bluuebunny/crossref_metadata_2025 huggingface dataset:
Electronic detector for conducting particles and fibrils
Authors: Shelton R. D. , Morrissey J. A.
Published: March 2003

When small airborne conducting particles and fibrils strike a conducting surface with an electric charge distribution on it, they acquire charge and are repelled from the surface. If the conducting surface is connected to a power supply of constant potential, a charging pulse is observed as each particle or fibril makes contact with the surface. A collection of such charging pulses can be processed by a pulse height analyzer to yield information about the size and frequency of conducting airborne particles.
Device for helical marking of cylindrical specimens
Authors: Domkowski Alexander J. , Burroughs Jo J. , Nicholson James E.
Published: March 2003

A device is described for holding and scratching to variable depth, small diameter wires extruded from soft metals. Drawings and relative dimensions are shown. Adescription of the helical guide strips used in the device is also contained.
Fiber optic probe for thermal profiling of liquids during crystal growth
Authors: Holmes D. E.
Published: March 2003

The applicability of quartz opitcal fibers to the thermal characterization of liquid solutions and melts during crystal growth was demonstrated in a Ga–As solution at 800°C. The measured response time and signal-to-noise ratio were 0.7 s and 71 dB, respectively. Fiber probes offer greater responsivity with less disturbance to fluid flow than conventional thermocouples with protective sheaths and are particularly suited for the investigation of semiconductor crystal growth.
Double-pendulum vibration isolator with three-dimensional isolation
Authors: Lorrain Paul
Published: March 2003

This isolator is an improved version of one that was described recently in this journal. It consists of a platform suspended by three springs, the damping being provided by a much smaller mass, suspended from the platform by a spring and damped in an oil bath. This simple device is a highly effective isolator, with a weak resonance peak and a transmissibility that decreases as 1/f2, both horizontally and vertically. None of the parameters are critical.
Concerning the instrumental profile of a double monochromator
Authors: Proffitt Michael H. , Frommhold Lothar
Published: March 2003

The response of a monochromator to an intense line, the so-called instrumental profile or slit function, is studied over a range of signals comprising seven orders of magnitude, which corresponds to a maximum frequency shift of about five times the slit width. For a 1-m double monochromator with concave, holographic gratings, the observed profile is approximately described by diffraction theory except for the extreme wings.
Uniform stress conditions in the diamond anvil cell at 200 kilobars
Authors: Besson J. M. , Pinceaux J. P.
Published: March 2003

Pressure gradients in a diamond anvil cell have been measured with a 4:1 methanol:ethanol mixture as a pressure medium up to 350 kilobars. When pressure is applied rapidly, stress gradients are shown to be negligible up to 200 kilobars and probably above. With this procedure it is possible to significantly increase the precision of pressure measurements above 100 kilobars.
Momentum transmission of a diaphragmed magnetic spectrometer: I. Analysis and definitions
Authors: Sanna G. , Donnetti M.
Published: March 2003

An experimental device consisting of a plane source of charged particles and of a magnetic spectrometer equipped with horizontal and vertical diaphragms is considered. An analysis intended to achieve an exact analytical expression to connect the observed particle flux to the source emission and spectrometer transmission characteristics is developed. An analytical expression for the average value of the source brightness that is actually obtained from corpuscular flux measurements is also given. The effectiveness of the diaphragms in defining the domains of the initial conditions of the particles is also emphasized and general definitions of these domains are introduced. These definitions are stated for exact optical transformations, i.e., accounting for geometric and chromatic aberrations, and for general positions of the diaphragms along the optical axis as well as for symmetrical or asymmetrical apertures of the same. The results obtained and the introduced definitions will be used in Part II of this work. The important case of a thick source is considered in Appendix A.
Momemtum transmission of a diaphragmed magnetic spectrometer: II. First-order calculations
Authors: Sanna G. , Donnetti M.
Published: March 2003

On the basis of the analysis developed in Part I and of the definitions therein introduced, a procedure for the calculation in the Gaussian approximation of the integral quantities characterizing the momentum transmission of a magnetic spectrometer is carried out. Such procedure applies both to symmetrical or asymmetrical diaphragm apertures and for diaphragms located anywhere along the optical axis.
Design and construction of an automatic thin film fabrication and simultaneous computer-controlled measurement equipment built in a cryostat
Authors: Chakupurakal Thomas
Published: March 2003

The classical way of preparing thin films under one set of conditions and measurement of their properties under a different set of conditions produces large variations in film properties. A system has been designed which provides for measurements of many thin film parameters without removal from the deposition chamber. These parameters include thickness as well as film structural, electrical, and magnetic properties. Such an automatic film fabrication/measurement equipment is highly desirable for thin film research.
Bosi’s method for solving Laplace’s equation
Authors: Lee-Whiting G. E.
Published: March 2003

Conformal mapping is used to obtain an implicit solution for a slightly specialized version of a planar electrostatic mirror for which Bosi claims to have obtained an exact solution by means of a Taylor series in the ratio of two dimensions. It is shown that the intervention of logarithmic terms invalidates Bosi’s series after the first-order term. Comparison of Bosi’s series for cylindrical and spherical mirrors with the exact expansion for an analogous planar problem suggests that in these cases not even the first-order terms are valid.
High-pass photocathode x-ray ionization chamber for surface EXAFS
Authors: Shevchik N. J. , Fischer D. A.
Published: March 2003

An x-ray detector that collects electrons emitted from a cathode plate and amplifies them through field intensified ionization in helium gas is described. The sensitivity of the detector to the photon frequency increases by nearly an order of magnitude as the photon energy exceeds the absorption edge of the photocathode. The detector current as a function of the x-ray frequency is shown to yield the extended x-ray absorption fine structure (EXAFS) of layers of copper as thin as 30 Å in a few minutes.
Picosecond photodetector for 257 nm to 1 μm laser pulses
Authors: Steinmetz Lloyd L.
Published: March 2003

Picasecond temporal response and broad spectral response photodetectors have been fabricated using commercially available diode chips. Improved photoresponse sensitivity is achieved by removing the anode gold contact which obscures the active region. Junction geometry is such that the depletion region is approximately normal to the surface being illuminated, making the device especially useful for fast UV photodetection.
Alternative methods for determining the electrical conductivity of core samples
Authors: Lytle R. J. , Duba A. G. , Willows J. L.
Published: March 2003

Electrode configurations are described that can be used in measuring the electrical conductivity of a core sample and that do not require access to the core end faces. The use of these configurations eliminates the need for machining the core ends for placement of end electrodes. This is because the conductivity in the cases described is relatively insensitive to the length of the sample. We validated the measurement technique by comparing mathematical models with actual measurements that were made perpendicular and paralled to the core axis of granite samples.
New type of self-excited oscillator
Authors: Lambeck M.
Published: March 2003

Using a novel feedback technique an oscillator generates nonresonant LC oscillations whose frequency increases with increasing damping of the circuit. Applications for contactless measurement of the conductivity, permeability, diameter, and thickness of materials, and displacement measurements are discussed.
Experimental determination of probe-length requirements for studies of the turbulent wake behind a cylinder
Authors: Sheih C. M. , Finnigan J. J. , Bradley E. F. , Mulhearn P. J.
Published: March 2003

The attenuation of turbulence and mean velocity signals due to the line averaging imposed by hot wires when used in the wake of an isolated circular cylinder has been investigated in a wind tunnel by measurements using several choices of hot-wire length, cylinder diameter, and freestream mean velocity. The results are presented graphically in order to provide a practical method for determining attenuation of the turbulence and mean velocity signals obtained in a wake. The length scale of the wake can be defined as L=0.6[(x−xo) d]1/2, where x is the downstream distance from the cylinder, d is the cylinder diameter, and xo=25d. For all the wires tested, the attenuation of the measured turbulence signal is limited to within 5% only if the wire length is smaller than 0.1 L. For a wire normal to the cylinder and cross wind, the attenuation of the signal of the mean velocity-defect factor, expressed as (1−u/u∞), where u and u∞ are local and free-stream velocities, respectively, is less than 5% only if the wire is less than 0.5 L in length.
Shielding of longitudinal magnetic fields with thin, closely spaced, concentric cylinders of high permeability material
Authors: Gubser D. U. , Wolf S. A. , Cox J. E.
Published: March 2003

Formulae for the longitudinal shielding effectiveness of N thin, closely spaced, concentric cylinders of high permeability material have been developed and experimentally tested. For shields which cannot be oriented, or which change their orientation in the ambient field, the shielding effectiveness for longitudinal fields is generally the limiting criterion and no design formulae have previously been published for more than two shields. A simple diagrammatical method of writing the shielding formula is presented. Use of these equations is demonstrated by application to the design of magnetic shields for hydrogen maser atomic clocks. Examples of design tradeoffs such as size, weight, and material thickness are discussed. Experimental data on three sets of shields fabricated by three manufacturers are presented.
Cold-stage microscopy system for fast-frozen liquids
Authors: Talmon Yeshayahu , Davis H. Ted , Scriven L. E. , Thomas Edwin L.
Published: March 2003

The least artifact-laden fixation technique for examining colloidal suspensions, microemulsions, and other microstructured liquids in the electron microscope appears to be thermal fixation, i.e., ultrafast freezing of the liquid specimen. For rapid-enough cooling and for observation in TEM/STEM a thin sample is needed. The need is met by trapping a thin layer (∼100 nm) of liquid between two polyimide films (∼40 nm thickness) mounted on copper grids and immersing the resulting sandwich in liquid nitrogen at its melting point. For liquids containing water, polyimides films are used since this polymer is far less susceptible to the electron beam damage observed for the commonly used polymer films such as Formvar and collodion in contact with ice. Transfer of the frozen sample into the microscope column without deleterious frost deposition and warming is accomplished with a new transfer module for the cooling stage of the JEOL JEM-100CX microscope, which makes a true cold stage out of a device originally intended for cooling specimens inside the column. Sample results obtained with the new fast-freeze, cold-stage microscopy system are given.
High-intensity x-ray diffraction apparatus for pressures up to 100 kilobars and temperatures down to 1.5 K
Authors: Thorwarth E. , Dietrich M.
Published: March 2003

A high-pressure diamond anvil pressure technique for x-ray structure investigations at temperatures down to 1.5 K is described. An energy dispersive method in conjunction with a newly developed conical x-ray shutter brings maximum intensity to the adjacent germanium detector. Superconductivity is detected by use of a SQUID. The 4096-channel analyzer data are evaluated on-line by a computer. The precision of the lattice parameter determination is discussed.
Spurious pulse rejection in a photon correlation experiment
Authors: Walraven Robert , Yeh Yin
Published: March 2003

A method has been developed to significantly suppress the effect of spurious pulses on the correlation spectrum in photon correlation experiments. When the correlation experiment is operated at a low count rate (<2 true pulses per total measured correlation time), the circuit rejects an incoming pulse stream whenever more than two pulses are detected in that interval. Details of this spurious noise pulse rejection circuit are presented. This circuit has been incorporated into an existing correlation computer system as an option selected by the operator. Application of this circuit to a test case where the spurious pulse correlations were excessive compared with the signal events yielded very accurate signal correlation spectra.
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u creep testing during irradiation with high-energy neutrons from a planar neutron source
Authors: Barmore W. L. , Ruotola A. W. , Vandervoort R. R.
Published: March 2003

An apparatus is described for investigating the in situ creep behavior of materials during irradiation with neutrons having a spectrum similar to that of a fusion power reactor. Techniques are discussed for remote, high-vacuum creep testing during irradiation with high-energy neutrons from a planar Be(d,n) source used on the 1.93-m Isochronous Cyclotron at the University of California at Davis. Significant effects of radiation damage on the creep of niobium at a flux of 2×1016 n⋅m−2 s−1 are reported.
Feedback-stabilized fractional fringe laser interferometer for plasma density measurements
Authors: Schneider John , Robertson Scott
Published: March 2003

A feedback stabilization technique is described for a fractional fringe interferometer measuring plasma electron densities. Using this technique, a CO2 laser Michelson interferometer with a pyroelectric detector exhibited a sensitivity of 3.4×10−4 fringe on a 1-ms time scale and, due to acoustic pickup, 1.8×10−2 fringe on a 10-ms time scale. The rise time is 45 μs. Stabilization against slow drifts in mirror distances is achieved by an electromechanically translated mirror driven by a servo system having a 0.2-s response time. A mechanical chopper in one of the two beam paths generates the signal which drives the servo system.
Application of direct current comparator apparatus in combustion calorimetry
Authors: Jochems Ria , Dekker Harm , Mosselman Cornelis
Published: March 2003

A method was developed for the application of direct current comparator apparatus in resistance thermometry and in voltage measurements in combustion calorimetry. The performance of the measuring system was checked by combustions of benzoic acid combined with electrical calibration of the calorimeter.
Fast ion beam–plasma interaction system
Authors: Breun R. A. , Ferron J. R.
Published: March 2003

A device has been constructed for the study of the interaction between a fast ion beam and a target plasma of separately controllable parameters. The beam of either hydrogen or helium ions has an energy of 1–4 keV and a total current of 0.5–2 A. The beam energy and beam current can be varied separately. The ion source plasma is created by a pulsed (0.2–10-ms pulse length) discharge in neutral gas at up to 3×10−3 Torr. The neutrals are pulsed into the source chamber, allowing the neutral pressure in the target region to remain less than 5×10−5 Torr at a 2-Hz repetition rate. The creation of the source plasma can be described by a simple set of equations which predict optimum source design parameters. The target plasma is also produced by a pulsed discharge. Between the target and source chambers the beam is neutralized by electrons drawn from a set of hot filaments. Currently under study is an unstable wave in a field-free plasma excited when the beam velocity is nearly equal to the target electron thermal velocity (vbeam≈3.5×107 cm/s, Te=0.5 eV).
Sensing volume and biasing corrections for dual counter LDA processors
Authors: Shemer Lev , Einav Shmuel
Published: March 2003

Most operable Laser Doppler Anemometry (LDA) systems employ the fringe mode geometrical configuration with a counting type signal processor. The fringes are contained within an ellipsoid volume, which is commonly described as the sensing volume of the LDA. Generally, the dimensions of the focusing volume are determined from the waist diameter of the beams and their intersection angle. However, the electronic processing system exerts several constraints upon the size of the focusing volume. In this study we will address ourselves to the constraints of the dual counter processing system, which is based on the individual realization mode of the LDA. Correction equations will be derived for the sensing volume and the individual realization biasing and applied to two-component flow fields, measured by a one-dimensional LDA system.
Frequency multiplexer for ultrasonic Doppler blood flow signals
Authors: Thomson F. J.
Published: March 2003

An instrument is described which uses single-sideband techniques to combine two channels of Doppler flow signals into a form suitable for simultaneous processing by a single-channel real-time spectral analyzer. The maximum input frequency range is 50 Hz to 10 kHz.
Microscopy in electron diffraction apparatus
Authors: Yamaguchi S.
Published: March 2003

A simple method was devised for observing electron micrographs as well as diffraction figures from a given object. A dielectric emulsion composed of paraffin and barium titanate acted here as an electrostatic lens when charged up with the incident electrons. Electron diffraction figures could immediately be observed from the same object as for microscopy when the lens was mechanically removed out of the electron path.
Semiautomatic mutual inductance bridge for magnetic susceptibility measurements
Authors: Kumano Masafumi , Ikegami Yusaku
Published: March 2003

A semiautomatic Hartshorn bridge has been designed to improve the complicated adjusting procedures of the bridge in the measurements of magnetic susceptibilities. The bridge is useful for a continuous recording of the susceptibility of a sample, especially when it varies with time.
Portable optical particle (0.06 μm) counter
Authors: Suda Kyo , Handa Takashi
Published: March 2003

An improved portable optical counter, using a He–Ne laser with 8 mW output, measures particles ranging in size from 0.06 to 10 μm in diameter in situ.
Stable, inexpensive, low-frequency sine wave generator using digital techniques
Authors: Podolske James
Published: March 2003

Presented is a circuit for the generation of low-frequency (0.001 Hz to 63 kHz) sine waves possessing stable amplitude and frequency characteristics using digital techniques. The circuit produces a 32-step approximation to a sine wave at a frequency 1/32nd of the selected digital time-base frequency. Also presented are a crystal-controlled time base to drive the generator, and an active filter for removing the high-order harmonics produced by the generator. Advantages of the digital sine wave generator over analog oscillator techniques are described.
Single-photon counting system for measuring laser parameters
Authors: Miller T. G. , Womack D. R. , Williams J. R. , Monahan M. J. , Murphree Q. C.
Published: March 2003

A single-photon counting system has been developed for measuring gas laser parameters. A linear accelerator provides nanosecond-wide pulses of heavy charged particles which are injected into a specially designed cell. The charged particles excite gas mixtures, and the temporal response of the emitted radiation is observed as a function of wavelength. The resulting data is analyzed to obtain pertinent parameters such as excited-state lifetimes, reaction rate constants, and quenching rate constants. At the present time nuclear pumper laser candidate gases are being examined.
A new type of x-ray absorption spectrometer
Authors: Bahgat A. A. , Gupta K. Das
Published: March 2003

A single-crystal spectrometer for x-ray absorption and emission with a microfocus x-ray source has been set up so that the divergent rays from the source can be analyzed over a wide range of Bragg angles with a high degree of resolution. The covered energy interval depends upon the exposed width of the crystal and the geometrical setup. Preliminary experiments are presented to show the effectiveness of the spectrometer.
A fast-scanning heterodyne receiver for measurement of the electron cyclotron emission from high-temperature plasmas
Authors: Efthimion P. C. , Arunasalam V. , Bitzer R. , Campbell L. , Hosea J. C.
Published: March 2003

We have developed a fast-scanning heterodyne receiver into a plasma diagnostic that measures the fundamental cyclotron emission from the PLT plasma and thus ascertains the time evolution of the electron temperature profile. The receiver scans 60–90 GHz every 10 ms and is interfaced to a computer for completely automated calibrated temperature measurements.
Recent studies of float and stall curves in controlled-clearance deadweight testers with a simple piston
Authors: Newhall D. H. , Ogawa I. , Zilberstein V.
Published: March 2003

The effect of piston rotation speed and fluid viscosity on the performance of free-piston gauges with a controlled clearance was studied as part of an experimental program aiming at the better evaluation of pressure by these primary pressure standards. Calculated effective area is shown to be greatly influenced by both speed of rotation and choice of a fluid. An optimum rpm resulting in the smallest possible uncertainty in effective area should be determined experimentally for each fluid and pressure range involved. When all the pertinent parameters are properly selected an appreciable improvement in accuracy can be achieved.
Vacuum photodiode detector array for broadband UV detection in a tokamak plasma
Authors: Zweben S. J. , Menyuk C. R. , Taylor R. J.
Published: March 2003

An array of vacuum photodiode detectors has been used to monitor discharge equilibrium, stability, and cleanliness in the Macrotor tokamak. These detectors use the photoelectric effect on small tungsten plates to measure UV emission in the band λ∼200–1200 Å, and so are sensitive mainly to impurity line radiation in Macrotor. The response of this system to controlled impurity contamination experiments and to disruptions is described. The design, construction, and background problems associated with these detectors are discussed in detail.
Automatic measurement of temperature in a nuclear reactor
Authors: Youssefkhani A.
Published: March 2003

A circuit has been developed to display the temperatures measured using platinum resistance thermometers. The thermometer number and the temperature are displayed sequentially together with the highest temperature and the number of the corresponding thermometer.
Low-distortion resistive anodes for two-dimensional position-sensitive MCP systems
Authors: Lampton M. , Carlson C. W.
Published: March 2003

Microchannel plates (MCPs) are frequently employed with resistive anodes to detect charged particles or photons and yield analog signals from which event positions can be decoded. We discuss an anode geometry devised by C.W. Gear that offers theoretically distortionless encoding of Cartesian event positions into pulse charge ratios. Electron beam images taken with such an anode are shown, and confirm the usefulness of the approach.
A new instrument for measuring surface pressure
Authors: Stenberg M. , Löfgren H.
Published: March 2003

A new instrument for surface pressure measurements using a floating-foil technique has been constructed. The instrument makes use of a probe in the form of a thin foil suspended at the gas/liquid or liquid/liquid interface tension. The present instrument has a dynamic range of 0.1–70 mN/m and a sensitivity better than 0.1 mN/m. Its speed of response is 50 ms but much faster measurements are possible. Measurements on behenic acid and cholesterol films on water and on a cerebroside film at a heptane/water interface are presented.
High-repetition-rate short-pulse gas discharge
Authors: Tulip John , Seguin Herbert , Mace Phillip N.
Published: March 2003

A high-average-power short-pulse gas discharge is described. This consists of a volume-preionized transverse discharge of the type used in gas lasers driven by a Blumlein energy storage circuit. The Blumlein circuit is fabricated from coaxial cable, is pulse-charged from a high-repetition-rate Marx-bank generator, and is switched by a high-repetition-rate segmented rail gap. The operation of this discharge under conditions typical of rare-gas halide lasers is described. A maximum of 900 pps was obtained, giving a power flow into the discharge of 30 kW.
Microwave radiometer blackbody calibration standard for use at millimeter wavelengths
Authors: Goldsmith P. F. , Kot R. A. , Iwasaki R. S.
Published: March 2003

We describe a high-temperature reference load designed for calibration of microwave radiometers at frequencies of 80–150 GHz. An effective temperature of 410 K and a power reflection coefficient of less than 5×10−4 have been measured at frequencies between 85 and 95 GHz.
Heterodyne CO2-laser interferometer with direct phase read-out
Authors: Hugenholtz C. A. J. , Meddens B. J. H.
Published: March 2003

A CO2-laser interferometer with heterodyne detection has been built to measure electron line densities of plasmas in the range of 1018 to 5×1022 m−2. Heterodyne operation is accomplished by using two counteracting acousto-optic modulators at a difference frequency of 500 kHz. A digital phase comparator is used to obtain direct read-out of the phase shift. The time resolution is 3.5 μs.
Measurement of magnetostriction coefficients of epitaxial garnet films
Authors: Vella-Coleiro G. P.
Published: March 2003

A technique for measuring the magnetostriction coefficients of epitaxial garnet films on 50-mm-diam wafers is described. The measurement is based on the shift of the microwave ferrimagnetic resonance produced by stressing the film, which is achieved by supporting the wafer around its circumference and reducing the atmospheric pressure on one side. A simple, nonresonant transmission microwave spectrometer which is well suited for measurements on large wafers is also described.
The tesla discharge as a spectroscopic source for the study of excimer laser transitions
Authors: McKeever Mark R. , Sur Abha , Hui Amit K. , Tellinghuisen Joel
Published: March 2003

A method for studying the pressure and temperature dependence of rare gas halide and halogen emissions is described. The tesla discharge utilized in this method is characterized in detail with respect to its temporal behavior and its radiant output. The light is found to be produced in moderately intense pulses as short as 0.5 μs in duration. Average dc radiant powers for strong emitters can exceed 5 mW. The method appears suitable for the study of most emitters that can be produced by electron beam excitation.
Multichannel, direct-reading spectrograph attachment
Authors: Cann M. W. P. , Shin J. B. , Nicholls R. W.
Published: March 2003

An instrument is described which provides a multichannel direct-reading capability for photoelectric spectrographic detection. The important feature of the instrument is the ability of the user to select at will any combination of channels for position adjustment and to move these while preserving the optical integrity of the enclosure. Photomultipliers are used and the results of performance tests are described.
Novel transformer designs for high-power high-repetition-rate applications
Authors: Merchant V. E. , Seguin H. J. J. , Dow J.
Published: March 2003

The construction technique and resulting electrical performance of high-voltage impulse transformers for ’’pulser-sustained’’ laser applications is presented. The compact structures exhibit excellent rise-time and power-handling capacity over a wide range of operating conditions. The distributed core geometry permits impulse power operation at several megawatts within the kilowatt average power regime. Reliable performance at a repetition rate of up to 40 kHz has been demonstrated. These simple condensed winding and torous core devices can be constructed in minutes and at negligible cost.
Estimation of temperature and fraction of superthermal electrons in laser-produced plasmas
Authors: Goel S. K. , Gupta P. D. , Bhawalkar D. D.
Published: March 2003

A simple method for the estimation of temperature and fraction of superthermal electrons in laser produced plasmas is discussed.
A convenient method for the measurement of species composition from an intense neutral beam
Authors: Smith R. R. , Stearns J. W.
Published: March 2003

We present a method to infer the approximate species mixture of neutral beam sources which accelerate positive hydrogen ions. An idealized neutral beam is specified by the accelerating voltage, the neutralizer thickness (molecules of hydrogen per cm2), and the currents of extracted H+, H+2, and H+3. These currents define two independent ratios which lie within a narrow parameter region and which can be determined by two independent measurements downstream from the source. The two suitable parameters are (1) the ratio of neutral beam to total beam power; and (2) the ratio of hydrogen produced by the neutral beam in the target volume to the hydrogen produced by the total beam. We give experimental results from the 10×10-cm2 120-KeV test stand at the Lawrence Berkeley Laboratory.
A DMA interface between a Biomation 8100 and an Intel MDS-800 microcomputer development system
Authors: Lynk Edgar T.
Published: March 2003

An interface is described which permits high-speed data transfer between a Biomation 8100 transient recorder and an Intel MDS-800 microcomputer system equipped with an MDS-501 DMA (direct memory access) channel controller. The interface is especially useful for data acquisition situations in which many successive traces must be recorded. For example, signal averaging can be performed within the microcomputer system.
A neutral beam sciopticon
Authors: Ryan P. M. , Whealton J. H. , Davis R. C. , Stirling W. L. , Tsai C. C.
Published: March 2003

A sciopticon based on the pinhole-camera effect is being used to determine individual beamlet contributions to the quality of neutral beams extracted from multiaperture ion sources. The technique outlined in this note can be used to study the effects on beam optics of nonhomogeneous source plasma density or acceleration gap nonuniformities, grid nonparallelism or aperture misplacement, and space-charge blowup or scattering in the neutralizer cell.
Surface trapping of primary electrons by multidipole magnetic fields
Authors: Hershkowitz Noah , DeKock James R. , Coakley Peter , Cartier Steven L.
Published: March 2003

Multidipole plasma devices are operated in an unconventional manner with primary electrons prevented by surface magnetic fields from entering the main plasma volume. Applications of this technique, to provide primary electron-free unmagnetized plasmas and to furnish a source for a large diameter magnetized plasma column, are given.
Digital integrator in scanning Auger electron microscopy
Authors: Goto K. , Ichimura S. , Shimizu R.
Published: March 2003

A digital integration technique based on the use of V/F and D/A converters accompanied by the digital scanning and the synchronous square-wave modulation has been introduced in the scanning Auger electron microscopy. This integrator allows us to perform integration in very high efficiency leading to high signal to noise ratio and to high spatial resolution of the Auger pictures.
Profile of a focussed collimated laser beam near the focal minimum characterized by fluorescence correlation spectroscopy
Authors: Sorscher Stanley M. , Klein Melvin P.
Published: March 2003

Central to the application of fluorescence correlation spectroscopy, to measure the self-diffusion coefficients and average concentration of fluorescent molecules in a volume determined by a focussed laser beam, is the determination of the focal spot size. As the focal spot size in the sample plane is varied by displacing either the focusing lens or sample position along the beam axis, the diffusion time and average number of molecules vary in a parabolic manner. Analysis of the parameters of the parabola leads to estimates of the beam radius at the waist. The results agree with theoretical predictions and provide an independent measurement of the beam profile.
Rapid, pulse counting low-energy electron diffraction instrument
Authors: Stair P. C.
Published: March 2003

A low-energy electron diffraction instrument has been constructed which allows one to visually observe a LEED pattern, record the pattern photographically and obtain immediate, quantitative intensity data from several diffraction beams in 5–10 s. The instrument operates at incident beam currents of a few picoamperes eliminating electron beam damage effects. This paper describes the design and construction of this new LEED instrument and reports on the operating parameters of sensitivity, signal-to-noise, image distortion, and angular resolution.
Comment on pulsed high-density source of cesium atoms
Authors: Wicke B. G. , Utterback N. G. , Tang S. P. , Friichtenicht J. F.
Published: March 2003

The use of laser flash vaporization of thin films is proposed as a source of intense atomic beams [AIP].
Oscillating beam spectrometer
Authors: Seki H. , Itoh U.
Published: March 2003

A sensitive visible spectrometer has been designed to detect very small differences in the transmission or the reflection of two adjacent areas of a substrate. A probing light beam of variable wavelength is deflected between the two areas by a galvanometer-type oscillating mirror in order to obtain a differential absorption or reflection. The absorption spectra of a dye incorporated in a Langmuir film, a monolayer of dye molecules covalently bonded to glass and molecules oriented in a stretched polyethylene film are presented as examples. The modification of the instrument to cover the near UV and IR regions is straightforward and will be discussed.
Silicon cell for the precise measurement of thermal expansion at low temperatures: Results for Cu and NaF
Authors: Villar R. , Hortal M. , Vieira S.
Published: March 2003

A three terminal capacitance dilatometer for low temperatures is reported in which the expansivity of a sample is compared to that of silicon, a material of very small expansivity at low temperatures. The thermal expansion of a standard copper sample is measured down to 3 K and the results compared with other authors. Values for the linear thermal expansion coefficient of a pure NaF single crystal below 5 K are reported for the first time.
Simple clamp pressure cell up to 30 kbar
Authors: Fujiwara Hiroshi , Kadomatsu Hideoki , Tohma Kiyokazu
Published: March 2003

A design of simple clamp type pressure apparatus utilized for measurements of magnetic susceptibility and electrical resistivity at low temperatures is presented. The cell consists of WC piston and Be–Cu cylinder which was autofrettage processed, and sample cavity consists of a teflon bucket and an electrode plug. In a temperature range from 300 K down to 77 K, pressure was determined by manganin gauge which was calibrated by Bi I→II transition pressure at room temperature and also the temperature dependence of pressure coefficient of manganin resistance was taken into account. As a result, the cell was capable of generating hydrostatic pressures up to 30 kbar at room temperature and at least up to 25 kbar at 4.2 K.
New high sensitive micromanometer
Authors: Leidenfrost W. , Ku J.
Published: March 2003

An instrument is described where the downwards or upwards displacement of menisci under the action of a pressure differential in a U-tube arrangement is magnified by a factor of 104 or more. This is accomplished by determining the volume of manometer fluid displaced via the very precise observation of motion of an air bubble inside a horizontal capillary tube connecting the large and equal diameter vertical legs of the manometer. Means of introducing and initially placing the air bubble are described as well as the use of a long capillary spirally coiled in one plane. This plane does not need to be placed horizontally because buoyancy forces cannot influence the bubble displacement. An instrument has been built and checked for surface tension effects which proved to be negligibly small. The instrument was used to measure velocity distribution of air flowing laminarly through a tube. The agreement between data and theory is excellent.
Modified Thomson parabola ion spectrometer of wide dynamic range
Authors: Sakabe S. , Mochizuki T. , Yamanaka T. , Yamanaka C.
Published: March 2003

A modified Thomson parabola ion spectrometer of a wide dynamic range for studies of flash ions emitted from laser produced plasmas was developed. The exact velocity distributions of different ion species were obtained separately with sufficient velocity resolution.
Pulsed magnet for magneto-optical experimentation
Authors: Trabjerg I.
Published: March 2003

A high field pulsed magnet system with its associated electronics has been modernized to obtain a device which is easy to use. The magnet has been synchronized to operate with an optical multichannel analyzer; the coil has been miniaturized and tested with success in a pumped conventional dewar with liquid helium and in a tube with flowing gaseous helium. Fields of 20 T have been obtained above 77 K and 14.2 T below that temperature.
Improved method for measuring tunneling conductance
Authors: Flesner L. D. , Silver A. H.
Published: March 2003

an improved electronic circuit has been used to measure tunneling conductance, dI/dV, and its derivative, d2I/dV2 as a function of applied voltage for superconducting junctions. The configuration described permits four-terminal measurements. A harmonic excitation voltage applied to the sample has low noise (<0.1 nV/Hz1/2) and low second harmonic contamination (<10−3%). One unique feature is the use of a digitally switched analog gate in a feedback circuit in order to maintain a constant excitation level over a wide range of dynamic resistance exhibited by typical samples. Furthermore, a balanced bridge circuit is not required and both dI/dV and d2I/dV2 can be measured simultaneously. Alternatively, one can measure dV/dI and d2V/dI2.
Standard deviation of averaged digital time interval measurements
Authors: Reider Georg A.
Published: March 2003

It is shown that the standard deviation of a counter in the time interval average mode is a periodical function of the length of the interval to be measured. Experimental results prove the theoretical considerations quite well. The derivation given allows to assign a realistic value to the measurement error. On the other hand, if only small changes of a time interval are to be measured, it may be used as a prescription to optimize the resolution of the measurement.
Afterpulsing effects in photon correlation experiments
Authors: Burstyn H. C.
Published: March 2003

The effect of afterpulsing upon photon correlation experiments is examined using various timebases. It is shown that the effect, to leading order, can be eliminated by calibrating the afterpulsing probability of the photomultiplier tube. Furthermore, it is shown that the calibration needs only to be performed at one particular timebase. The efficacy of the procedure is demonstrated.
Light-operated solid-state switch for pulsed microwave power generator
Authors: Bulliard A. , Hoegger B. A.
Published: March 2003

The design and construction of a new high voltage switch, using a series of transistors which are triggered simultaneously by optocoupler circuits is described. By means of this pulse generator, pulses of 10 kV and 2.5 A at a repetition rate of 50 Hz were obtained. The circuit is used to drive a power magnetron commonly used for plasma production and heating.
Method of measuring low pressures within evacuated, sealed glass tubes
Authors: Weirauch Donald F.
Published: March 2003

During the heating of evacuated and sealed glass tubes, small volumes of gas are usually evolved causing a pressure rise. A simple method of measuring these gas pressures by manometer without the necessity of opening the tube is described. The method requires that mercury and a small inner glass tube be sealed in the tube. Internal pressure changes occurring when an evacuated vitreous silica tube was heated up to 550°C are described. The maximum pressure reached in the tube was 2.5 torr.
Technique for the preparation of solid specimens for x-ray absorption studies
Authors: Eanes E. D. , Costa Jonathan L. , MacKenzie Alan , Warburton William K.
Published: March 2003

A method is described for the preparation of stable and uniformly thick solid specimens with properties suitable for x-ray absorption fine structure studies. A known amount of finely powdered solid material is dispersed in an appropriate solvent and filtered through a polycarbonate membrane filter. A solution of rubber cement is drawn through the solid, which is then covered with a second filter disc. By appropriate choice of the amount of solid to be filtered, specimens can be produced with a range of thicknesses, including those useful for examination of extended x-ray absorption fine structure and near-edge absorption fine structure.
Fourier transform photoacoustic spectrometer
Authors: Lloyd Lindsay B. , Riseman Stephen M. , Burnham Roger K. , Eyring Edward M. , Farrow Michael M.
Published: March 2003

A Michelson interferometer with step-and-integrate mirror motion is described for use in Fourier transform photoacoustic spectrometry (FTPAS) at visible wavelengths. An overview of mechanical and software construction is supplied and the advantages of FTPAS are illustrated with a spectrum of powdered erbium oxide at visible wavelengths. The relative merits of step-and-integrate and rapid scan mirror motion for FTPAS are considered.
Doppler shift spectroscopy of powerful neutral beams
Authors: Burrell C. F. , Cooper W. S. , Smith R. R. , Steele W. F.
Published: March 2003

An optical diagnostic is reported which measures the parameters of an intense hydrogen or deuterium neutral beam by observation of the Doppler shifted Balmer alpha or beta lines emitted by fast atoms in the beam at several locations in the neutralizer. The spectrum of blue shifted and red shifted light emitted along optic axes which lie in planes perpendicular and parallel to the grid rails of the ion source is recorded by an optical multichannel analyzer which is interfaced to a computer. The light is Doppler shifted sufficiently to resolve the three energy components of the beam resulting from the H+, H+2, and H+3 ions accelerated by the ion source. From the Doppler broadening of each peak the beam divergence parallel and perpendicular to the accelerator slots can be measured. A model is presented whereby the energy distribution can be determined from the intensity of each peak. The spectroscopic results for energy distribution are in agreement to within 5% with momentum analysis by a magnetic mass spectrometer.
Data acquisition system with 8 BIOMATION 8100 controlled by a 6800 microcomputer
Authors: Hollenberg K.
Published: March 2003

A 6800 microprocessor controlled data acquisition system with 8 BIOMATION 8100 transient recorders is described. The system allows programming the transient recorders and storing data on tape cassettes or punched tape for further computation. The system has been used successfully in shock tube experiments and for measuring shock pressures in solids by carbon resistors.
Three-zone Bridgman–Stockbarger crystal growth furnace
Authors: Mikkelsen J. C.
Published: March 2003

The construction of a furnace for growing crystals from the melt by the Bridgman–Stockbarger technique is described. The main feature of this design is the combined use of an auxiliary heater and a controlled thermal loss in the space between the two primary furnace zones to produce temperature profiles optimized for crystal growth.
Simple digital waveform averager for photon counting
Authors: Kono A. , Hattori S.
Published: March 2003

A simple, digital, waveform-averaging circuit is described for measuring very weak light signals by use of photon counting technique. The maximum time resolution of the circuit is 1.5 μs.
Interface for Biomation transient recorders to LSI-11 processors
Authors: Reiser Christopher
Published: March 2003

An interface is described which permits high-speed wordwise data transfer between a Biomation 820 Transient Recorder and a MINC (LSI-11/2) minicomputer. Using a DRV11-B direct-memory access card, up to 50 full 2 K records/s can be transferred to the MINC system; single word control data can also be passed from the computer to the Transient Recorder.
Feedback-stabilized dual-beam laser interferometer for plasma measurements
Authors: Yasuda Akio , Kanai Yasufumi , Kusunoki Junzo , Kawahata Kazuo , Takeda Susumu
Published: March 2003

A stabilized laser interferometer is proposed with two beams as the light source. The fringe shift for a 0.63 μm beam of a He–Ne laser is used to stabilize the interferometer against the effect of mechanical vibrations via a feedback controlled speaker coil, while another beam of 3.39 μm, for which consequently the effect of the mechanical vibrations is excluded, is used to measure the plasma density. A stability of ∼1/500 of one fringe for 0.63 μm is obtained during a long period for frequencies lower than a few Hz. The stability for higher frequencies is limited to ∼1/30 of one fringe for 0.63 μm, which correspondes to ∼1/200 of one fringe for 3.39 μm, by the acoustic noise picked up by the speaker coil. Furthermore, the total accuracy is limited by the detector noise to ∼1/60 of one fringe for 3.39 μm, which corresponds to a line electron density of ∼5×1014 cm−2. The detector noise may be reduced by cooling the detector. The advantage of this technique over the single-laser technique is that the frequency response of the interferometer extends down to zero frequency. The interferometer is tested with the measurement of a plasma in a dynamic magnetic arcjet. Since the effect of the neutral gas background is reduced in the present interferometer, the application has an advantage for the diagnostics of plasmas produced in high pressure gases.
Picosecond resolution of a Cerenkov cell-streak camera arrangement for monitoring charged particle bunches
Authors: Sheppard J. C. , Pantell R. H. , Gearhart R. A. , Miller R. H. , Chase L. F. , Monahan K. M. , Watson B. A.
Published: March 2003

An experiment is described in which the picosecond temporal structure of a Cerenkov radiation source has been measured using an optical streak camera. Electrons in the Stanford Linear Accelerator Center (SLAC) three kilometer linear accelerator, bunched by the 2856 MHz acceleration fields, are used to generate Cerenkov radiation in a helium-filled gas cell. We show that it is possible to construct a Cerenkov cell which introduces subpicosecond time spread and allows for nondestructive monitoring of the electron beam.
Simple apparatus for the measurement of thermal diffusivity between 80–500 K using the modified Ångström method
Authors: Vandersande J. W. , Pohl R. O.
Published: March 2003

An apparatus that is capable of measuring thermal diffusivity between 80–500 K using a modified Ångström method is described. The main feature of the apparatus is its simplicity. A detailed description of the equipment and the experimental procedure as well as the difficulties that can be encountered are given. The results of measurements on samples covering a wide range of thermal diffusivities are also given.