in the vapor, and the fact that no boiling chips or stream of gas are required. A vapor condenser which induces and exploits a centrifugal field and has several advantages over conventional models is also described.
Use of a sliding anvils apparatus for high temperature-high pressure studies
Authors: Epain R. , Bocquillon G. , Loriers-Susse C. , Loriers J.
Published: March 2003

We describe the pressure-temperature performances of a sliding anvils apparatus, the SAD 2, and present a refined calculation of its loading programs at normal and high temperature which takes account of the pressure gradient in the cell. We present typical cells and power-temperature curves determined by thermocouples at high pressure up to 100 kbar–1500 °C. The maximum volume of the sample for the above PT conditions is ∼60 mm3. The apparatus was tested as a tool for high temperature-high pressure synthese by synthetizing diamonds by the catalyst method.
Simple, inexpensive photodetector for subnanosecond sources
Authors: Harris J. M. , Barnes W. T. , Gustafson T. L. , Bushaw T. H. , Lytle F. E.
Published: March 2003

The design and construction of an extremely simple and inexpensive photodetector are described. Using a commercially available photodiode, the circuit is shown to be useful for observation of subnanosecond sources from the ultraviolet to beyond 1 μm.
Glass membrane manometer for high-temperature measurement
Authors: Numata Takashi , Nishimura Jiro
Published: March 2003

A glass membrane manometer usable up to 820 °C has been devised. It has an optically or nearly optically flat membrane which makes it possible to measure the pressure contactlessly. The sensitivity is 0.01 mm Hg when the thickness of the membrane is 0.12 mm and the diameter 22 mm.
Simple flying spot scanner for electron beam lithography on a scanning electron microscope without beam blanking capability
Authors: Grabbe P.
Published: March 2003

A novel low-cost flying spot scanner that allows a standard scanning electron microscope to be converted into an electron beam lithography system is described. Such a system is useful as a research tool for fabricating small arrays of submicron structures and devices.
Exponential decay and exponential recovery of modal gains in high count rate channel electron multipliers
Authors: Hahn S. F. , Burch J. L.
Published: March 2003

A series of data on high count rate channel electron multipliers revealed an initial drop and subsequent recovery of gains in exponential fashion. The FWHM of the pulse height distribution at the initial stage of testing can be used as a good criterion for the selection of operating bias voltage of the channel electron multiplier.
Procedure for loading diamond cells with high-pressure gas
Authors: Mills R. L. , Liebenberg D. H. , Bronson J. C. , Schmidt L. C.
Published: March 2003

We devised an apparatus and technique for loading diamond-anvil cells with gases at high pressure. Cells were filled quickly and conveniently at room temperature with helium and hydrogen isotopes to initial densities exceeding those of the normal liquids. We report preliminary values of 4He and D2 melting points based on the ruby pressure scale and compare them with extrapolations from our earlier melting curves measured to 20 kbar in a piston-cylinder device. Our filling procedure now makes it possible to use 4He as a pressure medium in diamond cells. The technique is also useful for loading cells with gaseous mixtures.
Thermal kinetics using a modified commercial stopped flow apparatus
Authors: Malyj M. , Smith P. D. , Balko B. , Berger R. L.
Published: March 2003

A commercially available optical and fluorescence stopped flow apparatus has been adapted for thermal detection methods. A minor modification was sufficient to permit the measurement of kinetics of chemical reactions with half lives in the range of 15 ms to several seconds. A detection sensitivity of 1 m °C was obtained.