bluuebunny/crossref_metadata_2025 huggingface dataset:
Adaption of a diamond anvil cell to an automatic four-circle diffractometer for x-ray diffraction
Authors: Denner W. , Dieterich Werner , Schulz Heinz , Keller R. , Holzapfel W. B.
Published: March 2003

A diamond anvil high-pressure device for x-ray diffraction on single crystals under hydrostatic pressures up to about 100 kilobars has been adapted to the automatic four-circle x-ray diffractometer Philips PW 1100. The mechanical adaption, the centering procedure, and quick pressure calibration on the diffractometer are described. Hints to improve the peak-to-background ratio of the intensity measurements are given.
SEM stroboscopy for the evaluation of I
C operating functions in the subnanosecond range
Authors: Hieke E. , Meusburger G.
Published: March 2003

A stroboscopic system has been applied to the scanning electron microscope (SEM) which operates with an electrostatic deflection system permitting pulse rates up to the GHz region, a value obtained with a very small electrode gap of 100/μm. The deflection voltage was 50 mV for a SEM acceleration voltage of 2.5 kV. The efficiency and limitations of this system are theoretically treated. Such a stroboscopic system has been used for an initial determination of the time interval required for a binary operation of an inverter stage. A delay time of 820 ps was calculated and a time interval of 3.8 ns per binary operation was measured.
Application of germanium resistance thermometers below 0.1 K
Authors: Roth E. P. , Matey J. R. , Anderson A. C. , Johns D. A.
Published: March 2003

Several commercially available germanium resistance thermometers have been studied at temperatures below 0.1 K. The major impediment to the removal of heat dissipated by the measuring current is the weak carrier–phonon interaction. Precautions required for the reliable use of these thermometers are dicussed.
Absolute determination of dose rate from energetic electron beams
Authors: Murray K. , Guenzer C. S.
Published: March 2003

A method for absolute dose rate determinations in the range of 107 rad (Si) s−1 to greater than 1010 rad (Si) s−1 is reported here. The method is useful in determining the simultaneous dose rate delivered to a device under test which is small enough that it does not significantly affect the beam current. The method requires (1) an instrument consisting of a Faraday cup, scattering plates, and collimators, (2) beam profile measurements, and (3) energy deposition calculations. The Faraday cup is designed for electron beams whose energy is in the range 5–50 MeV. This method is capable of providing dose rates accurate to 10% and total dose to 5%.
Universal computer interface for the Cary 118C spectrophotometer
Authors: Sutherland John Clark , Boles Thomas T.
Published: March 2003

We have constructed a simple interface which allows a computer to collect spectral data from and control the wavelength setting of a Cary 118C spectrophotometer. The interface is compatible with most types of computers; the computer need not be located near the spectrophotometer. Programs to operate the spectrophotometer can be written in high-level languages such as fortran or basic.
Improved technique for measuring intense pulsed ion beams by the nuclear activation method
Authors: Blaugrund A. E. , Stephanakis S. J.
Published: March 2003

A technique capable of measuring very high ion fluences by the nuclear activation method is described. The method eliminates the adverse effects of target blowoff by placing the target in a specially designed enclosure.
Automation of long-path absorption cell measurements
Authors: Watkins Wendell R. , Dixon Richard G.
Published: March 2003

Recent advances have been made in the operation of long-path absorption cells which make them easier to align and improve the accuracy of measurements made with them. Only one person is required now for routine measurements of low absorption coefficients of atmospheric absorbers. Unique gear designs for the adjustment of the cell mirrors are described which utilize low-torque linear drives and make possible rapid changes in pathlength and precision repositioning of the cell output beam at long pathlengths. Automation of cell operation by the use of remote Selsyn controls is described. Several techniques are discussed for precision optical alignment of long-path absorption cells, including the use of infrared radiation sources. The system accuracy which results from these refinements in operation is included.
Vacuum-sealed specimen stage for scanning microscopy of air-sensitive materials
Authors: Steger John , Alonzo Jack
Published: March 2003

A vacuum-sealed specimen stage for investigation of air-sensitive materials has been designed. This stage is useful for instruments equipped with a vacuum antechamber and allows facile sample mounting in a dry box or glove bag. The sample cell is subsequently introduced into the antechamber of the instrument and the appropriate measurement or photograph is taken. Sample integrity can be maintained in the cell for subsequent investigations.
Preparation and purity measurement of extremely pure helium gas
Authors: Yates J. T. , Zinck J. J. , Weinberg W. H.
Published: March 2003

A procedure is described for the production, storage, and handling of very pure helium gas and for the measurement of its purity in the part per 1011 range.
Preparation of micron thick specimens for high pressure study
Authors: Gupta Mool C. , Ruoff Arthur L.
Published: March 2003

The electrical resistance behavior of a material under very high pressure can be studied by pressing the material with a diamond indentor against a diamond flat. The high pressures generated can be calculated using Hertz’s theory provided the material thickness is about a micron or less. Here we describe a method of preparing micron thick specimens of a few millimeters in size. We have prepared micron thick specimens of a few millimeters in size of Si (100), Si (111), NaCl (100). The result of high pressure study on Si (100) is also presented.
Ratio of analog pulse height module for fluorescence activated cell sorter
Authors: Johnson G. E. , Dorman B. P. , Ruddle F. H.
Published: March 2003

We describe a simple and inexpensive circuit for producing output pulses of amplitude proportional to the ratio of analog pulse height (RAPH) inputs. Use of a diode to limit negative output excursions results in simplified design and is found to be suitable for Fluorescence Activated Cell Sorter (FACS) applications.
Expandable flash x-ray tube (FXT) having a 0.5-mm source size
Authors: Carmel Y. , Eylon S.
Published: March 2003

An inexpensive, expandable, continuously pumped, all-metal flash x-ray tube (FXT) was developed. It was coaxialy integrated at the end of a 70-Ω flexible coaxial transmission line. The tube, which has a small, 0.5-mm, x-ray source size when operated at 200 kV, produces a dose rate of 5×107 R/s (at exit port). The produced x-ray pulse has a duration of 20 ns, thus permitting the radiography of high-speed transient phenomena.
Infrared optical sensor for measuring internal interfacial wave motions
Authors: Koop C. G. , Rungaldier H. , Sherman J. D.
Published: March 2003

The absorption of infrared energy is used to infer internal interfacial displacements. The probe consists of an infrared emitting diode, operated in a pulsed mode, which projects a collimated beam of radiation across a fluid interface onto a silicon photodiode detector. The output of the diode feeds an amplifier and a sample-and-hold circuit. Through multiplexing, the electronics are capable of handling up to eight probes. The infrared sensor has a sensitivity of about 1 V/cm, and it may easily be used to resolve wave motions as small as 0.01 mm.
Temperature inhomogeneity in the glass mixing chamber of a 3He/4He dilution refrigerator
Authors: Kumano Masafumi , Ikegami Yusaku , Sato Takashi , Saito Shinhachiro
Published: March 2003

The temperature inhomogeneity in the glass mixing chamber of a 3He/4He dilution refrigerator has been studied. The inhomogeneity is reduced to 10 mK by inserting a cylindrical spacer in the mixing chamber.
X-ray magnifier
Authors: Boettinger William J. , Burdette Harold E. , Kuriyama Masao
Published: March 2003

A method for the magnification of x-ray radiographic images is described and demonstrated. This magnifier employs two successive asymmetric diffractions of an x-ray beam from highly perfect silicon crystals. The two diffractions magnify the beam in two perpendicular directions. A device with a magnification of 25× is demonstrated for Cu Kα radiation. This device preserves and sometimes improves the resolution inherent in the radiographic technique. The x-ray magnifier is particularly useful in circumventing the relatively poor spatial resolution of electro-optical imaging systems needed for real-time observations. Basic limits on magnification and resolution using this method are described.
High-energy spectrophotometer for rapid constituent analysis in the range of 0.25–2.4 μm
Authors: Landa Isaac
Published: March 2003

This publication describes a constituent analyzer which uses a concave holographic grating for high-energy throughput, a conjugate cam drive to allow up to ten spectral scans per second, a microprocessor for data gathering and system control, and a minicomputer for the complex statistical computations required in the interpretation of the spectral data gathered. The instrument was specifically developed for quantitative measurement of food constituents in food processing and quality control. However, as a general state-of-the-art spectrophotometer it was found to be a valuable tool in other disciplines such as industrial, clinical, and medical applications.
Dilatometer for the i
n s
i
t
u observation of high-temperature, high-pressure hydrogen attack
Authors: Sagüés A. A.
Published: March 2003

A differential dilatometer capable of detecting volume changes of 1 part in 105 in specimens exposed to a hydrogen atmosphere at 6.2 MPa and 500°C is described. The swelling of an alloy under hydrogen-attack conditions can be studied over a wide range of hydrogen pressures and temperatures by use of a single specimen.
Velocity sensing interferometer (VISAR) modification
Authors: Hemsing Willard F.
Published: March 2003

The VISAR (velocity interferometer system for any reflector) has become a common tool used in experiments where high surface velocities must be measured. A modification that uses previously wasted interferometer light to more than double output signals and to cancel noise is described. Laser power is used more efficiently, VISAR performance in the presence of intense target self-light is improved, and only two data signals are required instead of the usual three or four. Effects of changing light intensity and fringe visibility are eliminated using a novel detection system with a simplified solution for velocity.
Repetitive vacuum ultraviolet xenon excimer laser
Authors: Edwards C. B. , Hutchinson M. H. R. , Bradley D. J. , Hutchinson M. D.
Published: March 2003

A repetitive, tunable, high-power vacuum ultraviolet laser operating on the 172-nm bound–free transition in xenon has been developed for use in photochemistry, selective excitation spectroscopy, and in the generation of coherent radiation in the XUV spectral region. A compact high-voltage generator is employed in conjunction with a coaxial cold-cathode diode to pump high-pressure xenon at a repetition rate of up to 10 Hz, though at present gas heating limits the operation of the laser to 0.5 Hz. The apparatus has been designed for compatibility with fluorine, and is consequently a suitable pumping source for the rare gas halide exciplex lasers. The gas handling techniques which enabled reliable, reproducible laser action to be achieved in xenon for several hundred pulses are described.
Compact capacitor for wide-range dielectric constant measurements on small amounts of fluids
Authors: Straty G. C. , Younglove B. A.
Published: March 2003

A stable parallel-plate capacitor of unusually simple design is described which is suitable for wide-range dielectric constant measurements on fluids.
Spin and energy analyzed photoemission: A feasibility analysis
Authors: Pierce D. T. , Kuyatt C. E. , Celotta R. J.
Published: March 2003

New scientific opportunities, particularly for investigation of surface magnetism, will be provided by spin and energy analyzed photoemission. Electron-optical conservation laws and phase space concepts are summarized and applied to determine the feasiblity of an experiment consisting of a photoemitter in a magnetic field, a photoelectron energy analyzer and an electron spin analyzer. For the example of photoemission from a Ni crystal using He I resonance radiation and typical parameters for the energy and spin analyzers, a final signal count rate of approximately 220 counts/s is calculated. Ways to increase the count rate by orders of magnitude are described. In particular, a new experimental configuration is suggested which may avoid the large reduction in count rate caused by the magnetic field.
Simple low-noise power supply for electrical transient measurements
Authors: Vincett P. S.
Published: March 2003

A very simple means is described for rapidly applying and briefly maintaining a large, essentially noiseless, dc voltage across a capacitive load. The technique is suitable for various nonrepetitive electrical transient measurements, such as carrier mobility determination, occurring over timescales ranging from tens of microseconds to several seconds; it essentially eliminates capacitive currents caused by noise in the power supply voltage, which can interfere with measurement of the true transient current. In an example, the noise on a 10-ms transient current (driven by 2000 V dc, and observed as a voltage across a 100-kΩ load resistor) was barely more than the Johnson noise (∼2×10−11 A rms) to be expected from the resistor.
Open vacuum tube in space
Authors: Gonfalone A. A. , Arends H. J.
Published: March 2003

After having reviewed briefly the reliability of vacuum tubes on spacecraft, it is shown that the operation in space of a vacuum tube with an open structure is possible provided adequate measures are taken. The tube considered here is a multielectrode electron gun emitting electrons into space, in order to control the potential of a satellite. To avoid the failure of the most sensitive element of the gun, namely the impregnated tungsten cathode, the gun design includes such characteristics as a slow warming up of the heater element, a reactivation program used in case of cathode contamination, and a clean opening system which is not contaminant. Similarities with communication tubes are considered and the advantages of open tubes are mentioned.
Fast high-voltage high-current switch: Thyratron-spark gap hybrid
Authors: Gibson R. B.
Published: March 2003

A high-voltage high-current switch using a hydrogen thyratron in series with a two-element spark gap is described. The hybrid switch triggers like a thyratron, turns off like a spark gap, and holds off twice the potential of either element alone.
Effects of high-current input pulses upon Channeltrons
Authors: Kurz Edward A.
Published: March 2003

Experiments are described which detail the response of Channeltrons operated at high gains when exposed to large pulsed inputs. Some temporary gain depression was observed. A hypothesis is presented which describes the observed response.
Cell design for pressure to 25 kbar
Authors: Schoutens Jacques E. , Senesac Steven S.
Published: March 2003

A cell design is presented for experiments with hydrostatic pressures up to 25 kbar. The pressure-transmitting medium around the sample is candle wax, which is sealed in the cavity with molybdenum disulfide impregnated nylon and aluminum disks. This approach showed no detectable leakage to 25 kbar. Internal cavity pressure is computed from measurements of the applied load on the top piston, the transmitted load to the lower piston, and the frictional forces transmitted by the seals into the pressure vessel and the cell body. Internal pressure thus measured and phase-transition pressure data from RbCl and KBr are all within 9% of each other for the pressure range 3–25 kbar.
Laser velocimeter method for the inertial sizing of airborne particles
Authors: Russo A. J. , Hackett C. E. , Croll R. H.
Published: March 2003

A method of making real time measurements of airborne particle distributions above 1 μm is described. The method uses laser doppler velocimeter measurements of decelerating particles near the stagnation line of a cylinder in the flow. Experimental results for measurement of distributions in the 10–40 μm range indicate that the method works well in that range.
Compact, pulsed low-pressure far infrared laser for use in plasma diagnostics
Authors: Grossman J. G. , Peebles W. A. , Luhmann N. C. , Semet A.
Published: March 2003

The operation of a pulsed, watt-level, low-pressure far infrared (FIR) laser is described. Single mode output powers of 0.1–1 W are obtained from several molecular gases in the 300–1200 μm region. Plasma diagnostic applications are discussed.
Characteristics of the Berkeley multicusp ion source
Authors: Ehlers K. W. , Leung K. N.
Published: March 2003

The performance of a cubical permanent magnet generated line-cusp ion source has been investigated for use with neutral beam injectors. This source has been operated with discharge currents greater than 500 A and ion current densities higher than 400 mA/cm2 at the extraction grid. The uniformity of the density profile across the extraction area is found to be dependent on the gas pressure. By using a fast Langmuir probe sweeping circuit, the electron temperature and the plasma density and potential have been analyzed for different discharge powers and gas pressures. The heat load on the plasma grid when it is electrically floating or connected to the negative cathode has been compared calorimetrically. The use of lanthanum hexaboride and impregnated oxide cathodes have been investigated for the purpose of long pulse operation. The phenomenon of mode flipping is found to occur quite frequently during a discharge with these magnetic-field-free cathodes. Species composition as a function of discharge power and chamber length is measured by a mass spectrometer.
Novel experimental facility for the study of plane Couette flow
Authors: Aydin Mahir , Leutheusser Hans J.
Published: March 2003

An experimental facility for the realization of plane Couette flow is described. In this, the moving wall is a rigid plate propelled through air by the carriage of a towing channel, and the fixed wall is a stationary bench constructed alongside the towing tank. This particular arrangement makes it possible to introduce the important parameter of wall roughness into experimental investigations of this flow.
Wide bandwidth constant current source for ac galvanomagnetic measurements
Authors: Shacklette L. W.
Published: March 2003

A simple one-op-amp constant current source which has great versatility is described. Its important features include a wide bandwidth (≳10 kHz) and the ability to float from third-wire ground. Applications to three separate types of measurement are included, ac conductivity measurements on ionic conductors, Double-ac Hall effect measurements, and tunneling measurements.
Multiwavelength optical pyrometer for shock compression experiments
Authors: Lyzenga G. A. , Ahrens Thomas J.
Published: March 2003

A system for measurement of the spectral radiance of materials shocked to high pressures (∼100 GPa) by impact using a light gas gun is described. Thermal radiation from the sample is sampled at six wavelength bands in the visible spectrum, and each signal is separately detected by solid-state photodiodes, and recorded with a time resolution of ∼10 ns. Interpretation of the records in terms of temperature of transparent sample materials is discussed. Results of a series of exploratory experiments with metals are also given. Shock temperatures in the range 4000–8000 K have been reliably measured. Spectral radiance and temperatures have been determined with uncertainties of 2%.
Improved circuit for potential fluctuation compensation in the plasma during the electron energy distribution function measurement by a probe
Authors: Matsumura S. , Chen Sin-Li
Published: March 2003

An improved circuit consisting of a simple voltage follower for the measurement of electron energy distribution function in a plasma has been proposed. This circuit makes it possible to eliminate the fluctuation of plasma space potential, the deviation of dc probe voltage caused by the probe current drawing across the plasma resistance, and the attenuation of the second derivative signal during the measurement, simultaneously. Both the probe circuit considerations and the experimental results are presented.
Design and construction of a high temperature and pressure electrodeless conductivity probe
Authors: Koski O. H. , Danielson M. J.
Published: March 2003

An electrodeless conductivity probe has been designed and tested at temperatures up to 250 °C and pressures of 4.13 MPa (600 psi). A unique pressure seal permits temperature cycling. Design of the electronics permits accurate measurement of conductivities at various elevated temperatures in spite of the change of magnetic properties of the toroids with temperature. The design of the probe can be adapted for insertion, in-line, or bypass operation.
Composite torsional quartz transducer for shear ultrasonic measurements of aqueous liquids
Authors: Mitaku Shigeki , Ohsawa Koji , Matoba Akio , Ohtsuki Toshiya , Okano Koji
Published: March 2003

A composite torsional quartz transducer has been developed for the shear ultrasonic measurements of aqueous solutions in the frequency range from 10 to 100 kHz. In order to prevent the electric interaction and low contact angle between the transducer and water, a torsional quartz crystal transducer is attached to a fused quartz rod whose surface is partly gilded by evaporation. The accuracy of ±60 dyn/cm2 for the rigidity and ±0.03 cP for the viscosity is attained by use of this transducer.
Stability characteristics of carbon–glass resistance thermometers
Authors: Besley L. M.
Published: March 2003

Six commercial carbon–glass resistance thermometers have been subjected to thermal cycling between 15 and 300 K and tested for stability at 15, 20, and 27 K. The results reveal no common mode of behaviour but show the stability of these thermometers is an order of magnitude inferior to that of germanium resistance thermometers at these temperatures.
Holder for fast photodiodes in TO-18 package
Authors: Bebelaar Dick
Published: March 2003

The design of a holder for fast photodiodes is described. These holders have been tested with commercially available photodiodes in a standard TO-18 package using delta light pulses from a synchronously pumped cw dye laser. Results of the measurements are presented and the holder is shown to perform well even for an experimental photodiode with a rise time of less than 40 ps and a FWHM of 80 ps.
Simple pressure gauge for uranium hexafluoride
Authors: George Patricia M. , Swanson Mark N. , Beauchamp J. L.
Published: March 2003

A sensitive detector and pressure gauge for uranium hexafluoride in high-vacuum systems is described. Negative surface ionization of UF6 occurs on ribbon filaments operated at temperatures too low for electron emission to be significant. The ion current measured on a cylindrical collector surrounding the filament assembly varies regularly with UF6 pressure below 10−3 Torr. Different filament materials are considered, including rhenium, thoriated tungsten, and platinum. Rhenium is found to be the most satisfactory material for operation of diode emitters as a pressure gauge. Gauge constants (in A Torr−1) are derived from comparing negative surface ionization currents with the response of a capacitance manometer and are shown to be independent of temperature within a reasonable operating range. The effects of exposing the rhenium filament to various gases is considered, and it is shown that brief exposure to acetylene substantially improves the operating characteristics of the gauge.
Simple and economical capacitive displacement system for UHV operation
Authors: Chow Robert , Tiller William A.
Published: March 2003

A parallel plate capacitor was assembled as a displacement transducer for operation in an UHV environment. The capacitive displacement system was linear over a 2.5 μm range with a resolution of 0.051 μm. Components in the electric circuit were common laboratory instruments.
Fast new technique for measuring the resonance frequencies of high Q systems
Authors: Cosmelli Carlo , Frasca Sergio
Published: March 2003

A technique for measuring the resonance frequencies of an aluminum bar (used as a gravitational antenna) with high accuracy is presented. This method is based on the positive feedback of the bar, and is much faster than the others commonly in use.
Reliable, inexpensive microcomputer interface for the optical multichannel analyzer (OMA)
Authors: Holten Dewey , Cremers David A. , Pyke Stephen C. , Selensky Ronald , Shah S. Sadiq , Warner Dewey W. , Windsor Maurice W.
Published: March 2003

A microprocessor system and interface for the optical multichannel analyzer (OMA) is described. The interface hardware and software are very simple and easy to implement. The microcomputer is used in conjunction with the OMA in the 2-d (two-dimensional) mode as the data acquisition, analysis and storage system for a 8-ps-resolution transient absorption spectrometer. However, the microcomputer and interface hardware and software are of general use in any application where rapid transfer, processing and storage of spectroscopic information from the OMA are required.
Thin-foil fabrication
Authors: Kindel F. W. , Reinovsky R. E. , Clark M. C.
Published: March 2003

A method has been developed to produce seamless, freestanding plastic cylinders with dimensions up to 18 cm in diameter, 4 cm in height and with mass density from 15 μg/cm to 300 μg/cm (approximately 0.15 to 3 μ thick). The polyvinyl formal resin may be subsequently coated with a variety of material by vapor deposition. The method employs standard thin-foil fabrication techniques modified for use in cylindrical geometry and results in uniform reproducible cylinders.
Electropolishing the bore of metal capillary tubes: A technique for adjusting the critical flow
Authors: Stoffels J. J. , Ells D. R.
Published: March 2003

A technique has been developed for electropolishing the bore of metal capillary tubes. Although developed specifically for stainless-steel tubes, the technique should be directly applicable to other metals. Tubes with inside diameter as small as 0.20 mm and 110 mm long have been successfully electropolished. The electropolishing technique can be used to increase the critical flow of a capillary tube in a controllable way.
X-ray filter assembly for fluorescence measurements of x-ray absorption fine structure
Authors: Stern Edward A. , Heald Steve M.
Published: March 2003

Fluorescence detection, in principle, permits the detection of the extended x-ray absorption fine structure (EXAFS) of more dilute atoms than can be obtained in absorption. To take advantage of this it is necessary, in practice, to eliminate the background that normally accompanies the fluorescence signal. We describe an x-ray filter assembly that accomplishes this purpose. The unique characteristic of the assembly is a slit system that minimizes the fluorescence background from the filter. The theory of the slit assembly is presented and is found to agree with measurements made on the Fe EXAFS of a dilute sample. The filter assembly has a better effective counting rate in this case than that of a crystal monochromator design.
Mass analyzer using electron-beam-guiding type ion source
Authors: Kishi Tohru , Yamada Isao , Takagi Toshinori
Published: March 2003

A mass analyzer having a scanning electron microscopy (SEM) mechanism and using electron beam bombardment vaporization ion source have been submitted. Secondary ions from the surface trapped in the potential well formed by the incident electron beam can be guided into the slit of mass analyzer through the center of Ta pipe cathode. Efficiency of the collected ions to the evaporated molecules and a qualitative mass analysis with a pressed block of powdered NaCl have been examined. When subsidiary electrodes added above efficiency showed 6.4×10−4. A sample of 10-mm-thick NaCl has been analyzed along depth direction to the bottom with 0.02 mA at 5 kV in 16 min.
Computer-controlled system for measuring two-dimensional acoustic velocity fields
Authors: Ilić D. B. , Kino G. S. , Selfridge A. R.
Published: March 2003

An automatic system is described for measuring two-dimensional acoustic velocity fields in solid samples. The measurement is performed by a computer-controlled, mechanically scanned transducer in a liquid bath, and is based on measuring the phase delay of the acoustic wave by a two-pulse echo method. Applications include measuring stress fields due both to externally applied and residual stresses, and microstructure studies of solid samples.
Properties and operation of a 90° spherical deflector as photoelectron energy analyzer in connection with spin-polarization measurements by Mott scattering
Authors: Kisker E. , Campagna M. , Gudat W. , Kuhlmann E.
Published: March 2003

We discuss the electron-optical properties of the 90° spherical analyzer. A nearly parallel electron beam which can be extracted from a magnetic photocathode in an external magnetic field under suitable conditions is focused to the exit plane of the analyzer. Electron spin polarization detection using Mott scattering can be advantageously combined with such a 90° electron spectrometer so as to achieve energy analysis in spin-polarized photoemission. In this case the diaphragms of the Mott scattering detector play the role of virtual exit slits of the electron spectrometer. Thereby, the limits for variations of the apparatus asymmetry of the Mott scattering setup become reduced, eliminating the need of measuring this quantity in separate measurements.
Quartz tube orifice leaks for local, fast-response gas sampling to mass spectrometers
Authors: Kasemo B.
Published: March 2003

Simple and versatile quartz tube orifice leaks, suitable for sampling of gas mixtures to mass spectrometers, have been made by heating the tip of a quartz tube in a hydrogen–oxygen flame. With these leaks the requirement of expensive and clumsy differential pumping stages is removed. The quartz probes have been used in gas sampling from catalytic reaction cells at 1 atm to a mass spectrometer. The sampling position can be located within 0.1 mm from the catalyst. Continuous recording of the local gas composition is then achieved with a response time of about 0.05 s, and with a minimum perturbation of the gas flow. The probes have been used in ambient air and at temperatures around 1000 K for extended periods of time without deterioration or plugging. The high stability at elevated temperatures and chemical resistance seem to make these probes useful for various applications, e.g., in sampling from combustion flames. The gas flow through the leak is determined by a very short and narrow constriction at the tube tip. In a leak with a throughput of 1×10−4 Torr l/s at 1 atm inlet pressure, the constriction has a diameter of 5–7×10−4 cm and a length of about 0.015. cm.
Spectral analyzer for Thomson scattering
Authors: DeSilva A. W.
Published: March 2003

We describe here a four-channel spectral analyzer suitable for use in Thomson scattering diagnostics of plasmas, that incorporates several novel features and is inexpensive and physically compact. It is suitable for spectral analysis of light scattered from plasmas having densities down to ∼1014 cm−3 and temperatures up to several hundred electron volts.
Focusing x-ray spectrograph for laser fusion experiments
Authors: Yaakobi B. , Turner R. E. , Schnopper H. W. , Taylor P. O.
Published: March 2003

X-ray spectra from laser fusion targets are normally measured with flat crystal (nonfocusing) spectrographs. We describe here the characteristics of a focusing spectrograph which is capable of recording wide band spectra with significantly higher sensitivity. Measuring spectra in the (10–11) Å range from glass microballoons imploded by a two-beam Nd:Glass laser system we find intensity per unit area on film about 100 times higher with a curved mica than with a flat mica spectrograph.
Wave-number stability of a laser diode mounted in a closed cycle helium refrigerator
Authors: Steinberg G. N.
Published: March 2003

The wave-number stability of a laser diode mounted in a closed cycle helium refrigerator was examined using a CO2 laser heterodyne spectrometer. The set current supplied by a commercial laser diode supply appeared stable enough over the time periods normally used. Temperature control was achieved through both passive and active loop control. A stage of open loop control of the cold tip allowed the closed loop control of diode heat sink to be operated at higher gains than conventionally used. Long-term stability of the center of the line shape function was better than 10 MHz per hour and the 1-min average was better than ±5 MHz. Vibration of the diode mount determined the instrument line shape in spite of steps taken to eliminate the vibrations. The line shape had a half-width of 10 MHz with broad shoulders out to 50 MHz.
Device for reusing damaged laser mirrors
Authors: Prasad C. R. , Yoganarasimha A. , Venkateshan S. P.
Published: March 2003

A simple mirror holder which permits the use of locally damaged laser morrors by allowing the undamaged areas of the reflector to be aligned along the laser optic axis is described. The mirror holder has an eccentric step for housing the mirror and a concentric aperture through which the undamaged surface of the reflector is utilised. By varying the eccentricity and by rotating the mirror inside the step the entire surface area of the reflector can be used successively.
Variable resolution capability for multichannel filter spectrometers
Authors: Henry P. S.
Published: March 2003

In this paper we describe a new electronic instrument called a spectrum expander, which is a two-port digital signal-processing device whose output power spectrum Sout(Ef) is (approximately) a frequency-expanded replica of its input spectrum Sin(f): Sout(Ef) ≈Sin(f), where E is the expansion ratio (usually E>2). When inserted between a signal source and a spectrometer, the spectrum expander improves the effective resolution of the spectrometer, thereby permitting real-time, high-resolution measurements to be made. This capability is especially important in radio astronomy, where fixed-resolution multichannel filter spectrometers are common. Our treatment of the spectrum expander includes a discussion of its basic principles, formulation of design rules, a brief study of random noise and quantization effects, and presentation of data illustrating expander performance. The prototype expander, constructed from Schottky–TTL components, accepts any signal of bandwidth⩽12.5 MHz and expands it to fill a 128-channel spectrometer with 32-MHz total bandwidth. Signal degradation caused by processing with the spectrum expander is minimal; the signal-to-noise ratio at its output is measured to be ∼0.1 dB lower than at its input.
Fast recovery, high sensitivity NMR probe and preamplifier for low frequencies
Authors: Hoult D. I.
Published: March 2003

The design of a probe-preamplifier combination which reduces the NMR receiver recovery time following a pulse by a factor of at least twenty at 5 MHz is described. The preamplifier, which has a noise figure of 1.3 dB, employs negative feedback to damp the probe coil (a typical effective Q is 7), but maintains the signal-to-noise ratio that one would expect from an undamped coil. In addition, the use of a short phase-inverted pulse following the main transmitter pulse serves to reduce drastically the ring-down of the probe for those high voltages where the preamplifier is inoperative. Optimum utilization of transmitter power in achieving fast pulse rise times is also discussed, as well as elimination of ’’phase-glitch’’ by proper tuning and the use of a broadband transmitter.
Inflection-point method of interpreting emissive probe characteristics
Authors: Smith J. R. , Hershkowitz N. , Coakley P.
Published: March 2003

The use of emissive Langmuir probes in unmagnetized and weakly magnetized multidipole plasmas is investigated. It is shown that plasma potential, plasma electron temperature, and probe temperature can be determined from one probe characteristic curve. Data indicate that the inflection point of the current-voltage curve gives the plasma potential to an accuracy the order of the probe temperature Tw/e for weak probe emission. Effects of space-charge limiting and contamination of the probe are presented.
Control of ultralow pressures: an absolute thermodynamic manometer
Authors: Taborek Peter , Goodstein David
Published: March 2003

A method of accurately manipulating the pressure of helium gas in the range P=10−1 to 10−20 Torr, T<5 K is presented. The method requires only a very modest apparatus and makes use of thermodynamic measurements on the 4He–Grafoil system. A calibration curve and a pressure scale for the manometer are developed which will allow convenient application in other laboratories. An experiment which utilizes the technique is briefly disscussed.
Nanosecond response ’’gasket-type’’ magnetic loop current monitor for relativistic electron beam current measurements
Authors: Copeland Richard L. , Adamski John L. , Doggett Wesley O. , Morrow David L. , Bennett Willard H.
Published: March 2003

A fast response magnetic loop current monitor has been developed to measure relativistic electron beam return currents. The monitor has a rise time of about a nanosecond and a high degree of symmetry with moderate sensitivity, variable from about 1 to 10 V/kA. This simple monitor, with a thickness of 0.254 mm or less, is thin enough to be placed between segments of return current path in the diode or drift tube regions, is insensitive to flashover, beam and plasma bombardment, and radiation effects, and measures net current, thus offering some advantages over conventional magnetic probes, since the main components are outside of the vacuum region. Design criteria, an equivalent circuit analysis, and typical calibration waveforms are presented. Experimental current measurements for a pinched electron beam diode configuration using both conventional magnetic probes and ’’gasket-type’’current monitors with the FX-75 relativistic electron beam accelerator are presented.
Semiautomatic bridge for high-precision dc resistance measurements on pure metals at low temperatures
Authors: van Kempen H. , Neyenhuisen H. W. , Ribot J. H. J. M.
Published: March 2003

A self-balancing bridge system with a dc current comparator and a superconducting flux-gated galvanometer is described. The bridge is capable of measuring small resistances (10−4–10−7 Ω) at liquid helium temperatures with an accuracy of 1 ppm.
Wide energy range mass spectrograph
Authors: Wägli P.
Published: March 2003

The design and construction of a mass spectrograph, for the diagnostics of fast pulsed sources, is described. It is intended particularly for measurements on laser generated plasma. The special features of the instrument are a broad energy passband (Emax/Emin=5) and simultaneous energy independent mass-focusing for a mass range of (m/z)max/(m/z)min=4. The resolutions of the mass and energy spectra, respectively, are (m/Δm) =30 and Δε/ε=0.01. A theoretical analysis of the ion-optics is presented together with test results.
Energy distribution of output electrons from a single channel electron multiplier
Authors: Koshida Nobuyoshi , Yoshida Shigetomo
Published: March 2003

The fundamental characteristics of the energy distribution of output electrons from a single channel electron multiplier were studied experimentally in detail for a few types of straight channels. The width of the energy distribution curve, ranging from about 50 to 15 eV FWHM, is found to depend on the applied voltage VA and the length-to-diameter ratio α of the channel, and to vary with output current. The results can be explained in terms of the normalized field strength near the output end of the channel and generalized by a set of universal curves presenting the energy width as a function of output current level for different values of VA/α.
Temperature control of a tungsten incadescent lamp
Authors: Masi Charles G.
Published: March 2003

A thermostatic control for a tungsten incadescent lamp is described. The circuit employs an operational amplifier feedback circuit to adjust the filament current and thereby achieve a constant filament temperature. The filament temperature is adjustable over a wide range by adjusting a potentimeter. Since the calibration of the thermostat does not, in principle, require temperature or radiometric measurements, the design may be useful in setting up a primary radiometric standard.
Double frequency narrow-band grazing incidence pulsed dye lasers
Authors: Prior Yehiam
Published: March 2003

A double frequency operation of the recently introduced grazing angle dye laser is demonstrated. By using two mirrors to reflect different order of diffraction the laser oscillates at two different frequencies, independently tunable over the entire gain profile of the dye.
Magnetically collimated electron impact spectrometer
Authors: Tam Wing-Cheung , Wong S. F.
Published: March 2003

A new type of electron impact spectrometer using an axial magnetic field for electron collimation is described. The feasibility of this apparatus for collision studies at low impact energies (0.1−30 eV) is demonstrated with vibrational and electronic excitation in He, N2, CO, and C2H2. The potentials and limitations of this new approach are also discussed.
Pressure apparatus of split-octahedron type for x-ray diffraction studies
Authors: Ohtani Akihito , Onodera Akifumi , Kawai Naoto
Published: March 2003

An apparatus of split-octahedron type has been developed for the study of x-ray diffraction at high pressure. The apparatus consists of a cylinder, a sphere, and an octahedron, all split up and assembled in a multistaged arrangement. Three ways of splitting the innermost octahedron are utilized in matching the cell geometry to the standard camera method. High pressures in excess of 220 kilobars can be generated in the center of the split octahedron by using a composite mixture of diamond powder and epoxy resin as a pressure-transmitting medium. The pressures required for the semiconductor-to-metal transitions of ZnTe, ZnS, GaAs, and GaP are determined by simultaneously monitoring the electrical resistance of the semiconductors and the lattice parameter of sodium chloride.
High pressure cell for Raman scattering at low temperatures
Authors: Jodl H. J. , Holzapfel W. B.
Published: March 2003

An optical cell suitable for Raman studies and for absorption studies of gases, liquids, and solids is described. The cell has been used at temperatures down to 4.2 K and pressures up to 10 kilobars. It contains a sample chamber with special scattering geometry and a ruby manometer for in situ pressure measurements. Typical results are given for the impurity induced one phonon Raman spectra of doped alkali halides and for the fundamental vibrational Raman spectra of matrix-isolated molecules under pressure.
Wavelength dispersion of optical fibers directly measured by ’’difference method’’ in the 0.8–1.6 μm range
Authors: Sugimura Akira , Daikoku Kazuhiro
Published: March 2003

A novel technique to measure the wavelength dispersion of optical fibers in the 0.8–1.6 μm range, where germanium avalanche photodiodes possess adequate quantum efficiency, is described. Dispersion is defined as dτ/dλ, which can safely be changed to the difference formula Δτ/Δλ, when Δλ is small, where τ is the transit time of the wave and λ is the light wavelength. A monochromatic light, whose amplitude is modulated by a sinusoidal baseband signal, is launched into the optical fiber. The phase of the sinusoidal baseband signal changes with the monochromatic light wavelength variation due to the dispersion of the fiber. The phase variation gives an accurate value of Δτ. The wavelength dispersion is obtained directly from the values of both Δτ and Δλ. Using this technique, the wavelength dispersion of a single mode optical fiber, for example, is measured in the single mode wavelength range from 0.92 to about 1.6 μm.
RC-encoding for position-sensitive proportional counters using low-resistance, metal-wire anode and active load capacitance
Authors: Kopp M. K.
Published: March 2003

We developed a feedback-stabilized, active load-capacitance to use low-resistance, metal-wire anodes in RC-line encoded, position-sensitive proportional counters (PSPCs) of any length. A 12-cm-long experimental PSPC was tested using a 12-μm-diam Nichrome wire anode and an ∼21 pF active load capacitance. The spatial sensitivity and resolution are equivalent to those of similar PSPC with a carbon-coated quartz anode; but the ruggedness, ease of handling, and stability at high count rates are distinct advantages of the metal-wire anode.
Pulsed blowdown—electron gun facility for low-temperature and high-pressure supersonic flow electronic transition lasers
Authors: Forestier B. , Fontaine B.
Published: March 2003

The design of a small compact pulsed blowdown apparatus coupled to a cold cathode electron gun is described. This system allows the excitation of a gas mixture in supersonic flow at temperatures of 80 and 120 K and density of 1 amagat with a maximum electron beam current density of 20 A cm−2 at 300 kV and pulse length of 0.5 μs. With this facility it has been possible, using aerodynamic cooling, to achieve high-power, long-pulse ultraviolet laser operation in a high-pressure active medium on XeF and Ne ii ion transitions. A strong increase in fluorescence intensity was also obtained for numerous atomic lines and molecular bands of interest for the developement of high-power, high-efficiency, visible and ultraviolet lasers.
Cylindrical crossed-coil NMR limb blood flowmeter
Authors: Halbach R. E. , Battocletti J. H. , Sances A. , Bowman R. L. , Kudravcev V.
Published: March 2003

A nuclear magnetic resonance (NMR) flowmeter has been developed for noninvasive measurement of upper extremity blood flow in humans. Flow through major arteries and veins is determined by placing the arm into a 12.5-cm i.d. crossed-coil detector structure, contained in a 0.075 T (750 G) steady detector field. Venous flow is measured by passage of a demagnetized bolus of blood, generated by periodic application of a radio-frequency tagger field upstream from the detector. The self tag technique is applied to arterial flow. Detector output is a direct function of the pulsatile component of arterial volume flow, within the range of linear operation. Consideration has been given in flowmeter design to sensitivity, long term stability, and ease of operation.
New difference reflectance methods for study of small interfacial effects
Authors: Huber Edward D. , Sari S. O.
Published: March 2003

Two sensitive differential optical techniques useful for study of small reflectance or absorptive differences between two interfaces are described. The first scheme employs a mechanically chopped light beam impinging on an arrangement of symmetrical dual cells to allow detection of differential reflectances ΔR/R<10−3. The second is a polarization-modulated beam-split laser version of the same method yielding approximately the same sensitivity. Representative measurements of voltage-induced reflectance changes at liquid–solid interfaces using these methods are given.
Improved 10B-loaded liquid scintillator with pulse-shape discrimination
Authors: Greenwood L. R. , Chellew N. R.
Published: March 2003

An improved 10B-loaded liquid scintillator solution has been developed containing trimethylborate, 1-methylnaphthalene, and 9,10-diphenylanthracene. Cells up to 5 cm in diameter by 15.2 cm long have been prepared and tested with 10B-loadings up to 7.2% by weight (80% trimethylborate). The solution has excellent light output and pulse-shape discrimination properties and is stable at temperatures as low as −17°C. Neutron efficiency calculations are also presented.