bluuebunny/crossref_metadata_2025 huggingface dataset:
Compact externally heated discharge tube for metal vapor lasers
Authors: Singh B. , Bhadani P. K. , Mittal J. K. , Bhatnagar R.
Published: March 2003

A compact externally heated discharge tube of 25-mm internal diameter is described. The oven made of alumina tube, tungsten heater, and graphite felt insulation, takes about 45 min at 1.5-kW heater input power to reach temperatures in excess of 1500 °C. Its use with a copper vapor laser is demonstrated. The laser gives output power of 500 mW at 500-Hz repetition rate.
Some high-pressure x-ray diffraction studies using beryllium gasketing on a diffractometer with rotating anode x-ray source
Authors: Vohra Y. K. , Vijayakumar V. , Godwal B. K. , Sikka S. K. , Chidambaram R.
Published: March 2003

The beryllium gasketing technique is employed in a high-pressure (0–10 GPa) x-ray powder diffractometer using a NaI(T1) scintillation detector in conjunction with a high-brilliance rotating anode x-ray source. The beryllium gasket permits the use of a liquid pressure transmitting medium in the sample chamber giving rise to hydrostatic pressure conditions. This metal gasket also allows the use of softer Cu Kα radiation because of less absorption, thereby ensuring high resolution. The Be gasket is calibrated using sodium chloride and the equation of state (EOS) of strontium metal is measured up to 6 GPa using Cu Kα radiation in both the low-pressure (fcc) and high-pressure (bcc) phases. However, for high-Z samples like rare earths, Mo Kα radiation is employed to minimize absorption in the sample material. The high-pressure valence transition and the EOS of the rare earth alloy Ce0.92 La0.08 were studied up to 5.5 GPa. The γ→α transition in this cerium alloy is smeared out as compared to pure cerium metal.
Small sized NMR cell for high-pressure low-temperature experiments
Authors: Trokiner A. , Dahan N. , Theveneau H. , Papon P.
Published: March 2003

An apparatus for high-pressure, low-temperature nuclear-magnetic-resonance (NMR) measurements is described. The small sized pressure cell has been tested to 10 kbar. We controlled the temperature from 100 to 300 K with ±2-mK stability. This apparatus allows measurements of dynamic phenomena in the vicinity of phase transition. Experimental results of solid spin echoes are presented briefly.
Precision controller for rotating choppers
Authors: Conforti G. , Del Giallo F. , Pieralli F. , Ventura G. , D’Anna E. , Leggieri G.
Published: March 2003

A dc motor electronic controller, driving a rotating chopper, is presented. The controller uses an integral feedback technique, consisting of charging a storage capacitor by means of width modulated pulses. These pulses are obtained by comparing the revolution time of the chopper with a fixed time. It is shown that the steady-state angular speed is independent both of the friction coefficient and the feedback loop gain. The stability condition of the feedback loop gain is also derived.
Instrumentation for monitoring lingual pressure in vibrotactile research
Authors: Kingsbury Gary D. , Sansone Frank E. , Kelly Dan
Published: March 2003

In order to avoid obtaining variable measurement data it is critical to control pressure applied to the tongue by positioning clamps used in lingual vibrotactile research. A pressure sensing plate, associated electronics, and procedures are described which, when employed with positioning clamps in current use, will permit monitoring lingual pressure during vibrotactile investigations.
Simple multi-spark-gap tracer for Z-pinch experiments
Authors: Arad B. , Ruden E.
Published: March 2003

A simple inexpensive device has been constructed which enables us to know whether all the spark gaps fired simultaneously or what spark gap fired late and by how much it was delayed.
Preparation of self-supporting Si thin single crystals by solid phase epitaxy and selective etching
Authors: Ishiwara Hiroshi , Fujii Masahiro
Published: March 2003

A novel technique to prepare self-supporting single-crystalline Si films with submicron thicknesses is presented, in which their thicknesses are determined by those of amorphous Si films deposited on Si substrates. In the preparation Boron ions are implanted near the interface between the film and the substrate, the film is then epitaxially grown in solid phase by furnace annealing, and finally, the substrate is selectively etched. It was found that the thickness uniformity and crystalline quality of the films were rather good over an area of 3 mm in diameter.
Problem on a digitization of a time interval distribution
Authors: Igarashi Ryuji , Yamada Yuuki , Narita Yuichi
Published: March 2003

Distortion of a time interval distribution, due to digitization with an asynchronous clock counting method, is discussed for Poisson random signals. A condition enabling one to neglect the distortion is derived and is applied to measurements of GM-counter after pulses.
Continuous-wavelength monitoring of a dye laser output
Authors: Da-Yuan Wu , Zheng-Dong Huang , Yu-Zhou Liu , Jie Lu
Published: March 2003

A wavelength monitoring device for dye laser output is constructed and tested by using an étalon as a wavelength marker and an optogalvanic discharge tube as a wavelength calibration.
Homemade video digitizer interfaced to a PDP-11 minicomputer for multichannel resonance Raman spectroscopy
Authors: Meyer J. J. , Fontaine J. C. , Aubard J.
Published: March 2003

A homemade video digitizer has been designed to record analyze continuous or pulsed resonance Raman (RR) spectra.
Computerized data-acquisition and processing system for a tensile testing machine
Authors: Waters Peter J. , Williams Donald G.
Published: March 2003

An Apple II Plus microcomputer has been interfaced to an Instron Tensile Testing Machine (Model TM), using BASIC software, allowing automatic aquisition of data.
Novel ion acceleration tube design
Authors: Sumbar Edmund , Lawson R. P. W. , Vermeulen F. E.
Published: March 2003

This paper describes a 280-kV constant-gradient positive-ion acceleration tube in which the interelectrode voltage is established with a voltage divider chain of resistors that is mounted inside the vacuum of the tube. A single glass pipe serves as the vacuum envelope, flat aluminum disks are used for the tube electrodes, and resistance-paint-coated plastic cylinders compose the voltage divider chain. These construction features simplify tube construction and keep manufacturing costs low. During high-voltage tests, interelectrode voltage was estimated to deviate less than ±6% from uniformity, heat was adequately dissipated from the vacuum-mounted resistors, and the maximum design acceleration voltage of 280 kV was held. Furthermore, preliminary ion acceleration trials yielded from 0.7 μA of N+2 at 50 kV to 1.5 μA at 280 kV. The accelerated-beam cross section, as viewed on a ground quartz screen, remained stationary during those trials, indicating that the tube configuration provided adequate shielding of the beam from asymmetric charges on the interior insulating walls of the tube.
Real-time area-tracker records cellular volume changes from video images
Authors: Lindemann Bernd
Published: March 2003

High-contrast TV images of living cells are recorded from a light microscope. The video line signal is converted to binary and used to gate a 12.5-MHz clock driving a counter. After completion of each video frame the accumulated counts (proportional to the dark image area) are written onto a stack (FIFO) before the counter is reset. Thus, area information is actualized at a rate of 50 values per second and can be read out at speeds suitable for computer interfacing and (after D/A conversion) oscilloscope displays or paper chart recording. With two counting channels the time course of two areas of distinctly different gray shades can be recorded at once.
Three-circle goniometer for electron-paramagnetic-resonance measurements
Authors: Kobayashi T. , Hara H. , Suhara M. , Aono S.
Published: March 2003

A three-circle goniometer for a large-hole electron-paramagnetic-resonance (EPR) cavity is described which, by a very simple operation, enables us to rotate the crystal around arbitrary direction parallel to the static magnetic field, by rotating a sample holder about a redundant (or the third) axis accommodated in a spur and crown gear. By comparing not only the observed resonance field with the calculated one, but also the absorption intensity with the transition probability, the quantitative determination of the concentration of the unpaired electron center in a single crystal is possible.
Stand-alone pulse-echo-overlap facility for ultrasonic wave transit time measurements
Authors: Pathak L. , Murali N. , Amirtha V. P.
Published: March 2003

A completely stand-alone pulse-echo-overlap system which can be easily built using commercially available integrated circuits is described. The system uses a broadband pulse to excite the transducer. The equipment is relatively cheap and yet the sensitivity of the transit time (and, hence, velocity of sound measurement), is made high by making use of a digital frequency synthesizer of 0.01-Hz resolution, specially constructed for this purpose. Except for the oscilloscope the instrument does not require any other equipment for its operation.
Metal ion source using rf discharge combined with sputtering
Authors: Saito Yukinori , Mitsuoka Yasuaki , Suganomata Shinji
Published: March 2003

An ion source capable of producing a wide variety of ion species from elemental materials is described. Ion beams of metals can be produced by sputtering a disk, made of the materials to be ionized, placed on the cathode. In order to raise the rate of ionization of the sputtered materials an rf discharge is superimposed on the dc sputtering. Ions of refractory metals, such as Nb, can be easily produced without using halides.
Versatile zone refiner for liquids and low-melting solids
Authors: Martin C. B. , Martin R. J. , Nasir P. , Wieczorek S. A. , Romanco W. R. , Sivaraman A. , Kragas T. , Kobayashi R.
Published: March 2003

A versatile zone-refining apparatus which employs liquid nitrogen as the refrigerant to maintain the compound to be purified in the solid state while appropriately spaced resistance heaters generate the moving liquid zones to purify compounds whose melting point lies between 200 and 350 K is described. As much as 0.750 kg of substance can be purified at one time to a purity better than 99.95 mole %.
Miniature solenoid for the production of confined magnetic flux
Authors: Walker I. R.
Published: March 2003

For experiments involving SQUID’s it is sometimes desirable to have a small source of confined magnetic field in order to provide a dc or rf flux bias. This has been done by closely winding ♯50 AWG copper wire on a 250-μm-diam optical fiber. The resulting solenoid is very small and has excellent mechanical and electrical properties at 4 K.
Coplanar flip-chip mounting technique for picosecond devices
Authors: Schmid P. , Melchior H.
Published: March 2003

We present a coplanar flip-chip mounting technique for broadband microwave and high-speed opto-electronic devices. The technique is based on coplanar waveguides with tapered structures that can be fabricated with high precision by photolithographic means on planar dielectric substrates and device chips. It allows the inclusion of micrometer size devices into broadband circuits and serves for the transmission of high-speed signals with low reflection over waveguides with varying geometry and to external coaxial lines with millimeter dimensions. As demonstrated by flip-chip mounted high-speed photoconductors, by a coplanar pulse-forming circuit, and by a coplanar line termination, this technique allows broadband transmission with reflections not exceeding a few percent in the frequency range from dc to 25 GHz and signal durations at least as short as 20 ps.
Compact, low-cost cryogenic laser head
Authors: Eckardt R. C. , Storm M. E. , Linz A. , Marquardt C. L.
Published: March 2003

We describe a compact, low-cost cryogenic laser head suitable for use with fragile laser crystals which must be operated at low temperatures. Our design provides maximum mechanical stability and permits easy interchange of optical components in the laser cavity. One of our lasers was operated over a 1-year test period, and has survived more than 150 thermal cycles and 1000 hours of lasing without failure.
Laser interferometer enhanced positional precision of a scanning microdensitometer for astrometric plate scanning
Authors: Kinsey J. H. , Denman R. J. , Evzerov A.
Published: March 2003

Scanning microdensitometers used for astronomical plate scanning in connection with guide star selection for the Space Telescope have had their spatial resolution and accuracy increased by addition of a laser interferometer position measurement system. The standard Perkin–Elmer model 2020 GM PDS microdensitometer has a spatial resolution of 1 μm and an accuracy and repeatability of 5 μm. The addition of a Hewlett–Packard model 5501A Laser Transducer System increases the resolution to approximately 0.6 μm and the accuracy and repeatability to 0.5 μm. Utilization of this increased performance is dependent on the thermal environment of the systems.
An automated cryogenic charcoal trap system for helium isotope mass spectrometry
Authors: Lott D. E. , Jenkins W. J.
Published: March 2003

An automated seawater sample processing line employing a two-stage activated charcoal trap system cooled by a closed-cycle helium refrigerator is described. All dissolved gases except neon and helium are adsorbed on the first stage operating at 55 K with neon and helium quantitatively adsorbed on the second stage at 10 K. The second stage trap is heated to 40 K to release virtually 100% of the helium isotopes (3He, 4He) for mass spectrometer measurement followed by heating to 70 K to release the neon component. Performance data for helium isotope measurements on seawater samples and air standards [4He≊10−9 to 10−6 cm3 (STP) and 3He≊10−15 to 10−12 cm3 (STP)] are presented.
Loading dilatometer
Authors: De Jonghe L. C. , Rahaman M. N.
Published: March 2003

A loading dilatometer has been constructed to study the sintering behavior of powder compacts subjected to low uniaxial stresses between 0 and 0.4 MPa and at temperatures up to 1250 K. A novel feature of the instrument is a device for the application of a controlled and measured stress to the sintering compact. Constant, as well as transient, stresses can be applied and the atmosphere inside the dilatometer can be controlled. Some representative results are reported.
Cell fitted with thin beryllium windows for x-ray absorption under pressures up to 14 MPa and temperatures up to 700 K
Authors: Dalla Betta R. A. , Boudart M. , Foger K. , Löffler D. G. , Sánchez-Arrieta J.
Published: March 2003

A stainless-steel reactor cell is described. Its purpose is to permit in situ x-ray absorption spectroscopy study of three-phase catalytic reactions at temperatures up to 700 K and pressures up to 14 MPa. The x-ray beam enters and leaves the cell through thin (0.051 cm) beryllium windows. The design of the cell allows for high-temperature operation while keeping the beryllium windows at room temperature. The x-ray beam passes through a catalyst wafer wetted by a liquid reactant film trickling down the catalyst while a gas-phase reactant dissolves in the liquid and reacts with the latter on the catalytic surface.
Fast passive integrator
Authors: Raleigh M. , Pechacek R. E.
Published: March 2003

We describe a passive integrator capable of correctly giving outputs with rise times as short as ∼250 ps. The integrator can drive a 50-Ω load and is intended to exploit the capabilities of the 7A29 preamp in the Tektronix 7104 oscilloscope (tr≤380ps). The decay time for the integrator is ∼250 ns.
Data reduction technique for use with electrostatic energy analyzers
Authors: Hayes M. A.
Published: March 2003

A technique is presented which provides for direct calculation of average parallel energy from data taken by a simple electrostatic energy analyzer. An example is given of the technique’s use.
Simple resonator for 300-MHz NMR experiments
Authors: McGurrin M. , Gully W. J.
Published: March 2003

We describe the construction of a compact LC resonator that worked well as a probe for high-frequency pulsed NMR experiments at cryogenic temperatures.
Modifications to the Boonton 72BD capacitance meter for deep-level transient spectroscopy applications
Authors: Chappell T. I. , Ransom C. M.
Published: March 2003

For accurate determination of the activation energy of a deep-level trap by deep-level transient spectroscopy (DLTS), it is desirable to measure the thermal emission rate over at least two orders of magnitude. Thus, the least time required to acquire DLTS capacitance data over this range will be directly proportional to 100 times the minimum response time of the capacitance meter employed. When an unmodified Boonton 72BD capacitance meter is overloaded by a strong stimulating pulse, erroneous signals caused by the recovery of its overload detection circuitry and 1-MHz amplifier will be superimposed on the first 200 ms of a transient waveform. Therefore, accurate data would require that each transient be captured for times as long as 20 s. In this paper, simple modifications to this instrument are described which significantly improve data-acquisition speed and data quality. This is accomplished by eliminating overload recovery delays and by minimizing noise produced by digital circuitry. Specifically, overload recovery delays are avoided by installing a fast relay which grounds the input of the 1-MHz amplifier during application of the stimulating pulse and by deactivating the internal overload detection circuitry. The noise produced by digital circuitry is reduced by stopping the multiplexing of the light-emitting diode display.
High-temperature laser interferometer for thermal expansion and optical-length measurements
Authors: Aurora T. S. , Day S. M. , King V. , Pederson D. O.
Published: March 2003

A simple laser interferometer has been utilized to measure the thermal expansion and optical-length variation with temperature of highly reactive fluorides at high temperatures. The interferometer is a modification of the Jamin interferometer in which a laser beam is split into two parallel beams which traverse nearly identical paths and are reflected from the sample and a reference mirror. The reflected beams recombine to produce an interference pattern. The displacement of the front sample surface, relative to the reference mirror at the back sample surface, allows the thermal expansion to be measured. The sample and reference mirrors are made reflecting by depositing a platinum film on the surface. The same arrangement of beam splitters has been used to measure the variation in optical length with temperature. In this case, the sample is not coated with platinum. Measurements of thermal expansion have been made up to 1000 K above which the platinum film becomes unstable. Optical lengths of various fluorides have been measured up to 1100 K. The platinum is not observed to diffuse into divalent metal fluorides although these samples oxidize readily at certain high temperatures. The advantages and disadvantages of this method are discussed.
Optical multichannel detection system suitable for a Fabry–Perot interferometer
Authors: Fünfschilling J. , Brūlhart M. , Hidber H. R. , Zschokke-Gränacher I.
Published: March 2003

In order to detect the circular fringes of a Fabry–Perot interferometer with high sensitivity the electronic scanning of an optical multichannel analyzer (OMA) has been modified. Compared to the common scanning Fabry–Perot photomultiplier combination this modification yields a gain in sensitivity of more than a factor of 10. Furthermore, single pulses or strongly fluctuating sources may be measured without the noise problems of a scanning interferometer. The modified OMA is capable of resolving about 90 circles. The system is applied to the detection of the fine structure of weak laser-excited phosphorescence spectra.
High-sensitivity photoelectron spectrometer for studying reactive transient species
Authors: Morris Alan , Jonathan Neville , Dyke John M. , Francis Peter D. , Keddar Noureddine , Mills Jon D.
Published: March 2003

The construction and operation of a high-sensitivity photoelectron spectrometer, specifically designed for studying reactive transient species, is described. Fast data acquisition is used to minimize spectral drift problems caused by contamination resulting from species production conditions. The spectrometer is equipped with sample differential pumping to retard contamination of the electron optics and its modular design enables individual components to be readily dismantled for cleaning purposes. A microchannel-plate (MCP)/phosphor/silicon-intensified-target (SIT) camera detector is used, operated under modest voltage conditions. A unique, dedicated, dual-buffer, data interface is constructed, incorporating the use of a video window to select data. The interface can be used in a stand-alone mode for rapid data examination, when optimum spectrometer conditions can conveniently be established using the detector two-dimensional imaging capability and a standard TV monitor for assessment of line image quality. Preliminary results show reductions in data-acquisition times of up to 75 compared to equivalent single-channel detector experiments. Several studies of transient species have been performed, which had proved unsuccessful on earlier generation spectrometers.
Uniaxial stress apparatus for deep level transient spectroscopy studies
Authors: Lamp C. D. , Farmer J. W. , Meese J. M.
Published: March 2003

An apparatus for applying uniaxial stress >109 Pa at temperatures of 20–300 K is described. The apparatus is used with a deep level transient spectroscopy (DLTS) experiment, but it has more general applications. We have used this apparatus to observe the splitting of a DLTS defect level at Ec −0.17 eV in neutron irradiated silicon and have determined from the splitting, as a function of stress orientation, that the defect symmetry is consistent with the oxygen-vacancy A-center.
Heat switch for liquid-helium temperatures
Authors: Torre J. P. , Chanin G.
Published: March 2003

A cryogenic heat switch has been developed for use in low-temperature physics experiments. In the ‘‘on’’ position, it relies on the thermal properties of liquid helium, achieving a thermal conductance comparable to that of the electrolytic copper of which the conduction cell is constructed. The switching action is achieved without moving parts: it is switched ‘‘off’’ by removing the helium from the conduction cell with a self-contained cryopump and ‘‘on’’ by heating the cryopump to a temperature at which the gas is desorbed, eliminating the need for connecting tubing, external pumps, and gas handling accessories. The ratio of ‘‘on’’ to ‘‘off’’ conductance is greater than 104 with switching times of several minutes or less.
Low-temperature pressure variations in a self-clamping pressure cell
Authors: Thompson J. D.
Published: March 2003

A simple method is described that permits a consistent determination of thermally induced pressure variations in a piston-cylinder, self-clamping pressure cell at temperatures less than ambient. Significant pressure changes are found to be present even for T<75 K. It is also shown that the pressure coefficient of resistance of a manganin-wire gauge is, to within experimental uncertainty, independent of temperature over the range 0<T≤300 K.
Reactor for combined surface spectroscopic analysis and atmospheric pressure kinetic studies of catalysts
Authors: Weimer Jeffrey J. , Putnam Fredrick A.
Published: March 2003

A novel reactor system is described which permits ultrahigh-vacuum surface spectroscopic studies and atmospheric pressure reactions to be done without a dedicated apparatus. An application of this system to studies of metal single crystals is shown, although its use for kinetic studies of such samples is limited in the present design. The reactor is used to study the surface properties and reaction characteristics of platinum deposited on a sapphire surface. The major use of the system is to study such model-supported catalysts without exposing the sample to atmospheric contamination.
Noise characteristics of a cryogenically cooled GaAs metal semiconductor field effect transistor at 4 MHz
Authors: Bocko Mark F.
Published: March 2003

The noise near 4 MHz of a cryogenically cooled GaAs metal semiconductor field effect transitor (MESFET) has been measured. The input noise current is iN=1.1±0.2×10−14 A/(Hz)1/2 and the additive voltage noise is eN=1.2±0.4×10−9 V/(Hz)1/2 , which gives a noise temperature TN=0.5 K.
On-line realization of Marmet’s filter
Authors: Podgórski Andrzej
Published: March 2003

The possibility of ‘‘on-line’’ realization of Marmet’s filter is shown. An appropriate algorithm is described. Gain in memory occupation is demonstrated.
UHV compatible experiment setup for gas phase studies using synchrotron radiation
Authors: Eberhardt W. , Stöhr J. , Troxel C. , Feldhaus J. , Plummer E. W. , Sette F.
Published: March 2003

We have designed and tested an experimental setup which allows the study of photoabsorption, photoemission, and photon-induced production of ionic fragments of atoms and molecules in the gas phase. The differential pumping system keeps the pressure below 1×10−9 Torr at the connection to the UHV synchrotron radiation beam line while the experiment typically is in the 10−4-Torr range. The windowless design results in a structureless transmission function of the differential pumping stage and a general reduction of the available photon flux by a factor of 2 compared to the exit of the monochromator.
New method for stabilizing the output of a He–Cd laser
Authors: Chiu M. S. , Chou C. C.
Published: March 2003

With an axial magnetic field, the output of a He–Cd laser has been stabilized by means of feedback. The stability of the laser output was better than 1% for over 2 h.
100-kV test of the prototype neutral beam injector for JT-60
Authors: Horiike Hiroshi , Akiba Masato , Araki Masanori , Dairaku Masayuki , Itoh Takao , Kawai Mikito , Kuriyama Masaaki , Kitamura Shigeru , Matsuda Shinzaburo , Matsuoka Mamoru , Mizuhashi Kiyoshi , Oguchi Yoshiaki , Ohara Yoshihiro , Ohga Tokumichi , Okumura Yoshikazu , Shibanuma Kiyoshi , Shibata Takemasa , Shigematsu Hirotsugu , Shirakata Hirofumi , Sugawara Tadayoshi , Tanaka Shigeru , Watanabe Kazuhiro
Published: March 2003

A prototype neutral beam injector for JT-60 has demonstrated extraction of 100-kV, 70-A, 10-s ion beams, delivering neutral beam power of 1.43 MW into the target chamber. The power-flow measurements showed that all beam line components, including the ion sources, were operated successfully. This verified the validity of the design work related to the ion source and neutral beam cooling devices. No significant change in the beam divergence during the pulse has been observed up to the maximum rated beam extraction of 40 A at 100 kV for 10 s from each ion source. The measurement also indicated that the power distribution to the beam line components agreed well with independently obtained ion species ratio and gas pressure distribution. Efficiencies of 28% and 20% were obtained for the neutralization and neutral injection into the target, respectively, for 100-kV, 70-A, 10-s operation.
H− ion density measurement in a tandem multicusp discharge
Authors: Leung K. N. , Bacal M.
Published: March 2003

The H− ion density is measured by photodetachment in the source and target sections of a tandem multicusp discharge containing a ‘‘magnetic filter.’’ The results confirm previous observations based on the measurement of extracted currents, that a magnetic filter, together with a small positive bias on the plasma grid, produce a significant increase in the H− ion density and a reduction in the electron density in the target section.
Helium gas flow-type cryostat for the study of condensed layers of gases under ultrahigh vacuum conditions
Authors: Arakawa I. , Tuzi Y.
Published: March 2003

A helium gas flow-type cryostat was developed. The cryostat was designed for experiments in ultrahigh vacuum, especially for studies of adsorbed or condensed layers of gases on a crystal surface. The crystal surface was able to be kept at any temperature between 20 and 100 K. A temperature stability of 0.1 K was achieved by controlling the flow rate of cold helium gas.
High-precision flow densimeter for fluids at temperatures to 700 K and pressures to 40 MPa
Authors: Albert Henry J. , Wood Robert H.
Published: March 2003

A vibrating tube flow densimeter for measuring the density of fluids as functions of temperature and pressure is described. The apparatus allows relative density measurements to be carried out on 6 cm3 of solution in about 20 min with a precision of 30 ppm at temperatures to 700 K and pressures to 40 MPa. The accuracy of the densimeter has been verified by measurements on NaCl solutions. Good agreement with literature values was obtained.
Multifrequency cross-correlation phase fluorometer using synchrotron radiation
Authors: Gratton E. , Jameson D. M. , Rosato N. , Weber G.
Published: March 2003

The construction and operation of a cross-correlation phase and modulation fluorometer using the synchrotron radiation facility at the ADONE–Frascati electron storage ring is described. In the frequency domain the high repetition rate pulsed source gives a large series of equally spaced harmonic frequencies. Use of cross-correlation techniques in conjunction with such a light source permits one to isolate one harmonic frequency from the adjacent frequencies with high precision. The cross-correlation frequency required for the analysis of the phase delay and modulation ratio is obtained using two coupled frequency synthesizers, one of which drives the radio-frequency cavity of the storage ring and the other which modulates the response of the photomultipliers used for the signal detection. The accuracy, reproducibility, and sensitivity of the instrumentation have been determined on a number of systems and are reported.
Electronic analyzing light signal subtraction and measuring device for transient absorption spectrophotometry
Authors: Luthjens L. H. , Hom M. L. , Vermeulen M. J. W.
Published: March 2003

An electronic system is described that subtracts the analyzing light signal level from the analyzing light signal modulated by a transient absorption signal at the output of a photodetector in a transient absorption spectrophotometer. The system enables sensitive measurement of the transient with simultaneous measurement of the analyzing light level immediately before the transient. The shortest rise time is 50 ns. The time window for the measurement can be selected to a maximum of 20 ms with a droop of 20 μV. Input signals of 10 V of either polarity are permitted. The minimum detectable absorption signal is determined by the noise of the photomultiplier used and can be about 0.2% for an experiment without signal averaging.
Optical transmission measurements using computer response correction
Authors: Harper B. M.
Published: March 2003

A low-cost double beam spectrophotometer using separate detectors is described. This device, capable of transmission measurements as low as 0.001%, incorporates computer response correction for both beam differences and fluctuations in detector power supply and light source. This type of measurement is achieved without the use of high-quality optical components or hardware-based response correction.
Noise current measurements and signal-to-noise improvement in low-temperature, low-frequency nuclear-magnetic-resonance experiments
Authors: Lepaisant J. , Bloyet D. , Varoquaux E.
Published: March 2003

A NMR pickup coil cooled to low temperature generates virtually no noise. Advantage can be taken of this fact in the low megahertz range by proper design and, in particular, by taking the current noise sources in of the room-temperature input circuitry carefully into account. A low-noise rf line and a method to measure very small in’s in the 10-kHz–1-MHz frequency range are described.
Direct observation of electric field induced surface atomic displacements using the field ion microscope
Authors: Eaton H. C. , Bayuzick R. J.
Published: March 2003

Numerical calculations are used to determine the magnitude and directions of surface atomic displacements produced by imaging a tungsten specimen in a field ion microscope. These displacements are induced by surface forces resulting from the high electric field required for imaging in the instrument. The computations reveal that the maximum displacements occur in the brightly imaging regions of a tungsten emitter and can be as large as 0.1 nm. A color photographic technique is used to directly reveal the displacements in an actual experiment. The results of theexperiments corroborate those of the calculations.
Effects of viscosity, temperature, and rate of rotation on pressure generated by a controlled-clearance piston gauge
Authors: Sharma J. K. N. , Jain Kamlesh K. , Bean Vern E. , Welch B. E. , Lazos Ruben J.
Published: March 2003

The calculation of the pressure generated by a controlled-clearance piston gauge depends upon the jacket pressure corresponding to zero clearance between the piston and cylinder Pz. The dependence of Pz on the viscosity of the pressure transmitting fluid, the temperature, and the rate of piston rotation have been measured. The four fluids used in this study have viscosities ranging from 0.7 to more than 10 000 cP. The value of Pz is nearly independent of viscosity below 60 cP. Above 60 cP, Pz depends strongly upon viscosity. Variations of Pz with temperature and rate of rotation are more severe at higher viscosities. The results suggest that the best choice of fluid is the one having the lowest viscosity at the operating pressure. Such a fluid can be selected on the basis of having the most nearly linear plot of Pz as a function of pressure of the candidate fluids. These results are also a clear indication that, for the most accurate pressure measurements, a controlled-clearance piston gauge must be characterized using the same operational and environmental conditions with the same fluid as are used in normal operation.
Proposal for a time-of-flight Thomson backscattering technique for large fusion devices
Authors: Salzmann H. , Hirsch K.
Published: March 2003

The application of 180° Thomson scattering using ultrashort laser pulses for measuring electron temperature and density profiles in large fusion devices is proposed. Spatial resolution along the laser beam is achieved by high-speed detection allowing time-of-flight measurements. This LIDAR (light detection and ranging) technique uses a minimum number of window ports and reduces the number of optical components in the vicinity of the discharge vessel. As an example, the performance of such a system for the JET tokamak geometry is discussed on the basis of available laser and detection technology.
Influence of surface roughness on the momentum transfer by 350-keV hydrogen-cluster ions
Authors: Keller W. , Klingelhöfer R. , Krevet B. , Moser H. O. , Ries R.
Published: March 2003

The momentum reflection of accelerated H2 cluster ions in the energy range of 1 to 10 eV per atom on various surfaces differing by their roughness has shown to vary by more than 61%. By use of the surfaces having a higher absorptive power, the momentum of such particle beams can be measured more accurately.
High-resolution differential thermometry in flowing aqueous solutions
Authors: Fulton Scott P. , Cooney Charles L. , Weaver James C.
Published: March 2003

One approach to chemical measurement in aqueous solution involves the use of two thermistors, with a catalyst such as an enzyme attached to one while the other serves as a reference. Fundamental to this approach is measurement of a small temperature difference ΔT between the two thermistors. The present study uses a flow-through cell for investigation of ΔT measurement problems. There are important ΔT effects associated with thermistor separation, flow-rate variability, absolute flow rate, dissolved gas content, and thermistor excitation power. By using steady flow and passive but continuous partial degassing, a rms ΔT resolution of 2–3 μ°C can be achieved.
Current-limited capacitor charging power supply for spark-gap-driven high repetition rate laser pulser
Authors: Bhadani P. K. , Biswas D. J. , Agrawal P. K. , Bhawalkar D. D.
Published: March 2003

A short-circuit protected capacitor charging scheme for a spark-gap driven high repetition rate laser pulser is described. The possibility of using this scheme with a thyratron driven laser pulser is also discussed.
Pneumatic gate valve mounted inside an ultrahigh-vacuum chamber
Authors: Zinck J. J. , Weinberg W. H.
Published: March 2003

A simple modification of a commercial gate valve which allows the pneumatic actuating mechanism to be mounted in an ultrahigh-vacuum system is described.
Design of Faraday rotators and modulators
Authors: Duffy R. M. , Netterfield R. P.
Published: March 2003

Equations have been developed which allow the design of coils for Faraday rotators. It is shown that the sensitivity of rotation of the plane of polarization to the ampere turns of the coil is a function of ratios of coil dimensions. Equations and graphs are presented which allow the design to be optimized with respect to the power dissipated in the coil or to the temperature rise of the coil. It is shown that disk-shaped coils are inefficient as rotators.
Flexible detection optics for light scattering
Authors: Taratuta Victor G. , Hurd Alan J. , Meyer Robert B.
Published: March 2003

We have designed and built a compact, modular apparatus for the collection, viewing, and detection of scattered light for less than $1200, based on a commercially available optical bench. The novelty of our instrument is that it has the flexibility of modular design while allowing the user to see exactly what is happening: both the real image of the sample and the spatial coherence of the scattered light can be examined. There is built-in control over polarization, filtering, magnification, and other parameters.
Steady-state gas dissolution flow microcalorimeter for determination of heats of solution of slightly soluble gases in water
Authors: Dec Steven F. , Gill Stanley J.
Published: March 2003

A flow calorimeter of the heat conduction type is described, which is capable of measuring the heat effect associated with the process of dissolving slightly soluble gases into water. The calorimeter operates in a steady-state mode. Gas, fed at constant rate, is dissolved in flowing water within a specially designed microcalorimeter cell and the power is determined for the process. Computer control of the gas flow is used for convenient establishment of steady states. The calorimeter is calibrated electrically with a precision of 0.2% for power levels of 150–450 μW. Reproducibility of successive measurements of heats of solution of oxygen are within 1%. Results are presented for the enthalpy change for the dissolution of oxygen gas into pure water at 25 °C.
Gain characteristics of a microchannel plate operated in the reflection mode for low-energy positive ions
Authors: Koshida Nobuyoshi , Hatano Yoichi
Published: March 2003

Fundamental gain characteristics of a microchannel plate (MCP) operated in the reflection mode for low-energy (20–300 eV) positive ions were studied experimentally in detail. When a MCP with zero-bias angle was used, the gain in the reflection mode increased by about two orders of magnitude compared with that in the conventional transmission mode. Such a remarkable high gain supports the automatic preacceleration effect on incident ions suggested previously and also shows practical usefulness of this operation mode as a simple detector of low-energy positive ions. The reflection mode gain was also found to be highly sensitive to the ion’s incident angle and collector voltage. This suggests that the reflection mode has two additional functions: that of analyzer of the incoming ion’s direction and discriminator of incident ion energies. These properties can be explained in terms of the penetration depth of incident ions into the microchannels, which is the most important factor in this detection technique.
Microminiature refrigeration
Authors: Little W. A.
Published: March 2003

We present a review of the recently developed microminiature, Joule–Thomson cryogenic refrigerators. These extremely small devices are finding wide scale use in instrumentation and as coolers for the study of materials. They have recently become available through the development of a novel, low-cost photolithographic fabrication process. We present the essentials of heat exchanger design, upon which the refrigerators are critically dependent, discuss the fabrication process, and review some of the present applications and limitations of the refrigerators, together with possible future application for cooling SQUID devices.
Versatile damper for magnetic suspension systems
Authors: Sridharan G.
Published: March 2003

Magnetic suspension systems need an optimum amount of damping for stable operation. Viscous damping has proved very effective in controlling the radial instabilities of such systems. However, if the dynamics of the suspension system were not known exactly, it may be advantageous to use a damper having an adjustable coefficient. Here, a new configuration of radial viscous damper, possessing a variable coefficient of damping, is proposed.
Angular windowing system for rotating equipment tests
Authors: Moyer W. M.
Published: March 2003

Knowledge of the position of the unit under test at the time each data sample is acquired can improve the interpretation of results from tests of rotating equipment. The acceptance of data generated only while the unit is in a selected portion of its circular range can be useful. A system has been developed to provide both the angle tagging and the angular windowing of samples acquired from rotating systems. Options are provided so that the user can elect those system capabilities necessary in particular test situations. Interfacing with data source and data processor is addressed. The initial application of the system to a water tunnel propeller test is briefly described.
Adjustable fixed-flow restrictor with wide turndown ratio
Authors: Heisig Charles G.
Published: March 2003

This adjustable fixed-flow restrictor comprises a body fabricated from a 1/4-in.-o.d. tubing union tee using tools available in most laboratories and a 1/4-28 NF set screw as an adjustable plug. A soft setting screw thread locking material serves as a combination stem seal and means for locking the set screw in place following adjustment for desired flow rate. Air flow rates between 0.15 and 50 or more l/min (0.3 to 100+CFH) can be obtained with a pressure drop to atmospheric conditions of 1.3 atm (20 psi).
Dielectric measuring method at ultralow frequencies using a transient recorder
Authors: Kliem H. , Dederichs H.
Published: March 2003

A simple method for the measurement of the dielectric permittivity at ultralow frequencies is described. The method allows measurements in the frequency domain by comparing the signal of a reference condenser to the signal of the device under test.
Intracavity plasma shutter for transversely excited CO2 lasers
Authors: Znotins T. A. , Byron S. R. , Moody S. E. , Brimacombe R. K. , Reid J.
Published: March 2003

An electrically triggered intracavity plasma switch is used to control the pulse shape and duration of TE CO2 laser pulses. The shuttering mechanism is shown to be due to beam deflection. Two modes of shutter operation are demonstrated, one producing long pulses 2–12 μs in duration, the other producing isolated gain switched spikes 100–200 ns in duration.
Energy-dispersive x-ray diffraction with synchrotron radiation at cryogenic temperatures
Authors: Skelton E. F. , Webb A. W. , Qadri S. B. , Wolf S. A. , Lacoe R. C. , Feldman J. L. , Elam W. T. , Carpenter E. R. , Huang C. Y.
Published: March 2003

A facility is described which has been developed for the rapid acquisition of structural information through the use of heterochromatic synchrotron radiation from a sample pressurized in a diamond-anvil cell and simultaneously cooled to cryogenic temperature. The system employs a closed-cycle He refrigerator, which can be continuously operated, independent of any liquid cryogens, from a remote station. The compressive contact force between the diamonds, and hence the sample pressure, is also externally controlled, thereby providing remote control capabilities for both the pressure and temperature. NaCl has been used as an internal pressure calibrant and existing empirical equation-of-state calculations for NaCl have been extended to reduced temperatures for this purpose. Preliminary data on the lower pressure critical point associated with the isomorphic phase transition in Ce0.8Th0.1La0.1 are presented.
Computer-controlled performance of photoacoustic resonance experiments
Authors: Karbach A. , Röper J. , Hess P.
Published: March 2003

Acoustic modes in a spherical resonator are excited with a chopped 3.39-μm He–Ne laser by vibrational excitation of CH4. The recording of resonance curves is completely controlled by a microcomputer. This includes repeated registration of the resonator temperature, stabilization and determination of the modulation frequency, and integration of the acoustic signal detected with an electret microphone. A detailed description of the timing of such an automatic data acquisition for high-precision experiments is given. The accuracy of the resonance method is investigated by fitting the experimental resonance curves to the corresponding line profile and performing an analysis of the errors involved.
Two-stage electron energy analyzer for angle-resolved photoemission spectroscopy
Authors: Royer W. A. , Smith N. V.
Published: March 2003

A two-stage energy analyzer is described having a 127° cylindrical deflection analyzer as an injection stage followed by a 37° plane mirror analyzer with a resolution function ΔE/E∼1%. The design is very compact about the axis of analyzer rotation. The entire instrument including turntable and magnetic shields fits within a 150-mm tube, and is physically interchangeable with a commercial double-pass cylindrical mirror analyzer (CMA). The advantage it has over an angle-resolving CMA is that the directions of collected electrons all lie in a common plane. Construction details are described, and the performance of the analyzer is illustrated with some angle-resolved photoemission data on Ag(100) using synchrotron radiation.