bluuebunny/crossref_metadata_2025 huggingface dataset:
Simplified diamagnetic techniques for a field-reversed theta-pinch plasma
Authors: Tuszewski M. , Armstrong W. T.
Published: March 2003

Diamagnetic measurements of a field-reversed theta-pinch plasma are performed with a simplified diagnostic consisting of either a single-flux loop and several magnetic probes or magnetic probes only. Numerical and experimental evidence of the validity of these techniques is presented.
Characteristics of the neutral beam injectors for the Tandem Mirror Experiment Upgrade
Authors: Orzechowski T. J. , Carter M. R. , Munger R. H.
Published: March 2003

Neutral beams are used to fuel and heat the Tandem Mirror Experiment Upgrade (TMX–U) at LLNL. We have studied these beams spectroscopically to determine their species mix (H, H2, H+3) and impurity content (H2O). From the shapes of the spectral lines, we measured the divergences of the various components and compared them with the numerically determined divergence. By measuring the area under the various Doppler-shifted lines, we determined the species mix and found that the atomic species fraction is lower than expected (30% to 45% rather than 60%). Although there is good agreement between the measured and calculated divergence for the atomic component of the beam, the molecular components have larger divergences, part of which can be accounted for by the dissociation of the molecules.
Interactive system for scanning tracks in nuclear research emulsions
Authors: Gold Raymond , Roberts James H. , Preston Christopher C. , Ruddy Frank H. , Cooper Craig S. , Hendricks Carol A. , Johnson Dan T. , McNeece James P. , Main Gerald W. , Michaels Thomas E. , Spence Nehemiah E. , Svoboda Harry J. , Vargo George F.
Published: March 2003

A computer-based interactive system has been developed and successfully used for scanning proton-recoil tracks in nuclear research emulsions. To our knowledge, this system is the first truly interactive system developed and used for emulsion scanning. Interfaces have been developed between the three fundamental interacting entities, namely man, microscope, and computer. Computer codes can be developed for different applications, thereby providing wide flexibility and versatility. Use of this system for neutron metrology is described. Differential neutron spectrometry as well as integral neutron dosimetry have been carried out in both 4π and unidirectional neutron fields. Results are presented which quantify the accuracy attained with this system for each of these different neutron measurement emulsion techniques. This system provides a substantial advance in the state-of-the-art of emulsion scanning in terms of both accuracy and cost effectiveness. The ability to store, in computer memory, all relevant emulsion and track parameters enables off-line data analyses which were heretofore not practical. The uncertainty in track length measurements with this system is approximately 0.52μ (1σ). While emulsion scanning rates vary for the different modes of system operation, scanning rates of 30 to 40 tracks/h have been typically obtained.
Instrumentation and procedures for real time measurements of proton motive force, membrane potential, ΔpH, proton extrusion, and oxygen uptake in respiring cells and vesicles
Authors: Hendler Richard W. , Setty Oruganti H. , Shrager Richard I. , Songco David C. , Friauf Walter S.
Published: March 2003

The construction and use of two polyvinyl chloride, solid-state membrane ion-selective electrodes, one selective to tetraphenylphosphonium (TPP+) [to measure membrane potential (ΔΨ)] and the other selective to salicylate ion [to measure the pH gradient (ΔpH)], are described. A reaction vessel is fitted with these two electrodes plus a pH and an oxygen electrode. The signals from all four electrodes pass through an electronic interface to a microcomputer which filters out noise, corrects for relaxation time delay of electrodes as needed, converts the raw readings to real time kinetic values for rate of oxygen uptake, rate of proton extrusion, ratio of protons extruded per atom of oxygen consumed, membrane potential, the pH gradient across the membrane and the proton motive force. These values are continuously updated every 90 ms and passed to a multipen recorder for observation.
Differential sound velocity apparatus for the investigation of protein solutions
Authors: Gavish B. , Gratton E. , Hardy C. J. , St. Denis A.
Published: March 2003

A differential method for the measurement of sound velocity in solutions is described. The instrument uses two identical acoustic resonators and a newly developed electronic measuring system. The sound velocity is determined with a relative accuracy of ≊3×10−6 over the entire frequency range 0.5–10 MHz. The instrument has been used to determine the compressibility of protein solutions and to study their velocity dispersion.
Conversion of the energy of intense relativistic electron beams into high-power electrical pulses
Authors: Friedman M. , Serlin V.
Published: March 2003

Converting the energy of intense relativistic electron beams (IREB’S) into electrical energy can: (1) Enhance the efficiency of many electron devices, such as free electron lasers and microwave generators, and (2) generate trains of high-frequency high-power electrical pulses. An investigation of a converter was performed and efficiency of up to ∼60% was achieved. The converter was used with either a single pulse of IREB of ∼100 ns duration or with a modulated IREB at 280 MHz. An output electrical power of≳109 W was obtained.
Study of afterpulse effects in photomultipliers
Authors: Torre S. , Antonioli T. , Benetti P.
Published: March 2003

Ionic afterpulses in photomultipliers have been studied. Besides the afterpulse abundance, the experimental times of flight for several ions have been determined and compared with theoretical calculations. Furthermore, a method to evaluate the single-electron response from afterpulse pulse-height analysis has been derived.
Personal computer as an inexpensive lock-in analyzer operating at very low frequencies
Authors: Berger J. , Tannhauser D. S.
Published: March 2003

We describe inexpensive equipment and present a simple basic program which permits one to utilize a personal computer as a lock-in analyzer for frequencies below ∼0.1 Hz.
Precise regulator for low air pressures
Authors: Jacobs Henry R.
Published: March 2003

For the range of air pressure between 1 and 50 cm (water), a simple pressure regulator can be assembled from parts available in most laboratories. It performs very well.
Simple technique for preparing brittle materials for transmission electron microscopy
Authors: Davis B. I. , Clarke D. R.
Published: March 2003

A simple mechanical device is described for grinding a controlled concavity in thin, disk-shaped samples of brittle materials prior to ion beam thinning. Use of the device reduces the time required in ion beam thinning a sample to electron beam transparency.
Circuit for time-resolved photon counting
Authors: Kyle Thomas G. , Clements William E.
Published: March 2003

A circuit providing 64 channels of photon counting with time resolutions as small as 50 ns is presented. The circuit requires the photon flux to be sparse enough to neglect multiple photons arriving during a single time-resolution interval.
Method of making small-diameter tubing from porous film
Authors: Peterson John I. , Sullivan James V.
Published: March 2003

A method is described for preparing membrane or porous film in tubing form from sheet material by a heat sealing technique. This should be generally useful with a variety of materials which are not available in tubing form. Tubing sizes both smaller and larger than 1-mm diameter, of indefinite length, can be easily formed.
New version of toroidal SQUID sensor
Authors: Zarembiński Stefan , Kachniarz Jakub
Published: March 2003

A report is given on the design and fabrication of a mechanically stable and thermal shock resistant SQUID sensor. The sensor is vacuum sealed while the access to the adjustment of its point contact is left open.
Temperature-compensating pulsed reference light source using a LED
Authors: Yamashita Mikio , Takeuchi Satoshi
Published: March 2003

A pulsed light source using a green LED for use as a reference element in gain stabilization of scintillation detectors is described. The temperature effects are compensated for by a thermistor incorporated in the dc circuit of the current source. The light output has proved stable to ∼0.1% in the laboratory environments where the changes in temperature are within ±5°C or so.
Laboratory x-ray spectrometer for EXAFS and XANES measurements
Authors: Williams Arthur
Published: March 2003

An in-lab x-ray spectrometer is described which is capable of rapid acquisition of x-ray absorption fine structure data for either extended x-ray absorption fine structure measurements (EXAFS), or x-ray absorption near edge structure studies (XANES). Intensities in excess of 107 photons/s in an ∼10 eV bandpass near 9 keV have been obtained using only a conventional sealed, fixed anode x-ray tube operating at 1.5 kW. The spectrometer utilizes a focusing Johansson cut and bent single crystal as the monochromator and scans continuously from 8≲2θ≲160 degrees with only a single stepping motor driven movement. For 3d metal absorption edges, resolutions of ∼10eV are obtained in first order with a Ge(111) crystal and ∼1 eV in third order allowing in-lab acquisition of both EXAFS and XANES data of synchrotron-like quality.
Evaluation of a virtual phase charged-coupled device as an imaging x-ray spectrometer
Authors: Stern Robert A. , Liewer Kurt , Janesick James R.
Published: March 2003

The x-ray response of an 800×800 Texas Instruments virtual phase charge-coupled device (CCD) has been measured in the range 1–8 keV. In the single-photon counting mode, we find excellent energy resolution (∼250 eV FWHM) for single-pixel Fe55 x-ray events at a spatial resolution of 15 μm. The detector quantum efficiency for all events is 65% at 2.3 keV (S K line) and ∼34% at 5.9 keV (Mn K line from Fe55). The CCD response is linear in energy to a few percent over the 1–8 keV energy range. These results demonstrate that virtual phase CCDs are superior imaging x-ray spectrometers with applications for x-ray astronomy and laboratory plasma research.
Centro-symmetric technique for measuring shear modulus, viscosity, and surface tension of spread monolayers
Authors: Abraham B. M. , Miyano K. , Xu S. Q. , Ketterson J. B.
Published: March 2003

We have constructed an apparatus which enables one to measure, simultaneously, the shear modulus, the viscosity, and the surface pressure of a monomolecular film on water under a hydrostatic compression. It is particularly suitable for measurements of the static shear modulus of insoluble monolayers. A capillary wave generator/detector system was also incorporated to determine the surface pressure. The trough is a Teflon cup 12.7 cm (5.4 in.) in inner diameter with sloping interior sides. As the cup is raised, while maintaining the water elevation fixed, the film is uniformly compressed. A rotor suspended at the center from a fine torsion fiber is used to measure the mechanical properties (surface viscosity and/or surface shear modulus). To measure the quasistatic shear properties, the cup is rotated through a small angle and the residual deflection of the rotor determined. Dynamic shear response is probed by studying transient torsional oscillations following a sudden angular displacement of the torsion fiber. There are no barrier seals and circular symmetry is maintained at all times. The apparatus has a resolution of 5×10−4 surface poise of shear viscosity and 1×10−4 dyn/cm of static shear modulus.
Extensometer extender for conversion of room-temperature extensometers for high-temperature applications
Authors: Quesnel D. J. , Tsou J. C.
Published: March 2003

An extensometer extender has been constructed which allows the use of room-temperature extensometry for measurement of axial strain at high temperatures. The device can accept most commercial extensometers, is inexpensive to build, and easy to use. No modification of extensometer electronics are required. This paper describes the design requirements for high-temperature extensometry and shows how the present design meets these criteria. Drawings and rationale for construction are given so that the device may be easily modified for specific applications. Use of the device for strain controlled low-cycle fatigue of soft specimens at elevated temperatures demonstrates the success of this design.
Direct memory access (DMA) computer interface for an optical multichannel analyzer
Authors: Heider S. M.
Published: March 2003

A computer interface for a PARC model 1205A Optical Multichannel Analyzer (OMA) is described. This interface uses the output from the OMA’s internal analog-to-digital converter rather than the usual parallel I/O facility. The ADC output is transmitted from the OMA to the computer over a single 75-Ω coax cable. Since the data obtained from each OMA scan may be stored in the computer memory, extremely versatile processing algorithms may be used, and normal OMA operation is not affected. The software used is also described.
Compact repetitively pulsed excimer laser
Authors: Cohn D. B. , Conley E. E.
Published: March 2003

An excimer laser is described with a gain volume of 20 cm3 and capable of repetition rates on the order of 10 Hz using a simple pulse-charge circuit and gas flow loop. With gas mixtures typical of the XeCl species, maximum single-pulse output energies of 15 mJ are obtained at charge voltages of 30 kV and run times are on the order of hours for a single gas fill.
Production of positron emitting isotopes using a collective accelerator
Authors: Destler W. W.
Published: March 2003

Experimental studies of the production of C11, N13, O15, and F18 by collectively accelerated deuterons impinging on solid targets are presented.
Extended capabilities of a vibrating-reed internal friction apparatus
Authors: Berry B. S. , Pritchet W. C.
Published: March 2003

Two developments are described in a vibrating-reed technique used for internal friction studies of foils and thin films. One is an activation procedure that enables measurements to be made on the blank reeds of fused silica used as substrates for thin films. This procedure is also relevant to the study of insulating films. The other development is an ability to make measurements on electrically conducting samples in both torsional and flexural vibration.
Superconducting magnet image effects observed with a vibrating sample magnetometer
Authors: Zieba A. , Foner S.
Published: March 2003

The distortion of the sample flux by a superconducting material produces a change of magnetometer output known as an image effect. Image effects for three Nb–Ti magnets were examined using a small current-carrying coil as a source of a field-independent and adjustable, controlled moment of a vibrating sample magnetometer. This allowed determination of the initial image effect (in zero field) and the field-dependent image effect from zero to maximum magnetic field. The initial image effect (not detected by conventional calibration) can be large, and the field-dependent part was 0.25–0.35 of initial image effect. The variation of the field-dependent image effect on field sweep rate and magnet temperature, and the change of the spatial distribution of the detection coil sensitivity were also observed. The image effect is independent of sample moment and decreases rapidly with decreasing detection coil radius. The method of images was employed to calculate the image effect for perfect shielding as the function of detection coil dimensions relative to the magnet bore. For a small superconducting volume fraction λ, the initial image effect for multifilamentary wire magnets is smaller than calculated by an approximate factor λ/(1−λ) in agreement with observations for the three Nb–Ti magnets. Some influences of the multifilamentary structure of the superconducting wire on the image effect are discussed.
Sensing characteristics and crystalline structure of InSb films for magnetic sensors
Authors: Ohshita Masahide , Isai Masaaki , Tanaka Ikuo
Published: March 2003

InSb evaporated films for magnetic sensors are prepared by controlling the evaporation rate and the substrate temperature gradient in order to obtain elements of high sensitivity. There are In needles in the films which are precipitated parallel to one another during the evaporation process. The In needles have diameters of 0.5∼2 μm and lengths of 50∼200 μm. The films have thicknesses of 1.0∼3.5 μm. The results of the sensing characteristics and crystalline structure of InSb films are presented. The latter was analyzed by an electron microscope. A magnetoresistance value (ΔR/R0) of 1400% is obtained at a length-to-width ratio (l/W) of 0.1 and an applied magnetic flux density (B) of 1 Wb/m2 (=T), at room temperature.
Maximizing the quantum efficiency of microchannel plate detectors: The collection of photoelectrons from the interchannel web using an electric field
Authors: Taylor Richard Cordia , Hettrick Michael C. , Malina Roger F.
Published: March 2003

We report dependence of the extreme ultraviolet quantum efficiency (QE) of a microchannel plate (MCP) detector upon the electric field strength above its input face. Using an uncoated plate, we measured increases up to 80% as the field was raised from 0 V/μ to between 0.01 and 0.1 V/μ. Further increases in electric field resulted in a monotonic decrease in QE. Detector spatial resolution was found to degrade for these small field values but could be recovered, while maintaining most of the QE increase, by operating with fields in excess of 0.3 V/μ. Other detector parameters such as modal gain and output charge pulse-height distribution were not significantly affected by the applied electric field. We explain the QE and resolution variations in terms of photoelectrons ejected from the interchannel web and subsequently returned to the input face of the MCP by the applied electric field. We present a model and a computer simulation which quantitatively reproduce our experimental results. Applying our model to MCPs coated with photocathode materials, we conclude that the maximum QE is obtained by optimizing the combined contributions from the web area and open area of the MCP, rather than by maximizing the open area alone. In this case, most of the QE can arise from the interchannel web rather than from the directly illuminated channels.
Mass resolving charge-exchange system on the poloidal divertor experiment
Authors: Davis S. L. , Mueller D. , Keane C. J.
Published: March 2003

The charge-exchange system used on the Poloidal Divertor Experiment is comprised of four, ten-channel, mass-resolved, charge-exchange analyzers. Each analyzer is constructed with parallel electric and magnetic fields and is calibrated over an energy range of 0.5–40 keV. The mass rejection between hydrogen and deuterium has been measured as better than 1000 to 1. For Ohmic heated discharges the system can provide single shot radial ion temperature profiles (four point) with 1-ms time resolution. For neutral beam heated discharges, complete radial and temporal profiles can be obtained in two to four shots. The system is also equipped with a vertically aimed diagnostic neutral beam to allow local ion-energy distribution measurements. This report describes the analyzer system and its calibration, and presents results from Ohmic and neutral beam heated discharges.
Microcomputer-based image analysis system for quantitative area measurements
Authors: McCracken M. S. , Severance W. F.
Published: March 2003

A microcomputer-based video analyzer system has been developed to obtain area information from a variety of different sample types. Most programs are written in basic to analyze optical information with a conventional video camera and frame grabber. Intensity information from the image is used to automatically obtain area information, rather than the operator-directed approach used in many digitizing systems. Real-time operator modifications of the digitized image are possible, as well as image storage and retrieval and graphic display of the results.
Dynamic measurement of work function with the field emission microscope
Authors: Derochette J. M.
Published: March 2003

A technique to measure the work function of surfaces covered with adsorbate, during a linear temperature sweep of the emitter using the field emission probe hole microscope is described. A microcomputer records the field emission current values for each applied voltage and calculates the work function and the preexponential factor in real time with the Fowler Nordheim equation. The process is repeated for each temperature value of the desorption spectrum. The technique has been used to study the desorption of hydrogen from tungsten (111).
Simple reverse bending machine for low cycle fatigue at elevated temperatures
Authors: Yavari Parviz , Langdon Terence G.
Published: March 2003

A simple reverse bending machine is described for tests in low cycle fatigue at elevated temperatures. The machine is easy to construct, simple to operate, and it is especially useful for detailed metallographic investigations in low cycle fatigue. The machine has been used for strain amplitudes up to ±0.5% and frequencies of the order of 10−3–10−1 Hz. Some typical experimental results are described for high-purity aluminum tested in air at 300 °C.
New method of determining the onset of ring cracking
Authors: Grzybowski T. A. , Ruoff A. L.
Published: March 2003

When a spherical indentor is pressed with sufficient force against a flat piece of brittle material, fracture results. A new technique has been developed for the detection of the onset of these circumferential ring cracks in electrically insulating material. In this technique, thin metal films were deposited on both the insulating indentor (diamond) and the insulating brittle flat. A step in the monitored electrical contact resistance between the indentor and flat metal films versus the applied force curve signified the initiation of a ring crack. Tests performed on polished glass slides using diamond indentors demonstrated that the technique is both sensitive and reproducible. The onset of crack formation observed by optical means was observed to occur at the same time as the step in the contact resistance when both experiments were carried out simultaneously.
Fast optical position-sensitive detector for McPherson ESCA-36
Authors: Bertrand P. A. , Kalinowski W. J. , Tribble L. E. , Tolentino L. U.
Published: March 2003

An optical position-sensitive detection system was added to a McPherson ESCA-36 x-ray photoelectron spectrometer. The system contains a multichannel electron multiplier and vidicon TV camera and operates 250 times faster than the original single-channel electron multiplier.
Intense source of spin-polarized electrons using laser-induced optical pumping
Authors: Gray L. G. , Giberson K. W. , Cheng Chu , Keiffer R. S. , Dunning F. B. , Walters G. K.
Published: March 2003

A source of spin-polarized electrons based on a laser-pumped flowing helium afterglow is described. He(23S) atoms contained in the afterglow are optically pumped using circularly polarized 1.08-μm (23S→23P) radiation provided by a NaF (F2+)* color-center laser. Spin angular momentum conservation in subsequent chemi-ionization reactions with CO2 produces polarized electrons that are extracted from the afterglow. At low currents, ≲1 μA, polarizations of ∼70%–80% are achieved. At higher currents the polarization decreases, falling to ∼40% at 50 μA. The spin polarization can be simply reversed (P→−P) and the source is suitable for use in the majority of low-energy spin-dependent scattering experiments proposed to date.
Versatile curved crystal spectrometer for laboratory extended x-ray absorption fine structure measurements
Authors: Thulke W. , Haensel R. , Rabe P.
Published: March 2003

A laboratory spectrometer for x-ray absorption measurements is described which is adaptable to changing experimental requirements. The spectrometer is designed for the use of different types of curved crystals within large ranges of radii of curvature and of Bragg angles. Utilizing a 12-kVA rotating anode x-ray generator, Johansson-type monochromator crystals, and a helium-flow flexible beam line, photon fluxes between 105 and 107 photon/s are achieved in the photon energy range between 5 and 20 keV, where the energy resolution varies between 2 and 10 eV.
Microprocessor-controlled photon-counting spectrofluorometer
Authors: Gratton Enrico , Limkeman Mark
Published: March 2003

The construction details and performance characteristics for a fluorescence spectrophotometer are described. The system utilizes proton counting for signal detection and an Apple II microcomputer for data acquisition and analysis. Data-acquisition techniques are given along with typical excitation, emission, and polarization spectra. Particular reference is made to application of the instrument to fluorescence studies of protein/polymer films.
Dielectrophoretic manipulator
Authors: Batchelder J. S.
Published: March 2003

We report the development of a new technique manipulating the position of electrically neutral material using electronic signals. Dielectrophoresis, or the translational motion of neutral matter caused by polarization effects in nonuniform electric fields, is used in a geometry analogous to that of a charge-coupled device. Water droplets and steel ball bearings are stepped between a series of electrodes at velocities on the order of 1 cm/s. We find that the average velocity is roughly proportional to the drive voltage divided by the droplet or bearing radius. A variety of applications are discussed.
Single frequency scanning laser as a plasma diagnostic
Authors: Hill David N. , Fornaca Steven , Wickham Michael G.
Published: March 2003

In this paper we report the development of the single frequency dye laser as a plasma diagnostic for measuring ion velocity distributions with a resolution limited only by the natural linewidth of the laser excited resonance transition. For the 6S1/2–6P1/2 transition in Ba+ this corresponds to a velocity uncertainty of 103 cm/s. Velocity selection is performed by the laser as it scans the Doppler broadened plasma absorption line, in contrast with the usual method of scanning an emission line with a high-resolution spectrometer. Both sensitivity and resolution are improved by 2 orders of magnitude, allowing nonperturbing measurements to be made at densities below 107 cm−3. In addition to a description of the technique, sample measurements of time-resolved wave induced modifications of ion velocity distributions are shown.
Effect of outgassing on the performance of a TE CO2 laser sealed in an acrylic chamber
Authors: Biswas D. J. , Nath A. K. , Chatterjee U. K.
Published: March 2003

Outgassing of contamination in large quantity was observed in a helical TE CO2 laser housed in an acrylic (Perspex) chamber. This considerably reduced the sealed operational life of the device. In a helium-free mixture the laser energy initially improved and then reduced with time, while in the mixtures with helium it reduced monotonically. Water vapor seemed to be the main constituent in the contamination. By circulating the contaminated gas through a trap at dry-ice temperature, the water vapor was condensed, enhancing the sealed-off life of the device.
Measuring low coercive force using a vibrating sample magnetometer
Authors: Pesch Joseph A.
Published: March 2003

The coercive force Hc of commercially pure iron and an 80% NiFe alloy were measured on toroid samples using a hysteresigraph and on nontoroid samples of the same materials using a vibrating sample magnetometer. Within experimental error, the results were equal for each case. Values of Hc appeared to be insensitive to specimen shape. It appears that the demagnetizing field, which for nontoroid specimens affects the gross shape of the hysteresis loop, can be ignored in the region of low-field measurements for these materials.
Automatic echo selection logic for ultrasonic attenuation measurement system
Authors: Pathak L. , Murali N. , Rani S. Usha
Published: March 2003

A simple low-cost circuit for automatic selection of two successive echoes during measurement of ultrasonic attenuation is described. When ultrasonic attenuation is measured as a function of a varying parameter like temperature, the transit time through the sample also changes, resulting in the shift of echo positions. This calls for manual adjustment of sample pulses used for sample and hold circuits. The present logic eliminates the need for manual adjustment. Details of the logic circuitry along with salient features of peak detectors and sample-and-hold circuits used are described. The results of performance tests are presented.
Multispectral radiometer to measure crop canopy characteristics
Authors: Brach E. J. , Poirier P. , Desjardins R. L. , Lord D.
Published: March 2003

A spectroradiometer has been designed for the study of crop reflectance characteristics in the spectral range of 400–1000 nm. Since the instrument records the ratio of incoming to reflected radiation the values obtained are independent of variations in solar elevation, and azimuth angle and atmospheric conditions. A filter wheel with four interchangeable interference filters is used for wavelength selection. The spectroradiometer traverses above a crop canopy on a movable track. This makes it possible to compare measurements from various locations several times in an hour, and to study more than one canopy a day. This instrument provides agronomists with data to estimate crop canopy characteristics such as leaf area index (LAI) rapidly and nondestructively. It also measures the variability of canopy reflectance introduced by temporal and spatial factors.
Self-compensating optical frequency conversion
Authors: Weisman R. Bruce
Published: March 2003

A novel optical configuration is described for use with angle-tuned nonlinear frequency conversion crystals. By double passing the beams through the crystal, the new method suppresses wavelength-dependent beam displacements more thoroughly and conveniently than previous approaches. This configuration is useful in automatic phase-matching systems and experiments requiring overlapped beams.
Expendable bubble tiltmeter for geophysical monitoring
Authors: Westphal J. A. , Carr M. A. , Miller W. F. , Dzurisin Daniel
Published: March 2003

An unusually rugged highly sensitive and inexpensive bubble tiltmeter has been designed, tested, and built in quantity. These tiltmeters are presently used on two volcanoes and an Alaskan glacier, where they continuously monitor surface tilts of geological interest. This paper discusses the mechanical, thermal, and electric details of the meter, and illustrates its performance characteristics in both large (>10−4 radian) and small (<10−6 radian) tilt environments. The meter’s ultimate sensitivity is better than 2×10−8 radians rms for short periods (hours), and its useful dynamic range is greater than 104. Included is a short description of field use of the instrument for volcano monitoring.
Intracavity dye-laser photothermal deflection spectroscopy
Authors: Reddy K. V.
Published: March 2003

An intracavity, cw, dye-laser photothermal deflection (PTD) technique has been developed for gas-phase vibrational overtone spectroscopy. This new technique has a similar S/N ratio and significantly lower window noise than the intracavity photoacoustic technique under identical conditions.
Isotopic analysis of nanomole gas samples by means of dynamic flow mass spectrometry
Authors: Halas S. , Krouse H. R.
Published: March 2003

The sample size for conventional double collector isotope mass spectrometry has been reduced more than three orders of magnitude by using a ‘‘pushing’’ gas for precise stabilization of sample pressure. The sample is stored in a long microcontainer (50 cm, 0.5 mm i.d.) to moderate the effect of diffusive mixing of sample with the pushing gas. If the analysis is sufficiently rapid (e.g., a run of 1 min for the unknown sample between two runs on the standard), then almost total sample consumption is possible. This method retains the high precision and simplicity of dynamic flow, yet possesses the high sensitivity of static mass spectrometry.
Measurement system for temporal response of atomic and molecular systems using the correlation method with pseudorandomly modulated laser light
Authors: Baba Hiroshi , Sakurai Katsumi , Shimizu Fujio
Published: March 2003

A system to measure the temporal behavior of atomic or molecular fluorescence, which is disturbed by large noise background, has been developed. This system uses the pseudorandom modulation technique of length up to 1023, temporal resolution of approximately 83 ns, and a photon counting capacity of 107 counts/s. Data processing by a minicomputer and a hardware demodulation circuit enable quick analysis of a large volume of data. The signal-to-noise ratio of this measurement system is discussed with some experimental comparisons. The system is tested in the decay time measurement of I2 fluorescence.
Chart for estimation of conduction heat leak from specimens used in the measurements of properties by the transient calorimetric technique
Authors: Hsieh C. K. , Yang S. L.
Published: March 2003

In measuring thermophysical properties using the transient calorimetric method, conduction heat leak from test specimens can be a source of error if not properly accounted for. An analysis method is presented in this paper for determining the magnitude of this leak. The analysis consists of deriving the temperature profiles in the specimen support. These temperatures are then used to determine the heat leak using two different approaches. In the first approach, the heat penetration depth in the support is derived and used to obtain an added thermal capacitance to the specimen. In the second approach, the heat leak was considered to reduce the net heat input. Both small and large heat-leak cases were analyzed, with the latter estimated by means of two recurrence relations. A chart was also developed for a rapid estimation of this leak. In the absence of a reliable experiment to measure the heat leak, this paper provides a viable alternative for accurate leak determination.
Simplified vibrating-reed technique for the measurement of the temperature dependence of Young’s modulus of small samples
Authors: Aiello W. A. , Wolfe C. R. , Little W. A.
Published: March 2003

A simplified vibrating-reed technique for the measurement of the temperature dependence of Young’s modulus of small thin samples is described. The vibration of the reed is detected optically rather than with a capacitively coupled electrode as has been used by previous investigators. The optical coupling greatly simplifies the sample stage and electronic circuitry. It is made possible by the use of a microminiature Joule–Thomson-effect refrigerator which mounts directly onto the X–Y stage of a metallurgical microscope. Because of the refrigerator’s small size and lack of mechanical vibrations, the high-quality room temperature optics of the microscope can be used to detect the small amplitude vibration of the reed over a wide temperature range. We observe the Curie and Neel points of the magnetic phase transitions of terbium at Tc =221 K and TN =233 K, respectively. In addition, we measure Young’s modulus at 280 K to be 5.90×1011 dyn/cm2.
Airflow resistivity instrument for i
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i
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u measurement on the earth’s ground surface
Authors: Zuckerwar Allan J.
Published: March 2003

An airflow resistivity instrument features a novel specimen holder, especially designed for in situ measurement on the earth’s ground surface. This capability eliminates the disadvantages of prior intrusive instruments, which necessitate the removal of a test specimen from the ground. A prototype instrument can measure airflow resistivities in the range 10–5000 cgs rayl/cm, at specimen depths up to 15.24 cm (6 in.), and at differential pressures up to 2490.8 dyn/cm2 (1 in. H2O) across the specimen. Because of the close relationship between flow resistivity and acoustic impedance, this instrument should prove useful in acoustical studies of the earth’s ground surface. Results of airflow resistivity measurements on an uncultivated grass field for varying values of moisture content are presented.
Temperature-controlled microscope with millidegree stability
Authors: Yokoyama Hiroshi , Kobayashi Shunsuke , Kamei Hirotake
Published: March 2003

We constructed a simple polarizing microscope in which the sample temperature can be controlled with an accuracy of 10−3 °C from room temperature to about 60 °C. The temperature stability at a sample was directly assessed using the temperature-dependent birefringence of a liquid-crystal sample.
Observations on the stability of thermistors
Authors: Edwards T. J.
Published: March 2003

This paper investigates the long-term stability of three different types of thermistor with room-temperature resistances ranging from 80 to 150 kΩ. Precision measurements of thermistor resistance and temperature were made in a thermal environment controlled to ±3 μK. Measurements took place in between periods of limited thermal cycling and also during 100 days at constant temperature. Mechanical shock and strain appear to be the cause of the high drift rates observed in some thermistors; the majority of the thermistors were, however, very stable, with drift rates around 0.1 mK per 100 days and were unaffected by thermal cycling. Such low drift rates indicate that certain thermistors could be used as convenient temperature transfer standards with a reproducibility in the submillikelvin range.
Sonar location system for freely floating buoys
Authors: Bird I. G.
Published: March 2003

A rf interrogated sonar location system for freely floating buoys is described. The location of an array of up to three buoys may be determined on an almost continuous basis within a radius of 500 m from a shipboard monitoring station. Location accuracy of typically ±0.5 m at 200-m range, low cost, and ease of operation are the major features of the system.
Substrate heater and biasing electrode assembly for rf sputtering unit
Authors: Stone C. A. , Roz̆aj-Brvar A. , Davis R. F.
Published: March 2003

Heating and biasing of a thin film during deposition is frequently desirable to improve the structural quality of the film and to remove entrapped gases and loosely bound species on the surface. A large-diameter electrode assembly which allows both operations to occur simultaneously with a resulting variation in film thickness across a 2.54-cm wafer of ≤0.1 μm is described.
Voltage dependence of the d31 tensor element in Pb(Ti, Zr)O3
Authors: Tratt D. M.
Published: March 2003

Quasistatic measurements of the d31 piezoelectric strain coefficient are presented for PZT-5H material. Bulk data analysis techniques have been applied to assess the voltage-dependent contribution to the induced strain.
Simple mechanism for i
n s
i
t
u adjustment of gratings in UHV monochromators
Authors: van Bers W. A. M. , Franken A. J. J. , Larsen P. K.
Published: March 2003

A mechanism is described for adjustment under ultrahigh vacuum of the optical alignment of gratings in a vertically dispersing grazing incidence monochromator. The mechanism is based on two pairs of broad leaf springs and it allows rotation of the grating, of up to one degree, around two mutually perpendicular axes with respect to the photon energy scan axis. Measurements for a grazing incidence monochromator show that to achieve optimum resolution the adjustment of the grating should be better than 0.1°.
Dielectric permittivity measurements in the ultralow frequency region
Authors: Takeishi S. , Nozaki R. , Yagihara S. , Mashimo S.
Published: March 2003

A new dc transient method is described for fast measurements of dielectric permittivity in the μHz frequency region. A square-wave voltage pulse is applied to the dielectric instead of the usual step voltage pulse. The whole transient current is measured two times faster than in the conventional method using the step voltage.
Pulse transformer drive circuit for a molecular-beam source
Authors: Rorden Robert J. , Lubman David M.
Published: March 2003

We introduce the use of a pulse transformer as an improvement in the drive circuit of the ‘‘hairpin looppop’’sign for a pulsed molecular-beam source. The virtue of this device is that it can produce the high currents necessary to drive the hairpin at low voltage. In addition, it minimizes the I2R power loss of former designs while allowing for proper impedance matching of the leads to the power supply, thus lowering the voltage requirements necessary to drive the circuit.
Variable-temperature glass syringe
Authors: Larsen Steven A. , Scaife Charles W. J.
Published: March 2003

Methods are described for insulating and thermostating a glass syringe that can be manipulated by hand to transfer liquids over a temperature range from −100 to +80 °C. This syringe has been used to transfer liquid sulfur dioxide solutions at low temperatures and molten salts above room temperature.
10-Hz coherent anti-Stokes Raman spectroscopy apparatus for turbulent combustion studies
Authors: Goss L. P. , Trump D. D. , MacDonald B. G. , Switzer G. L.
Published: March 2003

A 10-Hz coherent anti-Stokes Raman spectroscopy (CARS) instrument capable of simultaneous thermometry and N2-concentration measurements in a turbulent flame has been designed and constructed and is described in detail. The instrument employs the doubled output of a pulsed Nd:YAG laser for pumping a broadband dye laser and also for the CARS pump beam. The broadband dye laser is used to excite, during a single pulse, the entire Q Branch of N2, the CARS signal of which is recorded by a multichannel analyzer. Special problems which were encounted with the multichannel analyzer include signal retention and limited dynamic range. The former was greatly reduced by employing cleansing scans between laser firings, and the latter was circumvented by employing a multiple beamsplitter arrangement in which the CARS signal was divided into four separate intensity regions, each of which covered a specific temperature range. The 10-Hz operation of the instrument required the use of a mass storage device such as an 800-bits-per-inch tape. CARS data recorded and digitized by the multichannel analyzer were transferred via machine-coded instructions to a minicomputer for storage on tape. Analysis of the CARS data consisted of a nonlinear least-squares fit of the CARS bandshape for thermometry and integration of the CARS signal for N2 concentrations. CARS measurements in a near-stoichiometric premixed propane flame and a turbulent diffusion flame are reported. Results of calibration measurements indicate that uncertainties of 4% in temperature and 6% in concentration are obtainable with this instrument.
UHV-compatible reaction cell for combined high- and low-pressure studies of surface reactions
Authors: Keck K.-E. , Kasemo B. , Höglund A.
Published: March 2003

The construction and performance of a combined reaction cell and sample exchange lock for studies of surface reactions at pressures up to a few atmospheres is described. In combination with a specially designed sample holder this construction allows simple and rapid transfer of the sample betwen the ultrahigh vacuum system and the reaction cell. The reaction cell is a self-contained unit that can be mounted on, e.g., a 2 3/4 -in. Con-Flat flange (or any other vacuum port with an I.D.≥38 mm). The sample holder can be mounted on any commerical sample manipulator. In both the high- and low-pressure positions the sample can be heated and cooled. Results are presented for the times involved in moving the sample from high- to low-pressure environments, pump-out times, etc. The use of this equipment in studies of the catalytic activity of Pt for the H2 oxidation is briefly described.
Polarization-independent beam splitter
Authors: Bergmann Ernest E.
Published: March 2003

We report a new type of beam splitter capable of producing a division of light in a polarization-independent manner. Most off-axis beam splitters have a pronounced polarization dependence. An experimental device with a splitting ratio of about 7 dB varied less than ±0.1 dB as a function of incident linear polarization. The device is fabricated from a thin plate of suitably oriented, uncoated, crystalline quartz.
Operation of a cw CO2 laser without a ballast resistance
Authors: Bhadani P. K. , Biswas D. J. , Nundy U. , Kukreja L. M. , Chatterjee U. K.
Published: March 2003

A cw CO2 laser has been successfully operated without using any ballast resistance. For stabilizing the discharge, the principle of a constant-current source employing the ac resonance technique is used. The stability of the laser output power has been very good and its fluctuation has been reduced to a value as low as 1% using only passive components.
Compact dye laser cell for high repetition rate operation
Authors: Krasiński J. , Radzewicz Cz. , Kowalczyk P.
Published: March 2003

A new dye laser cell for operation with pulsed pumping lasers is described. It can work up to 400 pps with a volume of dye solution as small as 2 cm3.
Modulation scheme for electron–electron double resonance spectroscopy
Authors: Mehlkopf A. F. , Kuiper F. G. , Smidt J. , Tiggelman T. A.
Published: March 2003

A modulation scheme for electron–electron double resonance (ELDOR) spectrometers is presented. With this scheme an optimum stabilization signal for locking the pump microwave generator to the pumped electron paramagnetic resonance (EPR) line is generated. A separate pump power level and a separate magnetic field modulation amplitude are used for the purpose of locking. In general, such a modulation scheme introduces false ELDOR lines. These false lines disturb the real ELDOR signals, or introduce an ELDOR signal in the absence of any communication between the observed EPR line and the pumped EPR line. With the described modulation scheme the frequencies of the false ELDOR signals are limited to even multiples of the frequency of the wanted ELDOR signals. This makes a suppression of the false ELDOR lines easy.
Analog/digital inelastic electron tunneling spectrometer
Authors: Ratinen H.
Published: March 2003

An analog electron tunneling spectrometer, based on a second harmonic detection technique, was digitalized with the aid of a small microcomputer. The method and the apparatus as well as some results obtained have been described in this report.
Use of a distributed processing data-acquisition system to control an acoustic spectrometer
Authors: Pickens Keith S. , Rzchowski Mark S. , Bolef D. I.
Published: March 2003

A powerful data-acquisition and processing system, which retains the low per-station cost of a microcomputer-based system while providing the resources for easy data reduction, is presented. The system uses microcomputer-based real-time data-collection stations and a larger central computer for data-reduction tasks. An application to the control of a continuous-wave ultrasonic spectrometer is shown. In particular, the precision measurement of acoustic velocity as a function of temperature is presented for single-crystal vanadium with a low concentration of interstitial hydrogen.
Resonant transformer command charging system for high repetition rate rare-gas halide lasers
Authors: Matera Manlio , Buffa Roberto , Conforti Giuliano , Fini Lorenzo , Salimbeni Renzo
Published: March 2003

A resonant transformer pulse generator for the pumping of high repetition rate rare-gas halide discharge lasers is described. Since with this design a low-voltage dc power supply is needed, command charging can easily be achieved by using a thyristor as the switching element. The pulse generator has been tested driving a thyratron-switched laser operating up to 100 pps free running and up to 200 pps in the burst mode.