bluuebunny/crossref_metadata_2025 huggingface dataset:
Design and construction of the front end of the 53-pole wiggler/undulator beamline
Authors: Koide Tsuneharu , Sato Shigeru , Kanaya Noriichi , Asaoka Seiji
Published: July 2002

The design considerations and technical details for components of the front end of a Photon Factory 53-pole wiggler/undulator beamline are described. Special attention is paid to the handling of the high-power densities produced by the wiggler.
Differences in quality of PF ring vacuum between positron and electron storage mode
Authors: Kobayashi Masanori , Hori Yoichiro , Takiyama Youichi
Published: July 2002

Electrons or positrons were stored in the electron storage ring of the Photon Factory (PF). The vacuum of the PF was so good that differences in the instantaneous beam lifetimes between electron and positron storage modes were very slight. Abnormal decrements of the stored beam current observed in the electron storage mode did not appear in the positron storage mode. Thus, the decay curves of the beam current in the positron storage mode were smoother than those in the electron storage mode. Though the instantaneous beam lifetime was nearly the same in storage modes, the practical beam lifetime of a positron was about 10% longer than that of an electron.
Micropole undulators: Novel insertion devices for synchrotron sources (invited)
Authors: Toor Arthur , Csonka Paul , Tatchyn Roman
Published: July 2002

Micropole undulators (wigglers) are undulators (wigglers) with submillimeter periods and are referred to, generically, as micropole insertion devices. Compared to ordinary insertion devices, whose period λu is typically ≥l cm, micropole devices have periods smaller by a factor f≤10. Therefore, the first-harmonic radiation emitted by a micropole undulator will have its photon energy Eγ increased by f and its spectral purity Δλ/λ by f, provided the total length of the undulator lu stays unchanged, and magnetic field errors, as well as the electron-beam emittance, are sufficiently small. Furthermore, to generate photons of the same Eγ as from the conventional device, the electron-beam energy Ee can be reduced by f 1/2 , resulting in significantly lower construction and operating costs. Radiative energy losses can be correspondingly diminished for the associated storage rings. In this paper we report on results recently obtained by us in the practical implementation and design of micropole undulators at the Stanford Synchrotron Radiation Laboratory (SSRL) and the Lawrence Livermore National Laboratory (LLNL). Based on our work, micropole undulators with f≤104 appear feasible at the present time.
HARWI—A hard x-ray wiggler beam at DORIS (invited)
Authors: Graeff W. , Bittner L. , Brefeld W. , Hahn U. , Heintze G. , Heuer J. , Kouptsidis J. , Pflüger J. , Schwartz M. , Weiner E. W. , Wroblewski T.
Published: July 2002

The construction of the wiggler W2 at DORIS is described together with the major components of the beamline. Details are given on the assembly and performance of the magnet structure. Three different monochromators are used in the beamline alternatively. One of them, a Laue–Bragg-type monochromator is described in more detail.
The TEXT data base
Authors: Wiley J. C. , Miner W. H. , Bravenec R. V. , Patterson D. M. , McCool S. C.
Published: July 2002

The TEXTDB data base organizes the analyzed experimental data from the TEXT experiment so as to aid in understanding the physics of a complete discharge. The data base was constructed using a commercial relational data base. The relational model provided a flexible structure for organizing data from many different diagnostics into a unified description of the plasma discharge.
High temperature capillary viscometer
Authors: Chu Benjamin , Wang Zhulun , Park Il Hyun , Tontisakis Antony
Published: July 2002

A new high-temperature capillary viscometer for measuring the viscosity of dilute polymer solutions has been designed, constructed, and extensively tested. The viscometer has combined several valuable capabilities: high-temperature operation (potentially to 280 °C and tested up to 250 °C), high precision (∼10−3 s with a temperature control of ±0.001 °C), variable shear rates (by changing the orientation of the capillary), and differential measurements (by using a twin viscometer arrangement). A description of the high-temperature viscometer and tests of its capabilities are presented.
Differential transducer for pressures up to 10 kbar
Authors: Verbrugge R. , Schouten J. A. , Schuijlenburg W. J. , Kortbeek P. J.
Published: July 2002

A differential pressure transducer has been developed for pressures up to 10 kbar. Both liquids and gases can be used as pressurizing media. A full-scale deflection of the meter represents a pressure difference of less than 0.5 bar.
Advanced light source at Lawrence Berkeley Laboratory (invited)
Authors: Cornacchia M.
Published: July 2002

The 1–2-GeV synchrotron radiation source will be a national user-based facility providing photon beams of unprecedented brightness in the ultraviolet and soft x-ray region of the electromagnetic spectrum. The facility design is optimized to emphasize the use of undulators to provide high-spectral brilliance in the few electron volt to 1-keV spectral range; wigglers provide high flux up to approximately 10 keV. Beam structure of a few tens of picoseconds will be available for time-resolved experiments. The facility is designed for operational flexibility and to assure rapid commissioning. The initial complement of experimental stations consists of five insertion devices (four undulators and our wiggler) and associated beamlines, and two white light beams from bend magnets. Six other straight sections are available for additional insertion devices, and the design provides for up to 48 ports for beams from bending magnets. The storage ring is optimized for operation at 1.5 GeV with a maximum energy of 1.9 GeV. The injection system includes a 1-Hz, 1.5-GeV booster synchrotron for full energy injection at the nominal operating energy of the storage ring. Filling time for the maximum stored current of 400 mA is expected to be 2 min, and the beam half-life will be about 6 h. Attention is being given to the severe requirements for beam stability and the need to independently control photon beam alignment. We describe the important characteristics of the facility, significant aspects of the technical design of accelerator systems, insertion devices and photon beamlines, and considerations related to addressing projected user needs in the development of the project.
High resolution microcalorimeters as detectors for inelastic scattering (invited)
Authors: Szymkowiak A. , Kelley R. , Madejski G. , Moseley H. , Schoelkopf R. , Edwards B. , Juda M. , McCammon D. , Skinner M. , Zhang J.
Published: July 2002

Small thermal calorimeters operated at temperatures near 100 mK are sufficiently sensitive to detect single photons, measuring the deposited energy to accuracies approaching 1 eV. A test device has demonstrated 17-eV FWHM for 6-keV x-rays—almost an order of magnitude better than a conventional Si(Li) solid state detector. Further improvement requires the development of monolithic fabrication techniques to reduce the parasitic heat capacities introduced in assembling a discrete device. Current technology should permit the construction of a detector about 1/2 mm2 with good efficiency for 35-keV x-rays and a resolution near 25 eV. The ultimate resolution achievable in practice and the tradeoff of collecting energy for resolution depend primarily on the low-temperature specific heat of the material used to absorb the x-rays and efficiently thermalize their energy. Finding the optimum absorber is particularly important at higher photon energies. We are studying absorbers that may offer considerably improved performance.
The spherical drift chamber used at LURE for protein crystallography; last developments, performances, and results (invited) (abstract)
Authors: Kahn R. , Fourme R. , Bosshard R. , Lewit-Bentley A. , Prangé T.
Published: July 2002

We have developed at LURE a multiwire proportional chamber with a spherical drift space. The wire chamber consists of two cathode planes, comprising 512 wires with a spacing of 1 mm, set on both sides of the anodic plane. The drift space, a gas filled region bounded by two spherically curved electrodes 144 mm apart, offers several advantages: high quantum efficiency, no parallax effect, equivalent spatial resolution in both directions, and smoothing of the pulsed structure of the synchrotron radiation. The gaseous mixture of argon-xenon (58%), ethane (40%), and ethyl alcohol (2%) is circulated in a closed circuit and is continuously purified. Ethyl alcohol, which avoids electrical discharges and sparks, is essential to operate the instrument at high counting rates (>300 000 events/s). The signal processing, which makes use of one amplifier per cathode wire and of fast priority encoders, determines both coordinates with a resolution of 1 mm and a dead time of 240 ns. Each encoded event is stored into a 512×512 16 bit CAMAC histogramming memory. The experiment is controlled by a PDP11/34 linked to a VAX by a direct memory access channel. A complete set of programs, which performs the data collection and an off line data reduction, is operational. The adaptation of madnes, a general software package which performs an on line data reduction, is under way. Data, collected on a lysozyme crystal to 3.4-Å resolution, give a reliability factor based on intensities of equivalent reflections of 4.7% without absorption corrections; the variation of the detector efficiency is <2.7%. A new version of the instrument is under realization. The position encoder, which uses flash ADCs and signal processors, has a resolution of 0.5 mm. Data are stored into a 1024×1024 16 bit VME histogramming memory linked to a micro VAX.
Grazing-incidence monochromator for the 15–800 Å wavelength range at the storage ring VEPP-2M
Authors: Gluskin E. S. , Kuzminykh V. S. , Trakhtenberg E. M. , Koscheev S. V. , Devyatov V. G. , Cherkashin A. E. , Blau W. , Meisel A. , Ehrhardt H.
Published: July 2002

A new Rowland monochromator with a fixed output slit, which operates according to the grazing-incidence scheme, is described. The device is notable for the capability to change the Rowland radius within 1–3 m. The monochromator was tested using synchrotron radiation from the storage ring VEPP-2M.
Some particular aspects of the physics of the ECR sources for multicharged ions
Authors: Melin G. , Bourg F. , Briand P. , Debernardi J. , Delaunay M. , Geller R. , Jacquot B. , Ludwig P. , N’Guyen T. K. , Pin L. , Pontonnier M. , Rocco J. C. , Zadworny F.
Published: July 2002

This article emphasizes a confinement model for electrons and ions in an ECR source for multicharged ions, on the basis of specific measurements performed on the 16.6 GHz MINIMAFIOS and 10 GHz CAPRICE facilities. The conclusions partially support the above model.
Characterization of InGaAs/GaAs strained-layer quantum wells grown on (311)A GaAs substrates
Authors: Takahashi Mitsuo , Vaccaro Pablo , Fujita Kazuhisa , Watanabe Toshihide
Published: July 2002

The fundamental properties of In0.2Ga0.8As/GaAs strained-layer quantum-wells (QWs) grown on (311)A GaAs substrates were studied. The radiative and nonradiative recombination rates as a function of temperature were obtained from the photoluminescence (PL) spectra and the time-resolved PL measurements. The radiative recombination rate is enhanced in (311)-oriented QW structures as compared to (100)-oriented ones. We fabricated graded-index separate-confinement heterostructure double quantum-well lasers on (311)A GaAs substrates. We demonstrate the low threshold current density of 360 A/cm2 for a 1.17 mm long laser at room temperature.
On-wafer Hall-effect measurement system
Authors: Mumford P. D. , Look D. C.
Published: July 2002

A novel system capable of making on-wafer Hall-effect measurements of a patterned wafer during the fabrication sequence has been developed. A flat, powerful rare-earth magnet provides the magnetic field required. The wafer need only have van der Pauw patterns available for on-wafer measurement capability. Measurement of room temperature Hall mobility can quickly and easily be obtained, making possible detailed study of carrier concentration and mobility variations during wafer fabrication.
Reply to ‘‘Comment on ‘Digital parallel acquisition in frequency domain fluorometry’ ’’ [Rev. Sci. Instrum. 6
, 2929 (1989)]
Authors: Feddersen Brett A. , Piston David W. , Gratton Enrico
Published: July 2002

The duty cycle problem referred to by Alcala has been discussed in our original manuscript, and we calculated the reduction of the signal quite explicitly. His comments on the harmonic content are in error, and the correct values were given in the original paper.
Hard x-ray detector with an MCP image intensifier working in the 100 keV 1 MeV x-ray range
Authors: Veaux J. , Cavailler C. , Gex JP. , Hauducoeur A. , Hyvernage M.
Published: July 2002

We present a high gain x-ray image intensifier with high sensitivity in the 1 MeV x-ray range and a good spatial resolution developed in order to improve the radiographic detection in our experiments. In particular the gold photocathode and MCP thickness have been optimized to give the best trade off between the dose sensitivity and the spatial resolution. The large useful 60-mm-diam photocathode set on the MCP input converts the x-ray emission into electrons that are multiplied in the MCP and proximity focused onto the P11 phosphor screen deposited on a fiber-optic plate. For x-ray quanta of 1 MeV energy the x-ray image converter is more sensitive than the most sensitive x-ray screen film systems. Using for instance a pulsed x-ray source we have been able to record pictures of a sphere or of a testing metallic chart for a dose lower than 100 μrad; under these conditions the spatial resolution was greater than 1 lp mm−1 and the dynamic range was still around 10. Using an x-ray screen film under same input level we have obtained a very low dynamic range and density values actually equal to the noise level. These unique performances fulfill the requirements of a large number of detonic experiments needing a high sensitivity in the 1 MeV x-ray range.
A moderately sensitive flow calorimeter for the investigation of highly adsorptive solids
Authors: Barton Stuart S.
Published: July 2002

The construction and operation of a simple flow calorimeter, suitable for the investigation of adsorption on highly adsorptive solids, are described. For strongly adsorbing solids the injection mode of operation is preferred. Applications involving the determination of enthalpies of ionization of acidic surface oxides on active carbon and calorimetric studies that support the application of the Dubinin isotherm equation to adsorption from binary aqueous solutions are given.
Measurement method for transitional dielectric constant of ferroelectric liquid crystal filled and aligned in a sandwich cell
Authors: Kimura M. , Maeda H. , Yoshida M. , Mochizuki A. , Kobayashi S.
Published: July 2002

A system for measuring the transitional dielectric constant of a ferroelectric liquid-crystal (FLC) medium aligned in a sandwich cell has been developed. The system developed in this work is shown to be capable of detecting the average molecular motion of the FLC during the course of the switching in terms of the measurement of the dielectric constant in the soft mode at 40 kHz by applying a triangular-voltage wave form ranging from 0.1 to 100 Hz to induce the Goldstone mode. This method is more accurate compared to the conventional method based on the observation of the switching current, since the latter usually accompanies the disturbances originating from ionic current, the charge/discharge as a capacitor, and electrical noise.
Detection of ozone using a silver coated quartz crystal rate monitor
Authors: Kucera J. T. , Perkins J. D. , Uwai K. , Graybeal J. M. , Orlando T. P.
Published: July 2002

A technique to measure ozone fluxes of 1014–1016 cm−2 s−1 using a thin silver film deposited on a quartz-crystal deposition-rate monitor is described. The technique involves measuring the rate of mass increase of the silver film due to oxidation when it is first exposed to ozone. Ozone is found to be an extremely efficient oxidant for silver at room temperature. By establishing an independent measure of the incident ozone flux the product of our ozone purity and intrinsic detection efficiency has been determined to be 26±5%.
Soldering diamonds into the diamond anvil cell
Authors: Dunstan D. J.
Published: July 2002

Diamonds can be obtained with a metal coating suitable for soldering to metal components. This provides a satisfactory method for mounting the anvils in diamond anvil high-pressure cells.
A backpack-portable mass spectrometer for measurement of volatile compounds in the environment
Authors: Hemond Harold F.
Published: July 2002

Environmental measurements of volatile pollutants and metabolic gases are preferably made in situ. In situ measurement provides immediate information to the investigator while minimizing disturbance and eliminating the need for sample collection, preservation, and transport. A self-contained mass spectrometer, capable of being carried by one person, has been designed and built for this purpose. The instrument is based on a compact crossed-field analyzer using a high-energy-product magnet and control circuitry optimized for low power consumption using a 12-V dc primary power source. An internal, rechargeable battery can provide up to several hours of operation in the field. Provision is made to facilitate the addition of an interface, via RS-232, to a compact battery-operated laptop microcomputer. A variety of inlet configurations is possible, the simplest being a probe, containing a small silicone-rubber membrane, which may be inserted into a gas- or water-containing environment of interest.
Prototype photon position monitors for undulator beams at the Advanced Light Source
Authors: Warwick Tony , Shu Deming , Rodricks Brian , Johnson Erik D.
Published: July 2002

Design criteria are described, and test results are presented, for prototype undulator beam position monitors at the Advanced Light Source (ALS). The design is based on monitors presently in use at the National Synchrotron Light Source, Brookhaven National Laboratory, with modifications to account for the widely varying and large K values of the undulators to be installed at the ALS. In particular, we have modified the design to simplify the thermal engineering and we have explored techniques to suppress the response of the monitors to soft photons, below 100 eV, so that the beam position can be determined by measuring the higher energy photons which are better collimated.
Production of sheet plasma with dc magnetron discharge source
Authors: Okuno Yoshihiro , Ishikura Hiroshi , Fujita Hiroharu
Published: July 2002

A production technique for sheet plasma with a dc magnetron discharge source is proposed. The magnetron discharge was realized by a cross field of permanent magnets and a rectangular-typed hollow cathode, which enhances the production of high-density plasma. The plasma produced was introduced into a low-pressure region where an axial magnetic field was applied through a slit anode to form the sheet plasma, of high electron density of 4.5×1010 cm−3, electron temperature of 2.8 eV for low discharge current (0.3 A) and low magnetic field (0.18 kG). The thickness of the sheet plasma is found to be almost the same as the ion cyclotron diameter. This plasma production technique would be useful for thin-film preparation on large-area substrates.
Experiment on direct irradiation of a beryllium window by undulator radiation
Authors: Asaoka Seiji , Maezawa Hideki , Kamiya Yukihide , Yanagihara Mihiro
Published: July 2002

Beryllium windows were tested as the first target in a project for experimental simulations of heat load effects on beamline optical elements under direct irradiation of undulator and wiggler radiation. Maximum temperature at the window center, vertical temperature distribution, and cooling capability by thermal conduction were studied. It turned out that thermomechanical failure occurred when the temperature difference between the window center and its peripheral edges exceeded about 200 °C. This fact was in good agreement with a simple maximum-shearing-stress theory of the failure condition.
Studies of insertion devices for producing circularly polarized radiation with variable helicity in ELETTRA
Authors: Walker R. P. , Diviacco B.
Published: July 2002

Insertion device sources of circularly polarized radiation with the capability of switching rapidly between right- and left-handed polarization are considered and two schemes are put forward: a ‘‘modulated asymmetric wiggler’’ and an electromagnetic elliptical wiggler. Recent studies of these devices and of the alternative crossed-undulator scheme are summarized, and their expected performance compared in ELETTRA. The optimum choice for a broadband, high flux source is an electromagnetic elliptical wiggler. Design parameters for a device with the potential of reaching a switching rate of 100 Hz are presented.
An 85-kJ high performance capacitor bank with double-mode trigatrons
Authors: Ron P. H. , Nanu K. , Iyengar S. T. , Nagesh K. V. , Rajawat R. K. , Jujaray V. R.
Published: July 2002

The present article describes the constructional aspects of an 85-kJ capacitor bank at 20 kV for the production of pulsed high magnetic fields. The discharge current magnitude is 56 kA at a ringing frequency of 1.1 kHz. The bank employs 8 double-mode trigatrons in parallel which are triggered into conduction by the application of 16 simultaneous low jitter high voltage pulses generated by a multiple trigger pulse generator. The performance of the bank with double-mode trigatrons is compared with that obtained by conventional single-mode trigatrons. The waveforms of discharge current in time domain and fast fourier frequency spectrum for single- and double-mode trigatrons are presented and analyzed for performance evaluation. The performance with double-mode trigatrons is characterized by distinctly superior synchronization in the closing of trigatron switches over a wide range of operating voltage resulting in high peak discharge current and low waveform distortion.
A high precision micropositioner based on magnetostriction principle
Authors: Wang Wanjun , Busch-Vishniac Ilene
Published: July 2002

A novel two degree-of-freedom precision micro-positioner has been designed and built using Terfenol-D magnetostrictive material. The device consists of a group of Terfenol-D rods which have been linked together to form a rigid, prism-shaped body. When the coils wrapped around the Terfenol-D rods are supplied with electrical current, the magnetic fields produced will cause the rods to strain, inducing a displacement at the end point. Controlling the electrical currents supplied to the coils allows very precise movements to be obtained. Another degree of freedom can easily be added to make the device capable of precise motions anywhere within a volume. The device discussed here fits into a 3 in. by 3 in. by 1.5 in. space, and is capable of addressing a 100 μm by 100 μm workspace with a maximum current of 1.5 A applied. The open-loop repeatability of the device is 50 nm over the workspace. With the implementation of a simple closed-loop controller, the accuracy of the device is limited by that of the sensing system, and the resolutions of the 12 bit A/D and D/A boards used. Much higher resolution can be expected if 14 bits or 16 bits A/D and D/A boards are used. Potentially the device can be used for high precision microprobing, cellular biology, microsurgery, and industrial work in the micromechanical area.
Output power stabilization of cw 337-μm HCN laser by feedback control aided by a microcomputer
Authors: Bi D. G.
Published: July 2002

The output power of a cw 337-μm HCN laser is maintenance-freely stabilized by a feedback control aided by a microcomputer. As a result, the laser power has no observable drift in the long term and its fluctuation in the short term is less than ±1%. This stabilizing method is especially useful when the laser is used in circumstances where the ambient temperature changes severely.
Synchrotron radiation from the Amsterdam Pulse Stretcher (AmPS)
Authors: Luijckx Guy , Maas Rob
Published: July 2002

The National Institute for Nuclear Physics and High-Energy Physics NIKHEF is constructing AmPS, a pulse stretcher ring, as an extension to its existing electron linac facility. The project is primarily funded to produce continuous electron beams for nuclear physics experiments. The first beam for nuclear physics experiments is expected by mid 1992. AmPS is designed for energies between 300 and 1000 MeV and circulating currents up to 200 mA. Synchrotron radiation will be generated in each of the 32 bending magnets of the ring. At least two of its long straights are well suited to install either wavelength shifters (wigglers) and/or undulators. For nuclear physics AmPS will be operated for 2500 hours per year, an additional 2000 hours per year for dedicated SR use seems feasible. AmPS will provide SR beams from the VUV to the soft x-ray region; with appropriate insertion devices extension is possible up to the medium energy x-ray region. Its SR brilliance can be made fully competitive with new generation sources by adding 32 quadrupoles to its lattice.
Influence of substrate temperature and deposition rate on the structure of erbium films deposited on glass and a-C substrates
Authors: Savaloni H. , Player M. A. , Gu E. , Marr G. V.
Published: July 2002

The structure of erbium films of 600 nm thickness deposited onto carbon (a-C) and glass substrates at 0.55 and 2.5 nm/s deposition rates for varying substrate temperatures is investigated. The cross section and surface structures are examined by electron microscope. Energy-dispersive x-ray diffraction is utilized for the structure analysis of these films. Results are compared with the results presented in H. Savaloni, M. A. Player, E. Gu, and G. V. Marr (to be published), for erbium films on molybdenum substrates. It is found that to produce films with strong preferred orientation on glass substrates low deposition rate (0.55 nm/s) is favorable. This is opposite to erbium on molybdenum substrates. The grain size of erbium films produced at higher deposition rate is much larger than those at lower deposition rate. The structure of thin films has implications for performance of multilayer reflectors, and preferred orientation may have other applications to x-ray instrumentation.
The Pohang light source project: Status report
Authors: Lee Tong-Nyong , Oh Saewoong
Published: July 2002

Design of a 2-GeV synchrotron radiation facility is well in progress in Pohang, Korea. The first portion of the injector linac has been delivered and installation will be from July 1991. Prototype storage ring magnets are to be delivered soon. Prototype magnet power supplies have been fabricated and tested. Detailed design studies are being carried out at present.
Elliptical-polarization measurements in the vacuum ultraviolet and soft x-ray regions with a reflection polarimeter
Authors: Koide T. , Shidara T. , Yuri M. , Kandaka N. , Fukutani H. , Yamaguchi K.
Published: July 2002

A complete polarization analysis has been successfully achieved for synchrotron radiation beams in the vacuum ultraviolet and soft x-ray regions using a reflection polarimeter. The Stokes parameters, which provide a full description of the polarization state of light, were experimentally determined along with three polarizing quantities of the polarimeter. The present result indicates the possibility of a simultaneous determination of the optical constants of mirror materials through polarization analyses.
Alignment of TFTR Thomson scattering system
Authors: Johnson D. , Dimock D. , Grek B. , Palladino R. , Tolnas E.
Published: July 2002

A technique is described for maintaining the highly precise alignment needed for accurate density profile measurements with the TFTR Thomson scattering system. The method uses the transverse coherence of the fiber bundles in the collection optics to encode the alignment information in the spatial distribution of the scattered light signal. A scheme for decoding this information is demonstrated and the limitations of this technique are discussed.
A comparison of fluctuation spectra from microwave scattering and beam emission spectroscopy on TFTR (abstract)
Authors: Bretz N. , Paul S. , Nazikian R. , Synakowski E. , Fonck R. , Durst R.
Published: July 2002

A comparison of fluctuation spectra from both microwave scattering and beam emission spectroscopy (BES) on TFTR has been done at similar values of k and in a plasma in which the toroidal rotation and density profile have been well characterized. The two systems measure somewhat different values of k (k<1.5 cm−1 for BES and k≳2.5 cm−1 for microwave scattering) and average over somewhat different regions of space (2–3 cm for BES and 30–40 cm for microwave scattering). As a result, the observed spectra can be different because of intrinsic differences in ‖〈δne(k)〉‖2 and because the spectra are affected differently by plasma rotation. Nevertheless, when beam induced toroidal plasma rotation is known or is minimized and the two systems are looking at similar spatial locations, the results from the two systems are similar and respond in the expected way to changes in toroidal rotation. A detailed discussion of several model cases will be presented.
Modeling of a diagnostic neutral beam for ITER
Authors: Schilling G. , Synakowski E. J.
Published: July 2002

A neutral hydrogen beam has been modeled to serve as an energetic particle source for the measurement of ion temperature profiles via charge-exchange recombination spectroscopy. Calculation of the neutral beam attenuation uses the multistep ionization cross sections of Boley, Janev, and Post. Whereas beam penetration toward the center of the discharge increases with increasing beam energy, the relevant charge-exchange cross section for the familiar C 5+ n=8–7 transition decreases above 50 keV, leading to an optimum beam energy that yields the maximum charge exchange brightness for each set of plasma conditions. This energy is in the range of 100–150 keV. As a consequence of the high plasma density, temperature, and machine size, the detected signal is dominated by visible bremsstrahlung integrated along the detector sightline, placing a premium on beam intensity, beam current density, and beam chopping with synchronous detection.
Application of the pulsed synchrotron radiation for investigation of the fast crystalline scintillators
Authors: Aleksandrov Yu. M. , Makhov V. N. , Yakimenko M. N.
Published: July 2002

A new family of the fast crystalline scintillators, so-called crossluminescence crystals, is proposed for using in high-rate detectors of x-ray synchrotron radiation. The results of the fast luminescence investigations in ionic crystals of different classes using the time-resolved spectroscopy technique under excitation by pulsed synchrotron radiation (5–30 eV) are presented. The general characteristics of crossluminescence in binary and some ternary ionic crystals as well as luminescence properties of rare-earth trifluorides are discussed.
LNLS status report
Authors:   Accelerator Physics and Instrumentation Groups of LNLS
Published: July 2002

In this report, we present briefly the status of the LNLS vacuum ultraviolet soft X-ray electron storage ring. The basic parameters of the magnet lattice and the program for the development of beam lines and experimental workstations are described.
Microgravity annealing system for thin-film superconductors
Authors: Murakami Hiroshi , Hosokawa Shunsuke , Kudo Isao , Endo Kazuhiro , Yoshida Sadafumi , Ichikawa Yo , Setsune Kentaro , Teramoto Akihiro
Published: July 2002

A mirror furnace system for annealing of superconducting thin films, which is adapted for the world’s longest dropshaft completed at Kamisunagawa, Japan, is described. The system must be designed for completing both melting and solidification processes during a short 10-s microgravity period, and also for withstanding the deceleration of a drop capsule in which the furnace system is contained. All moving components must be operated so as not to disturb the microgravity environment. A random vibration test for the entire system was carried out before the microgravity experiment, and structural compatibility was verified. The furnace system worked well, and the accumulated number of free falls was 19. Results of annealing of the superconducting material at one gravity and microgravity were compared using scanning electron microscopy and x-ray microanalysis.
Determination of Verdet constant from combined ac and dc measurements
Authors: Turvey K.
Published: July 2002

Two methods of determination of the Verdet constant (V) for an optically transparent medium are described. These methods use the same apparatus in which the intensity of a monochromatic beam of light is modulated by passing it, successively, through a polarizer, the medium under test (contained within a solenoid which carries ac of frequency f in its windings), and an analyzer. The emergent beam is incident on a detector which produces a steady output voltage Uo for the special conditions of the optical system set for maximum transmittance and, simultaneously, zero modulation. Methods I and II, which were tested by determining V for water for the wavelength 643.3 nm, are based, respectively, on the ratios u1/Uo and u2/Uo, where u1 is the rms value of detector output voltage varying at frequency f and u2 is the corresponding output varying at frequency 2 f. The three mean values of V from method I, method II, and a literature survey agree to within 1%. The standard deviation in the values of V by method I (eight determinations) is 0.8% of the mean and by method II (16 determinations) is 1.4%, leading to respective standard errors of the mean (attributable to random errors) of 0.3% and 0.4%. By either method there is, additionally, 0.4% systematic uncertainty in V arising from calibration accuracy of the instrumentation. The total range of Faraday rotation angles studied spanned the range 2×10−4–0.24 deg rms.
Magnetocrystalline anisotropy measurements in static or quasistatic magnetic fields
Authors: Bolzoni F.
Published: July 2002

Usually the singular point detection (SPD) technique, for measuring magnetocrystalline anisotropies, is easily performed in pulsed fields by direct differentiation of the obtained signal from special pick-up coils. On the other hand the use of static magnetic fields in permitted ranges has many advantages: the field enters completely the sample, there are no eddy current effects present, and there is the possibility of calibration with high precision. The present work analyzes the possibility of applying the SPD technique to static and quasistatic magnetic fields using single or double small modulation fields superimposed. Both amplitude and frequency modulation techniques are analyzed. In case of single amplitude modulations it is possible, from the signal detected by a pick-up surrounding the sample, to derive (d2M/dH2)H=H0 from the amplitude of the component with frequency 2ω and (d3M/dH3)H=H0 from the one with frequency 3ω, H0 being the static magnetic field. As in standard SPD measurements the peaks appearing in further derivatives of the magnetization curves, the order of which depends on the crystal symmetry, correspond to the specimen anisotropy field HA. Pulsed field experimental results are also used to evaluate the amplitude of the obtained signals; they are in the detectable range of available commercial lock-in amplifiers. The double modulation is also analyzed showing that it is very useful in case of large noise problems. The role of frequency modulation is shown as a further improvement of the signal-to-noise ratio. Schematic descriptions of different experimental apparatuses are also given.
Miniature actuator driven photothermally using a shape-memory alloy
Authors: Inaba S. , Hane K.
Published: July 2002

A miniature actuator, in which a shape-memory alloy is driven photothermally by a laser diode, is described. The force of 9.8 mN and the displacement of 58 μm were obtained by irradiation with a laser power of 10 mW for the shape-memory alloy. The cutoff frequency for the vibration amplitude of this actuator was 0.2 Hz.
Cycle-counting device for high-pressure soxhlet extraction
Authors: Scholsky Kevin M. , Rittenhouse David A. , Woodward Stephen
Published: July 2002

An electronic device is described which allows for counting of the filling/emptying cycles which occur during high-pressure soxhlet extraction. Previously, the number of cycles which occurred during an extraction run were counted manually from a strip chart recording of the thermal excursions associated with the cycling events. This device automates the detection, accumulation, and display of these events and was found to exhibit a counting accuracy of at least 94%. It extends the application of high-pressure soxhlet extraction to areas which routinely require a high degree of precision.
Electron suppression in the H− beam from a Penning surface-plasma source
Authors: Smith H. Vernon , Allison Paul
Published: July 2002

The ratio of electrons to negative ions extracted from Penning surface-plasma sources such as the 8X source is low even before any further steps are taken to suppress the electrons. For the 8X source the e−/H− ratio is typically four or five to one for H− operation and nine to one for D− operation. Because the coextracted e− present a power-loading problem to the 8X-source extraction system, methods to dissipate and/or reduce the power in the e− beam must be developed before extracting a dc H− or D− beam. Thus, we systematically varied the geometry of a cylindrical collar installed in the near-extraction region of the 8X source. The observed dependence of the extracted e− and H− currents on the collar radii and lengths suggests that a conical collar would provide superior electron suppression. The conical collar that we tested lowered the e−/H− ratio to 0.9/1 without reducing the extracted H− current.
Division artifacts in Ranicon imaging
Authors: Cox Colin , Douglas Bruce
Published: July 2002

Images digitally generated from a photon-counting detector exhibit spurious horizontal, vertical, and diagonal lines. We trace the effect to underlying properties of integer division.
A real-time sky tracking system for balloon-borne experiments
Authors: Cortiglioni S. , Trabisondi M.
Published: July 2002

A system to point and track a balloon-borne telescope with a pixel field of view of about 1.5 arcmin and extendible to a more general use is described. The system receives star field images from a CCD camera and generates error signals for the Telescope Control System, having as a reference a reduced star field database. Simulated tests show that real-time control of the telescope pointing is possible, depending on the capability of the payload primary attitude control system. The system accuracy depends mainly on the CCD pixel field of view. Using standard devices (CCD/optics) a pointing error of ≤1 arcmin, in both zenith and azimuth, is achievable. The software architecture is designed to simplify the experiment interfaces and to make the system as much as possible hardware independent. Thus, balloon-borne telescopes substantially different in scope such as infrared experiments, x-ray, and gamma-ray telescopes would not experience difficulties whenever the utilities described in this paper are applied.
Ultrahigh-vacuum chamber equipped with a reaction cell for studying liquid-phase catalytic reactions
Authors: Gardin Denis E. , Somorjai Gabor A.
Published: July 2002

We describe the construction and operation of a liquid-phase reaction cell designed in our laboratory that is attached to an ultrahigh-vacuum (UHV) chamber equipped with the traditional surface science techniques for structure and composition analysis. The sample surface can be prepared and characterized in the UHV chamber prior to transfer in the liquid-phase reaction cell. The transfer has been designed so that there is no loss of the UHV chamber vacuum integrity, as few parts as possible come into contact with the liquid, the surface stays clean during the transfer. The liquid-phase reaction cell itself is designed to study liquid-phase hydrogenation reactions at pressures up to 2 atm and temperatures up to 70 °C. A 1-mm-diam liquid jet with a velocity up to 6 m/s is produced by a gear pump that is incident on the sample surface to allow good mass transfer at the liquid-solid interface. The progress of the reaction is followed by gas chromatography. We report the reaction rate data for the hydrogenation of cyclohexene on a platinum foil.
Experimental method for preparing nanometer scale Pd probe
Authors: Huang L. , Lee Y. H.
Published: July 2002

Two-step electrochemical etching is used to fabricate a palladium microprobe having a tip diameter less than 20 nm. The first etching is done at 4–7 V in a solution containing 4:6 volume ratio of HCl:HNO3, while in the second the etching, low voltage pulses are used.
Electron optical design of a high-resolution low-voltage scanning electron microscope with field emission gun
Authors: Ximen Jiye , Lin P. S. D. , Pawley J. B. , Schippert M.
Published: July 2002

In the present study, a comprehensive description and a complete process for designing a high-resolution low-voltage scanning electron microscope with a field emission gun have been discussed, including the design of two types of magnetic immersion lenses optimized for low-voltage operation, the evaluation of their resolution, the design of the magnetic lens/secondary electron collector system, the calculation of three-dimensional trajectories for both secondary electrons and backscattered electrons, and the estimate of their collection efficiency. The computed results and the primary experiments indicate the possibility of achieving nanometer resolution, which basically approaches the electron optical predictable probe size for the low-voltage scanning electron microscope.
Thermal scanning ac susceptometry method for high-T
c superconductor studies
Authors: Bódi A. C.
Published: July 2002

Conventional ac susceptibility measurements and the conditions used in thermal analysis methods have been combined for normal-superconductor transition studies. Accordingly, during the ac susceptibility measurements, the Y-based sample is exposed to a temperature gradient. By controlling this gradient, the boundary between normal and superconducting region can be swept slowly at will across the specimen. The extended thermal scanning assures a high resolution to the new method. The observed fine details (even discontinuities) of the susceptibility spectra demonstrate its performance and basis.
Growth of highly doped p-type ZnTe films by pulsed laser ablation in molecular nitrogen
Authors: Rouleau C. M. , Lowndes D. H. , McCamy J. W. , Budai J. D. , Poker D. B. , Geohegan D. B. , Puretzky A. A. , Zhu S.
Published: July 2002

Highly N-doped (mid-1019 to ≳1020 cm−3) ZnTe/(001)GaAs epitaxial films have been grown by pulsed laser ablation (PLA) of a stoichiometric ZnTe target in a high-purity N2 ambient (50 to 200 mTorr) without the use of any assisting dc or ac plasma source. Unlike recent experiments in which atomic N, extracted from dc and rf plasma sources, was used to produce N-doping during molecular beam epitaxy, spectroscopic measurements performed during PLA of ZnTe in N2 do not reveal the presence of atomic N. This suggests that the high hole concentrations in laser ablated ZnTe are produced by a new mechanism, possibly energetic beam-induced reactions with excited N2 adsorbed on the film surface, and/or transient formation of Zn–N complexes in the energetic ablation plume.
A compact vibrating-sample magnetometer with variable permanent magnet flux source
Authors: Cugat O. , Byrne R. , McCaulay J. , Coey J. M. D.
Published: July 2002

An automated vibrating-sample magnetometer is described where the variable magnetic field in excess of ±1.1 T is produced in a 26 mm bore by an assembly of nested, rotating permanent magnet cylinders. The homogeneity is better than 0.3%±4 mT in 1 cc. The instrument has dimensions 200×420×700 mm, and its mass is 20 kg. Sensitivity is better than 0.4 μJ/T (4×10−4 emu), which permits study of the susceptibility, magnetization, and hysteresis of a wide range of magnetic materials, including ferromagnetic thin films.
Polarization modulation laser scanning microscopy: A powerful tool to image molecular orientation and order
Authors: Gupta Vinay K. , Kornfield Julia A.
Published: July 2002

To image the orientational order in a broad class of biological and manufactured materials, a new microscope has been developed that integrates laser scanning microscopy with polarization modulation polarimetry. Polarimetry allows quantitative characterization of the molecular orientation and the degree of order through characterization of optical anisotropy. Combined with laser scanning microscopy, it is used here to image the anisotropy with high spatial resolution, sensitivity, and speed. The design of the microscope is presented; and the vast improvement in sensitivity achieved using PM-LSM over conventional polarization microscopy is illustrated by imaging the linear dichroism of ultrathin Langmuir–Blodgett polymer films. PM-LSM allows imaging of the magnitude and orientation of linear dichroism in films as thin as three molecular layers (∼66 Å) at high resolution by rastering a diffraction limited spot of laser light across the sample. The rate of image acquisition is over 2000 pixels/s, two to three orders of magnitude faster than the previous methods of imaging optical anisotropy.
Electrostatic electron-optical crossed lens with controlled astigmatism
Authors: Baranova L. A. , Read F. H.
Published: July 2002

A crossed lens consisting of square and rectangular apertures in four equally spaced electrodes has been studied. The two inner apertures are rectangular with their longer directions mutually at right angles and the outer apertures are square. The strength and astigmatism of the lens can be separately controlled through the voltages applied to the rectangular apertures, enabling line images of variable position and length to be produced from point objects.
New optical cell design for laser flash photolysis studies in supercritical fluids
Authors: Ji Qin , Eyring Edward M. , van Eldik Rudi , Bal Reddy Kedika , Goates Steven R. , Lee Milton L.
Published: July 2002

A high-pressure optical cell has been designed that achieves an effective separation between the chemical sample and the pressurizing medium and system. This design limits possible sample contamination and catalytic effects under supercritical fluid sample conditions. Laser flash photolysis experiments were carried out on molybdenum hexacarbonyl dissolved in supercritical CO2. The thermal ring closure reaction of the species Mo(CO)5L, where L is 2,2′-bipyridine was found to proceed at rates comparable to those measured previously in liquid benzene or toluene. Much larger activation volumes were found for the reaction in supercritical CO2 than in liquid toluene.
Frequency locking of a Nd:YAG laser using the laser itself as the optical phase modulator
Authors: Cantatore G. , Valle F. Della , Milotti E. , Pace P. , Zavattini E. , Polacco E. , Perrone F. , Rizzo C. , Zavattini G. , Ruoso G.
Published: July 2002

We report frequency locking of a Nd:YAG tunable laser to a 2000 finesse 87-cm-long Fabry–Pérot cavity in air using the Pound–Drever technique. The novelty is that the necessary phase modulation of the beam is obtained using the laser directly instead of an external phase modulator (Pockels cell). The spurious relative amplitude modulation using this method was ∼3×10−5 with a modulation index β∼1 and the spectral density of the frequency difference between the laser and the cavity is below 1 mHz/√Hz in the region 1–500 Hz.