bluuebunny/crossref_metadata_2025 huggingface dataset:
Automatic x-ray beam position tracking circuit: Experimental tests at DESY
Authors: Chance B. , Powers L. , Bartunik H. , Schick D.
Published: July 2002

A previous communication has described a beam intensity modulator for detecting noise intensity of the x-ray beam at the user end station and a noise compensating circuit which has resulted in significant improvements of signal to noise. Intensity and position noise modulations of synchrotron orbital radiation were not distinguished in that study. This paper describes the use of phase information from the modulator to detect positional changes of the x-ray beam. A circuit has been developed for continuously following the phase angle of the modulation. This position detector is sensitive to 3 nm with a 20-Hz bandwidth. Experimental studies at an end station at DESY indicate very low-frequency (<1 Hz) noise of the beam position of several hundred microns and a higher-frequency noise centered near 10 Hz with a peak amplitude of 24 nm. The use of this position tracking signal to correct the sample position is described.
Operation of a microchannel plate counting system in a mass spectrometer
Authors: Murphy Daniel M. , Mauersberger Konrad
Published: July 2002

A multiplier detector system has been developed as part of a mass spectrometer in an ion counting mode. During its operation ions striking a microchannel plate release pulses of electrons which are accelerated to a phosphor layer. The resulting flash of light is carried by a fiber-optic bundle to a photodiode array. The detector simultaneously counts ions throughout a mass spectrum covering more than 30 amu. It extends the mass spectrometer’s operation toward low count rates for trace gas analysis. Each mass peak can be independently measured at count rates between 0.1 and 1000 counts/s. Higher rates on a few peaks do not blind the entire detector. The detector’s capabilities have been demonstrated by measuring Kr and Xe isotopes in air at natural abundances. The mass spectrometer, detector, and readout electronics are sufficiently compact to permit use in a balloon-borne experiment.
Diamond-anvil high-pressure cell for optical spectroscopy at low temperature
Authors: Kobayashi Toshihiko
Published: July 2002

A diamond-anvil high-pressure cell is described which allows optical studies at low temperatures and variable pressure to 260 kbar and higher. A bellows assembly has been designed to drive diamond anvils and connected helium gas pressure source. The sample pressure can be changed remotely while the sample is maintained at operating temperature. Examples of the application to the optical absorption in InP under high pressure are shown. Tests using different pressure transmitting fluids are reported.
Electrical-transport measurements on fragile single crystals to 7.5 GPa in the diamond anvil cell
Authors: Tozer S. W. , King H. E.
Published: July 2002

A four-probe method is presented for the study of electrical-transport properties of materials ranging from insulators to metals. Development of several experimental procedures and apparatuses and the fabrication of a composite gasket has permitted quasihydrostatic electrical resistivity measurements of fragile single crystals. Using a fluid to transmit pressure to the sample, the integrity of the crystal is assured. Pressures to 7.5 GPa have been obtained using the diamond anvil cell.
Inexpensive computer data-acquisition system
Authors: Galvin James E. , Brown Ian G.
Published: July 2002

A system based on an Apple II+ personal computer is used for on-line monitoring of ion-beam characteristics in accelerator ion source development.
Multichannel heterodyne radiometer with computer control for electron cyclotron emission measurements of a tokamak plasma
Authors: Cima G. , Ramponi G. , Simonetto A.
Published: July 2002

A multichannel heterodyne radiometer in the frequency range 50–75 GHz which has been used to measure the second-harmonic cyclotron emission of the Thor Tokomak plasma is described. Real-time frequency switching, analog output averaging, autocalibration, data-acquisition, and graphical display are all functions performed under control of an Apple II personal computer. Typical experimental results are presented to illustrate the measuring capabilities of the instrument.
Versatile photostimulated exoelectron microscope with measurement capabilities in SEM mode
Authors: Yamamoto Shigeyuki , Yokogawa Hiroshi , Hashimoto Hiroshi
Published: July 2002

Photostimulated exoelectron microscope (PSEM) for observing mechanically damaged surfaces has been developed, which enables one to observe a photostimulated exoelectron (PSE) image in an EXO mode and the corresponding secondary electron image of the same region in a SEM mode, without reassembling an electron optical system. Typical results obtained with this microscope are presented.
High-pressure, thermal-pulse, liquid flow meter
Authors: Albert Henry J. , Wood Robert H.
Published: July 2002

A liquid flow meter for operation at high pressures is described. The meter uses a thermal pulse with time-of-flight detection to measure the flow rate. The thermal-pulse generator and detector are located outside a metal capillary tube.
Inexpensive method for measuring shutter intervals of a motor driven camera
Authors: Tochitani Yoshiro
Published: July 2002

A household audio magnetic tape recorder can be used for recording pulses which are given by successive shots of a 35-mm motor driven camera. The pulses transmitted from an X contact of the camera are recorded on a magnetic tape by the recorder through an electronic circuit. Time interval between successively recorded pulses can be measured by use of an electronic counter. This simple method permits to record 20 pulses per second and measures the interval between any neighboring pulses.
Rapidly tuned frequency stabilized CO2 laser
Authors: Walsh C. J. , Brown N.
Published: July 2002

A cw CO2 laser capable of tuning through a preselected number of rotational lines is described. The use of a line-center servo lock technique allows rapid tuning and high-frequency stability to be achieved.
Balanced puff valve for imploding gas-puff experiments
Authors: Wong S. , Smiley P. , Sheridan T. , Levine J. , Buck V.
Published: July 2002

The design of a fast-acting high-pressure puff valve for use in imploding gas-puff experiments is presented. By using a pressure-balanced valve design, the valve can operate at pressures up to 500 psia. Fast opening (≊200 μs) is achieved by using a fast-moving sliding hammer to open the valve. Balanced valves as well as fast-opening valves using sliding hammers are both well-known technologies; however, this design is the first one to incorporate both features in a single design resulting in a fast-acting high-pressure puff valve.
Fast computer-controlled deep level transient spectroscopy system for versatile applications in semiconductors
Authors: Hölzlein K. , Pensl G. , Schulz M. , Stolz P.
Published: July 2002

A fast computer-controlled and fully automated deep level transient spectroscopy (DLTS) system is described. Various DLTS techniques can be operated without changing the hardware. Simultaneous data acquisition and data processing considerably reduces the measurement time. The sensitivity of the system is increased by digital compensation of the sample capacitance and by averaging of a high number of transients. All the trap parameters are determined during one temperature scan.
High-performance waveform-sampling analysis based on digital multipoint signal averaging
Authors: Parisi J. , Mühlemeier B. , Buck W.
Published: July 2002

This paper describes a versatile digital multipoint waveform-recording system utilizing computer-aided signal-averaging procedures. Basically, it consists of a Biomation 8100 transient recorder coupled to a DEC PDP 11/04 computer via an electronic interface device and a CAMAC I/O-register NE 9066 supported by an appropriate software system. Additional use of an extremely low-noise wideband preamplifier system together with proper shielding, filtering, and differential measuring techniques minimize the disturbing influence of random and coherent electromagnetic noise. Employing our waveform-recording system to sensitive time-resolved flux-flow measurements in superconductors yields both a voltage resolution approaching 1 nV and a time resolution of 10 ns at a recording bandwidth of 25 MHz. Such a novel scheme of high-performance waveform-sampling analysis yields an overall efficiency limited at the characteristic rise-time sensitivity product of about 10−17 V s, corresponding to a magnetic flux sensitivity far better than a single quantum. An outline of the present uses and future prospects indicates that this method represents an important tool in such advanced fields as low-temperature solid-state physics and cryoelectronics and deserves more attention both from a fundamental point of view and for many technological applications.
Time-of-flight characterization of pulsed supersonic helium free-jet expansions
Authors: Kay Bruce D. , Raymond T. D. , Rice J. K.
Published: July 2002

A synchronous time-of-flight (TOF) technique is employed to make velocity distribution measurements in pulsed supersonic free-jet expansions. For helium expansions, the flow attains a steady–state condition with a terminal Mach number of 80, on a 50-μs time scale. The transient behavior is primarily due to the mechanical action of the valve. For a 650-μs-wide pulse, greater than 95% of the atoms issuing from the pulsed nozzle can be described by the steady-state parameters. However, the velocity dispersion increases at both the leading and trailing edges of the pulse. This dispersion can be quantitatively described by incorporating a time-dependent Mach number into the standard steady-state flux velocity distribution function.
Multichord, near infrared interferometers for the CTX and ZT-40M experiments
Authors: Newman E. W. , Buchenauer C. J. , Hoida H. W.
Published: July 2002

A versatile, multichord CO2 interferometer design with a wide dynamic range is adapted to several different experiments. The systems are double pass, Mach–Zehnder, heterodyne, interferometers [that employ a single germanium Bragg cell and 2n+1−1 (n is an integer) 50% beamsplitters to produce 2n interferometer chords], and a single reference beam with matched optical path lengths. Heterodyne signals detected with room-temperature HgCdTe photoresistors are demodulated with digital phase detectors that can track several fringes per microsecond. The real-time electron density readouts provide a considerable savings in ADC channels and computation time when compared with quadrature phase detection schemes. High reliability is achieved with a temperature-controlled wave guide CO2 laser operating on a single mode at intermittent duty. The CTX instrument has been operating with eight chords since March 1984. The ZT-40M instrument, which is under construction, employs a second wavelength to correct for room vibrations in the 0.01 fringe density range.
Particle sizing in the electrodynamic balance
Authors: Sageev Gideon , Seinfeld John H. , Flagan Richard C.
Published: July 2002

We report a new technique for sizing particles in the electrodynamic balance. In this technique, the trajectory of a falling particle is followed with a photomultiplier tube. Particle velocities are measured by placing a mask between the particle and the detector. The masked region in the particle trajectory is roughly 0.6 mm wide. Output from the PMT is sampled every millisecond by an A/D converter and stored in a computer. Flight times of several hundred milliseconds are measured and the size is then computed from the particle’s terminal velocity. With a modification of the mask, the technique is used to verify the uniformity of the electric field through which the particle is falling. In the present work we use the technique to determine size of polystryrene latex microspheres having nominal diameters of 10 and 20 μ. The technique can be used on any size particle, independent of its charge-to-mass ratio, and provides the size information in a short time.
Reentrant cavity as a low-power plasma source
Authors: Brown M. R. , Sheridan T. E. , Hayes M. A.
Published: July 2002

A low-power source of plasma employing ECRH microwave breakdown in a reentrant cavity is described. The cavity has the following features: its dimensions can be made much smaller than its resonant wavelength, cavity Q values of several hundred are not difficult to achieve, and the vacuum rf electric field is uniform near its center. The plasma density to power ratio is roughly 109 cm−3 per watt for powers up to about 10 W. A smooth radial profile and a temperature of 5–10 eV are observed, and the plasma is very quiescent (δn/n is less than 1%). The cavity’s construction and performance is described and compared to the performance of a simple loop antenna in a nonresonant structure.
Microcollimated energy-dispersive x-ray diffraction apparatus for studies at megabar pressures with a synchrotron source
Authors: Brister Keith E. , Vohra Yogesh K. , Ruoff Arthur L.
Published: July 2002

A new high-pressure energy-dispersive x-ray diffraction apparatus is described. Two major features distinguish this system from previous ones: the ability to collect diffraction data from small sample areas subjected to pressures over 1 Mbar and to scan across the sample. This system also has the ability to calibrate the diffraction angle without making any assumptions about the lattice spacings of the sample.
Wavelength dependence of temperature coefficients of the quantum efficiency in PMTs with bialkali photocathode
Authors: Yamashita Mikio
Published: July 2002

Absolute temperature coefficients of the quantum efficiency of the bialkali photocathode in RCA 8850 photomultiplier tubes (PMTs) have been measured precisely as a function of wavelength over a range of 520–700 nm, using the photon-counting technique. The measurements were greatly facilitated by particular features of the experimental apparatus and techniques employed.
Performance of an analog phase follower
Authors: Campani E. , Giazotto A. , Passuello D.
Published: July 2002

We describe the performance of an analog phase follower used together with an active pendulum with interferometric sensing. The pendulum length is increased electronically by moving the suspension point horizontally by means of a piezoelectric transducer. This is driven by a feedback signal proportional to the relative displacement of the pendulum mass with respect to the suspension point. This displacement creates a phase shift Ψ in the optical path of the interferometer which in turn gives an output proportional to sin Ψ and not to Ψ, as this is required as the feedback signal. The device described here performs in an analog way the transformation sin Ψ ■ Ψ. At 0.5 Hz the dynamic range is ±500 rad corresponding to ±25-μm elongation of the pendulum mass.
Microprocessor-based data-acquisition system for thermo-fluids laboratories
Authors: Ball Kenneth S. , Farouk Bakhtier
Published: July 2002

A simple, relatively inexpensive and very flexible microprocessor-based data-acquisition system is described for use in thermo-fluids laboratories. The system, which is currently being used in natural and mixed convection heat transfer experiments, is completely programmable and can be expanded to meet growing needs. It is capable of receiving a variety of inputs, storing and processing the data, as well as controlling the entire data collection procedure. The data-acquisition system described can be assembled at about the same cost as a single, commercially available, one function data-logging device.
Accurate positional servo for use with pneumatically supported masses and vibrationally isolated tables
Authors: Greene G. L.
Published: July 2002

A noncontacting electropneumatic servosystem for the positional control of vibrationally isolated tables is described. Employing a ‘‘live zero,’’ integrating servo, the system has been used to position an ‘‘air spring’’ supported optical table to within a few microns and a few seconds of arc for a period of several months. If needed, the system can be extended to provide for control of all six degrees of freedom. This system provides an improvement in positional stability of between 2 and 3 orders of magnitude over typical commercial systems.
Ion source with plasma cathode
Authors: Yabe Eiji
Published: July 2002

A long lifetime ion source with plasma cathode has been developed for use in ion implantation. In this ion source, a plasma of a nonreactive working gas serves as a cathode in place of a thermionic tungsten filament used in the Freeman ion source. In an applied magnetic field, the plasma is convergent, i.e., filamentlike; in zero magnetic field, it turns divergent and spraylike. In the latter case, the plasma exhibits a remarkable ability when the working gas has an ionization potential larger than the feed gas. By any combination of a working gas of either argon or neon and a feed gas of AsF5 or PF5, the lifetime of this ion source was found to be more than 90 h with an extraction voltage of 40 kV and the corresponding ion current density 20 mA/cm2. Mass spectrometry results show that this ion source has an ability of generating a considerable amount of As+ and P+ ions from AsF5 and PF5, and hence will be useful for realizing a fully cryopumped ion implanter system. This ion source is also eminently suitable for use in oxygen ion production.
Versatile, low-cost, real-time data-acquisition and processing system
Authors: Aviani I. , Horvatić M. , Cooper J. R.
Published: July 2002

A multitasking extension has been developed for computers based on the Z80A CPU; it enables the Sinclair ZX Spectrum 48 K to be used for data acquisition and analysis simultaneously.
New heating apparatus for dynamic small x-ray scattering measurements during phase decomposition in amorphous alloys
Authors: Yavari A. R. , Osamura K.
Published: July 2002

The study of phase decomposition and crystallization of amorphous alloys by small-angle x-ray scattering requires in situ measurements during heating to avoid statistical errors due to variation in sample thickness and irradiated volume. The early stages of structural changes and phase transformations are best followed by dynamic measurements using high-intensity x-rays as obtained from synchrotron radiation. In this paper we present a new heating apparatus designed and constructed for dynamic small-angle x-ray scattering measurements on amorphous alloys during heating. Measurements are conducted on wide ribbons of amorphous alloys self-heated by joule heating. The arrangement is particularly appropriate for such measurements due to the very high electrical resistivity of such amorphous tapes.
Method for the preparation of protective coatings by low-temperature metal–organic chemical vapor deposition (MOCVD)
Authors: Kaloyeros Alain E. , Williams Wendell S. , Constant Georges
Published: July 2002

A simple and effective method is reported for the deposition of protective coatings of titanium carbide using low-temperature (as low as 150 °C) metal–organic chemical vapor deposition. This method is based on the thermolysis of metal–organic molecules containing titanium and does not require the high temperature (<1100 °C) involved in the standard TiC–CVD technique. Furthermore, the structure of the films produced (crystalline or amorphous) and their purity (inclusion of organic clusters or hydrogen) can be tailored easily by simple variations in the deposition parameters. This technique permits the coating of polymers and low-melting metals that are thermally too fragile for other deposition techniques. The process could be applied to produce films of other materials, e.g., niobium carbide, silicon carbide, titanium diboride, and gallium arsenide.
Complex conductivity measurements at several frequencies in the millimeter wave spectral range
Authors: Kim Tae Wan , Beyermann W. P. , Reagor D. , Gruner G.
Published: July 2002

A method where the complex conductivity σ(ω)=Re σ(ω)+j Im σ(ω) can be measured conveniently at several selected frequencies within each millimeter wave band using a complex impedance bridge is discussed. A sample is placed at a position where the electric field is maximum in a waveguide. The complex conductivity is obtained from the change in phase and attenuation in the bridge system used in the theory of dielectric rod in a waveguide. The method is demonstrated on low and intermediate loss materials.
Interpretation of the outputs from a double ion chamber
Authors: Hill Peter
Published: July 2002

A double ion chamber can be used to measure absolute intensities of UV light, and the absorptivity and photoionization yield of gases. New methods have been developed and tested which make double ion chambers simpler to build and use. These methods allow for collection regions of unequal length and for a body of absorbing gas in front of the chamber. Such methods make it possible to mount the chamber away from the source of ionizing UV light without displacing other experiments. The methods described use the relationship between the outputs of a chamber of nominal dimensions, over a range of gas pressures, to obtain information about the light and the gas in the chamber and the effective dimensions of the chamber. Some errors due to pressure fluctuations and uncertainties in the construction of the chamber are avoided by these methods.
Improved CuSO4 HV pulse divider
Authors: Li Zheng-ying
Published: July 2002

The response characteristics of a two-stage CuSO4 solution ‘‘tube’’ resistive divider placed in another CuSO4 solution ‘‘tube’’ in a concentric cylindrical configuration for measuring high-voltage nanosecond pulses have been studied. The test results showed that it was capable of maintaining pulse rise time less than 10 ns, and the hold-off voltage for pulses with rise times less than 10 ns was 600 kV.
Automatic shutter control for molecular-beam epitaxial reactors
Authors: Niki Shigeru , Chu Peter , Chang W. S. C. , Wieder H. H.
Published: July 2002

A simple, flexible, and relatively inexpensive microcomputer-controlled shutter system intended, principally, for use with molecular-beam epitaxial reactors is described. Eight pneumatic shutters, each one controlling the molecular-beam emission of a corresponding effusion cell, can be operated in any combination simultaneously or sequentially. Such a system has been built and is being used to grow heterojunction and superlattice structures of binary and ternary III-V alloys.
Pseudotomographic fitting algorithm for density profile reconstruction from a sparse 1-D interferometer array
Authors: Casey J. A. , Sevillano E. , Irby J. H. , Lane B. G.
Published: July 2002

An algorithm has been developed for fast analysis of a sparse multichord interferometer array, yielding peak density, Gaussian width, radial offset, ellipticity, and instability amplitude and frequency from line-integrated density measurements. A nonlinear least-squares fit is performed over many short time intervals, with independent variables reduced to one dimension. Assumptions of plasma rigidity and slowly evolving rotation rate are necessary to trade temporal resolution (on instability timescales) for spatial resolution across the moving plasma column. Results from the Tara tandem mirror experiment are shown.
Magnetic field evolution and measurement of fast rise-time electron beams
Authors: Mitrovich Dushan
Published: July 2002

In charged particle beam experiments, the electromagnetic signal produced at the beam injection point (conducting foil or aperture) by a fast-rise beam will reflect off conducting boundaries (pipe walls) to produce constructive and destructive interference. B-dot loop diagnostics can, in that case, give rather complicated signal histories that are difficult to interpret. An idealized, cylindrical model of a sudden rise beam on axis is solved analytically and shows, in the relativistic limit, how the interference is manifested. Results of the model corroborate and provide interpretation of corresponding PIC simulation results. B-dot loop diagnostics of fast-rise charged particle beams are most easily interpreted when the loops are close to the beam axis, or far downstream from the injection plane, and when frequency filtering of the signal is performed.
Low-cost calorimeter for simulating shape memory effect heat engines
Authors: Jardine A. P.
Published: July 2002

A novel, inexpensive calorimetry system is described for the analysis of the specific heat anomalies of shape memory effect (SME) alloys cycled through the martensitic transformation. By loading the sample on heating through the martensitic to austenitic transformation and unloading on cooling through the reverse transformation, a typical SME heat engine cycle is simulated. Analysis of the specific-heat anomalies from these simulations gives a direct measure of the thermal efficiencies of the SME alloy. The requirements of externally stressing the sample as well as a changing sample shape produced heat losses which were difficult to estimate. An algorithm is described which estimates the combined heat losses by thermal base-line subtraction. Measurements of the specific heats and enthalpies of transformation for heating and cooling through the transformations are presented, from which the thermal efficiencies were calculated.
Vacuum ultraviolet and ultrasoft x-ray diode detectors for tokamak plasmas
Authors: Lee Ping , Gernhardt J. , Armentrout C. J. , Snider R. T.
Published: July 2002

Ultrasoft x-ray diode (USXRD) arrays have been used on DIII-D and ASDEX to study plasma edge radiation, in the photon energy range from 10 eV to 10 keV. The detectors are extremely useful and versatile due to their simplicity and compactness. Furthermore, absolute quantum efficiencies (QE) of many photocathodes such as vitreous C, Al, Cu, CuI, CsI, and Au have been measured in recent years. With filter technique, broadband resolution, E/ΔE∼1, is possible. Quantum-efficiency comparison of USXRD with semiconductor XRD is also presented to better understand the regions of applicability for each detector.
Collinear laser and slow-ion-beam apparatus for high-precision laser-rf double-resonance spectroscopy
Authors: Sen A. , Goodman L. S. , Childs W. J.
Published: July 2002

A new apparatus has been constructed for high-precision hyperfine structure measurement of atomic ions by laser-radio-frequency double-resonance technique involving a slow ion beam and a laser in collinear geometry. The low ion energy (1–1.5 keV) leads to longer interaction time with the applied rf field. Consequently, extremely narrow linewidths of ∼60 kHz have been observed for the first time in such systems. The apparatus has been used for the measurement of hyperfine structure of the 4f7(8S0)5d9D02,3,4,5 metastable levels in 151Eu+ and 153Eu+. The magnetic dipole and the electric quadrupole hyperfine constants, A and B, respectively, have been determined with higher precision (2–3 orders of magnitude).
Paralleled transconductance ultralow-noise preamplifier
Authors: Hallgren Robert B.
Published: July 2002

A simple NJFET preamplifier was constructed from commercial parts using parallel input devices in a cascode configuration. The equivalent input noise resistance was 8.5 Ω (0.38 nV/(Hz)1/2) at 1 kHz, and 12 Ω (0.45 nV/(Hz)1/2) at 100 Hz, measured at room temperature, independent of the source resistance. For 50-Ω sources, a gain of 29 dB was achieved from 3 Hz to 13 MHz. The input noise equivalent resistance is verified by measuring the thermal noise of low-valued wire-wound resistors. Circuit utility is demonstrated by noise measurements performed on GaAs Ohmic contacts at room temperature, under various bias conditions. Design considerations for using parallel input devices, the bias criteria for them, and possible design extensions are discussed.
Comparison between time-of-flight spectra measured at a spallation source and at a high flux reactor
Authors: Holland-Moritz E. , Loewenhaupt M. , Walter U. , Loong C.-K.
Published: July 2002

We give a comparison for inelastic neutron scattering experiments performed at the high flux reactor in Grenoble and at the spallation source in Argonne. These experiments were performed at the IN4 (I. L. L. Grenoble) and at the HRMECS (IPNS Argonne) with nearly identical conditions using E0≂50 meV as energy of incident neutrons. We conclude that the neutron counting rate for a given scattering angle is less by a factor of about 30 at HRMECS than at IN4. This is due to a rather small neutron flux at HRMECS. Thus the background to signal ratio is worse by a factor of 2 at HRMECS compared to IN4.
Modified operation of the seven-element electrostatic Chutjian–Kuyatt lens system
Authors: Boesten L.
Published: July 2002

We reconsider the properties of the seven-element electrostatic zoom-lens system of Chutjian and Kuyatt [Rev. Sci. Instrum. 50, 347 (1979)] from our experience with a ‘‘visual’’ beam-tracing program, and propose a modified operation of this lens system to achieve simultaneously correct focusing, zero beam angle, and constant target size over the zoom range. Rational function fits to all driving voltages are given. A ray-tracing program for a personal computer is described in the Appendix.
Simplified attenuated total reflection apparatus
Authors: Villagrán J. C. , Thompson J. C.
Published: July 2002

We offer a version of the Kretschmann configuration of an attenuated total reflection measurement in which there is only one rotating element. Significant simplifications in construction and operation are thereby attained.
Electrostatic lens potentials with small relativistic spherical aberration
Authors: Kiss L.
Published: July 2002

We discuss a computerized systematic investigation to find axially symmetric electrostatic lens potentials with acceptable first-order properties and small spherical aberrations. The calculation of the spherical aberration is based on the direct solution of the relativistic trajectory equation in paraxial and nonparaxial approximation. The potentials are characterized by their properties in infinite magnification mode. Conditions for the computations and constraints to satisfy practical requirements are prescribed. A successful axial potential distribution and its relativistic spherical aberration coefficient, the spherical disk radius, and some first-order optical parameters, are also presented in the paper as an example.
Modification of an Inrad Autotracker II for automated second harmonic generation angle scanning with a mode-locked laser
Authors: Sulkes Mark , Teh Chin Khuan
Published: July 2002

Modifications are described that allow an Inrad Autotracker II angle-tuned SHG crystal tracker to be used with a mode-locked Ar+ /dye laser system.
Apparatus for i
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u measurement of light scattering during heat-treatment
Authors: Huntebrinker Klaus , Wemheuer Bärbel , Grubić Mladen , Würz Ulrich
Published: July 2002

A fully automated apparatus is described for the in situ measurement of light scattering in glass forming systems during heat treatment. Its furnace and regulator provide high-temperature change rates of the order of several K/s. Additionally the sample temperature can be kept constant to within 0.1 K for several days in ranges up to 900 °C. A He–Ne laser provides linearly polarized light and the light scattered under 90° (or 15°) is detected using photodiodes and lock-in amplifiers.
Electrodynamic radioactivity detector for microparticles
Authors: Ward T. L. , Davis E. J. , Jenkins R. W. , McRae D. D.
Published: July 2002

A new technique for the measurement of the radioactive decay of single microparticles has been demonstrated. Although the experiments were made with droplets of order 20 μm in diameter, microparticles in the range 0.1–100 μm can be accommodated. An electrodynamic balance and combination light-scattering photometer were used to measure the charge-loss rate and size of a charged microsphere suspended in a laser beam by superposed ac and dc electrical fields. The charged particle undergoes charge loss in the partially ionized gas atmosphere which results from radioactive decay of 14C-tagged compounds, and the rate of charge loss is proportional to the rate of decay here. The charge on a particle was determined by measuring the dc voltage necessary to stably suspend the particle against gravity while simultaneously determining the droplet size by light-scattering techniques. The parameters which affect the operation of the electrodynamic balance as a radioactivity detector are examined, and the limits of its sensitivity are explored. Radioactivity levels as low as 120 pCi have been measured, and it appears that by reducing the background contamination inside our balance activity levels on the order of 10 pCi can be detected. This new technique has application in the measurement of activity levels and source discrimination of natural and man-made aerosols and smokes and is also useful for studies involving specifically labeled radio-chemical probes.
Methods for determination of microwave cavity quality factors from equivalent electronic circuit models
Authors: McKinstry Kevin D. , Patton Carl E.
Published: July 2002

Simple analytic methods have been developed for high-accuracy measurement of the quality factor Q of reflection and transmission microwave cavities. These methods are based on the consideration of cavity equivalent electronic circuit models and use measured cavity parameters over a narrow frequency range spanning the cavity resonance frequency to determine the Q factor. Since only straightforward frequency and power measurements are necessary, these methods are well suited to computer-aided data acquisition and analysis. Specific results are presented for a standard X-band reflection cavity with a Q of 2699.1±0.5 and a high-Q X-band cylindrical cavity with a Q of 23112±4.
All-optical switching in rare-earth doped channel waveguide
Authors: de Araújo Cid B. , Gomes A. S. L. , Srivastava R.
Published: July 2002

The operation of an all-optical switch in a rare-earth doped channel waveguide is described. The switching mechanism is based on an optically induced intramodal energy exchange, driven by a resonantly enhanced nonlinearity of a Nd3+ ion. Switching times around 410 μs at a repetition rate of 1 kHz was demonstrated.
Photopyroelectric thermal wave detection via contactless capacitive polyvinylidene fluoride (PVDF)-metal probe-tip coupling
Authors: Mieszkowski Marek , Leung Kwan F. , Mandelis Andreas
Published: July 2002

In the past, thin-film photopyroelectric detectors have provided a simple means of measuring thermal properties of solid samples. This article presents a theoretical model and experimental results demonstrating a new contactless capacitively coupled photopyroelectric detection technique. The photopyroelectric (P2E) effect with contactless capacitance PVDF-metal probe-tip coupling was demonstrated and used to obtain thermal information from a solid. Due to the small diameter of the probe, the local values of the thermal wave field in the solid were measured. The modulated photothermal source on the surface of the sample induces an oscillating temperature field in the pyroelectric material, which produces a displacement current proportional to the temperature change. The metalized surface of the pyroelectric thin film and a metal tip electrode facing the opposite unmetalized surface form a capacitor which is charged at the same frequency as the modulated light beam. The oscillating capacitive voltage provides a noncontact mechanism to extract photothermal information, since the electric field generated in the capacitor does not require plate contact with the PVDF element.
Resistive anode photomultiplier tube optimum operating conditions for photon correlation experiments
Authors: Floryan R. F. , Johnson C. B.
Published: July 2002

Performance characteristics of a microchannel plate photomultiplier tube having a resistive anode readout were measured under a wide variety of applied potentials. Some general conclusions were reached regarding spatial resolution and counting efficiency. The photocathode-to-VMCP and VMCP applied potentials should be as high as possible, consistent with the dark-current performance and safe operation. The VMCP-to-ZMCP applied potential should be retarding, about −100 to −300 V. The ZMCP applied potential must be chosen to put the average pulse height in an optimum range for the position electronics and the gain values resulting from the VMCP and VMCP-to-ZMCP applied potentials. Finally, spatial resolution is a strong function of the ZMCP-to-anode applied potential, and a typical optimum value is 100 V. The smallest measured line-spread function full width at half maximum was approximately 50 μm.
Laser-induced density changes in supersonic Ar beams
Authors: Fröchtenicht R. , Knuth E. L. , Rubahn H.-G.
Published: July 2002

The nonresonant heating of a supersonic beam nozzle induced by antiparallel coaxial irradiation by a cw Ar+ laser has been investigated time dependent using a mass spectrometer and an Ar beam. The resulting laser-induced decrease of beam density as a function of laser power and source pressure is quantitatively modeled, leading to an accurate measure of effective nozzle temperature and beam heating.
X-ray framing camera for picosecond imaging of laser-produced plasmas
Authors: Stearns D. G. , Wiedwald J. D. , Cook B. M. , Hanks R. L. , Landen O. L.
Published: July 2002

We describe the development and characterization of an ultrafast x-ray framing camera capable of recording images with a temporal resolution of 50 ps and spatial resolution of 22 μm at the image plane. The unique design incorporates an x-ray photocathode directly into a suspended-strip transmission line. The photocathode is gated using a high-voltage (−5-kV) pulse of short duration generated with a photoconductive switch. The photoelectrons are extracted through an unbiased microchannel plate and are directly detected with a charge-coupled device in the electron-bombardment mode. We discuss applications of the camera to investigate the dynamics of laser-produced plasmas.
Ultrasensitive thermal lens-circular dichroism spectropolarimeter for small-volume samples
Authors: Tran Chieu D. , Xu Minren
Published: July 2002

A novel, ultrasensitive crossed-beam thermal lens-circular dichroism spectropolarimeter (CBTL-CD) has been developed. In this instrument, the two excitation beams, left circularly polarized light (LCPL) and right circularly polarized light (RCPL), were derived from the same argon-ion laser. The chiral sample was sequentially excited by these two beams, and the corresponding thermal lens signals were monitored by a He-Ne probe laser intersecting perpendicularly with the two pump beams inside the sample. The apparatus is about three orders of magnitude more sensitive than the conventional circular dichroism spectropolarimeter. In addition, it can be used to detect chiral samples having very small volumes. A detection limit of 180 ng of optically active Co(en)3 complexes whose volume was as small as 8 μℓ has been estimated for this apparatus using 11-mW excitation laser power modulated at 2.3 Hz. The optics and instrumentation of the apparatus are described in detail.
High-spatial and high-mass-resolution SIMS instrument for the surface analysis of chemically complex materials
Authors: Schuetzle D. , Prater T. J. , Kaberline S. , deVries J. E. , Bayly A. , Vohralik P.
Published: July 2002

A secondary ion mass spectrometer (SIMS) has been developed for the surface analysis of chemically complex samples. The instrument has an ion transmission efficiency of 12% and an abundance sensitivity of better than 107 at 500 mass resolution. A computer system has been developed to acquire, store, and process images with up to 1024×1024 pixel resolution. Complex SIMS spectra were resolved using either high-resolution (30 000) mass analysis (HRMS) or mass spectrometry/mass spectrometry (MS/MS). Ion images of insulators or conductors were obtained with approximately 2000 Å resolution. Surface studies of electronic devices and chemical sensors are presented. SIMS–MS/MS analysis was used to identify contaminants on the surface of a failed pressure sensor. The MS/MS analysis of secondary ions minimized interferences and facilitated identification of molecular species.
Simple way to improve a tunable argon fluoride laser
Authors: Wodtke A. M. , Hüwel L. , Schlüter H. , Andresen P.
Published: July 2002

The locking efficiency and stability of a Lambda Physik EMG150 tunable ArF laser was significantly improved in a simple way. The active gain volume of the oscillator laser was increased by a factor of 5 by replacing the 1-mm circular holes supplied with the original laser by 1 mm×5 mm rectangular apertures. The resulting rectangular output of the oscillator was condensed with a cylindrical telescope and used for injection locking. The scanning range, locking efficiency, and stability of the laser were significantly improved.
Notch filter and fast current amplifier for use with time-resolved quadrupole mass spectrometers
Authors: Marsh Eugene , Prat Luis , Gilton Terry , Cowin James P.
Published: July 2002

Insertion of an LC single-stage notch filter (of the shunt variety) between the output of a quadrupole mass spectrometer and a fast current amplifier greatly attenuates the rf noise typically present on the signal output. The 2.5-MHz rf was significantly reduced with negligible interference of the 1-μs resolved time of flight (TOF) work. Also presented is the fast current amplifier design.
Effect of primary electron distribution on ion species yield in an ion source
Authors: Watanabe Kazuhiro , Araki Masanori , Dairaku Masayuki , Horiike Hiroshi , Ohara Yoshihiro , Okumura Yoshikazu , Tanaka Shigeru , Yokoyama Kenji
Published: July 2002

Effect of primary electron distribution on ion species yield is studied using a semicylindrical, multicusp plasma generator. Experimentally obtained, ion species yields were correlated with primary electron orbits estimated by computer simulation in several magnetic field configurations, where primary electron distributions were considered to be different. The result showed that a magnetic field configuration which produced lower proton yield had denser primary electron orbits in the neighborhood of the plasma grid. The floating potential of the plasma grid was also measured to suppose a distribution of the primary electrons. As a result, the proton yield increases with an increase of the floating potential of the plasma grid. These results lead us to confirm that the proton yield is determined by distribution of the primary electrons in the neighborhood of the plasma grid, in addition to the ratio of the plasma volume and the effective ion loss area. The highest proton yield of 93% and the lowest proton yield of 83% were obtained at the floating potential of the plasma grid of −5 and −21 V with respect to the anode potential, respectively, at an extraction current density of 150 mA/cm2.
On a drop quasi-isodiabatic calorimeter
Authors: Cacciamani G. , Borzone G. , Ferro R.
Published: July 2002

A drop calorimetric apparatus is described. The receiving calorimeter is isoperibolic and quasi-isodiabatic (an almost constant heat flow is maintained during the measurement by means of a fixed temperature difference ΔT between the calorimeter and the surrounding metallic block). The incremental ΔH of a sample dropping from the furnace into the calorimeter (at room temperature) is obtained by ΔH=ΔE1+ΔE2 where the energy ΔE1 is evaluated electrically, and ΔE2 (which should be zero if the calorimeter were perfectly isodiabatic) is computed by integration of the small ΔT perturbations. ΔE2 is about 1% of the total energy involved. Results of preliminary tests and examples of applications in metallurgical thermochemistry are reported.
A cell for extended x-ray absorption fine structure studies of oxygen sensitive products of redox reactions
Authors: Furenlid Lars R. , Renner Mark W. , Fajer Jack
Published: July 2002

We describe a cell suitable for extended x-ray absorption fine structure (EXAFS) studies of oxygen and/or water sensitive products of redox reactions. The cell utilizes aluminized Mylar windows that are transparent to x rays, provide low gas permeability, and allow vacuum to be maintained in the cell. The windows are attached to the glassware with an epoxy that resists attack by common organic solvents. Additional side arms allow multiple spectroscopic probes of the same sample under anaerobic and anhydrous conditions.
Operation and dynamics of ZnSe/ZnMgSSe double heterostructure blue laser diode at room temperature
Authors: Okuyama Hiroyuki , Kato Eisaku , Itoh Satoshi , Nakayama Norikazu , Ohata Toyoharu , Ishibashi Akira
Published: July 2002

Room-temperature operation of ZnSe-active-layer double heterostructure laser diode has succeeded. The lasing wavelength was 471 nm. The emission energy shift with the increasing current is explained by the band filling and the band shrinkage. The threshold carrier density is calculated to be 4×1018 cm−3. The mechanism of the stimulated emission of II–VI double heterostructure laser diode is concluded to be the recombination of the electron-hole plasma.
New counting system for detection of charged particles: application to ions generated by a pulsed laser beam
Authors: Ichimura S. , Goto K. , Kokubun K. , Shimizu H. , Hashizume H.
Published: July 2002

A new counting system for charged particles, which is suitable for the counting of pulse trains arriving in a short time, was constructed. The system is composed of a microchannel-plate intensifier, a CCD camera, a frame buffer, a particle counter, and a personal computer. Ion (or electron) pulses incident on the microchannel plate are amplified and then converted to photoradiating spots on a fluorescent screen. The image of the bright spots on the screen is taken by the camera and stored in the frame buffer. The computer processes the stored data and counts the number of bright spots. The performance of the system was examined by applying it to the detection of ions generated by a pulse laser. More than 300 photoions generated by one laser pulse (pulse width: 30 ns) were successfully counted, indicating that the peak counting rate of the system exceeds 1010 cps.
A pulsed plasma gun for intense ion beam injectors
Authors: Lindenbaum R. , Fisher A.
Published: July 2002

We have constructed a plasma gun which can produce a homogeneous plasma over a large area in high-voltage diodes. The gun has an independent power supply, and is able to create a plasma on the high-voltage electrode as well as on the low-voltage electrode of the diode. Plasma density as well as production time can be controlled. The gun consists of a battery-operated high-voltage circuit embedded in the diode shank, and a TiH2 filled, arcing grooves flashboard. Negative ion beams with an intensity of 6 A/cm2, a divergence of tens of milliradians, and a total current of about 1 kA have been produced with this gun in racetrack and annular magnetically insulated diode configurations.
Rapid and efficient transfer of energy between inductors, with application to magnetic resonance imaging
Authors: Hoult D. I. , Turner R.
Published: July 2002

Several circuits are proposed which store energy in an inductor and which, upon command, efficiently and rapidly transfer that energy to another inductor. In one of the proposals, a device is described that employs three capacitors to create, with the inductors, a doubly tuned circuit. The capacitors isolate the inductors insofar as direct current is concerned, and remove the need for ‘‘floating’’ switches. To transfer energy, the current through the primary inductor is simply switched off, and the current is then ‘‘picked up’’ in the secondary inductor a half cycle of oscillation later. Validation of this concept is provided by an instrument that switches 20 A between 350 μH inductors in 75 μs, the limitation on speed/current being the 400 V limit of the circuit employed. Loss of 5% of the current is ascribed totally to the resistance of the circuit during the half cycle switching period.