bluuebunny/crossref_metadata_2025 huggingface dataset:
Submicron entrance windows for an ultrasoft x-ray camera
Authors: Huizenga H. , Bleeker J. A. M. , Diemer W. H. , Huben A. P
Published: March 2003

During the development of an imaging proportional counter suited for observing celestial objects in the XUV waveband (10–250 Å), we investigated the feasibility of producing a reliable plastic entrance window having a thickness ⩽ 0.3 μ and good uniformity over an area of several tens of square centimeters. After evaluating several candidate materials and production techniques, we selected film casting of pure Lexan as an appropriate technique for providing strong 65 mm diameter, 0.3-μ thick windows having low gas diffusion leakage (<3.10 −4 bar cm3/s cm2) and adequate opaqueness for short wavelength UV radiation. A prototype XUV camera equipped with such a window was used to make a picture of a multipinhole mask irradiated by the emission line spectrum of ionized He (243, 256, and 304 Å). This gave very satisfactory performance, as is shown at the end of this paper.
Instrument for combining reflection–absorption infrared spectroscopy with other surface-sensitive techniques
Authors: Campuzano Juan Carlos , Greenler Robert G.
Published: March 2003

An apparatus is described which allows the study of adsorption on single-crystal surfaces to be carried out by Reflection–Absorption Infrared Spectroscopy, Low Energy Electron Diffraction, Changes in Work Function, and Thermal Desorption Spectroscopy in situ. The apparatus also has facilities for sample cleaning by ion bombardment, sample characterization by Auger Electron Spectroscopy, and Secondary Ion Mass Spectroscopy. The infrared and work function measurements can be carried out with gas atmospheres anywhere in the range between UHV and atmospheric pressure. Infrared radiation in the range 4000–400 cm−1 can be used.
Cleaving machines for soft and hard crystals
Authors: Hallberg F. C. , Woodgate B. E. , Benedicto J. S. J.
Published: March 2003

In the past, soft crystals such as Rubidium Acid Phthalate (RAP), Potassium Acid Phthalate (KAP), and hard crystals such as Lithium Fluoride (LiF) have been cleaved by hand methods with varying degrees of success. The limited demand for thin crystals from 0.08 to 0.8 mm thick did not justify development of machines to perform the cleaving operation. However, the crystal requirements of a large-area spectrometer for x-ray astronomy1 and other specialized optics applications made necessary the development of two cleaving machines for soft and hard crystals, respectively.
Simple cryogenic temperature regulator: the Zener diode
Authors: Storey J. W. V.
Published: March 2003

This note describes a simple and effective method of stabilizing the temperature of a FET or other small device over the range 77°K to room temperature. By driving a Zener diode from a constant voltage source, a self-heating effect is produced which increases sharply when the temperature falls below a preset value.
Simple interface for a transient recorder
Authors: Hennau F. , Ceuterick F.
Published: March 2003

A simple interface for a transient recorder to a PDP-11 computer, running under RSX-11-M, is described. The data from the transient recorder are sent to the computer through an RS-232 terminal port, using terminal driver software support.
Fast digital data acquisition and on-line processing system for an HB5 scanning transmission electron microscope
Authors: Strahm M. , Butler J. H.
Published: March 2003

The Fast Digital Data Acquisition System (FDDAS) links a Vacuum Generator’s HB5 Scanning Transmission Electron Microscope and a PDP-11/34 minicomputer, to enable high-speed collection and storage of digitized images for analysis, processing, and display, either in real time (using hardware) or later (via software). The FDDAS hardware consists of a digital scan generator, a programmable quad scaler with quad discriminator, an on-line processor with digital gray level generator, an analog to digital converter, and a joystick. These devices are interconnected as addressable locations on the FDDAS bus line, the ’’System Bus,’’ on which they can act as data sources or sinks. The FDDAS also contains the circuitry for interfacing the system bus to the PDP-11 UNIBUS, allowing it to read or write image data into the computer at memory cycle speeds. The FDDAS software consists of data transfer, data reformatting, and test pattern generation modules which are linked in an overlay structure and designed to execute under Digital Equipment Corporation’s RT11 operating system.
Passively mode-locked Nd:glass laser oscillator optimized for TEM00 selectivity and long term stability and reliability
Authors: George S. M. , Harris C. B.
Published: March 2003

A passively mode-locked Nd:glass laser oscillator optimized for TEM00 selectivity and long term stability and reliability is presented. The important aspects of the optimized design are explained in detail. A detailed alignment procedure is also included. This laser oscillator is capable of producing TEM00, bandwidth-limited, ≃9 picosecond pulses for ⩾12 hours.
Adjustable long duration high-intensity point light source
Authors: Krehl P. , Hagelweide J. B.
Published: March 2003

A new long duration high-intensity point light source with adjustable light duration and a small light spot locally stable in time has been developed. The principle involved is a stationary high-temperature plasma flow inside a partly constrained capillary of a coaxial spark gap which is viewed end on through a terminating Plexiglas window. The point light spark gap is operated via a resistor by an artificial transmission line. Using two exchangeable inductance sets in the line, two ranges of photoduration 10–130 μs and 100–600 μs can be covered. For a light spot size of 1.5 mm diameter the corresponding peak light output amounts to 5×106 and 1.6×106 candelas, respectively. Within these ranges the duration is controlled by an ignitron crowbar to extinguish the plasma. The adjustable photoduration is very useful for the application of continuous writing rotating mirror cameras, thus preventing multiple exposures. The essentially uniform exposure within the visible spectral range makes the new light source suitable for color cinematography.
Simple single phase and homogeneous multiphase bidirectional flowmeter
Authors: Kendall E. J. M. , Smerek P. L.
Published: March 2003

The flowmeter described is based upon the bending of a slender spring steel beam in a fluid stream. The pressure exerted on the beam is determined by attaching strain gauges to the beam. The direction of flow can be determined by the sign of the bridge current when inbalance occurs, singe the gauges will change from the tension to the compression mode. The flowmeter may be used with corrosive and hot fluids since coated beams may be used, and for increased sensitivity silicon strain gauges with temperature compensation can be used, and the system may then be used for determining gas flow rates.
Application of a digital computer to data acquisition and shield temperature control of a high-temperature, adiabatic calorimeter
Authors: Cash W. M. , Stansbury E. E. , Moore C. F. , Brooks C. R.
Published: March 2003

The use of a digital computer, operating under real-time, time-sharing mode, for the operation of a high-temperature (300–1300 K), adiabatic calorimeter is described. The specimen temperature and power to the specimen heater are logged continuously, from which the heat capacity is calculated for specified temperature intervals (e.g., 20 K). The determinate error in the calculated heat capacity is about ±0.6%. The temperature control of the adiabatic shields is quite comparable with that obtained previously with analog controllers. The temperature difference between the specimen and a shield can be maintained to about ±0.1 K. The heat capacity of a pure titanium specimen has been measured from 320 to 1020 K using the computer and also using the analog control. No discernible difference in results can be seen. The heat capacity data scatter about ±1% from a smooth curve fitted through the 325 data points.
Electronic analogs of double-junction and single-junction SQUIDs
Authors: Henry Richard W. , Prober Daniel E.
Published: March 2003

We describe electronic analogs of a double-junction (dc) SQUID and a single-junction (rf) SQUID that are simple to construct and operate, and are considerably more flexible than those previously reported. The Josephson junction analog is based on the Resistively-Shunted Junction (RSJ) model, and uses a novel method based on a sample-and-hold circuit to generate the sin ϑ ’’supercurrent.’’ Examples are shown of the single-junction I–V characteristics, threshold curves of critical current vs applied flux and I–V curves for the double-junction SQUID analog, and rf SQUID characteristics as a function of applied flux and rf drive current. Other applications of the analogs, including the incorporation of a nonsinusoidal current-phase relation, are discussed.
Minicomputer-based test system for analyzing the electronic components of a large scale scientific research instrument
Authors: Pecina R. J. , Travis D. J. , Guercio J. S. , Hedtke P. A.
Published: March 2003

Large scale research experiments often require the use of highly specialized and sophisticated electronic equipment including computer-based data acquisition systems capable of gathering large amounts of data over very short time intervals. Equipment malfunctions can mean a loss of experimental data integrity and valuable research time. A diagnostic test system has been developed to monitor the electronic equipment of such an experiment, the Fast Neutron Hodoscope at the Transient Reactor Test Facility in Idaho. The system allows hodoscope electronics designers at Argonne National Laboratory in Illinois, and hodoscope maintenance engineers in Idaho, to observe simultaneously digital and analog signals from the hodoscope electronics while the hodoscope is in operation. The diagnostic test system can be controlled either locally by the engineers at the research site in Idaho or remotely by the designers in Illinois via a computer to computer telephone link between the two sites. As a result potential equipment problems as well as actual failures can often be pinpointed and corrected with minimal lost time and cost to the research program.
Microautomatic data acquisition system
Authors: Generosi R. , Selci S.
Published: March 2003

We have built a system for collecting, accumulating, and computing data from optical-type measurements, by coupling a commercial desk computer (TEXAS TI59 with PRINTER PC 100 C) to the experimental apparatus through a simple, but effective, interface. Our purpose is to use the full computing capability of a microcomputer such as TI59 on line with the experimental apparatus.
Density measurements from crossed beams at high extinction
Authors: Johnson J. A. , Ramaiah R. , Santiago J. P.
Published: March 2003

The formulation of the crossed beam correlation technique is generalized to include strongly absorbing media. The first measurements of point density fluctuations at contact surfaces have been obtained. The presence of turbulent bursts is confirmed and a characteristic spectral frequency of approximately 400 Hz is estimated.
Multiple crossing devices for laser-molecular beam spectroscopy
Authors: Gough T. E. , Gravel D. , Miller R. E.
Published: March 2003

The construction of a multipass device for laser-molecular beam spectroscopy is described. The device increases signal to noise ratios by a factor of 10 does not contribute to the width of the signal, and in addition provides an indication of the orthogonality of laser and molecular beams.
Mass spectrometric analyzer for individual aerosol particles
Authors: Allen Jonathan , Gould Robert K.
Published: March 2003

A new analytical instrument has been developed to give real-time chemical composition and size data on individual aerosol particles. It separates the particles from the entraining gases by means of aerodynamic nozzles and differential pumping, so that they enter the high vacuum region as a collimated beam. Each arriving particle is flash vaporized, the vapor ionized, and the ions analyzed by a quadrupole mass spectrometer. The instrument has been tested with several inorganic and organic aerosols and has yielded mass spectral peaks corresponding to a series of fragment ions. The more stable compounds yielded the parent ion as well. Particles 0.9 μm in diameter are readily detected with signal-to-noise ratios of 12:1 on the dominant peak. On this basis, the small-size sensitivity limit is well under 0.5 μm diameter and, with design improvements, can probably be extended to 0.1 μm or smaller.
Performance of the new high mass resolution time of flight atom probe
Authors: Nishikawa Osamu , Kurihara Kazuaki , Nachi Masahiro , Konishi Morikazu , Wada Minoru
Published: March 2003

Detectability and mass resolution of a newly built high mass resolution time-of-flight atom probe were examined. In order to maximize the detectability, the specimen tip apex, the probe hole, and the entering side of the energy-compensating deflector were aligned by a laser beam. Transmittance of ions through the deflector and mass resolution were optimized varying the combinations of deflector electrode voltages. The detectability, defined as the ratio of the number of all atoms in the area aimed by the probe hole to the number of field evaporated ions arriving at the detector, was found to be dependent on the crystallographic plane and its aimed area, possibly due to the rolling motion of the field evaporating atoms in a certain preferable direction. The observed detectability ranges from only 10% at the central area of the W (011) plane, which is dark in a multiatom-layer desorption image, to 91% at the (011) plane side of the W(114) plane, which is significantly higher than the maximum detectability limited by the effective area of a chevron detector, 55%. Thus, the overall detectability might be as high as 50% and the transmittance would be nearly 100%. The mass resolution Δm/m was 1/1100 at half peak height which was comparable to the theoretically expected mass resolution limited by the pulse width and the time resolution of the timer, 5 ns, and each of the detected W ions was clearly discriminated corresponding to each W isotope. The atom probe also successfully demonstrated its unique capability of the atomic layer-by-layer mass analysis providing the ultimately fine depth profile.
Fast electronics for time-of-flight measurements
Authors: Hudor A. M.
Published: March 2003

High speed circuitry for measurement of particle flight times over the range from 15 ns to <1 μs with event rates as high as 105 s−1 was developed for use in a time-of-flight field-ionization mass spectrometer for neutral particles. The circuits were designed for space flight applications and have low power consumption (∼2 W), low weight (<50 g), and small physical size (6×13 cm). The circuitry is easily interfaced with standard pulse height analysis equipment or a microprocessor.
Novel charged particle analyzer for momentum determination in the multichanneling mode: I. Design aspects and electron/ion optical properties
Authors: Engelhardt H. A. , Bäck W. , Menzel D. , Liebl H.
Published: March 2003

We present a novel electrostatic, energy-dispersive particle analyzer whose astigmatism can be used to measure the polar angle distribution of charged particles originating in a sample spot, in a multichanneling mode. The analyzer consists of a toroidal prism and a truncated conical lens, both coaxial on an axis through the particle source. The toroidal prism is used in an unusual way, in that the axial radius of the central equipotential surface varies from infinity to a certain minimal value for varying deflection angles in the prism. We develop design criteria for an analyzer using this principle, suitable for measurements on solid samples. The energy resolution of the analyzer lies between those of a 127 ° cylindrical and of a 180 ° spherical analyzer. Angular resolutions of <2.6 ° (FWHM) can be achieved.
Potentiometric nondestructive testing of surface-hardened materials
Authors: Omini M. , Iazzi F. , Rastaldo A. , Turco C.
Published: March 2003

A new nondestructive method for the determination of the depth of surface-hardened layers in steels is presented. It is based on the measurement of the electric potential difference between points on the surface of the sample, as induced by a dc current flowing through the sample itself. The resulting hardening depths are found to be in excellent agreement with those determined through destructive hardness tests on the sectioned samples.
Microprocessor-based multiscaler for angular correlation of annihilation radiation experiment
Authors: Dai C. C. , O’Yang J. Y. , Chuang S. Y. , Tseng P. K.
Published: March 2003

A microprocessor-based multiscaler system for angular correlation of annihilation radiation (ACAR) experiments is reported. This system is capable of registering three 64-channel multiscaling spectra simultaneously in order to satisfy special requirements of ACAR experiments. The system is low cost and simple and can be modified for other special applications by minor changes in the software in the microprocessor.
Integrator for measuring magnetic fields
Authors: Peshkin Michael A.
Published: March 2003

A voltage integrator designed for interface to a computer is described. It is used to integrate the EMF developed around a loop of wire when the magnetic field through the loop is changed. The integrator is inexpensive, stable, and provides field measurements accurate to 0.1%.
New ion implant technique for low-cost solar cell fabrication
Authors: Tokiguchi K. , Itoh H. , Sakudo N. , Koike H. , Kanomata I. , Tokuyama T.
Published: March 2003

A new implant technique, in which a single magnet carries out mass separation and ion beam scanning, is described. Dose uniformity and energy conversion efficiency of a solar cell fabricated using this technique are investigated.
Novel method of traversing a forward scatter laser-Doppler anemometer
Authors: Bertschy J. R. , Abernathy F. H.
Published: March 2003

An arrangement is described by which a laser-Doppler anemometer (LDA) can be used to measure velocity profiles quickly and inexpensively. Two mirrors are rotated simultaneously to achieve the traverse; all remaining equipment is held stationary. When the LDA and mirrors are properly arranged, the receiving optics remain focused on the scattering volume during a traverse.
Self-detecting microwave spectrometer based on the BARITT diode
Authors: Walsh W. M. , Rupp L. W.
Published: March 2003

An improved microwave oscillator using a commercial BARITT device as a self-detecting source of 12–14 GHz radiation is described. As an electron-spin-resonance spectrometer the sensitivity is on the order of ∼ 1.5×1012 standard spins. Operation is particularly easy since the BARITT readily self-rectifies at all oscillation levels.
Characteristics and performances of a streak camera operating in repetitive mode
Authors: Heisel F. , Miehe J. A. , Sipp B.
Published: March 2003

A picosecond streak camera that can be used in variable repetitive mode in conjunction with a mode-locked synchronously-pumped or a cavity-dumped dye laser has been developed, as well as an acquisition system which allows digitization and accumulation of the streak records. Time resolution better than 20 ps for the overall system has been obtained with a reproducibility in the time scale of the order of 2 ps.
Simple circuit for feedback stabilization of a single-mode optical fiber interferometer
Authors: Fritsch Klaus , Adamovsky Grigory
Published: March 2003

Single-mode optical fiber interferometers used with fiber hydrophones and other types of fiber sensors must be feedback stabilized to achieve maximum sensitivity and linearity in the presence of differential phase drift in their arms resulting from temperature fluctuations and other types of disturbances. A simple and effective electronic circuit for stabilizing such interferometers is described. The bandwidth of the feedback loop is 5 kHz, sufficiently wide to include information signals in addition to the drift correction signals. A high pass filter is used to remove the drift correction signals from the information signals.
Accurate method for locating fringes on an interferogram
Authors: McKeen W. J. , Tarasuk J. D.
Published: March 2003

This report describes a hard-wired circuit for measuring the fringe locations on an interferogram. An electronic device based on this method has been constructed and used. This device, which is simple to operate and construct, has an accuracy better than 0.01% for locating fringe positions.
Optimization of gasket thickness in a Bridgman anvil system
Authors: Bandyopadhyay A. K. , Chatterjee S. , Gopal E. S. R. , Subramanyam S. V.
Published: March 2003

The effect of gasket thickness on the pressure in the Bridgman anvil system has been studied experimentally. The existence of the optimum thickness from the experimental data has been interpreted in a theoretical model of stress distribution in an anvil system.
Novel charged particle analyzer for momentum determination in the multichanneling mode. II. Physical realization, performance tests, and sample spectra
Authors: Engelhardt H. A. , Zartner A. , Menzel D.
Published: March 2003

Following a design described in a preceding paper, an energy dispersive analyzer system has been constructed for the simultaneous determination of polar angle (ϑ) distributions of charged particles originating on a solid surface in the range 0 °⩽ϑ⩽90 °. The analyzer is a toroidal prism used in an unusual geometry, followed by a truncated cone lens. The starting polar angle is preserved in the spectrometer and translated into the arrival position on a position sensitive detector based on the charge division method. The dependence on azimuthal emission angles (φ) is obtained by recording energy and polar angle dependent spectra after mechanical variation of the azimuth. Total N(E, φ, ϑ) spectra are accumulated with a minicomputer, using a multichannel analyzer as buffer; the point-by-point subtraction of two spectra, e.g., to extract the spectral changes brought about by adsorption on a surface, is possible. Test procedures to check the performance (preservation of angles; energy and angular resolution; invariance of transmission with angle) are described. The analyzer can be used for electron (LEED, AES, UPS, ELS, INS, etc.) and ion (ISS, ESD) spectroscopies of clean surfaces and adsorption layers; sample spectra for LEED, AES, UPS, and ISS are shown.
Effect of ion current in the collisionless theory of floating ac probe measurements
Authors: Mosburg Earl R.
Published: March 2003

Previous treatment of the theory of floating ac probes has considered only the electron current voltage dependence. In this paper the effect of including the voltage dependence of the ion current is examined, and equations are derived which allow the use of the calculations by Laframboise of the ion current to cylindrical probes having arbitrary ratios of probe diameter to Debye length. The error in electron temperature measurements introduced by neglecting the ion current variation, and the range of usefulness of the technique, is discussed. For example, in the normally expected range of floating potential, a measurement of the electron temperature could be in error by as much as ∼13% if the voltage dependence of ion current is ignored.
Fast opening toroidal gas valve
Authors: Myers B. R. , Levine M. A. , Shaw R. S.
Published: March 2003

A pulsed toroidal gas valve is described. The valve, which has a 10-cm aperture through the center, is designed to be used in toroidal plasma experiments where current-carrying conductors must pass through the axis of symmetry. The valve uses a coil and magnetic flux concentrator to displace an aluminum diaphragm by magnetic forces. Upon energizing the coil, the diaphragm opens in a few tens of microseconds and releases the gas (hydrogen) contained in a toroidal plenum. The resulting gas distribution outside the valve contains up to 1019H2 molecules and has a high degree of toroidal symmetry.
Picosecond framing technique using a conventional streak camera
Authors: Niu H. , Chao T. , Sibbett W.
Published: March 2003

A picosecond digitally-restored image-dissected framing method involving a conventional streak camera and new computer software is described. The preliminary result gave 5 frames with an exposure time of 13 ps and spatial resolutions of 2 1p/mm on the screen and 6 1p/mm on the photocathode. A framing speed of 7.7×1010 frames/s for frame sizes of 15×15 mm has been demonstrated.
Phase-sensitive 3.39 μm Doppler interferometer
Authors: Gokay M. Cem , Fusek Richard L.
Published: March 2003

The phase-sensitive 3.39 μm Doppler interferometer is designed to make relative optical phase measurements by permitting measurements of optical phase independent of the source amplitude fluctuations. This interferometer utilizes a Doppler shifting technique to produce relative optical path length information from the optical component under test. This information is in the form of phase differences between two audio frequencies. These phase differences are sensed and displayed by a high-resolution zero crossing electronic phase meter. The phase angle displayed is directly correlated with the optical phase difference between the sample and the reference beam. Normal laboratory environment accuracy of the instrument is λ/16 at 3.39 μm.
Constant pressure viscometer to measure viscoelectric effect based on a drop counter
Authors: Mechetti H. , Zakowicz E. , Ronchietto V. , Bustos V.
Published: March 2003

We describe a viscometer based on the fact that a succession of drops created at constant pressure and temperature exhibit equal weights. This viscometer was used to detect small flow changes due to the presence of an electric field applied transversally to the liquid flow.
Simple profile monitor for low intensity, low-duty cycle pulse ion beams
Authors: Iida Toshiyuki , Maekawa Yoshimi , Taniguchi Ryohich , Byakuno Masami , Sumita Kenji
Published: March 2003

A simple beam profile monitor useful for rapid optimization of low intensity, low duty cycle pulse ion beams is described. It is based on a fixed multiwire beam detector.
m-spectrum analyzer on Alcator-C
Authors: Granetz R. S.
Published: March 2003

An experiment currently being developed on the Alcator-C magnetic fusion device uses a set of poloidal B-field pick-up coils and unique analyzing circuits to continuously yield the amplitudes, frequencies, and rotational directions of the m = 1,2,3,4, and 5 resistive MHD tearing modes. The experiment is being used to study the growth and coupling of tearing modes of different helicities due to density, temperature, and current profiles.
New sensitive marginal oscillator
Authors: Rahf L.
Published: March 2003

A new type of a sensitive marginal oscillator has been developed for the determination of high magnetic inductions by means of nuclear magnetic resonance. Obtaining a high sensitivity with this measuring principle demands a soft behavior of the oscillator which is a particular feature of the circuit presented. It is shown that this behavior is due to the fact that a very weak positive feedback is established by the inner capacitances of the single field effect transistor used in the circuit. Optimal values for the operation parameters are calculated.
Microwave Hall measurements in the intermediate conductivity regime using a bimodal cavity
Authors: Ong N. P. , Bauhofer Wolfgang , Wei Ce-jun
Published: March 2003

We study the Hall signal which arises from the resistive unbalance of a bimodal microwave cavity when a sample sits in a magnetic field. When the sample conductivity exceeds a certain value determined by its depolarization factor, screening currents are dominant and the simple expressions used by earlier investigators are no longer valid. We suggest new equations using the samples’ depolarization factors which are analogous to the quasistatic approximation for cavity perturbation techniques. Experimental tests of these equations are carried out with six n-type Si samples with resistivities varying from 300 to 0.1 Ωcm. A systematic variation of the measured Hall mobility with resistivity is found in agreement with published dc values. However, our values are consistently 40% higher. The change in sign of the Hall signal when the samples screening currents dominate the induced currents is experimentally confirmed. We also discuss two major defects which prevent ideal balancing of the cavity and suggest corrective measures.
Determination of time constants of cold wires
Authors: Antonia R. A. , Browne L. W. B. , Chambers A. J.
Published: March 2003

The time constant of a fine cold wire used as a resistance thermometer can be obtained by a technique which is based on ideas developed for the pulsed-wire technique for velocity measurement in highly turbulent flows and in regions of flow reversal. The cold wire is placed downstream of, and at right angles to, a wire of larger diameter which is pulsed with a short duration voltage pulse. The response of the cold wire to the change in the temperature of the flow is used to determine the time constant of the wire, once the pulsed wire time constant is known. Frequency responses based on measured time constants for cold wires of 2.5, 1.3, and 0.63 μm diameters are presented as a function of flow velocity.
Pulse-echo ultrasonic interferometer for the automatic measurements of velocity and attenuation changes
Authors: Gorodetsky G. , Lachterman I.
Published: March 2003

An automatic pulse-echo ultrasonic interferometer for continuous measurements of sound velocity changes is described. Velocity resolution of about 1 ppm was obtained for a single transit echo. It is an improvement over results obtained by a previous unautomated version of the pulse-echo interferometer. A simultaneous detection of the amplitude of the measured echo is also possible in this system. Measurements of velocity and attenuation shifts of a surface acoustic wave propagating on an ST-cut quartz, while being copper deposited, are given.
New instrument for rapid measurement of changes in ultrasonic velocity
Authors: Taki S. , Furuta Y. , Takemura T.
Published: March 2003

A new instrument for rapid measurement of changes in ultrasonic velocity in a material has been developed. The changes in velocity are recorded automatically with the time difference between reflection and transmission waves. The minimum recording interval is 1 ms. The relative accuracy is from 10−3 to 10−4 for the velocity change in a sample length of about 6 mm. Two applications are reported.
Apparatus for thermopower measurements of organic conductors under pressure
Authors: Chaikin P. M. , Weyl C. , Malfait G. , Jérome D.
Published: March 2003

We describe the design and operation of a simple apparatus for the measurement of the thermoelectric power under pressure. Its performance has been optimized especially for low thermal conductivity solids such as organic quasi-one-dimensional conductors, and it may be used with a pressure medium that is in either the solid or liquid state. These materials have an absolute thermopower of the order of magnitude of ten μV K−1 at ambient temperature. The uncertainty of the apparatus is about 5% and its sensitivity considerably better. Measurements have been made from 300 to 2 K and 0 to 25 Kbar.
Direct coupling of a dense (supercritical) gas chromatograph to a mass spectrometer using a supersonic molecular beam interface
Authors: Randall L. G. , Wahrhaftig A. L.
Published: March 2003

A detecting mass spectrometer has been successfully coupled to a dense gas (supercritical fluid) chromatograph to produce an instrument (DGC/MS) that may be an alternative to high performance liquid chromatograph/mass spectrometer instruments (HPLC/MS) and gas chromatograph/mass spectrometer instruments (GC/MS) for analysis of involatile and/or thermally labile compounds. The mobile phase in DGC is a gas held at temperatures above the critical temperature and at pressures sufficient to obtain nearly liquid-like densities. DGC combines advantages of GC and HPLC: rapid separations, moderate operating temperatures, and analysis of involatile compounds. An advantage unique to DGC is the solvent power dependence upon pressure. While several groups have studied DGC, its development has been limited by the lack of a sensitive and selective detector. Hence, work has been directed towards the design and construction of a DGC/MS resulting in a trial instrument capable of chromatographic pressures of at least 300 atm and temperatures from 10° to 60°C. The DGC/MS coupling has been accomplished by the use of a supersonic molecular beam interface. This application of molecular beam formation appears to be unique in its requirements of a large pressure ratio (∼108), low flow rates, and low final pressures. The authors outline characteristics of supersonic jets and molecular beams pertinent to the design of such an instrument. The interface which uses pumping speeds of 2400 and 1200 l/s in the beam forming chambers is described in detail, while the other components—the detecting mass spectrometer, the dense gas supply, and the DGC—are briefly described. Preliminary work with this instrument has established the feasibility of DGC/MS as an analytical technique and further development is recommended.
Measurement of small charge transfer optical absorption bands by modulation spectroscopy
Authors: Potasek M. J. , Beeson K. W.
Published: March 2003

An optical modulation apparatus is described for the measurements of very weak (ε<1 M−1 cm−1) charge transfer optical absorption bands between electron donor–acceptor complexes. Such small bands, which are of interest in understanding the mechanism of electron transfer in physical, chemical, and biological systems, are undetectable by more traditional methods of optical spectroscopy due to their small size and their superposition on much larger background sample absorptions. An additional feature of the method is that the kinetics of the electron returning to its equilibrium state following photo-induced charge transfer can be measured.
Photoacoustic cell for reflection and transition measurements
Authors: Cahen David
Published: March 2003

A photoacoustic cell is described in which the sample can constitute one of the cell walls. The cell, which can be used alone or in a combined unit with a reference cell, allows nondestructive investigation of a variety of samples either in a normal reflection mode (pressure wave generated at illuminated surface) or in a thermal or elastic transmission mode (pressure wave generated at opposite surface). Simultaneous sample illumination from both sides is possible, too. The cell sensitivity, as measured for an electrically-generated thermal wave, is about 10−2 V/W at 34 Hz. Use of the cell is illustrated by the dependence of the photoacoustic signal, generated by transmitted thermal and/or elastic waves, on the thickness of copper plates, and by the photoacoustic spectrum resulting from illumination through Begonia leaves.
New type of rapid scanning circular dichroism spectropolarimeter using an acoustic optical filter
Authors: Hatano M. , Nozawa T. , Murakami T. , Yamamoto T. , Shigehisa M. , Kimura S. , Takakuwa T. , Sakayanagi N. , Yano T. , Watanabe A.
Published: March 2003

A new circular dichroism (CD) and magnetic circular dichroism (MCD) system with narrow bandwidth and high scanning rate has been developed. The versatility of the system for the measurements of transient changes in CD and MCD has been also described. This new CD and MCD system is composed of an acoustic optical (AO) filter of TeO2 as a monochromator, a stress modulator, and a photomultiplier together with their operating devices and a computer system. The linearly polarized light from the AO filter is modulated to left- and right-circularly polarized light by a stress modulator operated at 50 kHz. The absorbance difference of the left- and right-circularly polarized light is detected by a photomultiplier, after passing through the sample. The whole optical system and detector system are matched in time by the same computer system. A rapid scanning was performed successfully at the rate of 50 nm range/10 ms, with better spectral resolution and higher signal-to-noise ratio than other commercially available CD spectropolarimeters. Finally, we showed several applications of the new CD and MCD system for the observations of CD and MCD spectral changes in biological molecules.
Electron intensity measurement in a scanning diffraction camera
Authors: Solliard C.
Published: March 2003

We describe a system which compensates for variations of electron-diffracted intensities during a measurement; these variations are due to a spatial variation of the quantity of diffracting matter, including sample and supporting grid. This system has been used in a study of polycrystalline samples deposited on amorphous carbon films supported on electron microscope grids. In this case the intensity variations correspond to the grid transparency modulation when the beam is scanned across the sample.
Application of the Texas quartz spiral gauge to the measurement of interaction second virial coefficients
Authors: Bell T. N. , Dunlop P. J.
Published: March 2003

A procedure is described which enables a Texas Instruments quartz spiral gauge to be calibrated sufficiently accurately so that excess virial coefficients can be measured with an accuracy of approximately ±0.3 cm3⋅ mol−1. The gauge and a Loschmidt cell have been used to measure BE values for the system He–N2, which agree well with the data reported in the literature.
New type electron monochromator
Authors: Calicchio M. , Grisenti R. , Zecca A.
Published: March 2003

A simple low-energy electron monochromator is described. The monochromating action takes advantage of the observation that the radius of the exit pupil at the diode stage is a function of the emission energy of the electron from the cathode. Energy dispersion was achieved by means of an electrostatic electron lens system and the analysis by means of a circular aperture. A prototype version was built and tested. This produced a 120-MeV FWHM beam with 10−7A at 5-eV energy. The same monochromator produced a 60-MeV beam with 10−10A by changing the voltage so as to introduce chromatic abberation.
Powerful timing generator using mono-chip timers: An application to pulsed nuclear magnetic resonance
Authors: Saint-Jalmes Hervé , Barjhoux Yves
Published: March 2003

We present a 10 line–7 MHz timing generator built on a single board around two LSI timer chips interfaced to a 16-bit microcomputer. Once programmed from the host computer, this device is able to generate elaborate logic sequences on its 10 output lines without further interventions from the CPU. Powerful architecture introduces new possibilities over conventional memory-based timing simulators and word generators. Loop control on a given sequence of events, loop nesting, and various logic combinations can easily be implemented through a software interface, using a symbolic command language. Typical applications of such a device range from development, emulation, and test of integrated circuits, circuit boards, and communication systems to pulse-controlled instrumentation (radar, ultrasonic systems). A particular application to a pulsed Nuclear Magnetic Resonance (NMR) spectrometer is presented, along with customization of the device for generating four-channel radio-frequency pulses and the necessary sequence for subsequent data acquisition.
Laboratory EXAFS spectrometer for catalyst studies
Authors: Khalid S. , Emrich R. , Dujari R. , Shultz J. , Katzer J. R.
Published: March 2003

A laboratory x-ray absorption spectrometer is described which allows very high quality x-ray absorption edge and extended x-ray absorption fine structure (EXAFS) data to be obtained. The spectrometer utilizes a channel-cut crystal configuration monochromator for absorption edge studies and a fully focusing Johansson cut bent crystal monchromator operated on the Rowland circle for high flux, high resolution EXAFS studies. X-ray generation is by a rotating anode generator. Photon fluxes are about 104 higher than for a sealed-tube flat-crystal spectrometer; it is shown that data of quality comparable to that obtained from a synchrotron source (SSRL) can be obtained in comparable time.
Simple burner for laser probing of flames
Authors: Beyer Richard A. , DeWilde Mark A.
Published: March 2003

A research burner for the study of combustion of premixed gases is described. Advantages include access to preheat and primary reaction zones of flames for laser probing, very low heat loss to the burner, and ease of construction. Measurements made with two flame systems to demonstrate performance are reported.
Simple reusable hermetically-sealed spectrophotometer cuvette for turbidity studies near binary liquid critical points
Authors: Eden Don
Published: March 2003

Simple cells were designed for measuring the turbidity of binary liquids near their critical point. The cells were constructed by fusing a general purpose, high-vacuum, high-pressure, Teflon and glass stopcock to a commercial cuvette. No sample contamination, as indicated by a shift in critical temperature, has been observed in a sample immersed in a water bath for six months.
Digital image processing for speckle flow velocimetry
Authors: Meynart Roland
Published: March 2003

A new method is presented for the analysis, by digital acquisition and processing, of speckle fringes in fluid mechanics.
Cold trapping efficiencies for collection of tritiated water entrained in a gaseous stream
Authors: Phillips J. E. , Easterly C. E.
Published: March 2003

Detection of small quantities of tritium frequently entails bubbling a tritium vapor containing gas stream through a liquid. When very small concentrations of tritium are present, the lower limit of detection may be reduced by dilution in the liquid. Collection by means of liquid nitrogen cold trapping can lower the detection limit. By observing certain precautions, this method can provide quite reproducible results at high efficiencies.
Field emission thermal desorption spectroscopy
Authors: Derochette J. M.
Published: March 2003

Thermal desorption spectra from single crystal planes of a field emitter are obtained with the technique described. The specimen temperature is varied linearly and the field emission current from the face of interest is recorded vs temperature. Heating current and temperature measurements are transmitted to and from the tip using digital techniques via fiberoptic links to assure the high isolation necessary. A microcomputer is used to control the entire system, produce the linear temperature sweep, and acquire and treat the data. The desorption of hydrogen from the (111) plane of field-evaporated tungsten is presented as a test of the technique; a comparison between our spectra and the data reported in the literature shows a good correlation between the field emission and the classical thermal desorption spectroscopy. A good facet selectivity is obtained as proved by a result concerning H2 on W (210).
Calorimeter for the direct measurement of enthalpy of vaporization at high pressure and high temperature
Authors: Parisod Ch. J. , Plattner E.
Published: March 2003

An isothermal calorimeter for measuring enthalpy of vaporization at elevated temperature and pressure is described. Through the use of a low inertia PID regulated internal heater and three PI regulated external heaters, isothermal conditions (±0.12 °C) were achieved during measurements. The calorimeter was tested by measuring the enthalpy of vaporization of pure water at 300°, 320°, 340°, and 360 °C and was found to produce data with good reproducibility (±2%). The agreement with published values is good (<1%). The calorimeter was designed for the study of salt solutions, and some experimental values of the molar enthalpy of vaporization of the system NaCl–H2O at 300° and 340 °C are given.
Expendable bathythermographs as temperature microstructure profilers
Authors: Lange R. E. , Johnson B. P.
Published: March 2003

A data-acquisition bridge circuit, and an analytical processing technique are described for rapid, high-spatial resolution sampling of temperature fine structures using commercially available expendable bathythermographs. The construction of the bridge circuit appears to be unique, designed to eliminate common sources of electrical noise. An error budget analysis of noise sources is performed, and field data are presented. It is shown that thermal fine structure can be resolved to five microdegrees over 10-cm vertical length scales without appreciable spectral attenuation of the temperature signal. An attempt is made to determine a spectral correction scheme to extend this resolution to finer scales, and an example is compared to expected oceanic signals in regions of relatively small thermal activity.
Fast deformation velocity measurement using laser Doppler velocity interferometer
Authors: Kim Jai Ki , Lee Sang Soo
Published: March 2003

A mild steel projectile (65.6 g) with an elevated impact area (1.0 cm in diameter) is driven to 25.6 m/s by shock wave toward the fixed target plate with thickness 0.5–0.8 cm and the bulging deformation at the polished free surface is measured by using a laser Doppler velocity interferometer. Initially thick target (1.2–2.4 cm) is used for the determination of the velocity of the elastic wave in the solid. In the thinner targets, the free surface gets bulging plastic deformation. Its maximum bulging velocity, which is thickness dependent, is determined for the thickness 0.5–0.8 cm. It is found the maximum bulging velocity decreases approximately inversely with respect to the thickness of the target. The time-dependent and target thickness behaviors of bulging plastic deformation of the mild steel target are obtained for the constant impact velocity, and they are discussed on the basis of data obtained by using the laser Doppler velocity interferometer.
Grating diffraction instrument for measuring ultrasonic phase velocity in liquids
Authors: Papadakis Emmanuel P. , Meeker Thrygve R.
Published: March 2003

An instrument is described for the measurement of ultrasonic phase velocity in liquids. The principle of measurement is grating diffraction which diverts an incoming ultrasonic wave generated by a transmitting transducer and aims it at a receiving transducer. The relationship between the phase velocity, the input and output angles from the grating, and the periodicity of the grating serves to define the frequency of the wave which will reach the receiver and be detected. Transmitter, beam, and receiver are many wavelengths across. The output beam is detected in the direction normal to the planes of the grating and the receiver. To study phase velocity vs frequency, several gratings of different periodicity are used. Several pairs of ultrasonic transducers may be needed depending on the frequencies of interest and the bandwidth of the transducers. Theory, instrument construction, system operation, and experimental results are presented.
Use of zinc iodide solutions in flow research
Authors: Hendriks F. , Aviram A.
Published: March 2003

The advantages of using transparent flow boundaries and liquids with matched index of refraction are demonstrated for internal flow research, when the internal boundaries of the flow are of complicated shape. In particular, a new technique involving aqueous solutions of zinc iodide is described, as applied to the study of secondary flows in aerodynamic devices used in ink jet printing. Zinc iodide solutions offer large freedom in the choice of index of refraction, without being excessively viscous. When used in conjunction with transparent conducting electrodes, the solutions afford internal electrochromic flow visualization as well. The electrochromic property is demonstrated for the case of classical circular Couette flow. In contrast with many other candidate liquids, zinc iodide solutions are safe and compatible with transparent plastics. These properties extend the scope of optical flow diagnostics, such as laser Doppler velocimetry.