bluuebunny/crossref_metadata_2025 huggingface dataset:
Simple sub-50-ps rise-time high voltage generator
Authors: Kekez M. M.
Published: July 2002

This article relates to the development of an ultrafast (nanoseconds–picoseconds time scale) compact system(s) readily applicable to the field of EMP/radiation, x-ray-induced nondestructive testing, plasma fusion (energy) experiments, bioelectromagnetic (food-drug) sterilization, drivers for x-ray preionized XeCl laser and similar applications. The present work shows that the Marx and the Pulse forming section can be integrated into a single unit. The stray capacitance present in each stage acts as a peaking capacitor. For a charging voltage per stage of <40 kV, the rise time of the output pulse is below 50 ps at 200 kV into a 100-Ω load. Work is in progress to extend the voltage amplitude to 1.6 MV while maintaining the relative pulse waveform. With a contemporary optical diagnostic technique it is believed that the present concept may achieve 1–10 ps rise-time pulses at a megavolt level in ‘‘smart gas mixtures.’’ In addition a solution for the classical peaking circuit has been obtained and presented in the Appendix.
Above room temperature near ultraviolet lasing from an optically pumped GaN film grown on sapphire
Authors: Yang X. H. , Schmidt T. J. , Shan W. , Song J. J. , Goldenberg B.
Published: July 2002

Optically pumped near ultraviolet lasing from single-crystal GaN grown by metalorganic chemical vapor deposition has been achieved over a temperature range from 10 K to over 375 K by using a side-pumping geometry on small barlike samples. The laser emission threshold was measured as a function of temperature and the threshold was found to show weak temperature dependence: ∼500 kW/cm2 at 10 K and ∼800 kW/cm2 at room temperature (295 K) for one particular sample studied. The longitudinal lasing modes were clearly observed. The characteristics of the temperature dependence of the laser emission threshold suggests that GaN is a suitable material for the development of optoelectronic devices required to operate at high temperatures.
Motions of trapped dust particles around the electron beam in the TRISTAN accumulation ring
Authors: Saeki Hiroshi , Momose Takashi , Ishimaru Hajime
Published: July 2002

High-energy bremsstrahlung synchronized with the electron beam in the TRISTAN accumulation ring was observed accompanied by a sudden decrease in the electron beam lifetime which occurred due to dust trapping in the electron beam. The bremsstrahlung observed with gamma-ray detectors was obviously different from that caused by interactions between residual gases and the electron beam. Other bremsstrahlung observations showed a trapped dust particle passing through the periphery of the electron beam in the bending magnetic field; the transit time through the periphery of the electron beam was 0.15 ms; the half period of the horizontal oscillation perpendicular to the orbit of the electron beam was about 200 ms and the period of the vertical oscillation was 1 s. Simultaneous observation at two adjacent gamma-ray detectors showed that a trapped dust particle in the bending magnetic field moved in a longitudinal direction at the average speed of about 0.191 m/s. These observations coincide with the results based on our newly developed theory for motions of a trapped dust particle in a bending magnetic field. Furthermore, we introduced sample dust particles into the TRISTAN accumulation ring and carried out an experiment to trap the dust particles in the electron beam, in a straight chamber with no magnetic field and observed their motion with a gamma-ray detector. The beam lifetime suddenly decreased when the sample dust particles directly under the electron beam were caught up into the beam. High-energy bremsstrahlung and a pressure rise caused by the destruction of the dust particles were also observed at the same time. After that, beam lifetime recovered gradually. Our theoretical analysis shows that vertical oscillation of a trapped dust particle with no magnetic field continues and that the dust particle is destroyed by the heat deposited by the electron beam in less than a second. The calculated variation in the beam lifetime coincides approximately with the actual variation in the beam lifetime. Compared results of the observations and experiment show that our theory for motions of a trapped dust particle is useful.
Interaction of InGa liquid alloy coolant with gold-coated optical materials
Authors: Hulbert S. L.
Published: July 2002

A significant reaction is reported between gold surfaces and an indium-gallium eutectic liquid alloy often used to transfer heat away from optical elements in high power synchrotron radiation beam lines. This reaction proceeds at the slightly elevated temperatures (70 °C) typical of conservative bakeouts used to achieve ultrahigh vacuum in the chambers which house these optical elements (mirrors, gratings, and crystals) without damaging their highly precise figure and finish. The nature and extent of this reaction is discussed, based mostly on the experience gained recently during the vacuum commissioning of two mirror chambers for a VUV wiggler-based synchrotron radiation beam line.
Construction and performance of an x-ray undulator beamline at the TRISTAN Accumulation Ring
Authors: Zhang Xiaowei , Mochizuki Tetsuro , Sugiyama Hiroshi , Yamamoto Shigeru , Kitamura Hideo , Sioya Tatsuro , Ando Masami , Yoda Yoshitaka , Ishikawa Tetuya , Kikuta Seishi , Suzuki Carlos K.
Published: July 2002

An in-vacuum type undulator and its beamline NE3 with a Si(111) double-crystal monochromator is under commissioning. Spectra of synchrotron radiation measured in the energy range of 5–25 keV from the undulator shows a very good agreement with theoretical calculation. Some experiments of resonant nuclear scattering using 57Fe have been carried out using the third harmonics of the spectra. It has been proved that the undulator x rays are quite suitable for experiments of very small scattering cross sections.
The multiply charged ion production in ECR ion sources
Authors: Shirkov G.
Published: July 2002

The ion confinement and loss conditions in the open magnetic traps have been analyzed in this article. In ECRIS the ions are confined in the negative potential well. The ions with higher charge states have the longer lifetimes and the less probability of output in the negative potential well. The mean ion charged state in the trap is higher than in the output ion beam. The general methods for increasing the multiply charged ion extraction from the ECRIS are determined. The usage of ion cooling mode for the increasing ion charge states in the plasma is substantiated. The large output pulse of multiply charged ions in the rf pulse mode is explained. The numerical simulation of the ion cooling and rf pulse processes for Minimafios-type ECRIS have been carried out. Some other ways are proposed in the present paper to obtain the pulse beams of multiply charged ions in ECRIS.
Effects of permanent magnet arrangements and antenna locations on the generation of multicusp electron cyclotron resonance plasma
Authors: Namura Takashi , Arikata Ichio , Fukumasa Osamu , Kubo Makoto , Itatani Ryohei
Published: July 2002

A comparative study on the generation of 2.45-GHz multicusp electron cyclotron resonance (ECR) plasma is performed. Looped cusp structures such as the ring-cusp give a low-power and low-pressure ignition, and vice versa, indicating an importance to keep the electron trajetory of gradient-B drift motion inside the chamber even in the case of ECR plasmas. The importance of the antenna location in such multicusp fields is elucidated by comparison in two cases of the axial antenna located in the weak magnetic field region, generating a hydrogen plasma of limited density (ne<7.4×1010 cm−3), and a radial antenna located in the strong magnetic field region, generating an overdense plasma (ne∼2×1011 cm−3).
TELL-TERAS, NIJI-I, II, III, IV, and positron facilities
Authors: Tomimasu Takio
Published: July 2002

The installation of the experimental facilities, TELL, TERAS, NIJI-III, NIJI-IV and slow position and pion facilities is disscused. The beam characterics from the storage rings is also discussed. (AIP)
Fabrication and characterization of reactive ion beam etched SiC gratings
Authors: Ishiguro E. , Yamashita K. , Ohashi H. , Sakurai M. , Aita O. , Watanabe M. , Sano K. , Koeda M. , Nagano T.
Published: July 2002

A holographic SiC grating has been fabricated by means of reactive ion beam etching in Ar+CHF3 mixture and by using photoresist as an etching mask. The etch rates of SiC and photoresist depend on the CHF3 concentration in Ar+CHF3 mixture. A maximum value for a ratio of the etch rate of SiC to that of photoresist was found to be 1.29 for 67%Ar+33%CHF3 mixture. Diffraction efficiency of an ion-beam etched grating of 1200 ℓ/mm grooves coated with Au was measured by using synchrotron radiation and the Al kα emission line from an x-ray tube. The diffraction efficiency of the first order was 4.5%–9.3% in the soft x-ray region between 8.34 and 120 Å with a small amount of the higher order and the scattered light components. In addition, it is demonstrated that SiC can be etched in SF6 gas by synchrotron radiation excitation.
New instrumentation concepts to exploit the ultrahigh brightness of ELETTRA (invited)
Authors: Rosei R.
Published: July 2002

The paper concentrates on several aspects which have been taken into account in designing the first generation of beam lines of ELETTRA, the new ultrahigh brightness third-generation Synchrotron Radiation Facility under construction in Trieste. These include new concepts for monochromators which give very high resolving power; several ways of dealing with the unusually collimated beams and concentrated heat loads and also particular solutions for the experimental setups which should indeed allow us to perform experiments which will take the maximum advantage of the high brilliance of the machine.
Vacuum ultraviolet beam lines at Laboratório Nacional de Luz Síncrotron, the Brazilian synchrotron source
Authors: Fonseca P. de T. , Pacheco J. G. , d’A Samogin E. , de Castro A. R. B.
Published: July 2002

A TGM beamline for the spectral range 12–310 eV is being built at Laboratório Nacional de Luz Síncrotron (LNLS). This beam line consists of safety devices, a condensing mirror, a toroidal grating monochromator, and a refocusing mirror. This beam line has been assembled up to the exit slits. A spherical grating monochromator beam line has been designed for the spectral range 200–1000 eV. The performance is limited by the surface slope error in the gratings. If the rms figure error is 2 μrad, the expected resolving power is better than 3000.
Kinematic mounting systems for National Synchrotron Light Source beamlines and experiments
Authors: Oversluizen Tom , Stoeber Walter , Johnson Erik D.
Published: July 2002

Methods for kinematically mounting equipment are well established, but applications at synchrotron radiation facilities are subject to constraints not always encountered in more traditional laboratory settings. Independent position adjustment of beamline components can have significant benefits in terms of minimizing time spent aligning, and maximizing time spent acquiring data. In this article, we use examples taken from beamlines at the National Synchrotron Light Source to demonstrate approaches for optimization of the reproducibility, stability, excursion, and set-up time for various situations. From our experience, we extract general principles which we hope will be useful for workers at other synchrotron radiation facilities.
Dynamic observation of the secondary recrystallization process at high temperatures in grain-oriented silicon steel using synchrotron x-radiation
Authors: Kawasaki K. , Iwasaki H. , Kawata H. , Nose K.
Published: July 2002

Taking advantage of the high brightness of synchrotron radiation, changes in the microstructure of silicon steel sheets in the secondary recrystallization process at 1233 K were measured by consecutive recording of the pole figure using a newly developed system consisting of the x-ray diffractometer and the translating imaging plate and by real-time observation of Laue topographic pattern using two kinds of TV camera. It was shown that {110} 〈001〉 oriented grains grew, after a certain incubation period of time, at a burst and occupied most of the sample volume. There was an appreciable anisotropy in the migration of the recrystallization front. When tensile strain was applied to the sample, growth of the {110} 〈001〉 oriented grains was appreciably delayed.
Construction of a precision diffractometer for nuclear Bragg scattering at the Photon Factory
Authors: Ishikawa Tetsuya , Yoda Yoshitaka , Izumi Koichi , Suzuki Carlos Kenichi , Zhang Xiao Wei , Ando Masami , Kikuta Seishi
Published: July 2002

A versatile precision diffractometer for nuclear Bragg scattering was designed and constructed at the Photon Factory. Standardized component goniometers can be arranged to address various requirements of incident beam conditioning for nuclear Bragg scattering, including a high-energy resolution monochromator with wide angular acceptance as well as a circularly polarized incident beam.
Multiwavelength anomalous diffraction and diffuse scattering beam line project on a bending magnet at ESRF
Authors: Simon Jean Paul , Geissler Erik , Hecht Anne Marie , Bley Francoise , Livet Frédéric , Roth Michel , Ferrer Jean Luc , Fanchon Eric , Cohen-Addad Claudine , Thierry Jean Claude
Published: July 2002

The multiwavelength anomalous diffraction and diffuse scattering (D2AM) beam line project is designed for a 0.8-T bending magnet at the ESRF for scattering experiments with multiwavelength anomalous techniques in the fields of (1) Materials Science (small angle and diffuse scattering) and (2) Crystallography of Biological Macromolecules (in particular MAD diffraction). Symmetric optics (a horizontally focusing double monochromator placed between two long, pseudoparabolic, vertically focusing mirrors) are planned. The optics, tested using the program shadow, should achieve a focus of 0.3×0.3 mm2 with an estimated flux of 1011 photons/s in a relative bandwidth of 2×10−4. Details of the beam line design are described in this note.
A new macromolecular crystallography Station (9.5) on the SRS wiggler beam line for very rapid Laue and rapidly tunable monochromatic measurements: Commissioning and first results
Authors: Thompson A. W. , Habash J. , Harrop S. , Helliwell J. R. , Nave C. , Atkinson P. , Hasnain S. S. , Glover I. D. , Moore P. R. , Harris N. , Kinder S. , Buffey S.
Published: July 2002

A new instrument (Station 9.5) has been established on the wiggler line at the Daresbury Synchrotron Radiation Source (SRS). It extends the experimental capability at Daresbury for macromolecular crystallography beyond what is provided for with Stations 7.2 (Ref. 1), 9.6 (Ref. 2), and 9.7 by providing a point focused white beam (from a Pt-coated toroid mirror) and/or a rapidly tunable monochromatic beam (using a water-cooled double-crystal monochromator (Ref. 3). The design principles of the new Station 9.5 have been published (Ref. 4). A CCD detector for the station is being developed (preliminary work is described in Ref. 5, or see the additional poster at this meeting) to allow time slices of part of a diffraction pattern to be measured. Laue patterns are currently recorded on film, but access to an image plate detector will shortly become available. Shutter speeds down to 50 μs are routinely available using a rotating disk shutter (Ref. 6). Fluorescence detectors are available for optimized anomalous dispersion data collection. The experimental bench is long enough to accommodate a camera system, and downstream from it an ‘‘on-line’’ image plate scanner. Data collected on the instrument in various modes of operation will be described for a variety of macro and small molecule crystal systems.
The Australian diffractometer at the Photon Factory
Authors: Barnea Z. , Creagh D. C. , Davis T. J. , Garrett R. F. , Janky S. , Stevenson A. W. , Wilkins S. W.
Published: July 2002

Outlined are design features of a versatile high-resolution two-axis diffractometer that is being constructed for operation at the Photon Factory as an Australian national facility. The instrument features optional use of multiple-imaging plates on a translating cassette to allow rapid recording of an almost complete range of data covering both the high-angle and small-angle scattering regime or alternatively the use of electronic detectors. The instrument will be capable of operation in various modes including the following: (i) high-resolution powder diffraction with single-channel counter and crystal analyzer, (ii) high-resolution, high-speed powder diffraction in the Debye–Scherrer mode with imaging plates as recording medium, either stationary or translating (for time-dependent studies), (iii) small-angle x-ray scattering with imaging plates as recording medium, (iv) protein crystallography in screenless Weissenberg mode, and (v) two- or three-axis single-crystal diffractometry. The salient features of the instrument are the use of a double-crystal sagittal focusing monochromator as primary monochromator together with the optional use of a condensing–collimating channel-cut (CCCC) monochromator or other channel-cut monochromator as secondary monochromator. The use of a CCCC monochromator enables fine tuning of beam position on sample, harmonic suppression, beam-condensation, and variation of wavelength bandpass. Further features include the use of high-precision incremental encoders on both axes, together with the capability of operating the whole diffractometer, including secondary monochromator and detectors, in vacuum of order 10−3 Torr in order to reduce absorption and parasitic scattering, and the use of a large camera radius (approximately 0.57 m) for the imaging plate cassette in order to increase angular resolution and signal to noise.
A high stability and low drift atomic force microscope
Authors: Hug H. J. , Jung Th. , Güntherodt H.-J.
Published: July 2002

Impressed by the high resolution and easy operation of the new generation scanning tunneling microscopes (STMs), we built a pocket-size high-stability atomic force microscope (AFM) with deflection measurement by tunneling. It was our aim to reach high mechanical and thermal stability of the tunnel junction as well as full compatibility with our existing STM system. Our first AFM scanhead, designed for large scan ranges up to 15 μm, stably measured an artificial grid structure on SiO2, reproducibly showing details of less than 1 nm in size. On this well-defined sample we compared constant force with variable deflection measurements.
A general method for determination of Brillouin linewidths by correction for instrumental effects and aperture broadening: Application to high-pressure diamond anvil cell experiments
Authors: Oliver W. F. , Herbst C. A. , Lindsay S. M. , Wolf G. H.
Published: July 2002

A general method for determining true acoustic-mode linewidths from Brillouin scattering data is presented. The method is specifically applied to diamond anvil cell experiments to obtain accurate hypersonic attenuation data at high pressure. This work was motivated by the noticeable lack of acoustic attenuation data at high pressure in the literature and by our own attempts to obtain relaxation data from Brillouin experiments in the diamond anvil cell. A detailed discussion of both instrumental and finite aperture contributions to the measured acoustic-mode linewidth is given, as well as specific algorithms for calculating these effects. Fits to Brillouin scattering spectra obtained at high pressures in different organic liquids are shown. Finally, a discussion is given of experimental details for obtaining accurate Brillouin linewidths in high-pressure diamond anvil cell experiments.
A reflectance anisotropy spectrometer for real-time measurements
Authors: Acher O. , Drévillon B.
Published: July 2002

A new reflectance anisotropy (RA) spectrometer, in the 0.23–0.83-μm range, is presented. The numerous similarities with phase-modulated ellipsometry (PME) are emphasized. In particular, the RA spectrometer takes advantage of the high-frequency modulation (50 kHz) provided by a photoelastic modulator. The use of optical fibers in both optical arms allows an increase of the compactness of the spectrometer. Four detectors can be used simultaneously providing the real-time spectroscopic capability. The numerical data acquisition system of the detected signal is based on the use of a high precision analog-digital converter and a fast Fourier transform processor. However, as compared to ellipsometry, RA can be only sensitive to the crystal surface. The adaptation of RA to a III-V growth reactor by metalorganic chemical vapor deposition is described in detail. The high sensitivity of the RA spectrometer is emphasized. In particular real-time variations of the RA signal ranging from 10−4 to 10−3 are reported. Then, the various RA techniques are compared. In particular, it is shown that this RA spectrometer allows the determination of both the real and the imaginary part of the signal. Finally the origin of the RA signal is discussed.
Bragg spectroscopy of impurities during the JET preliminary tritium experiment
Authors: Barnsley R. , Brzozowski J. , Coffey I. H. , Lawson K. D. , Patel A. , Patel T. K. , Peacock N. J. , Schumacher U.
Published: July 2002

Two Bragg spectrometers shared a shielded beamline, and monitored all significant plasma impurities throughout the Joint European Torus (JET) preliminary tritium experiment. The JET Active Phase Double Crystal Monochromator and a Bragg rotor spectrometer together monitored K-shell lines of Be, C, O, and Cl, and L-shell lines from metals such as Ni and Zn, in the wavelength range 0.2–11 nm. Background radiation was recorded during and after discharges, to assess the signal-to-noise ratio, and to monitor any activation or tritium ingress. Bragg spectroscopy was shown to be suitable for all impurities in magnetically confined D–T plasmas, using a thin foil to isolate tritium, and a low f-number shielded beamline. Future improvements to the signal-to-noise ratio are discussed in the context of a next-step machine such as ITER.
Quantitative x-ray emission from a DPF device
Authors: Burkhalter P. G. , Mehlman G. , Newman D. A. , Krishnan M. , Prasad R. R.
Published: July 2002

The x-ray emission was measured from a Dense Plasma Focus (DPF) device. The high density plasma is generated by an electrical discharge in rarefied-neon gas between electrodes in a Mather-type plasma focus configuration. A curved-crystal x-ray spectrograph, a pinhole camera, and an active-filtered photodiode were the diagnostics viewing the axial output of the pinched-plasma region. The x-ray pinhole images indicate a pinched volume roughly 8 mm in length with a nearly circular cross section of about 300 μm in diameter. The digitized spectral traces were computer processed to obtain absolute x-ray line intensities. The neon plasma yielded 10–15 J of K-shell radiation into 4π with the hydrogenlike and heliumlike alpha lines totaling 55%–65% of the total spectral emission. The x-ray emission of the DPF device was studied as a function of discharge current and anode diameter.
Observation of density fluctuations from the infrared bremsstrahlung emission on TFTR
Authors: Grek B. , Bartolick J. , Johnson D.
Published: July 2002

The infrared emission of beam heated TFTR discharges is studied using the high collection efficiency TFTR Thompson scattering system. It is found that emission in the vicinity of 9800 Å can be used to study fluctuations in the bremsstrahlung emission. Low-frequency (<40 kHz) fluctuations that are associated with MHD modes and high-frequency (≳200 kHz) bursts of fluctuations are observed. Both coherent and incoherent fluctuations exist. In some cases, the observed coherent fluctuations can be interpreted as being due to density fluctuations as high as 5%. The rms value of broadband density turbulence in the near central regions of the plasma is estimated to be about 1%.
Instrumentation for high-pressure x-ray diffraction research at HASYLAB
Authors: Olsen Janus Staun
Published: July 2002

The properties of the x-ray diffraction equipment for high-pressure experiments are described. The construction has a modular structure which facilitates its use. Three different modes are possible: (i) Energy dispersive method using a polychromatic incident beam; (ii) monochromatic method using a position sensitive detector; (iii) monochromatic scan method, using a detector at a fixed angle and a monochromator scan through the energy range of interest. By employing a nitrogen cryostat and a diamond anvil cell, high-pressure work in the temperature range of 135 up to 500 K can be performed as well. High-pressure work at temperatures lower than 135 K is made with a Helium cryostat.
Absolute measurement of spatial and spectral characteristics of bremsstrahlung using the photoexcitation of nuclear isomers
Authors: Carroll J. J. , Richmond D. G. , Sinor T. W. , Taylor K. N. , Hong C. , Standifird J. D. , Collins C. B. , Huxel N. , von Neumann-Cosel P. , Richter A.
Published: July 2002

A method of obtaining absolute, direct measurements of the spatial and spectral characteristics of bremsstrahlung is discussed. This technique, called x-ray activation of nuclei (XAN) is based on the use of well-known photonuclear reactions which populate long-lived nuclear isomers. These populations sample incident photon continua at discrete excitation energies and effectively store this information for convenient retrieval following the irradiation of gram-sized targets. Recently a series of experiments has been conducted which has significantly expanded the available data for the photoexcitation of a wide range of isomers at higher energies. Thus it has become feasible to extend the use of XAN to energies approaching 4 MeV. The utility of this technique is demonstrated by the characterization of bremsstrahlung from the newly installed research linac at the University of Texas at Dallas.
New method of adjusting and aligning a grazing incidence grating spectrometer
Authors: Shaotang He , Yuan Chen , Shutai Chunyu , Hansheng Peng
Published: July 2002

A compact grazing incidence grating spectrometer with spectral range of 2–32 nm resolution of 0.0005 nm, and about 3.6-kg weight has been manufactured, which can meet the requirements of current x-ray laser experimental research. During the construction, as a new method, we used a 3D measuring machine to finish the adjustment of spectral elements and invented a new method of alignment with a fiducial plane when using the spectrometer in an experiment.
A new design of a semiconductor bolometer on rigid substrate for fusion plasma diagnostics
Authors: Iborra E. , Sanz-Hervás A. , Rodríguez T.
Published: July 2002

A new, fast, and very sensitive semiconductor bolometer has been designed and developed for the measurement of radiative energy losses in fusion devices in which the hard radiation level is not too high. Special care was taken in the design of the bolometer to simplify both the construction technology and the installation in fusion devices. The major novelty of this bolometer is the use of a low thermal conductivity rigid substrate, instead of the typical thin foil stretched on a rigid frame. In spite of large detector-substrate contact area, the cooling time constant reaches values as high as 150 ms. The rigid substrate allows the detector to be very robust and reliable; moreover, the monolithic integration of array structures is straightforward. The detector has been fabricated with a thin-film multilayer technology achieving very low thermal capacitance (<2 mJ/K) and very low response time (<5 μs). High responsivity (20 V/W) is obtained using GeOx thin film with a high thermal coefficient of the electrical resistance (−4.5%/K) as sensing thermistor.
Nd:glass laser control system using intelligent CAMAC crate controllers
Authors: Watt R. G.
Published: July 2002

Trident, a TW class Nd:glass laser system has been constructed in the Inertial Confinement Fusion (ICF) Program at Los Alamos National Laboratory for use in x-radiographic imaging of targets and for diagnostic development in support of the ICF program. The laser utilizes intelligent CAMAC crate controllers to provide rapid time response during the charge and fire cycle, while allowing use of an inexpensive desktop computer for the operations station. Operator setup of the laser configuration before a shot and data collection after a shot are performed by the desktop computer, while time critical tasks are handled by the local intelligence. The control system architecture and details of the local control program will be discussed.
Long coherence length interferometer
Authors: Statman David , Kuo Y. S. , McIver John K. , Latham William P.
Published: July 2002

An interferometer has been developed which is capable of measuring the envelope of the coherence function of lasers whose mode lifetimes exceed 300 ns, corresponding to lengths over 100 m. The precision of this interferometer is determined to be 6.0%. The interferometer utilizes optical fibers for the purpose of optical delay. The minimum resolvable bandwidth of the interferometer is 64 kHz. This interferometer is capable of measuring not only the coherence function of a single laser, but also the mutual coherence function of coupled lasers. Its resolution is limited only by the total length of the interferometer and the losses in the optical fiber.
Optical measurement of crack propagation with high resolution
Authors: Koizumi H. , Kuroda K. , Suzuki T.
Published: July 2002

A new optical method is established to measure the crack length and its velocity in transparent crystals by utilizing the total reflection of light beam at the cleavage crack plane. The optical system is constructed by using a laser, a PIN photodiode sensor, and a wave memory. With the apparatus the crack propagation velocity can be measured at any desired position inside the specimen with a time resolution of less than 1 μs. The measurement on a cleavage crack in NaCl reveals that the maximum speed of the crack is about 800 m/s and the fluctuation of the velocity occurs prior to the arrest.
Intermodulation distortion measurements of a microstrip band-pass filter made from double-sided YBa2Cu3Ox films
Authors: Yoshitake T. , Tahara S. , Suzuki S.
Published: July 2002

A microstrip three-pole band-pass filter, with a midband frequency of 9.5 GHz and a fractional bandwidth of 2%, has been fabricated using double-sided YBa2Cu3Ox (YBCO) films on MgO substrates. The nonlinear behavior of this filter was studied by intermodulation distortion measurements. The insertion loss at the midband frequency was less than 0.1 dB and the return loss was better than 15 dB throughout the passband at 55 K. This filter showed relatively high power handling capabilities, with third-order intercept larger than +60 dBm at 55 K. The third-order intermodulation distortion products of this filter were found to vary with frequency in the passband, being larger near each of the band edges than at the midband. These increases in the nonlinearity near the band edges are attributed to the increase in the average stored energy in the filter, which is confirmed by the increase in the group delay near the band edge.
A high-temperature Bonse–Hart ultrasmall-angle x-ray scattering instrument
Authors: Chu Benjamin , Li Yingjie , Harney Paul J. , Yeh Fengji
Published: July 2002

A Bonse–Hart ultrasmall-angle x-ray scattering (USAXS) instrument has been designed, constructed, and tested employing a synchrotron x-ray source. The instrument permits experiments ranging from below 0 °C up to about 400 °C, as well as temperature scanning, jumping, quenching, and annealing experiments. The mechanical elements used Super Invar as the basic building material in order to minimize the thermal expansion effect. As the synchrotron beam after the beamline optics is already somewhat collimated and monochromatized, a very fine tuning of the first crystal was necessary. The high-temperature Bonse–Hart instrument increased the performance by a factor of about 10 when compared with our earlier room-temperature Bonse–Hart instrument using the same set of channel-cut germanium crystals. The instrument was tested by using a suspension of polystyrene latex spheres and by combining the USAXS measurement, for the first time, with measurements of the same latex suspension by means of laser light scattering.
Derivation of the effective E field for short electromagnetic pulses
Authors: Scholfield D. W. , Hendricks K. J. , Agee F. J. , Gahl J. M.
Published: July 2002

As the time duration of an electromagnetic pulse becomes shorter the bandwidth of the pulse increases. This presents a problem in the selection of a frequency for the calculation of the effective E field. This paper discusses a method for calculating the effective E field of a short electromagnetic pulse.
In situ uniaxial drawing apparatus for polymeric materials in compressed gases
Authors: Kajitani Takahiro , Uosaki Yasuhiro , Moriyoshi Takashi
Published: July 2002

An in situ uniaxial drawing apparatus is described for polymeric materials in compressed gases up to 30 MPa. Polymeric materials plasticized by sorption of compressed gases can be drawn at a constant rate by use of this apparatus. Polystyrene films in CO2 at 10 MPa and 318.15 K were stretched with the draw ratios of 2 to 4 without rupture.
Single-mode, frequency-stabilized LNA ring laser
Authors: Soletsky P. A. , Bixler D. L. , Dunning F. B.
Published: July 2002

A single-mode, frequency-stabilized LNA (lanthanum neodymium magnesium hexaluminate) ring laser developed for application in optical pumping and optical manipulation of He(2 3S) metastable atoms is described. This laser routinely provides output powers ≳300 mW at 1.083 μm when pumped with 5 W from an argon-ion laser.
Characterization of a two-dimensional, thermoluminescent, dose-mapping system: Uniformity, reproducibility, and calibrations
Authors: Fehl D. L. , Muron D. J. , Sujka B. R. , Vehar D. W. , Lorence L. J. , Westfall R. L. , Jones S. C. , Sweet J. A. , Braunlich P.
Published: July 2002

Initial testing of a new, commercially available, thermoluminescent dosimetry system is reported. The radiation detectors consist of two-dimensional arrays of 104 CaF2:Mn dosimeters, deposited on flexible polyimide sheets. The spatial resolution is 3 mm, and the combined thickness of the dosimeters and the substrate is 185 μm. Exposed sheets are processed by laser heating. This system is compatible with intense, pulsed Bremsstrahlung fields and electronics hardness testing. A two-step calibration procedure is described. In spatial uniformity tests at 66 Gy the detectors exhibited random fluctuations of 1%–3% superposed on broad spatial drifts of ∼±5%. Reproducibility for strips of 288 elements, cut from sheets and given absorbed doses of 100 Gy, was ∼2%. For absorbed doses in the 10 Gy–1.5 kGy range, response vs exposure curves show reasonable features of linearity, supralinearity, and saturation for CaF2:Mn phosphor. Small systematic effects (<7%) can be observed for sheets and strips stacked during exposure; these effects are explained by radiation transport calculations and impact the dosimetric technique.
Improved model of plasma column erosion in a silicon surface barrier detector
Authors: Kanno Ikuo , Inbe Takashi , Kanazawa Satoshi , Kimura Itsuro
Published: July 2002

An improved model of the plasma column erosion is proposed for the understanding of the resistivity dependence of the plasma delay in a silicon surface barrier detector (SSBD). The resistivity of a SSBD has influence in the electric field strength in a depletion layer with the presence of a dielectric plasma column. The plasma delay for two SSBD’s with different resistivities was measured with 61 MeV 16O ions, and the results are clearly reproduced by this model.
Sheet-shaped plasma produced by electron cyclotron resonance heating
Authors: Shibata Kanetoshi , Yugami Noboru , Nishida Yasushi
Published: July 2002

A new production technique of sheet-shaped plasma by means of electron cyclotron resonance heating (ECRH) is proposed. The sheet plasma is produced in a vessel with rectangular cross section set in a rectangular magnetic field coil. The maximum density and electron temperature of the sheet plasma are about 2.6×1011 cm−3 and 7 eV, respectively, in a typical argon gas pressure of P0=5×10−4 Torr. The sheet plasma has several peaks of the density profile across the plasma width. These modes appear according to the change of working gas pressure. Those parameters including plasma density, density profile, and ion energy are controllable. This plasma is expected to be useful for material processing or plasma-based high-energy particle accelerators.
Ultrahigh vacuum surface science chamber with integral scanning tunneling microscope
Authors: Leavitt Andrew J. , Han Taejoon , Williams John M. , Bryner Roger S. , Patrick David L. , Rabke Carol E. , Beebe Thomas P.
Published: July 2002

The construction of an ultrahigh vacuum (UHV) surface science chamber equipped with the standard surface analytical techniques and a connected companion UHV chamber containing a scanning tunneling microscope (STM) has been completed. The novel aspects of this experimental system are: the combination of many spatially averaging techniques with STM; a sample holder which is capable of in situ transfer between these various capabilities; variable temperature operation; in situ tip-sample approach without mechanical feedthroughs; and various novel software aspects. The sample transfer mechanism allows the sample to be transferred onto the main manipulator and heated or cooled with thermocouple monitoring while electrical isolation from the chamber ground is maintained. The sample then can be transferred in vacuo to the UHV STM for further study. STM tips can be transferred into and out of vacuum and positioned for sputtering and UHV analysis. The various design details which allow for in vacuo transfers will be discussed.
Influence of gas added to the MEVVA discharge on the extracted ion beama)
Authors: Spädtke P. , Emig H. , Wolf B. H. , Oks E.
Published: July 2002

The presence of background gas in the discharge chamber of the metal vapor vacuum arc source influences the extracted beam. We have observed a strong influence of the background gas pressure in the arc region on the total extracted beam current and on the charge state distribution of the metallic ions. Different gases have been investigated together with different cathode materials. Up to 90% of the total beam current can be gaseous ions, depending on the arc and gas injection conditions.
Electrostatic low-energy beam transport systems for the SSC linaca)
Authors: Raparia D. , Guy F. , Saadatmand K. , Funk W.
Published: July 2002

This paper provides arguments to choose electrostatic low-energy beam transport (LEBT) over the magnetic LEBT for the SSC linac. We will outline the rules to design the electrostatic LEBTs with examples of SSC LEBTs.
Channeling of vacuum ultraviolet radiation down tapered capillaries and prospects for a photoemission spectromicroscopy
Authors: Smith N. V. , Royer W. A. , Rowe J. E.
Published: July 2002

The transmission of linear tapered silica-glass capillaries is calculated both numerically and analytically for photon energies in the vacuum-ultraviolet region (10–200 eV). The channeling factor C (ratio of transmitted to line-of-sight flux) is given to a good approximation by 2γ/β, where β is the taper angle and γ is a characteristic decay angle determined entirely by the optical constants. The angular divergence (FWHM) of the output flux is 2.4 (βγ)1/2, and the useful length of the capillary is 2dγβ−3/2, where d is the diameter of the exit aperture. Experimental measurements of photoemission spectra on Au samples using tapered capillaries attached to the end of a conventional resonance lamp confirm these expectations. Channeling factors greater than 103 should be achievable with submicron values of d.
Electric and magnetic characteristics of a Co-Fe-Si-B-based amorphous wire and its application to a multivibrator-type magnetometer at low temperature
Authors: Sakasai K. , Ara K. , Itoh H. , Kishimoto M. , Katagiri M.
Published: July 2002

Electric and magnetic characteristics of a Co-Fe-Si-B-based amorphous thin wire with a diameter of 120 μm were investigated at low temperatures from an applicative point of view. The electric resistivity decreases with the decrease of temperature and has the minimum point at about 30 K. The maximum decrease of the resistivity is, however, only 2.7% as compared with that at room temperature. The magnetic characteristics in term of the coercive force, the saturation induction, and the maximum permeability are all increased with the decrease of temperature. The coercive force shows the increase of 25% at 4.4 K as compared with that at room temperature; and the saturation induction and the maximum permeability about 15%. The very slight decrease of electric resistivity and the increase of the coercive force with the decrease of temperature promise a high-frequency application of the wire at low temperature. These results led to the fabrication of a multivibrator-type magnetometer being able to work at low temperature below 77 K. The magnetometer has a sensitivity of about 1 mV/mG at room temperature in a magnetic field range between +1 and −1 Oe. The sensitivity change is less than 0.5% even at low temperature of 6 K, as compared with that at room temperature.
Microwave ion source with linear antennaea)
Authors: Wada Motoi , Hamabe Makoto , Tsuji Kousei , Tsuda Hiroshi , Miyamoto Naoki , Ohtani Yoshiaki
Published: July 2002

A microwave ion source equipped with two linear antennae set parallel to the wall of the source chamber has been designed and built. A homogeneous plasma of Ar was produced in an aluminum chamber of 22 cm long, 9 cm wide, and 6 cm deep. Beam forming grids produced a rectangular beam of 17 cm by 3 cm. The current density of the extracted Ar+ beam was 0.16 mA/cm2 at the center of the extraction area when the input power to the magnetrons was 360 W. The energy distribution function of the extracted ions was measured with an electrostatic analyzer. The measured energy distribution showed a presence of high energy ions in the extracted beam.
How to select the best condition for operating a positive ion source of molecular beam surface ionization typea)
Authors: Kawano Hiroyuki , Ohgami Katsushi , Funato Kiyohiko , Nakamura Junji
Published: July 2002

In easily attainable high vacua (Pr≊20–0.2 μTorr), the efficiency (β+) for producing ions (M+) from diatomic molecules (MX) incident on a polycrystalline surface of W, Mo, or Re was measured as a function of surface temperature (T≊800–2300 K). Theoretical analysis of β+ elucidated the temperature dependence of the effective work function (φ+) for the ionization. Namely, (1) above ∼2000 K, each surface is kept virtually clean, having φ+≊5.2, 4.9, and 5.4 eV for W, Mo, and Re, respectively. (2) At ∼1400–1200 K, the range of which depends upon Pr, φ+ is increased up to ∼7 eV by adsorption of residual gas molecules (RGM), thereby yielding β+=1 for even Tl and the current density of ∼10 μA cm−2 for the flux of 1014 molecules cm−2 s−1. (3) Below ∼1200 K, however, φ+ is much decreased by coadsorption of MX and RGM. A theoretical diagram of T vs φ+ is devised to predict the best condition for β+=1. The best condition (φ+, T, and Pr) to make β+ as large as possible may readily be selected according to the diagram and the present data on φ+.
Improved Ashby–Jephcott interferometer for temporal electron density measurements in plasmas
Authors: Rasiah Ignatius J.
Published: July 2002

The Ashby–Jephcott interferometer is used to measure the temporal variations in electron densities in plasmas. A double-ended HeNe laser is used as part of an interferometer to make these measurements. In the present work, the experimental setup of the original method has been modified to prevent the drift in the temporal fringe patterns that are observed. This allows for more precise measurements of electron densities in plasmas. Further, the modification allows for commercially available HeNe lasers to be used to measure electron densities. The fringe patterns observed in a Z-pinch discharge using the original Ashby–Jephcott method and the modified method are shown. The differences in the temporal variation of the electron density measurements using the two methods are discussed.
A new end-loss-ion energy analyzer with obliquely placed multigrids for open-ended plasma diagnostics
Authors: Kuwabara T. , Cho T. , Sakamoto Y. , Takahashi E. , Nakashima Y. , Hirata M. , Yatsu K. , Tamano T. , Miyoshi S.
Published: July 2002

A new type of end-loss-ion energy analyzer (ELA; a multigridded Faraday cup) is applied to measure plasma ion temperatures Tip and plasma potentials ΦP in the GAMMA 10 tandem-mirror device. As compared with conventional-type ELA, this new ELA has obliquely placed ion- and secondary-electron-repeller grids and a collector plate with respect to external tandem-mirror magnetic fields. One of the most useful capabilities of this new ELA for precise ion measurements is to greatly reduce the current of high-energy electrons onto the collector plate. Also, this compact-sized ELA is scannable in the plasma to obtain radial profiles of Tip and ΦP without providing any perturbations of the tandem-mirror magnetic fields because it neither adds its own magnetic field nor needs to shield against the ambient magnetic field. Ion trajectories in the new ELA are numerically calculated so as to make a further understanding of its physics principles and to optimize its design. The energy-calibration experiments for the new ELA are carried out using ion beams; a fairly good agreement in the analyzed beam energies from the new ELA data and from conventional-type ELA data is attained. Furthermore, the first application of the new ELA to plasma diagnostics is made; a substantial reduction in energetic-electron influxes onto real ion signals makes a significant improvement in the analyses of Tip and ΦP.
A high sensitivity momentum dispersive multichannel electron momentum spectrometer for studies in experimental quantum chemistry
Authors: Todd B. R. , Lermer N. , Brion C. E.
Published: July 2002

The design and characterization of a high sensitivity multichannel momentum dispersive electron momentum spectrometer is reported. Electron pair coincidences are detected over a ±30° range of azimuthal angle at the exit slit of a cylindrical mirror analyzer configured to measure symmetric (θ=45°) noncoplanar (e,2e) scattering. A position sensitive microchannel plate/resistive anode encoder electron detector and a channeltron electron multiplier are employed in a novel multichannel coincidence detection system based upon detection of ‘‘pile-up’’ of pairs of timing pulses from the detectors. Proof-of-concept results, exhibiting significantly higher coincidence count rates and statistical precision than have been previously observed in electron momentum spectroscopy, are presented for argon.
A dynamic model for analyzing piezoelectric stepmotors
Authors: Yuan Yang Sheng , Wen Hao Huang , Tian He
Published: July 2002

A new dynamic model is developed for analyzing the dynamic process of piezoelectric stepmotors. In this model the voltage applied to the piezoelectric stepmotor is equivalent to the force acting on the end of the piezoelectric stepmotor. The model is simple and convenient for applications. As an example, a model of analyzing the rotatable sample stage is presented. The theoretical results are in good agreement with the experimental results. The structural damping of the piezoelectric material is also discussed.