bluuebunny/crossref_metadata_2025 huggingface dataset:
Linac with integrated power source based on radio frequency energy compression
Authors: Smirnov A. V. , Smirnov V. N.
Published: July 2002

The basic feasibility of a proposal to simplify the conventional low energy rf electron linear accelerator (linac), is considered. The design suggested foresees replacement of the traditional high power systems of external rf generator and modulator by a more passive switched energy storage system. The proposed conception of a compact linac is based on known rf energy compression techniques and an efficient self-excited oscillation in a special accelerating/oscillating linac structure. The principal relations, performance estimations, and one-dimensional time-dependent simulation results for such a linac are presented. The possibility of self-excited oscillation by an unbunched low voltage beam in a waveguide linac section is proved and investigated experimentally. The common features and differences compared with a conventional backward-wave tube are analyzed. An application of this effect is proposed for impedance and group velocity measurements in slow-wave structures. Since the rf energy commutation may be one or two orders faster than the electric high voltage energy commutation (conventional modulator), combining the structure proposed and rf energy compression system can give high levels of the average beam power (10–100 kW). The linac facility would have considerably reduced weight and sizes (more than 2.5 times) as compared to similar industrial linacs. The power supply required is in 40–120 kV range dc source, and an estimated overall wall plug efficiency is a few percent.
Finnish beamline at MAX-laboratory: Progress in the photon energy resolution
Authors: Aksela S. , Kivimäki A. , Sairanen O.-P. , Naves de Brito A. , Nõmmiste E. , Svensson S.
Published: July 2002

The photon energy resolution of the modified SX-700 plane grating monochromator at the Finnish beamline (BL51) at MAX-laboratory in Lund, Sweden, has improved considerably after proper alignment of the monochromator. Resolving powers of about 10 000 at hν≊90 eV and 5000 at hν≊400 eV have been achieved at the first diffraction order, as inferred from total ion yield measurements at the Kr 3d5/2→5p and N2 N1s→π* resonances. The total linewidth of ≤121 meV recorded for the Ar 2p3/2→4s excitation suggests that the lifetime broadening could be smaller than 116 meV obtained from electron energy-loss spectroscopy.
Optical windows for a flow cell to contain aqueous solutions at high pressure and temperature
Authors: Bowers W. J. , Bean V. E. , Hurst W. S.
Published: July 2002

A flow cell to contain aqueous solutions at pressures up to 40 MPa and temperatures up to 600 °C that is equipped with sapphire windows for the transmission of visible light is described. There are four windows, two for the entrance and exit of a laser beam, and two located at 90° that feature f/1 (53° included angle) collection apertures with a 9 mm diameter unobstructed view for Raman spectroscopy, absorption measurements, or studies using full-field back illumination. The window-to-metal seals are gold o-rings; the metal-to-metal seals are gaskets prepared by pressing a gold o-ring onto a gold foil washer. This cell has been used for two years for Raman studies of aqueous solutions at high pressures and temperatures both below and above the supercritical point of water.
A two color mm-wave interferometer for the JET divertora)
Authors: Prentice R. , Edlington T. , Smith R. T. C. , Trotman D. L. , Wylde R. J. , Zimmermann P.
Published: July 2002

An interferometer with compensation for vibration and large scale mechanical movements has been designed and built to measure the line integral electron density along three different lines of sight through the JET divertor plasma. Overcoming the effects of a long transmission path, having an estimated 65 dB loss, requires oversized waveguide transmission lines, sensitive heterodyne detection, low loss quasioptical circuits, and highly stable sources. The sources are frequency doubled, phase-locked, Gunn oscillators producing 15 mW at 130 GHz and 10 mW at 200 GHz. Waveguide Schottky mixer diodes generate reference and output signals at an IF of 10.7 MHz and the LO Gunn diodes are phase locked to the reference IF. Corrugated feedhorns and ellipsoidal mirrors are used for beam control and polarizing wire grids for beam splitting and recombination. To minimize unwanted, direct coupling of source power into the signal detectors, Brewster angle beam dumps and Faraday rotation isolators are used in the transmit and receive QO circuits, which in turn are separated, on opposite faces of a vertical plate. Martin–Pupplet polarizing interferometers are used to multiplex the two colors into a single coaligned, copolar output beam and to demultiplex the return beam. Constant fraction discriminators are used to optimize the accuracy of the phase detectors, which have sampling and recording rates of 1 MHz and a resolution of ∼7° (0.02 fringe).
Ultrahigh vacuum compatible superconducting quantum interference device magnetometer system for studies of magnetic thin films
Authors: Spagna S. , Sager R. E. , Maple M. B.
Published: July 2002

In this article, we describe an ultrahigh vacuum (UHV) compatible superconducting quantum interference device (SQUID) magnetometer system for investigations of surface, interface, and thin film magnetism. This system provides a new capability for a commercial SQUID magnetometer to characterize freshly deposited thin film samples transported from a separate molecular-beam epitaxy deposition facility without breaking vacuum. Magnetic measurements can be performed over a wide range of temperatures down to 4.2 K in applied magnetic fields as high as 1 T, and under a variable vacuum environment in which pressures as low as 10−10 Torr can be achieved. The combination of the extremely high sensitivity of the SQUID for magnetic measurements with UHV analysis techniques offers the unique capability for films to be prepared, processed, and characterized repeatedly without substantial contamination. The capabilities of the UHV-SQUID magnetometer system are demonstrated by in situ measurements of the magnetic properties of Co/CoO bilayered thin films grown on Si(100) single-crystal substrates by electron-beam evaporation.
Measurement of 1 cm2 surface areas by krypton adsorption using an adsorption apparatus with a temperature-compensated, differential tensimeter of symmetrical design
Authors: Suzuki Isao
Published: July 2002

Areas of solid surfaces as small as 1 cm2 were determined by krypton adsorption at liquid nitrogen temperature using an adsorption apparatus with a temperature-compensated, differential tensimeter of symmetrical design. The BET monolayer volume of krypton for 50, 100, or 150 of 1 mm steel ball bearings was proportional to the number of balls used. The coefficient of proportionality agreed with the result on 10 000 ball bearings. The surface area of 50 ball bearings is to 1.57 cm2, which suggests that it is feasible to measure surface areas as small as 1 cm2.
Separating the coherent and incoherent effects in optical correlation experiments on semiconductors and other saturable absorbers
Authors: Bello A. F. , Erskine D. J. , Radousky H. B.
Published: July 2002

In some pump–probe optical correlation experiments, the measured signal versus delay between pulses generally consists of two components: the convolution of the pulse autocorrelation with the sample impulse response, and a coherent artifact. The latter can obscure the first component near zero delay where fast time scale processes will be manifest. We present a mathematical description of the relative shapes and sizes of the two components, so that a fitting process can separate them. This can yield both the dephasing and relaxation times of saturable absorbers such as semiconductors. The method is particularly appropriate when the orientational dephasing and relaxation times are of the same time scale as the laser pulse width.
Profile measurements of high intensity-low energy ion beams
Authors: Rezzonico L. , Olivo M.
Published: July 2002

A noninterceptive beam profile monitor based on the measurement of the light arising from the collision of the beam with the residual gas is being implemented in the 60 and 870 keV high intensity dc-beam lines of the Paul Scherrer Institute accelerator complex. Beam profiles measured with this monitor are compared to those obtained with a calorimeter at 60 keV, and with a wire scanner at 870 keV. Wire scanners are presently used in the 870 keV beam line. Because of heat load limitations in the scanner wires the beam has to be pulsed when profiles are taken. However, because of space charge neutralization effects, the profile of a pulsed beam may differ from that of a dc beam.
Measurement of polar anchoring coefficient for nematic cell with high pretilt angle
Authors: Subacius D. , Pergamenshchik V. M. , Lavrentovich O. D.
Published: July 2002

A method to determine the surface anchoring energy of a nematic liquid crystal is proposed. The technique implies the measurements of optical retardation of a nematic cell as a function of a strength and direction of the applied magnetic field. It enables one to get both pretilt angle α and anchoring coefficient Wa in the course of the same experiment. As an example, both parameters (α=10.9° and Wa=1.5×10−5 J/m2) are measured at the interface between the nematic 5CB and rubbed polyimide film.
A high-efficiency positive (negative) surface ionization source for radioactive ion beama)
Authors: Alton G. D. , Mills G. D.
Published: July 2002

A versatile, new concept, spherical-geometry, positive (negative) surface-ionization source has been designed and fabricated which will have the capability of generating both positive- and negative-ion beams without mechanical changes to the source. The source utilizes a highly permeable, high-work-function Ir ionizer (φ≡5.29 eV) for ionizing highly electropositive atoms/molecules; while for negative-surface ionization, the work function is lowered to φ≡1.43 eV by continually feeding cesium vapor through the ionizer matrix. The use of this technique for negative ion beam generation has the potential of overcoming the chronic poisoning effects experienced with LaB6 while enhancing considerably the efficiency for negative surface ionization of atoms and molecules with intermediate electron affinities. The flexibility of operation in either mode makes it especially attractive for radioactive ion beam applications and, therefore, the source will be used as a complementary replacement for the high-temperature electron impact ionization sources presently in use at the Holifield radioactive beam facility. The design features and operational principles of the source will be described in this report.
Closed-form solutions for a disk, a filter, and a window for an x-ray beamline at the Advanced Photon Source
Authors: Nian H. L. Thomas , Kuzay Tuncer M.
Published: July 2002

Several temperature closed-form solutions are developed and presented in this paper. The heating on a one-dimensional thin disk and a two-dimensional thin plate are analyzed. Parametric studies are also included to determine the optimized temperature for the designs.
Piezoelectrically driven rotary stage for use in ultrahigh vacuum
Authors: de Haas E. , Barsingerhorn W. , van der Veen J. F.
Published: July 2002

We have developed a compact high-precision rotary stage for use in ultrahigh vacuum. Its drive mechanism incorporates along its circumference two sets of diametrically opposed piezoelectric devices with combined clamping and pushing action. The maximum torque load is 0.7 Nm. The rotation is bidirectional over 360° and proceeds in steps down to 1 mdeg at a maximum speed of one revolution per 2 min.
An apparatus to load gaseous materials to the diamond-anvil cell
Authors: Yagi Takehiko , Yusa Hitoshi , Yamakata Masa-aki
Published: July 2002

An apparatus to load gases to the sample chamber of the diamond-anvil cell has been devised. The apparatus is driven by a conventional 50 ton hydraulic press and no gas compressor is required. The gas from a commercial gas bomb is compressed to 150 MPa and loaded into the diamond-anvil cell sample chamber. After loading, the pressure of the diamond-anvil cell is increased further using the lever and spring mechanism. This kind of gas loading apparatus will become indispensable not only for studying gaseous materials themselves, but also for making precision measurements at high pressures and high temperatures under hydrostatic conditions.
Self-referencing resonant fiber optic intensity sensor based on a Mach–Zehnder topology
Authors: Baptista J. M. , Cavaleiro P. M. , Santos J. L.
Published: July 2002

An investigation is performed on the characteristics of the self-referencing resonant fiber optic intensity based sensor supported by a Mach–Zehnder topology. Both transmissive and reflective configurations are analyzed. Via the definition of the measurement parameter (R parameter) the linearity and sensitivity of the sensor are addressed. Theoretical and experimental results are compared. The problem of sensor design is under consideration.
Comparison of reflectometer fluctuation measurements from experiment and two-dimensional numerical simulation
Authors: Conway G. D. , Schott L. , Hirose A.
Published: July 2002

A comparison is made between the statistical properties of phase and power signals from a homodyne reflectometer on the STOR-M tokamak and simulated signals from a two-dimensional distorted surface model. Experimental results from edge density fluctuations show phase fluctuations of less than half a fringe with a Gaussian distribution and no phase ramping. Reflected power fluctuations are substantial (up to 45%) and are non-Gaussian distributed. Both phase and power signals display broadband turbulent frequency spectra with spectral indexes of −3.5. Fluctuations in the scattered electric field are calculated in the model using physical optics principles with a Gaussian reflectometer incident beam profile and structured surface distortions to replicate variations in the plasma cutoff layer. Simulation results display a wide range of features depending on three parameters, surface fluctuation amplitude, transverse wavenumber spectrum, and incident beam width. With the beam width fixed by the experiment (50 mm) and (realistic) fitted values of 1–2 mm for the root mean square fluctuation depth and 2 cm−1 for the k-spectral width—good agreement is found with the experiment.
A near-field optical microscope with normal force distance regulation
Authors: Stephenson R. J. , O’Shea S. J. , Barnes J. R. , Rayment T. , Welland M. E.
Published: July 2002

Near-field imaging is a means of exceeding the diffraction limit in optical microscopy to yield subwavelength resolution optical images of a sample surface. In order to achieve such high resolution, it is necessary to scan the measurement probe above the surface at a height of only a few nanometers which requires careful control of the separation between tip and sample. In the implementation of the near-field optical microscope (NFOM) reported here, the distance regulation scheme is based on an inverted noncontact atomic force microscope (AFM) in which a cantilever is used as the sample substrate and imaging is performed with a fiber optic tip. In this way, both the benefits of AFM and NFOM are realized simultaneously.
A tungsten filament high temperature heater for thin film deposition
Authors: Bellman Robert , Raj Rishi
Published: July 2002

A reliable high temperature substrate heater for thin film deposition was constructed. The heater has a modular design and is built from parts that are easy to fabricate. The heater consists of a square arrangement of four tungsten filaments in a disk-shaped molybdenum susceptor. The electrical connections are placed near the edge where they are easily accessed. A finite element analysis shows that this design produces a more uniform temperature distribution than typical radial arrangements of filaments. The excellent performance of the new heater is demonstrated by thickness variations of less than 2% in thin films of lithium tantalate films grown on a 3.75 cm diam substrate by a high vacuum metal-organic chemical vapor deposition process.
Front-end equipment protection system at the Advanced Photon Source
Authors: Friedman N. , Hawkins J. , Travis D. , Laurence G.
Published: July 2002

The front-end Equipment Protection System (FE-EPS) at the Advanced Photon Source (APS) is a high reliability, fail-safe single-chain interlock and control system. It consists of an Allen-Bradley PLC-5/30 processor, local and remote I/O racks, monitoring and control panels, serial communication links, and field devices. Each front end is equipped with a dedicated EPS. The system monitors a variety of sensors (e.g., vacuum, cooling water, temperature, pneumatic pressure), and controls front-end (FE) photon shutters and UHV valves. The main functions of the FE-EPS are to guard the integrity of the storage ring vacuum against vacuum excursions in the FE and beam transport line, as well as to protect the front-end and beamline components from being damaged by synchrotron radiation. The FE-EPS interfaces to six other APS interlock and control systems. Information about FE interlocks and devices is displayed on UNIX machines using the EPICS software tool kit. The system design is presented.
Earth, soil and environmental science research facility at sector 13 of the Advanced Photon Source. I. Sector layout and optical design (abstract)
Authors: Eng Peter , Jaski Yifei R. , Lazarz Nancy , Murray Paul , Pluth Joseph , Rarback Harvey , Rivers Mark , Sutton Stephen
Published: July 2002

The earth, soil and environmental science component (GSECARS) of the Consortium of Advanced Radiation Sources (CARS), is designing a national research facility to be built at sector 13 of the Advanced Photon Source. The bending magnet beam will be split to allow simultaneous operation of two stations, a monochromatic (8–15 keV) side station and a multipurpose, white beam/monochromatic end station. The undulator beamline will have two white beam stations, which may operate simultaneously using a double-crystal monochromator (cryogenic Si) with a thin first crystal. In this mode, the upstream station will accept the monochromatized (4.5–22 keV) beam deflected horizontally by a third (bendable) Ge crystal, while the end station accepts the high energy component (blue beam) transmitted by the first crystal. The need for small x-ray beams and broad spectral range have led us to base the focusing aspects of the optic design on grazing incidence mirrors. Both our bending magnet and insertion device beamlines will have long (∼1 m), bendable mirrors (demagnification <11, E(cut-off) ≳70 keV; beam sizes ≳tens of micrometers). For smaller focal spots, we will use small, dynamically bent Kirpatrick-Baez mirrors (demagnification 100–400; E(cut-off) <70 keV; beam sizes ∼1 micrometer). A unique aspect of our insertion device beamline is the ability to deliver focused white beam to the sample, through the incorporation of a power management pinhole in the first optics enclosure.
Bent crystal analyzer without grooves for inelastic x-ray scattering
Authors: Kushnir V. I. , Popovici M.
Published: July 2002

A new design of analyzers for inelastic x-ray scattering is proposed. In the usual design, special measures are taken to avoid the influence of bending strains on the resolution. The novel design suggests keeping the backscattering geometry but using reflecting planes that are not parallel to the crystal surface in conjunction with nonspherical bending. Conditions can be ensured in order that a) the bending strains not affect the x-ray diffraction, and b) the radiation emitted by a point sample is focused back to a point detector. Examples of configurations satisfying those conditions are given for Si and Ge crystals.
Initial time-resolved particle beam profile measurements at the Advanced Photon Source
Authors: Yang B. X. , Lumpkin A. H.
Published: July 2002

The commissioning of the 7-GeV Advanced Photon Source (APS) storage ring began in early 1995. Characterization of the stored particle beam properties involved time-resolved transverse and longitudinal profile measurements using optical synchrotron radiation (OSR) monitors. Early results include the observation of the beam on a single turn, measurements of the transverse beam sizes after damping using a 100 μs integration time (σx∼150±25 μm, σy∼65±25 μm, depending on vertical coupling), and measurement of the bunch length (στ ∼25 to 55 ps, depending on the charge per bunch). The results are consistent with specifications and predictions based on the 8.2 nm-rad natural emittance, the calculated lattice parameters, and vertical coupling less than 10%. The novel, single-element focusing mirror for the photon transport line and the dual-sweep streak camera techniques, which allow turn-by-turn measurements, will also be presented. The latter measurements are believed to be the first of their kind on a storage ring in the USA.
Measurement of the absolute energy and energy spread of the ESRF electron beam using undulator radiation
Authors: Tarazona E. , Elleaume P.
Published: July 2002

Two simple methods of characterizing the average energy and energy spread of the electron beam have been developed at the ESRF. Both are based on analysis of the x-ray spectrum from an undulator. The first allows the absolute energy of the electrons to be determined. It is based on the dependence between the harmonics wavelengths and the electron beam energy. The x-ray beam is monochromatized at 21 keV by a silicon crystal in backscattering geometry. By adjusting the magnetic gap, one makes the third harmonic of the radiation from an undulator coincide with the energy selected by the crystal. The main errors come from the uncertainties in the undulator’s magnetic field and period. By operating the undulator at low field (K=0.36), an absolute accuracy of 10−3 is reached for the electron energy. The energy spread measurement is performed by analyzing the broadening of the harmonics’ profile. It is deduced from the measured ratio between the height of the peak of the seventh harmonic at 29 keV and the height of a secondary maximum at lower energy. The measured low current energy spread is 1.1×10−3±20%. It increases with the single bunch current due to turbulent bunch widening.
Electric-field measurement near a ring antenna by a new field sensor using piezoelectric resonance
Authors: Lee Daehaeng , Lee Soonchil
Published: July 2002

It is demonstrated that the pulse spectroscopy in combination with piezoelectric resonance makes an ideal nondisturbing tool for the measurement of electric field near an antenna. The dependence of the picked up resonance signal on the amplitude and direction of external electric field was quantitatively evaluated. This new field sensing technique was used to investigate the field of a ring antenna the near field of which is widely used.
A micro-fluorescent/diffracted x-ray spectrometer with a micro-x-ray beam formed by a fine glass capillary
Authors: Yamamoto Naoki
Published: July 2002

The technique of forming a micro-x-ray beam with a fine capillary was studied. It was shown that lightweight materials, such as glass, were suitable for the capillary in terms of their x-ray refractive indexes. A fine glass capillary with a parabolic cross-sectional inner wall surface was made. Using the capillary, a fluorescent and diffracted x-ray spectrometer with a 0.8-μm-φ x-ray beam was developed for the analysis of stress, crystal structure, and metal contamination in micro regions of ultra-large-scale integration (ULSI) devices. A micro-focus x-ray generator with a membrane-type target was also developed for use with the capillary. The crystal phases of very thin Ti-silicide fine lines and the strain in Al interconnections of ULSIs were analyzed using the equipment.
High-transition temperature superconducting quantum interference device microscope
Authors: Lee Thomas S. , Dantsker Eugene , Clarke John
Published: July 2002

A microscope has been constructed in which a high-transition temperature dc superconducting quantum interference device (SQUID) in vacuum is brought to within 140 μm of samples at room temperature and pressure. The SQUID is mounted on the upper end of a sapphire rod, cooled to liquid nitrogen temperature, below a 75-μm thick sapphire window. Samples can either be placed directly on the window or scanned over the SQUID to produce magnetic images. A square-washer SQUID with inner and outer dimensions of 30 and 50 μm can resolve 130 μm magnetic features. The instrument is intended primarily for biological applications.
Design of an electronic charged particle spectrometer to measure 〈ρ𝓡〉 on inertial fusion experiments
Authors: Hicks D. G. , Li C. K. , Petrasso R. D. , Séguin F. H. , Burke B. E. , Knauer J. P. , Cremer S. , Kremens R. L. , Cable M. D. , Phillips T. W.
Published: July 2002

The design and fabrication of a new diagnostic that measures the energy spectra of charged particles from targets on the Omega Upgrade are actively underway. Using seven 512×512 charge coupled devices (CCDs) and a 7.5 kG permanent magnet, this instrument will uniquely determine particle identities and measure particle energies from 1 MeV up to the maximum charged particle energies of interest for ρR measurements (10.6 MeV knock-on tritons, 12.5 MeV knock-on deuterons and 30.8 MeV tertiary protons). The resolution of the diagnostic will be better than 5%. We have tested the response of SITe back-illuminated CCDs to 1.2–13.6 MeV protons from our Cockcroft–Walton accelerator and to alpha particles from an Am241 source, and the results agree extremely well with predictions. With its high density picture elements, each CCD has 105 single-hit detectors. In the case of a low DT yield of 109 neutrons, about 100 knock-on charged particles will be detected when the spectrometer aperture is 60 cm from the implosion. Measurements of ρR up to 150 mg/cm2 can be obtained from knock-on D and T spectra, and values up to 300 mg/cm2 can be determined from secondary proton spectra. The sensitivity of the CCDs to 14 and 2.5 MeV neutrons has been experimentally determined using our Cockcroft–Walton accelerator source and indicates that by incorporating neutron shielding, the signal to neutron noise ratio at a yield of 1011 will be better than 100:1. In the development phases of this program, we plan to utilize CR-39 track detectors concurrently with the CCDs.
Native point defects in low-temperature-grown GaAs
Authors: Liu X. , Prasad A. , Nishio J. , Weber E. R. , Liliental-Weber Z. , Walukiewicz W.
Published: July 2002

We present structural and electronic data which indicate that the dominant defects in GaAs grown at low temperatures (LT GaAs) by molecular beam epitaxy (MBE) are As antisites (AsGa) and Ga vacancies (VGa), with negligible amounts of As interstitials (Asi). We show that the change of lattice parameter correlates with the concentration of AsGa, and that AsGa alone can account for the lattice expansion. We also show that the total concentration of AsGa has a characteristic second power dependence on the concentration of AsGa in the positive charge state for the material grown at different temperatures. This can be understood provided that VGa defects are the acceptors responsible for the carrier compensation. Our results are consistent with most experimental results and the theoretical expectation from the calculation of defect formation energies. We find that the conclusion may also be true in As-rich bulk GaAs.
Thomson scattering from two-species laser-produced plasmas (invited)
Authors: Glenzer S. H. , Back C. A. , Estabrook K. G. , Kirkwood R. K. , Wallace R. , MacGowan B. J. , Hammel B. A. , Cid R. E. , De Groot J. S.
Published: July 2002

We report on recent Thomson scattering measurements from two ion species laser-produced plasmas. A flat disk coated with multiple alternate thin layers of gold and beryllium was irradiated with one laser beam of the Nova laser facility and the resulting two ion species plasma was probed with a second laser beam at a distance of 500 μm with time-resolved spectroscopy of the Thomson scattered light. A controlled variation of the Au fraction of the plasma was achieved by changing the relative thicknesses of the individual multilayers of the target. Two ion acoustic waves belonging to the Au and Be species were clearly observed. Besides their usual application to deduce electron temperatures, the relative damping of both waves provides an accurate measurement of the ion temperature of the plasma. In addition, the relative ion densities can be measured with high accuracy from the relative phase velocities of both waves if the ion charge state is known independently or vice versa.
A novel wide range electrometer with quasilinear output
Authors: Shaw Sen-Yen , Chang Ruey-Shyan
Published: July 2002

An electrometer using complementary metal–oxide–semiconductor bilateral switches for automatic range control is described. Based on a dual-switching configuration, the electrometer is capable of current measurement over eight orders of magnitude. Together with a voltage shifter, this circuit provides a quasilinear analog output for the measurement of input dc current between 10−3 and 10−12 A. The application of integrated circuits makes the whole system compact and extremely low cost.
Pulsed photoelectron microscope for imaging laser-induced nanosecond processes
Authors: Bostanjoglo O. , Weingärtner M.
Published: July 2002

A flash photoelectron microscope, driven by 4 ns KrF excimer laser pulses, is introduced. The microscope is equipped with a solid state laser for in situ processing of metals with focused nanosecond pulses. Transient stages during laser-induced melting, solidification, and alloying of Al films on bulk substrates have been imaged with an exposure time of 4 ns. The photoelectron microscope is proved to be a powerful real-time probe for fast-proceeding incipient laser-induced damage, sensing changes of surfaces being too shallow to be detected by light interference and electron scanning microscopy. The combined time/space resolution is limited by lens aberrations, space charge, shot noise, and detector efficiency to about 4 ns/1.3 μm, at present.
An arc discharge nitrogen atom source
Authors: Xu Ning , Du Yuan-cheng , Ying Zhi-feng , Ren Zhong-min , Li Fu-ming
Published: July 2002

An intense nitrogen atom beam source of simple construction, with easy handling and maintenance was built and tested. Nitrogen atom beams with an intensity estimated to be 1019 atom/sr s and with an average kinetic energy of 0.8–2 eV in the forward direction were obtained. This novel atom source can be successfully ignited using pure nitrogen gas and operated stably during several hours of continuous performance. The temperature-rise effect of calorimetric sensors due to the bombardment of the N atom beam was used to analyze the intensities and kinetic energies of nitrogen atom beams. The emission spectra from the arc also show that a high concentration of atomic nitrogen was produced using this source. Experiments such as the nitrogen atom beams interacting with substrates to form a TiON film and a carbon nitride film indicate the high concentration of atomic nitrogen in the beam.
Nitrogen doping of tellurium-based II–VI compounds during growth by molecular beam epitaxy
Authors: Baron T. , Saminadayar K. , Magnea N.
Published: July 2002

We report p-type doping of tellurium-based compounds (CdTe, ZnTe) and alloys (CdMgTe, ZnMgTe, ZnCdTe) in molecular beam epitaxy using nitrogen atoms from a plasma source. The dominant shallow acceptor, as deduced from transport and optical measurements, has an ionization energy close to the effective mass value. A systematic decrease of the doping efficiency is observed as the Zn content decreases. We discuss the key role of the Zn content in the material in the framework of two factors: (i) local strain induced in the lattice by the presence of nitrogen and (ii) formation of compounds involving nitrogen atoms.
Monte Carlo calculations for the design of Mott scattering spin polarimeters
Authors: Qiao S. , Kakizaki A.
Published: July 2002

Using the Monte Carlo method, we have calculated, for 50 keV electrons incident on a gold target, the dependence of the effective Sherman asymmetry function and scattered intensity on the target thickness and inelastic energy loss window for scattering angles from 90° to 180°. Our results show that, when the gold target is thicker than 700 Å or the inelastic energy loss window is larger than 1200 eV, the scattered intensity is maximum at a scattering angle of about 120°, and the effective Sherman function is almost constant over a wide range of scattering angles. Thus, for Mott scattering spin polarimeters, the electron detectors should be positioned at ±120°, and the larger the collection angle for scattered electrons, the higher the efficiency of the Mott polarimeter.
Noninvasive probing of high frequency signal in integrated circuits using electrostatic force microscope
Authors: Hong J. W. , Khim Z. G. , Hou A. S. , Park Sang-il
Published: July 2002

We report a noninvasive high speed voltage sampling technique by using atomic force microscope. This technique is based on the mixing of interaction forces between a conductive probe-tip and a device interconnect line. Mixing phenomena allow measurements of signals with frequencies far above the mechanical resonance frequency of the cantilever. To increase the sensitivity and stability of the signal detection in ambient environment, we employed a delayed pulse sampling and lock-in amplifier detection of the small electrostatic force resulting from a high frequency signal on integrated circuits. The probing pulse is first modulated by a low frequency sinusoidal voltage using a double-balanced diode mixer. The junction between probe-tip and integrated circuit interconnection line works as the second mixer which mixes the probing voltage with the high speed waveform in the interconnection line. This technique can sense voltage signals even through a passivation layer of a 0.5 μm in thickness. We sampled an 8-bit vector signal repeating at 50 MHz through a passivation layer by using this technique.
Fast thickness profile measurement of a thin film by using a line scan charge coupled device camera
Authors: Liang N. Y. , Chan C. K.
Published: July 2002

A technique based on counting the interference fringes produced by a thin film with a fast line scan charge coupled device camera is developed to measure the thickness profiles of the film every 50 μS. When this technique is applied to the bursting of a soap film, the dynamics of the bursting can be reconstructed from these thickness profiles. A method of thickness calibration by using a white light laser as a multiwavelength light source and a video camera as a detector is also introduced. The merit of this calibration technique is that with the help of digital image processing nearly no alignments of the optics are needed.
High pressure cell for small- and wide-angle x-ray scattering
Authors: Pressl K. , Kriechbaum M. , Steinhart M. , Laggner P.
Published: July 2002

A compact high pressure cell and its control environment designed for small- and wide-angle x-ray scattering experiments under hydrostatic pressure up to 3000 bar and temperatures between −20 °C and +80 °C are described. With this system x-ray scattering experiments can be performed at constant pressure and temperature with a conventional laboratory x-ray source and it can be easily modified to carry out time resolved pressure jump studies at synchrotron radiation sources. The computer-aided pressure adjustment has a calibrated accuracy of ±0.5%, and temperature is computer-controlled to a precision of ±0.05 °C. The instrument has been designed to investigate systems of biological interest, especially lipid-water dispersions, but it is equally possible to measure highly viscous or solid samples. The performance is illustrated by a pressure dependent small- and wide-angle x-ray scattering study of a phospholipid-water dispersion at constant temperature.
Microchamber for optical observation of freeze-drying phenomena
Authors: Bayard J. , Cléris H. , Varnier S.
Published: July 2002

In this paper, we describe an apparatus that allows the characterization of freeze-drying phenomena. For that, the sample to freeze is put into a microchamber where temperature and pressure are controlled. During the freeze-drying process, an optical observation of the sample is made thanks to a microscope fitted with a video camera. Images are stored on a video band, whereas temperature and pressure are stored in a file. The connection between the kinetics of the reaction (available from to the video band) and the physical parameters (stored in the file) is obtained by means of a synchronization between the storage of both images and the physical parameters.
Radio frequency driven multicusp sources (invited)
Authors: Leung Ka-Ngo
Published: July 2002

The radio frequency (rf)-driven multicusp source was originally developed for use in the superconducting super collider injector. The source can routinely provide 30 mA of H− beam at 0.1% duty factor. By adding a minute quantity of cesium to the discharge, H− beam current in excess of 100 mA and e/H∼1 has been achieved. The rf-driven H∼ source is being further developed for 6% duty factor operation to be used in the national spallation neutron source. Application of the rf-driven multicusp source has been extended to radioactive ion beam production, ion projection lithography, and compact neutron tubes.
A superconducting probehead applicable for nuclear magnetic resonance microscopy at 7 T
Authors: Odoj F. , Rommel E. , Kienlin M. v. , Haase A.
Published: July 2002

A practical cryogenic probehead for NMR microscopy is described. The superconducting coil is composed of a YBa2Cu3O7 layer on a LaAlO3 substrate. The probehead consists of a continuous flow cryostate with a room temperature bore for the sample. For better performance the sample can be positioned in the center of the coil. To evaluate the gain in sensitivity, spin-echo images are presented which compare the YBa2Cu3O7 (YBCO) resonator to a room temperature and a cryogenic Cu resonator. These results are corroborated through theoretical calculations. To estimate the potential of superconducting coils for NMR microscopy we have made a theoretical comparison of an YBCO resonator with a microscopic solenoid with three winding.
Imaging spectrometer based on an acousto-optic tunable filter
Authors: Romier J. , Selves J. , Gastellu-Etchegorry J.
Published: July 2002

This article describes an imaging spectrometer developed for remote sensing applications. The instrument consists of an acousto-optic tunable filter (AOTF), a high sensitive charged coupled device camera and optic lens. The selected AOTF was designed to have a large entrance aperture and to diffract light between 600 and 900 nm with a high spectral resolution. The signal was digitized by the camera and acquired with a developed WINDOWS executable software which drives the instrument. The spectrometer has been operated in a classical mode and in an imaging mode for its evaluation. In the imaging mode, images including different types of targets were acquired in reflection and transmission mode and were used to investigate image homogeneity, spatial resolution, chromatic and geometric aberrations, sensitivity and reliability. Spectra have been extracted from images and were successfully compared with spectra from the same sample area obtained with classical nonimaging spectrometers. This confirms the ability of this instrument to clear up many problems in surface analysis, particularly in the case of laboratory and field measurements used in remote sensing studies.
A new method of finding the pole profile in quadrupole magnets for obtaining high field quality
Authors: Sarma P. R. , Bhandari R. K.
Published: July 2002

The field quality in quadrupole magnets depends mainly on the pole profile. One often uses a circular pole of optimized radius to reduce the field errors. Hyperbolic profiles which are modified at the pole edges are also used. In the design of these magnets one first chooses a profile and then calculates the error harmonics. Here we have described a new method in which we choose the error harmonics first and then find the profile thus ensuring that the field quality is good. The method can also be applied to other multipole magnets.
A timing discriminator for space flight applications
Authors: Lampton Michael
Published: July 2002

A timing discriminator design for space flight delay line image systems is presented. This discriminator processes delay line signal pulses having a few ns width and recovers event timing centroids with an accuracy better than 100 ps full width at half maximum. For space flight use, it is important to minimize parts count and power consumption. Because it is difficult or impossible to adjust equipment on orbit, it is very desirable to eliminate all adjustments, yet provide generous timing margins against component aging or drift. The discriminator described here uses a simple linear passive network to produce the required internal waveforms. Performance data are reported for the first flight implementation of this design.
A rheo-optical apparatus for simultaneous detection of rheology, small-angle light scattering, and optical microscopy under transient, oscillatory, and continuous shear flows
Authors: Matsuzaka Katsuo , Hashimoto Takeji
Published: July 2002

A rheo-optical apparatus is constructed by installing a small-angle light scattering instrument and an optical microscope in a rheometer to investigate relationships between rheological properties and structures in complex liquids (or soft condensed matters). The apparatus is designed in such a way that it really enables us to measure simultaneously the rheological properties, light scattering, and transmission optical micrographs under both steady and dynamic shear field. It covers over a wide range of torque: it is applicable to systems having only the small viscosity of water ∼1 mPa as well as polymer systems in bulk having a high shear modulus G′∼109 Pa. An assembly of lens and a cooled charge coupled device camera allow us quantitative measurements of 2D light scattering patterns. For dynamic shear field, both light scattering measurements and optical microscopy observations can be synchronized with a given strain phase φ, defined in the text. Preliminary experiments with the apparatus are demonstrated for polymer mixtures with a common solvent and for semidilute polymer solutions.
A superconducting quantum interference device magnetometer system for quantitative analysis and imaging of hidden corrosion activity in aircraft aluminum structures
Authors: Abedi A. , Fellenstein J. J. , Lucas A. J. , Wikswo J. P.
Published: July 2002

We have designed and built a magnetic imaging system for quantitative analysis of the rate of ongoing hidden corrosion of aircraft aluminum alloys in planar structures such as intact aircraft lap joints. The system utilizes a superconducting quantum interference device (SQUID) magnetometer that measures the magnetic field associated with corrosion currents. It consists of a three-axis (vector) SQUID differential magnetometer, magnetic, and rf shielding, a computer controlled x-y stage, sample registration, and positioning mechanisms, and data acquisition and analysis software. The system is capable of scanning planar samples with dimensions of up to 28 cm square, with a spatial resolution of 2 mm, and a sensitivity of 0.3 pT/Hz1/2 (at 10 Hz). In this article we report the design and technical issues related to this system, outline important data acquisition techniques and criteria for accurate measurements of the rate of corrosion, especially for weakly corroding samples, and present preliminary measurements.
Very low frequency quadrature oscillator
Authors: Bayard J.
Published: July 2002

We propose a low-cost, practical, quadrature oscillator with a period, Tq, which may be very long (Tq⩾1 s). We illustrate this design with an oscillator that produces two quadrature sinusoidal waves with a 1 s period. This design can be modified to provide signals of any shape by adjusting the value of one or more resistors. This design uses digital integrated circuits (ICs) and analog multiplexers. Digital ICs and an analog multiplexer are used to generate a stair-step waveform approximation by switching between the four members of a set of constant voltages. The duration, Tc, of each constant voltage is held constant (Tc=Tq/16). Then, a set of linear ramps, each ramp with a period Tc, is generated and selectively added to the stair-step approximation with another analog multiplexer. The use of multiplexed linear ramps, together with the stair-step approximation to the desired waveform, results in a smooth analog wave. The period, Tc=Tq/16, of the necessary linear ramp can be reduced as needed by increasing the number, 16, of stair-step per period, Tq, of the desired overall waveform. In this way, the values and sizes of components needed to generate high-quality waves with extremely long periods are made small enough to be practical. Experimental results of a detailed study of waveform quality are included.
Recovery of cesium in the hydrogen negative ion sources
Authors: Belchenko Yu. I. , Oka Y. , Kaneko O. , Takeiri Y. , Krivenko A. S. , Osakabe M. , Tsumori K. , Asano E. , Kawamoto T. , Akiyama R.
Published: July 2002

Cesium recovery from the polluted layers in the 1/3 scale hydrogen negative ion source for LHD-NBI system has tested. It was found that the cesium recovery can be produced by additional discharges as from the cesium layer, aged by tungsten and residual gas, so as from the cesium layers, polluted by an occasional water leak. The highest cesium recovery to negative ion production was produced by a xenon arc, while glow discharge and arcing in hydrogen were less effective. The mechanism of recovery is the ejection of cesium from the underlying enriched layer by the arc and its transport to the surface.
Recent performance of Japanese electron cyclotron resonance ion sources (invited)
Authors: Nakagawa T. , Yano Y.
Published: July 2002

Since the first Japanese electron cyclotron resonance ion sources (ECRISs) constructed, several tens of ECRISs have been used in many Japanese laboratories. Even if we choose the ECRIS which has an operational frequency higher than 6 GHz, 20 ECRISs are used for various purposes. At the end of the 1990s, three 18 GHz ECRISs were successfully operated and produced an intense beam of highly charged ions at JAERI Takasaki, NIRS and RIKEN; i.e., 1 mA of Ar8+ and 300 eμA of Ar11+. Various improvements to increase the beam intensity have been done, concerning the aluminum cylinder, biased electrode method. In the last decade, over 50 kinds of metallic ions have been produced from ECRIS using various methods. In 1998, we started to construct new superconducting ECRIS and to perform new experiments of mass spectrometry using ECRIS. This article will review the ECRIS progress and discuss the mechanism to increase the beam intensity of highly charged ions. We also describe a future plan and its new application in Japan.
Auger electron spectroscopy study of silver incorporation in epitaxial Y–Ba–Cu–O superconducting films grown on MgO by laser ablation
Authors: Hart C. , Arés O. , Peña J. L. , Bartolo-Pérez P. , Sosa Victor , Cauich W. , Hirata G. A. , Cota-Araiza L. , Farías M. H.
Published: July 2002

We have studied by Auger electron spectroscopy the incorporation of silver in epitaxial YBa2Cu3O7 (YBCO) thin films fabricated by pulsed laser deposition using YBCO+Ag 10% targets. Films were grown on MgO substrates. The silver was found in a thin layer, of approximately 50 nm in depth. X-ray photoelectron spectroscopy confirmed that the Ag is in its metallic form.