bluuebunny/crossref_metadata_2025 huggingface dataset:
System to phase lock a self-scanning photodiode array to an external signal
Authors: Harvey K. C. , Lea Patrick W. , Morris J. E.
Published: July 2002

We describe an external control circuit for a commercial, real-time, self-scanning photodiode array system. It had a phase-locked loop that synchronized the scan of the photodiode array to an external reference frequency. The signal from the photodiode array had, in principle, an infinite signal-to-noise ratio at the reference frequency. The circuit allowed independent adjustment of the integration time of the array and was simple and inexpensive to build. It was useful in measuring periodic or pulsed spectra such as occurs in laser or communications experiments.
Attractive mode force microscopy using a feedback-controlled fiber interferometer
Authors: Nonnenmacher M. , Vaez-Iravani M. , Wickramasinghe H. K.
Published: July 2002

We present a force microscope which uses a feedback-controlled differential fiber interferometer for the measurement of the deflection of the force-sensing cantilever. Due to the differential principle, and the feedback control, the influence of thermal and mechanical drifts or fluctuations is minimized. Topographic images in both modes, the attractive ac mode and the repulsive dc mode, have been taken to demonstrate a first performance of the instrument.
A dual zero-crossing detection circuit for fractional fringe interferometry
Authors: Fehr T. W. , Pierce W. F.
Published: July 2002

An easily constructed zero-crossing detection circuit, used in conjunction with common background fringe signal control techniques, vastly improves the dependability and accuracy of a fractional fringe interferometry system.
Sheet plasma production by means of rf magnetron discharges
Authors: Okuno Yoshihiro , Ishikura Hiroshi , Fujita Hiroharu
Published: July 2002

A production technique for sheet plasma with a radio frequency (rf, 13.56 MHz) magnetron discharge source is proposed. The magnetron discharge was realized inside the rf-excited electrode of rectangular hollow type with a magnetic field which also maintained the plasma sheet geometry. The typical density and temperature of electrons in the sheet plasma was 4.3×1010 cm−3 and 1.8 eV, respectively, at the gas pressure of 5 mTorr and the magnetic flux density of 0.3 kG. A comparison with the sheet plasma produced by a dc magnetron discharge source, which we proposed previously, is also given.
Pulsed Q-switched CO2 waveguide laser
Authors: Al-Shiraida Y. S. , Paulson M. , Rosadiuk T. , Tulip J. , Pace P.
Published: July 2002

The performance of an rf-excited CO2 waveguide laser which was synchronously pulsed and electro-optically Q switched is described. Output power of up to 14 kW in 50 ns was achieved which was significantly higher than powers previously obtained from reported Q-switched CO2 waveguide lasers. Acoustical perturbations were created in the optical waveguide by the pulsed discharge. This resulted in discontinuous variation in the laser pulse energy as the pulse repetition frequency was varied. Extremely marked thermal effects on Q-switching performance were observed.
Acoustic wave velocities in ceramics and other materials measured by a broadband goniometric method
Authors: Challis R. E. , Alper T. , Freemantle R. J. , Crean G. , Zhang D.
Published: July 2002

This article describes an economical short-pulse ultrasound system with a goniometer stage, with which both compression and shear wave reverberations in thin ceramic or other material samples may be separately time resolved. Arrival times of individual reverberations are compared to estimates made by computer simulation of the wave system by means of a parameter fitting routine. The system output gives compression and shear velocities based on several reverberations in the test material. Wide frequency bandwidths are achieved by using acoustically thick PZT transducers in time intervals less than one half period of their fundamental compression wave frequency.
A new design for an ultrahigh vacuum surface analysis chamber with optical scatter measurement capability
Authors: Simonson R. J. , Altamirano M. M. , Champetier R. J. , Cohen M. R. , Snyder J. , Stapp R. S.
Published: July 2002

An ultrahigh vacuum (UHV) surface analysis chamber coupled with a visible light-scattering apparatus is described. This combination of UHV surface analysis capabilities and bidirectional reflectance distribution function measurements permits investigation of effects of various surface treatments such as gas adsorption and ion bombardment on optical scatter. Stray light reflections from the UHV windows and components are temporally rejected by use of a picosecond pulsed laser source and synchronized, time-gated detector. This system allows measurement of optical scatter levels in the range of 10−7 sr−1.
A low-cost induction power supply for substrate heating
Authors: Meiners L. G. , Hemmelman B. T.
Published: July 2002

The design and construction of a 1-kW induction heating supply is described. The system was optimized for applications in which the power is coupled into a graphite susceptor which is the substrate holder for samples placed in the reaction chamber of a chemical vapor deposition system. The supply draws power from a 120-V, 20-A service outlet and delivers a 10-kHz output which is proportional to the magnitude of a 0–5 Vdc control signal. Presently available power n-metal-oxide-semiconductor field-effect transistors permit the construction of a compact unit which is small enough to be installed inside of a deposition cabinet.
Inexpensive high-speed intensified CID camera controller
Authors: Shakal J. S.
Published: July 2002

Image intensifiers are an essential part of many qualitative and quantitative imaging experiments. When temporal resolution is desired, continuous mode intensifiers such as first-generation intensifiers and ungated second-generation intensifiers are not suitable, and a gateable intensifier must be used. For laser fluorescence experiments, a controller providing synchronization on the order of nanoseconds between the microchannel plate of the intensifier and laser is usually needed. Such controllers are expensive and often designed for general purpose use, e.g., multichannel delay generators. However, by utilizing recently introduced integrated circuits, a low-cost, accurate, and versatile controller can be constructed. The device described in this article has an overall insertion delay of under 40 ns and jitter of under 3 ns. It can be controlled by front-panel switches or by a personal computer for automated operation. The device permits asynchronous triggering of a CID camera while leaving the camera-frame grabber timing cycle uninterrupted. Other uses are also suggested, and construction details are given.
Computational thermal-wave slice tomography with backpropagation and transmission reconstructions
Authors: Padé Offer , Mandelis Andreas
Published: July 2002

Computational aspects of a new matrix equation-based thermal-wave subsurface diffraction tomographic method for object field reconstructions of transverse slices (planes) perpendicular to a material surface are presented. The method can be implemented on conventional workstations and mainframe computers. It uses the photothermally measured backpropagation (front detection) or transmission (back-surface detection) scanned thermal-wave field data in the solution of the Helmholtz thermal pseudowave equation, by solving the equivalent integral equation. The numerical computations of the inverse problem used in the slice image reconstruction were satisfactorily carried out via the Born approximation. Simulated thermal-wave tomographic data/case studies were used to evaluate the imaging characteristics of large-scale computational thermal-wave diffraction tomography as a quantitative measurement and nondestructive evaluation imaging discipline.
Gravimetric/FT-IR apparatus for the study of vapor sorption on clay films
Authors: Tipton T. , Johnston C. T. , Trabue S. L. , Erickson C. , Stone D. A.
Published: July 2002

An apparatus was built to collect simultaneous gravimetric and Fourier transform infrared sorption/desorption data on self-supporting clay films in a controlled-environment cell. This apparatus enables the masses of several sorbed species to be continuously monitored in situ. Its primary purpose is to characterize physisorption and chemisorption of arenes on clays.
Quadrature sampling phase detection
Authors: Howard John , Landgraf Hans-Peter
Published: July 2002

A fast sampling demodulation method for phase modulated carriers is described. A reference wave is used to generate clock pulses for a digitizing instrument that measures directly the in-phase and quadrature components of the modulation. Application to demodulation of signals from a multi-channel phase-sensitive polarimeter is discussed.
A simple experimental setup for the simultaneous measurement of ESR and absorption spectra
Authors: Gescheidt Georg
Published: July 2002

A simple experimental setup for the simultaneous measurement of ESR and optical-absorption spectra at the same position inside the microwave cavity is described. It is shown that only very little effort is necessary to obtain electronic-absorption spectra of good quality.
Photoacoustic cell for routine analysis
Authors: Williamson C. K. , Coleman G. N.
Published: July 2002

A photoacoustic cell was designed for routine studies (e.g., samples adsorbed on filter paper). Teflon disks that are easily cleaned and removed are used as the sample holders. The cell was characterized by recording the photoacoustic waveform with a digital oscilloscope.
A method to measure weak short-lived photoconductivity induced by laser excitation in low-resistance samples
Authors: de Sande J. C. G. , Balmaseda M. Sánchez , Pérez J. M. Guerra
Published: July 2002

The present article describes a simple four point-probe method to measure weak and short-lived photoconductivity in low-resistance samples. The method is based on biasing the sample with a short and intense pulse of current which permits a high sensitivity of measurement. This pulsed and synchronized bias current is induced in a Rogowski coil by the laser flash-lamp current. We also analyze the performance and inherent limitations of this system.
Current distribution in a high T
c superconductor
Authors: Smith H. J. T. , Keith V.
Published: July 2002

An experimental technique to measure the spatial surface B field distribution in a high Tc superconductor in the temperature range 15–90 K and low applied magnetic fields (less than 300 Oe) is described. A model of magnetic dipoles has been used to describe the magnetic properties of these superconductors. The surface B field is calculated and compared with the experimental data. The experimental surface B field data are used to calculate the spatial current distribution in the superconductor by a two-dimensional Fourier transform.
An experimental apparatus for the characterization of rf properties of superconducting samples near the transition temperature
Authors: Gemme G. , Fabbricatore P. , Musenich R. , Parodi R. , Rossi T. , Zhang B.
Published: July 2002

An experimental apparatus for accurate characterization of rf properties of superconducting samples near the transition temperature has been designed and realized. It is composed of a standard liquid helium cryostat equipped with a variable temperature insert. A feedback system allows temperature stabilization within 10−2 K around a chosen temperature. A simple, while exhaustive, thermodynamical model of the cryostat operation is presented together with the description of the temperature control system. The rf measurement technique is also presented with the first results obtained on a niobium sample used for calibration.
Cryostat for fatigue tests down to liquid-nitrogen temperatures
Authors: Malarría Jorge , Sade Marcos , Taglialavore Eduardo
Published: July 2002

A cryostat was constructed and installed in a MTS 810 servohydraulic testing machine for studying fatigue properties associated with pseudoelastic cycling of shape memory alloys down to liquid-nitrogen temperatures. Special attention was focused on eliminating temperature fluctuations during the fatigue experiments. In order to perform long time fatigue tests, an automatic controlled system which supplies the cryostat with liquid nitrogen was developed and described in detail.
High-resolution field ionizer for state-selective detection of Rydberg atoms in fast-beam laser spectroscopy
Authors: Stratmann K. , Hohmann R. , Kluge H.-J. , Kunze S. , Lantzsch J. , Monz L. , Otten E. W. , Passler G. , Stenner J. , Wendt K. , Zimmer K.
Published: July 2002

The design of a novel electrode structure for electric-field ionization of Rydberg atoms in a fast atomic beam is described. It allows the resolution of the ion signal from Rydberg atoms with adjacent effective principal quantum numbers n* in the range of 14≤n*≤40 and minimizes the volume where field ionization takes place. These features drastically reduce the number of background events arising from collisions of fast atoms with residual gas molecules and thus are essential for trace analysis applications of the technique of resonance ionization spectroscopy in collinear geometry.
A pulse sequencer and transient nanoammeter system for membrane voltage-dependent capacitance measurements
Authors: Fielder Scott S. , Noglik Horst , Pietro William J.
Published: July 2002

A highly sensitive system for producing and time-resolving small-signal current transients in bilayer lipid membranes separating two ionic solutions is described. The circuitry can be constructed from inexpensive and readily obtainable electronic components, and may be interfaced with a variety of digital oscilloscopes or data acquisition systems. The system consists of a driver, fast nanoammeter, and timing sequencer. The driver is capable of delivering a stable, very low impedance voltage pulse (−2.0 to +2.0 V) superimposed on a clamping voltage adjustable within the same range. The pulse can be of any width between 500 μs and 5000 s, and can be delayed with respect to an oscilloscope synchronization trigger, which is also provided. The nanoammeter is accurate between 10 pA and 100 mA and has a time resolution of better than 10 μs. The driver and nanoammeter were designed specifically to be stable under the conditions of a highly capacitive load with very high dc resistance, as is typical of a bilayer lipid membrane. The system can be used with either reference or blocking electrodes. Ideal and actual membrane transient response curves, along with noise assessment data, are provided for calibration purposes.
A scanning electron microscope based microindentation system
Authors: Daniel A. M. , Smith S. T. , Lewis M. H.
Published: July 2002

The design and characterization of a scanning electron microscope based microindentor is presented. Dynamic, high magnification imaging of the indentor–specimen contact zone is possible, permitting observation of indent events. Applied load as a function of indentor tip displacement is continuously monitored during indentation. The maximum applied load capability of 20 N is measured to a resolution of 1 mN with a piezoelectric transducer mounted on the indentor shaft. Displacement is measured with a specially developed capacitance gauge that is again mounted on the indentor shaft near the indentor tip and records tip displacement with respect to the specimen surface to a resolution of 10 nm over a 100 μm range. The instrument is vacuum compatible, capable of remote operation, has a short measurement loop, and a potentially high bandwidth response. Results from a fiber push-down test on a SiC fiber reinforced glass ceramic are reported to illustrate the capability of the instrument in performing measurements across the nanoindentation and microindentation ranges.
Polarization characterization of circularly polarized vacuum-ultraviolet and soft-x-ray helical undulator radiation
Authors: Koide T. , Shidara T. , Miyahara T. , Yuri M.
Published: July 2002

A vacuum-compatible reflection polarimeter has been designed and constructed for monitoring the polarization state of circularly polarized radiation from a helical undulator installed on beamline BL-28A at the Photon Factory. The rotational axis of the polarimeter can be adjusted to coincide with the axis of the monochromatized beam. The polarimeter was used to measure the Stokes parameters of the beam emerging from BL-28A at given energies in the 50–80 eV region with the first-harmonic-peak energy of undulator radiation kept at ∼75 eV. Numerical calculations were also made by considering the undulator-radiation characteristics and further by taking into account the effects on the polarization of the beamline optics and of the mixing of bending-magnet radiation. Comparison of the experimental results with the calculations is given.
Status of the booster synchrotron for SPring-8
Authors: Suzuki H. , Yonehara H. , Aoki T. , Tani N. , Kaneda T. , Ueyama Y. , Sasaki Y. , Nagafuchi T. , Hayashi S. , Yokomizo H.
Published: July 2002

The specification and the layout of the booster synchrotron for SPring-8 were decided. The synchrotron is designed to accelerate electron or positron beams from 1 to 8 GeV with a repetition cycle of 1 Hz. The construction of the synchrotron was started in 1993. First, one bending, one quadrupole, and one sextupole magnet were made and the results of the magnetic field measurement were acquired. Two septum, one bump, and one kicker magnets for the beam extraction have been made, the field measurement and a few improvements have progressed. The high power test of the first rf cavity was finished successfully. The calibration test of the button position monitor with the signal treatment circuits is advanced now. The residual components of the synchrotron are designed and constructed, and the commissioning of the synchrotron will start in 1996. This paper presents the first measurement of each component.
Construction and beam experiment of a compact storage ring at MELCO
Authors: Nakanishi T. , Ikegami K. , Kodera I. , Maruyama A. , Matsuda T. , Morita M. , Nakagawa T. , Nakamura S. , Nakata S. , Ohishi N. , Okuda S. , Shimohata K. , Takeuchi T. , Tanaka H. , Tsukishima C. , Yamamoto S. , Yokoyama S. , Yamada T.
Published: July 2002

A compact storage ring has been developed for industrial research such as x-ray lithography and material analysis. This machine is of a racetrack type with two superconducting bending magnets and only two normal conducting quadrupole magnets. The circumference is as short as 9.2 m. One quadrupole magnet per cell contributes to making the smaller machine. The injector is a synchrotron, and a full energy injection of 600 MeV is performed. The bending magnets excite a field of 3.5 T, and are operated in a persistent current mode. A decrease in a coil current is ΔI/I<3×10−3/year. The helium consumption is as low as 2 ℓ/h for two magnets. An iron shield of the magnet decreases a leakage flux to a terrestrial level at a point 3 m from the magnet. A beam current of 380 mA has been stored with no beam instability in spite of there being no correction of the chromaticities. Beam emittances were obtained from measured beam sizes and were in good agreement with calculated values. The coupling coefficient εy/εx is calculated as around 0.04.
Performance of photon position monitors and stability of undulator beams at the advanced light source
Authors: Warwick Tony , Andresen Nord , Portmann Greg , Jackson Alan
Published: July 2002

Position monitors are implemented in three undulator beamlines at the ALS. Their performance has been studied carefully on one of these lines and is reviewed. The monitors work as expected and show the ALS to be an exceptionally stable source of synchrotron radiation.
A simple in-hutch mirror assembly for x-ray harmonic suppression
Authors: Latimer Matthew J. , Rompel Annette , Underwood James H. , Yachandra Vittal K. , Klein Melvin P.
Published: July 2002

A double mirror harmonic suppressor has been constructed for use in the experimental hutch on hard-x-ray beamlines. The apparatus consists of two flat, gold-coated float glass mirrors mounted in a face-to-face ‘‘periscope’’ arrangement. This device reduces the second harmonic to 0.5% of the total flux (much better than monochromator detuning) while retaining ∼50% of the flux at the fundamental.
The new 1.5 GeV storage ring for synchrotron radiation: MAX II
Authors: Andersson Å. , Eriksson M. , Lindgren L.-J. , Röjsel P. , Werin S.
Published: July 2002

The MAX laboratory at Lund University, Sweden, today operates an accelerator system consisting of a 100 MeV racetrack microtron and a 550 MeV storage ring (MAX I). At the moment (July 1994) a new storage ring MAX II is near completion and will start first injections within 2 months. This work gives an overview of the MAX II project including the first beamlines and a description of the accelerator system. MAX II is a 1.5 GeV third generation light source optimized for the VUV and soft-x-ray region. It consists of a ten cell double bend achromat lattice forming the 90 m circumference ring. Injection is done at 500 MeV from the existing storage ring MAX I, and ramping up to full energy will take place in MAX II. The straight sections have a length of 3.2 m and eight sections are free to house insertion devices. At start up the ring will be equipped with one 7.5 T superconducting wiggler and one 1.8 T multipole wiggler. Two more undulators are ordered and under construction. To be able to achieve the project a few shortcuts have been made in the design of the storage ring: (1) Nonzero dispersion is allowed in the straight sections, (2) chromaticity correction is built into the quadrupole magnets, and (3) the length of the straight sections is limited to 3.2 m. The project is progressing on time. Extraction of an electron beam from the MAX I storage ring has been achieved and has successfully been transported into the MAX II building. The MAX II ring is under assembly with most of the sections already mounted. First injection is planned to take place in August 1994.
Upgrade of the Photon Factory storage ring for a high brilliance configuration
Authors: Katoh M. , Hori Y. , Nakamura N. , Kitamura H. , Kobayakawa H.
Published: July 2002

A high brilliance configuration of the 2.5-GeV Photon Factory storage ring has been designed and proposed. In the new configuration, the beam emittance will be reduced to 27 nm rad, which is one-fifth of the present value (130 nm rad). The brilliance will be typically increased by a factor of 10. The beam lifetime and beam stability are discussed from a standpoint of the total effective brilliance. All of the improvements for this upgrade are being carefully designed and planned so as to be achieved (1) with minimum influence for the existing beamlines, (2) within the shortest shutdown time, and (3) at low cost.
Beam position control of SOR-RING
Authors: Kudo Hirofumi , Nagatsuka Toshiya , Shinoe Kenji , Takaki Hiroyuki , Koseki Tadashi , Nakamura Norio , Kamiya Yukihide
Published: July 2002

Recently, a global feedback of beam position was switched on at SOR-RING of Tokyo University. At a low beam current, the vertical orbit drift was suppressed almost within a few μm and the horizontal orbit drift within several μm. On the other hand, the suppression became worse at a high current because of a longitudinal instability, which deteriorated the accuracy of the beam position monitor system. It was also observed that at 21 Hz, the repetition rate of the electron synchrotron close to SOR-RING, the horizontal orbit tends to vibrate uniformly around the ring, i.e., monopolelike expansion and contraction, while the vertical orbit has a dipolelike vibration; a result expected if a uniform magnetic field is impressed on the ring.
New mechanism to balance the torque induced in a goniometer axis
Authors: Kikuchi Toshiharu , Takagi Yasuo , Mizutani Toshiyuki , Sasaki Satoshi , Mori Takeharu , Kohzu Hiroyuki
Published: July 2002

A new mechanism to balance the torque induced on goniometer arms was developed to prevent serious mechanical difficulties of goniometers. Since the amount of the torque induced by its own weight depends on the goniometer angle, a new angle-dependent torque is applied to the goniometer arms to balance the original torque. A system based on this mechanism consists of an angle sensor, a function calculator, and an actuator. The goniometer angle is detected by a displacement gauge, and subsequently converted to the appropriate value of the air pressure applied by an electropneumatic controller. A new torque is applied by the controller through a wire to the goniometer arm to balance the original torque. Nearly ‘‘torque-free’’ operation of the goniometer became possible by this system, which was installed on the 2θ axis of the four-circle goniometer in the triple-axis/four-circle diffractometer, SIN-1, at PF-BL3A. The axis has been able to scan as fast as 2θ=100°/min under a maximum torque of 500 Nm without any mechanical difficulties, for more than two years.
Vacuum tests of a beamline front-end mock-up at the Advanced Photon Source (abstract)a)
Authors: Liu C. , Nielsen R. W. , Kruy T. L. , Shu D. , Kuzay T. M.
Published: July 2002

A mock-up has been constructed to test the functioning and performance of the Advanced Photon Source (APS) front ends. The mock-up consists of all components of the APS insertion-device beamline front end with a differential pumping system. Primary vacuum tests have been performed and compared with finite element vacuum calculations. Pressure distribution measurements using controlled leaks demonstrate a better than four decades of pressure difference between the two ends of the mock-up. The measured pressure profiles are consistent with results of finite element analyses of the system. The safety-control systems are also being tested. A closing time of ∼20 ms for the photon shutter and ∼7 ms for the fast closing valve have been obtained. Experiments on vacuum protection systems indicate that the front end is well protected in case of a vacuum breach.
Conceptual design of SPring-8 front ends
Authors: Sakurai Y. , Oura M. , Sakae H. , Usui T. , Kimura H. , Oikawa Y. , Kitamura H. , Konishi T. , Shiwaku H. , Nakamura A. , Amamoto H. , Harami T.
Published: July 2002

The conceptual design of the front ends have been completed for the SPring-8 under construction in Japan. Standardizing the front ends and sharing the heat load among the beamline components are the philosophy for the design. Taking the beam properties into consideration, three types of the front ends which correspond to the undulator, multipole wiggler, and bending magnet beamlines are designed.
Design of an elliptic multipole wiggler beamline for high-energy inelastic scattering at the SPring-8
Authors: Sakurai Y. , Yamaoka H. , Kimura H. , Marechal X. M. , Ohtomo K. , Mochizuki T. , Ishikawa T. , Kitamura H. , Kashihara Y. , Harami T. , Tanaka Y. , Kawata H. , Shiotani N. , Sakai N.
Published: July 2002

An elliptic multipole wiggler beamline will be constructed for inelastic scattering (Compton scattering) experiments at the SPring-8. This beamline will provide monochromatic x rays with linear or elliptic polarization in the energy range of 100–300 keV. It will extend the application of the Compton scattering experiments to the study of materials science. An outline of the beamline is given.
The vacuum system for insertion devices at the advanced photon source
Authors: Trakhtenberg E. M. , Gluskin E. , Xu S.
Published: July 2002

A vacuum system for the insertion devices at the advanced photon source was designed; a prototype of this system was manufactured and successfully tested. The system consists of two vacuum chamber sections with distributed vacuum pumps, two boxes containing the vacuum pumps, vacuum analyzers and special transition sections, and finally two support structure sections. The vacuum chambers are made of extruded aluminum. The wall thickness of the insertion-device vacuum chamber section is 1 mm in the area of the insertion device’s magnetic gap on the length of 2.4 m. An ultimate pressure of 5.1×10−11 Torr was achieved in the prototype, which contains the insertion device vacuum chamber section with a 12-mm vertical aperture.
DDX diffraction system: A combined diffraction system with EDX and ADX for high-pressure structure studies
Authors: Kikegawa Takumi , Chen JiuHua , Yaoita Kenichi , Shimomura Osamu
Published: July 2002

A dual dispersive x-ray (DDX) diffraction system which combines energy dispersive x-ray (EDX) diffraction with angle dispersive x-ray (ADX) diffraction has been developed on the cubic-type multianvil press named MAX80 at the beamline NE5C at the TRISTAN Accumulation Ring (6.5 GeV) of the Photon Factory. With the DDX diffraction system, quick recording of the diffraction pattern is made in the EDX diffraction mode for pressure determination and sample identification, and high-quality diffraction patterns with reliable diffraction intensities are obtained in the ADX diffraction mode for structure analysis. It requires only three minutes to switch between the EDX and ADX diffraction modes. The structure relation between Bi iii and Bi iii′ which was suggested by previous researchers has been investigated with this system. The volumetric compressibility was obtained by the EDX diffraction mode and the atomic arrangement was determined from the data collected in the ADX diffraction mode. No significant change was found around the suggested transition pressure. The crystal structure of Bi iii′s is therefore determined to be identical to that of Bi iii.
Structural study of the high-pressure phases of bismuth using high-energy synchrotron radiation
Authors: Iwasaki H. , Chen J. H. , Kikegawa T.
Published: July 2002

An x-ray diffraction study was carried out on the crystal structure of the high pressure phases of bismuth, Bi III, Bi III′, and Bi IV, using high-energy monochromatic synchrotron radiation from the TRISTAN Accumulation Ring (6.5 GeV). Powdered samples were compressed in a cubic-type multianvil press MAX80 at pressures ranging from 3 to 6 GPa. In some compression runs, the sample temperature was raised up to 550 K. It was possible to obtain diffraction patterns containing many diffraction peaks and assign unambiguously indices to them. The crystal structure of Bi III is tetragonal with ten atoms contained in the unit cell. It has been shown that, when pressure is increased across the transition pressure between Bi III and Bi III′, no change in the diffraction pattern takes place, indicating that the two phases have the same structure. Bi IV which exists in the high temperature region in the P-T diagram has been shown to have the structure with a monoclinic symmetry and eight atoms in the unit cell. All the structures determined can be regarded as a distorted body-centered-cubic lattice structure.
Response to ‘‘Comment on ‘Simple shutter circuit for protecting microchannel plate photomultipliers from excess light exposure’ ’’ [Rev. Sci. Instrum. 66, 5387 (1995)]
Authors: Kauffman J. F. , Liu C. S.
Published: July 2002

The value of a resistor was in error by a factor of 1000 due to the omission of a ‘‘k.’’
New inductively coupled plasma source using a multispiral coil
Authors: Okumura Tomohiro , Nakayama Ichiro
Published: July 2002

The authors have developed a new inductively coupled plasma source (ICPS), using a multispiral coil with 1/3 the inductance of the conventional ICPS coil. This source can produce plasma of 1011 cm−3 or higher density with ±5% fluctuation, at pressures below 10 mTorr.
Design and implementation of a heatable, all-glass doser for sensitive organometallic compounds in an ultrahigh vacuum environment
Authors: Jones L. A. , Wei F.-X. , Thomas D. F.
Published: July 2002

We report the design of an ultrahigh vacuum compatible vapor dosing system for organometallic compounds. A unique feature of this doser is the elimination of all metallic surfaces in order to reduce the reactivity of the organometallic molecules towards the doser walls. The vapors only come in contact with glass, Teflon, and Kalrez and the doser is heatable to temperatures of 150 °C. A novel modification to a commercial glass stopcock is described. These modified valves are used in the doser to seal the ultrahigh vacuum system from the organometallic sample compartment and have been shown to be able to allow the vacuum system to maintain ultrahigh vacuum conditions even when the sample compartment is vented to atmosphere. Spring-loaded Teflon seals are used to seal the valve shaft against the glass wall thereby maintaining ultrahigh vacuum conditions and a chemically inert surface for the organometallic compounds. A further modification to these commercial valves is described allowing it to function as the sample compartment for the organometallic material. This compartment features a heatable reservoir, vacuum seals to ultrahigh vacuum levels, and a rapid exchange design to permit the interchange of dosing materials.
Errors in ac susceptibility measurements from surrounding dc solenoids
Authors: Barnard R. D.
Published: July 2002

ac susceptibility measurements may contain significant errors when performed against a background magnetic field produced by a surrounding solenoid. The errors arise from mutual inductance between the field coil and excitation coil. An analysis of this source of error is given and a simple means by which this error may be largely eliminated is described.
5 kHz high repetition rate and high power XeCl excimer laser
Authors: Goto Tatsumi , Kakizaki Koji , Takagi Shigeyuki , Okamoto Noboru , Sato Saburo , Kosugi Shinichiroh , Ohishi Takashi
Published: July 2002

A 5 kHz high repetition rate excimer laser has been developed. An average laser power of 0.56 kW at 5 kHz operation, which remains stable for 1 s, is obtained. This duty time is limited only by overheating of the switching thyratrons. The 5 kHz operation is attained by some improvements to the gas conditions, the UV-preionization scheme, and the gas flow speed in the discharge region. The gas is circulated at an effective flow velocity of 137 m/s by a newly developed two-stage axial blower. The gas conditions are optimized experimentally to achieve 5 kHz operation. To obtain uniform preionization, the locations of pin electrodes for the preionization are determined on the basis of numerical results.
Description of an acquisition unit for optical interferometry treatment: Application to the pollution imagery of SO2 gas
Authors: Nguyên Chi Thanh , Journet Bernard , Fortunato Gérard
Published: July 2002

An optical analyzer has been conceived to achieve outdoor pollution imagery. The experimental apparatus associates an interferometric correlator with a linear charge-coupled device (CCD) image sensor and a data acquisition unit for PC-compatible computers. This paper presents the principle of measurement and describes the optical head and the main parts of the acquisition unit. A laboratory experiment of SO2 gas imagery is presented, proving the feasibility of our method; results and performance are reported.
An efficient trap for the collection of a cadmium atomic beam
Authors: Bauman R. P. , Martin N. L. S.
Published: July 2002

Precautions are described for the successful operation of a crossed-beam apparatus which uses an atomic cadmium target. These include a novel type of high-voltage trap for the collection of cadmium vapor.
An unbalanced magnetron sputtering device for low and medium pressures
Authors: Muralidhar G. K. , Musil J. , Kadlec S.
Published: July 2002

The discharge characteristics of an unbalanced magnetron sputtering device, equipped with a 100-mm-diam planar circular target and with two electromagnetic coils, have been analyzed in a range of operation pressures from 0.02 to 1 Pa. The variation of discharge extinction and ignition pressures and target voltage is presented as a function of the ratio of currents in the magnetron coils and discharge current. A maximum discharge current beyond which it is not possible to sustain the discharge at low pressures has been observed. This extinction current increases with operating pressures. An explanation for the effect is based on the loss of gas from the plasma due to gas heating with energetic sputtered particles and subsequent gas density rarefaction in the near target region. Higher pressure is thus necessary to keep constant gas density in the magnetron plasma when the discharge current is increased. The magnetic field configuration is presented for several values of the ratio of currents in the magnetron coils and correlated to the variation of discharge extinction and ignition pressures, extinction current, and target voltage. The low pressure operation of the magnetron strongly depends on optimization of the magnetic field shape on the sputtered target. The deposition rate of titanium films is a linear function of magnetron power up to 2.5 kW and does not depend on Ar pressure in the pressure range studied (0.08–0.6 Pa).
An optimized experimental method for measuring thermal conductivity of thin, boron-doped diamond films
Authors: Herr S. A. , Beck J. V. , McGrath J. J. , Sahli S. , Aslam M.
Published: July 2002

A novel experimental method has been developed and applied to measure the thermal conductivity of a thin (5.6 μm thick) boron-doped diamond film produced by a hot filament CVD process. Thermal fields were created by Joule heating in a 3-mm-diam, free-standing diamond diaphragm; infrared imaging thermography was used to quantify these fields. Parameter estimation was applied to determine the thermal conductivity of the film using more than 100 temperatures in each property determination. The experimental design chosen was selected on the basis of an analysis which maximized the sensitivity for the determination of thermal conductivity while minimizing the uncertainty in the estimation of this property. Parameters such as characteristic length, film resistivity, and thickness were chosen from the model to reduce convective effects, obtain the desired temperature rise, and minimize the uncertainty in the estimation of the thermal conductivity. Preliminary results for the thermal conductivity were obtained using the method of least squares to minimize the error between the measured temperatures recorded by the infrared temperature acquisition system and the calculated temperatures determined by the optimal radial heat flow model. A single doped film was energized at three power levels in five experiments. The thermal conductivity was determined to be 240±11 W/m K. The measured standard deviation of the mean matched the estimated uncertainty closely and the relative contributions to the experimental uncertainty have been quantified.
Optimization of step-scanning registration with radiation counters
Authors: Zorn Reiner
Published: July 2002

If an intensity distribution of radiation (x-rays, neutrons, etc.) is scanned by a movable counterdetector, the step-scanning method is used often. The detector stops at certain positions of the region to be scanned and is left there at rest for the time of counting. Then the experimentalist has to decide where to set these positions, especially how dense the scan should be. This decision is usually done by ‘‘rule of thumb.’’ In this article an optimization method will be described which uses calculus of variation to determine the registration positions (at least their density) on an objective basis. To do this, the statistical error and the error due to coarse scanning will be considered together in a figure of merit which has to be minimized. The main result is that the density of steps is proportional to the 2/5th power of the second derivative of the intensity distribution. This reflects the customary design principle, to scan regions with ‘‘more structure’’ more densely. In short an application of the method on x-ray diffraction in the low angle regime will be reported.
Accurate, repetitive, linear motion from biased piezoelectric actuators
Authors: Deck Leslie
Published: July 2002

A method is described for producing accurate, repetitive, linear motion from biased piezoelectric actuators without the need for feedback from external distance measuring sensors. A precalibration of the actuator determines a voltage profile that produces repeatable linear motion but whose slope is uncertain due to actuator gain variations stemming from bulk polarization changes in the piezoelectric ceramic. Monitoring the current flowing through the actuator at a specified point in the linear part of the motion profile is used to determine and correct for the slope variations.
A wire scanning type position monitor for an undulator radiation
Authors: Zhang Xiaowei , Sugiyama Hiroshi , Ando Masami , Xia Shaojian , Shiwaku Hideaki
Published: July 2002

A scanning wire position monitor for insertion devices was designed and installed in an x-ray undulator beam line. It consists of a graphite wire, a copper mesh for electric shielding, and a motor-driven linear guide. The wire of the monitor was tested under the undulator radiation thermal load. It has been found that the signal level of the monitor was proportional to the radiation power density on the wire. Even when the wire crossed the beam during the x-ray experiment, no detectable influence on the experiment was observed.
Improved arrangement of shock-detecting pins in shock equation of state experiments
Authors: Erskine David J.
Published: July 2002

Shock wave speeds are often measured by comparing arrival times at the tips of electrical shorting pins in a hexagonal array over two elevations (called up and down). In the conventional arrangement, the center pin is solely responsible for measuring the curvature of the wave front. Without this datum the shock speed cannot be precisely determined. In some experiments this pin fails frequently enough to be a problem. We report a simple rearrangement between up and down designated pins which eliminates the critical reliance on a single pin.
Resonance frequency estimation of a bridged loop-gap resonator used for magnetic resonance measurements
Authors: Hirata Hiroshi , Ono Mitsuhiro
Published: July 2002

This paper presents a method for estimating the resonance frequency of a bridged loop-gap resonator (BLGR). It first describes the structure of the BLGR and its equivalent electrical circuit, and then a procedure for calculating the resonance frequency is revealed. In this procedure, node analysis, which is a circuit theory, is applied to calculate the branch voltages of the equivalent circuit. Finally, this paper reports on the calculations and measurements of the resonance frequency, and the validity of the method for estimating resonance frequency.
Pseudorandom time-of-flight analysis with a time-of-flight mass spectrometer
Authors: Bewig L. , Buck U. , Gandhi S. R. , Winter M.
Published: July 2002

We describe the advantages of using the pseudorandom time-of-flight (TOF) technique for measuring velocity distributions together with the TOF mass spectrometric detection. The basic idea of the method is the successive measurement of abundance spectra with the TOF mass spectrometer correlated with each channel of the pseudorandom sequence. Extraction of the intensities of each mass and subsequent cross correlation with the pseudorandom sequence leads to the TOF and thus the velocity distributions. The proposed technique can substantially reduce the data acquisition time in systems for which many different reaction products are expected such as in cluster research. An illustration of the efficiency is presented using angular resolved TOF distributions for products of the reaction of sodium clusters Nan with O2.
Investigation of a small, closed electron drift, stationary plasma thruster
Authors: Guerrini G. , Vesselovzorov A. N. , Bacal M. , Pokrovsky I. B.
Published: July 2002

The interest in low-power electric thrusters stimulated our research on a small stationary plasma thruster. The first results on the dependence of the thrust, the discharge current, the ion current, and the axial electron current on gas flow are reported. It was also shown that the drop of the discharge current with magnetic field is strongly affected by the emission current of the filament neutralizer.
Use of a diode laser to measure the polarization of an optically pumped ensemble of He(2 3S) atoms
Authors: Wallace C. D. , Bixler D. L. , Huang D. , Wagman A. H. , Dunning F. B. , Walters G. K.
Published: July 2002

A simple technique is described for determining the polarization of He(2 3S) atoms contained in an active discharge or afterglow. The polarization (and alignment) is obtained by measuring the attenuation of a circularly polarized probe beam provided by a 1.083 μm laser diode whose output frequency is scanned to allow separate measurements on the 2 3S1→2 3P0, 2 3S1→2 3P1, and 2 3S1→2 3P2 transitions.
Production of high-brightness continuous wave proton beams with very high proton fractionsa)
Authors: Spence D. , McMichael G. , Lykke K. R. , Schneider J. D. , Sherman J. , Stevens R. , Hodgkins D.
Published: July 2002

This article demonstrates a new technique to significantly enhance the proton fraction of an ion beam extracted from a plasma ion source. We employ a magnetically confined microwave driven source, though the technique is not source specific and can probably be applied equally effectively to other plasma sources such as Penning and multicusp types. Specifically, we dope the plasma with about 1% H2O, which increases the proton fraction of a 45 keV 45 mA beam from 75% to 90% with 375 W 2.45 GHz power to the source and from 84% to 92% for 500 W when the source is operated under nonresonant conditions. Much of the remaining fraction of the beam comprises a heavy mass ion we believe to be N+ impurity ions resulting from the conditions under which the experiments were performed. If so, this impurity can easily be removed and much higher proton fractions could be expected. Preliminary measurements show the additive has no adverse effect on the emittance of the extracted beam, and source stability is greatly improved.
The use of ‘‘mixed’’ beams in microprobe imaging
Authors: Saint A. , Breese M. B. H. , Legge G. J. F.
Published: July 2002

This article will demonstrate the production and application of ‘‘mixed’’ beams for a magnetically focused nuclear microprobe. A ‘‘mixed’’ beam is defined as any two beams of ions of different species, or energy, or both that can be quickly and easily made to have the same magnetic rigidity (Rm) so that they transport, focus, and scan the same in a magnetic nuclear microprobe. Two techniques for the production of such beams will be presented. These methods include the extraction of different ions from the same source and scanning the terminal potential to produce the same Rm, and the use of a postacceleration stripper to change the charge state of one ion species to give it the same Rm as another ion species. The application of mixed beams to ion beam induced charge, scanning transmission ion microscopy, and ion microlithography will also be presented.
Role of the collecting resistive layer on the static characteristics of a 1D a-Si:H thin film position sensitive detector
Authors: Fortunato E. , Martins R.
Published: July 2002

The aim of this work is to present an analytical model able to interpret the role of the thin collecting resistive layer on the static performances exhibited by 1D amorphous silicon hydrogenated p-i-n thin film position sensitive detectors. The data obtained show that the devices present a linearity and a spatial resolution, of respectively, better than 99% and 20 μm for a spatial detection limit of about 80 mm, highly dependent on the characteristics exhibited by the collecting resistive layer that should have sheet resistivities in the range of 10 to 103 Ω/sq, as predicted by the model proposed.