bluuebunny/crossref_metadata_2025 huggingface dataset:
InGaAs/InP quantum wells with thickness modulation
Authors: Brasil M. J. S. P. , Bernussi A. A. , Cotta M. A. , Marquezini M. V. , Brum J. A. , Hamm R. A. , Chu S. N. G. , Harriott L. R. , Temkin H.
Published: July 2002

We investigated the optical properties of lattice-matched InGaAs/InP quantum wells grown by metalorganic molecular beam epitaxy on top of patterned InP buffer layers with elongated features along the [01̄1] direction. The resulting quantum wells present a periodic thickness variation following the elongated features. Low temperature luminescence measurements exhibit double emission bands, attributed to distinct regions of the well. Temperature evolution of the photoluminescence spectra gives qualitative information about the effect of exciton localization.
On the validity and range of applicability of the particle in a box model
Authors: Burt M. G.
Published: July 2002

A recent theory establishing the validity of the particle in a box model is illustrated using numerical results for a one-dimensional nanostructure with atomically abrupt boundaries. The dominant criterion for validity is that the envelope function be slowly varying. The effective mass related kink in the envelope function due to the current conserving boundary condition is seen to model an actual feature in both the exact envelope function and the exact wave function.
Evidence for grain boundary hopping transport in polycrystalline diamond films
Authors: Fiegl B. , Kuhnert R. , Ben-Chorin M. , Koch F.
Published: July 2002

We have investigated electrical transport in undoped diamond films prepared by chemical vapor deposition. Using an electrolytic decoration scheme we prove that currents flow predominantly on grain boundaries. From the temperature and the frequency dependencies we conclude that hopping transport takes place. The conductivity at different temperatures is shown to scale according to a universal curve from a random walk model.
Mode-locked pulse operation of GaAs/AlGaAs field effect transistor self-electro-optic effect device smart pixels and saturation considerations
Authors: Boyd G. D. , Livescu G. , Chirovsky L. M. F. , Lentine A. L.
Published: July 2002

The input/output ports of Smart Pixels are the optical signal receivers and transmitters. We have tested the simplest, lowest power dissipating, receiver-transmitter pair circuit with mode-locked (ML) laser pulses and find switching times as short as 200 ps. We also observe that the product of the set optical energy and switching time is a constant. In addition we present a comparison of the saturation properties of quantum well modulators when operated with short ML pulses, versus bit-period length pulses (quasi-continuous wave operation). Although the read pulse energy requirements of smart pixel optical signal transmitters are near saturation conditions, we conclude that with careful design, operation with short pulses, which gives the minimum switching time, should be possible.
In situ infrared study of chemical state of Si surface in etching solution
Authors: Niwano Michio , Kimura Yasuo , Miyamoto Nobuo
Published: July 2002

We have ‘‘in situ’’ investigated the chemistry of Si(100) surfaces during immersion in hydrofluoric acid (HF) solution, using infrared spectroscopy in the multiple internal reflection geometry. During immersion in dilute HF solution, hydrogen termination is not completed and hydrogen-associated Si fluorides may be generated on the surface. We demonstrate that water rinse following treatment with HF solution leads to the complete hydrogen termination of Si surfaces.
Assessment of single crystal p-toluene sulfonate as an all-optical switching material at 1.3 μm
Authors: Kim Dug. Y. , Lawrence Brian L. , Torruellas William E. , Stegeman George I. , Baker G. , Meth J.
Published: July 2002

We evaluate the potential of single crystal PTS (p-toluene sulfonate) for all-optical applications at the 1.32 μm communications wavelength by measuring the electronic and thermo-optic nonlinearities, and the multiphoton absorption with picosecond pulses. With appropriate heat sinking, duty cycles greater than 25% should be possible without significant cumulative thermal effects for 1 W operating powers.
Magneto-optical indicator film observation of domain structure in magnetic multilayers
Authors: Bennett L. H. , McMichael R. D. , Swartzendruber L. J. , Hua S. , Lashmore D. S. , Shapiro A. J. , Gornakov V. S. , Dedukh L. M. , Nikitenko V. I.
Published: July 2002

A new method is developed using a transparent indicator ferrimagnetic magneto-optic film with in-plane anisotropy for visualization and direct experimental study of dynamic magnetization processes and nondestructive characterization of the defect structure of magnetic multilayers. Some examples of its application to the investigation of peculiarities of the as-grown magnetic structure of electrochemically produced CoNiCu/Cu multilayers with a giant magnetoresistance (GMR) effect and magnetization reversal by domain wall motion are described.
Growth of epitaxial MgO films on Sb-passivated (001)GaAs: Properties of the MgO/GaAs interface
Authors: Tarsa E. J. , Wu X. H. , Ibbetson J. P. , Speck J. S. , Zinck J. J.
Published: July 2002

The growth of epitaxial MgO films on Sb-passivated (001)GaAs using pulsed laser deposition has been investigated. The temperature at which the Sb-passivation layer was desorbed was found to have a significant effect on the interfacial properties of MgO/GaAs heterostructures. Heating the substrates to 350–380 °C in vacuum resulted in a (1×3) GaAs surface reconstruction suitable for the growth of epitaxial MgO films. However, residual Sb was found to persist on the GaAs surface at temperatures as high as 500 °C. MgO growth after Sb desorption at 350–380 °C resulted in a nonuniform interfacial layer which varied in thickness from ∼0.1 to 1.5 nm, whereas substrates heated to 500 °C prior to MgO growth displayed abrupt interfaces. Capacitance–voltage measurements indicated a qualitative difference in the interfacial electronic properties for the two cases.
Small simple hydrogen plasma gun
Authors: Baranga A. Ben-Amar , Fisher A. , Tzach D.
Published: July 2002

A small hydrogen plasma gun was constructed using graphite plates and TiH2. The gun, as small as 5 cm in diameter and 7 mm thick, produces ∼1013 cm−3 plasma in a volume of ∼0.1 m3. A 10-kA current for ∼15 μs is needed to drive the gun. One or more guns can be connected to the same system, an arrangement which allows flexibility in controlling the plasma profile in the experiment. A system employing four similar plasma guns connected in parallel is described.
High-pressure cell closure and pressure connector
Authors: Newman Kenneth E.
Published: July 2002

A modification is described to a previously published, simple, and highly reliable high-pressure cell closure so as to allow ready control and monitoring of the applied pressure.
High-precision low-cost quartz-crystal thin-film monitor with temperature control
Authors: Kremer G. , Moraga L. A.
Published: July 2002

An accurate thin-film thickness monitor capable of a resolution of at least 0.01 nm is described. The errors arising from the temperature dependence of the crystal resonant frequency are minimized by heating a closely matched reference crystal until their temperatures are equalized; and by subtracting their frequencies of oscillations. These functions are performed by simple electronic devices.
Status of the ATLAS accelerator
Authors: Aron J. , Benaroya R. , Bogaty J. , Bollinger L. M. , Clifft B. E. , Den Hartog P. , Johnson K. W. , Kutschera W. , Markovich P. , Nixon J. M. , Pardo R. C. , Shepard K. W. , Zinkann G.
Published: July 2002

The construction of the ATLAS superconducting heavy-ion linear accelerator is complete. The first beam acceleration occurred on March 22, 1985. The first experiment with the ATLAS linac took place during the week of October 7, 1985. The project was completed on time and within budget. Initial system performance has met our expectations.
Operating experience with β=0.16 superconducting resonators
Authors: Zinkann Gary P.
Published: July 2002

The ATLAS heavy-ion accelerator at Argonne National Laboratory was completed in early 1985. This paper discusses early operating experience with the ATLAS linac, with particular attention to performance of the new β=v/c=0.16 resonators. The average operating field level achieved for these resonators on line is 3.2 MV/m. Results of off-line tests of the β=0.16 resonators are also presented.
Optical characteristics of the KSU superconducting linac
Authors: Needham Vincent
Published: July 2002

The J. R. Macdonald Laboratory at Kansas State University is now constructing a superconducting linac to be used for investigating ion collision physics. These atomic physics experiments call for ion beams with high charge states and a wide range of projectile velocities. To provide such beams, the linac will act as both an accelerator and as a decelerator of beams injected from an EN tandem. Preliminary studies of the longitudinal and transverse phase spaces of these beams are discussed, and projected beam characteristics are reported for several ions. Special attention is given to the characteristics and problems of deceleration.
Comparison between the installations of Vivitron porticos in MP 7 and MP 10
Authors: Wagner Pierre , Letournel Michel
Published: July 2002

After the installation of the portico in MP 7, the behavior of the machine exhibited some difficulties. In this paper, the main differences between MP 7 and MP 10 are analyzed, especially the effect of the different sizes and configurations of the terminal electrodes. In addition, some other differences are discussed, for example, the fact that MP 7 has additional column spark gaps with smaller openings than those used in MP 10.
Status of the Oak Ridge 25 URC Accelerator
Authors: Ziegler N. F. , Richardson E. G. , Mills G. D. , McPherson R. L. , Mann J. E. , Juras R. C. , Jones C. M. , Hoglund D. E. , Haynes D. L. , Biggerstaff J. A. , Alton G. D.
Published: July 2002

Beam from the accelerator for research was available for a total period of 3900 h last year and unscheduled maintenance time was reduced by a factor of almost 2. An arc discharge tube conditioning test was conducted on the top five units of the accelerator and a test with macropulsed beam was accomplished. The main problems during the year were vacuum leaks and voltage ‘‘tics.’’
Low-temperature photoacoustic measurements by a transducer technique
Authors: Ikari T. , Shigetomi S. , Koga Y. , Shigetomi S.
Published: July 2002

A simple technique for photoacoustic spectroscopy at low temperature using a rf-sputtered ZnO film transducer is described. We succeed in obtaining the spectra of InSe at low temperatures. The signals due to the free exciton annihilation and the nonradiative donor to valence band transition are clarified by the present technique. These results establish the usefulness of low-temperature photoacoustic spectroscopy for studying transition processes in semiconductors.
Transmission characteristics and fringing field effect of a 270° spherical electrostatic analyzer
Authors: Mukai T. , Miyake W.
Published: July 2002

Three-dimensional transmission characteristics of a 270° spherical section electrostatic analyzer are studied with respect to both theoretical calculation and calibration experiment. A fairly good agreement is obtained between both results which confirm a well-defined response as a function of energy and angle of incident particles and a high-resolution ability of a 270° analyzer in contrast with a 90° analyzer which has a strong energy-angle coupling. A particular particle guide is used as the entrance slit of our analyzer in order to suppress the fringing field effect. When we replace this particle-guide slit by a simple slit of square shape, the transmission characteristics of the analyzer become distant from the calculated one. The numerical solution of a two-dimensional fringing field of an approximated model is derived and the ray tracing calculation of particles in this field is done. This model calculation approach also suggests the strong effect of the fringing field near the entrance aperture in the case of the analyzer with a simple slit. These investigations demonstrate the effectiveness of the particular slit at the entrance aperture used.
Simple time-resolving spectrometer for plasma impurity diagnosis
Authors: Yamada Kimio , Kanamori Takahiro
Published: July 2002

A simple time-resolving vacuum ultraviolet spectrometer system has been constructed and its utility demonstrated through performance tests on the Hitachi Tokamak. The system consists of a Seya monochrometer and a 30-anode microchannel plate detector to provide simultaneous measurements over all anodes with a time resolution as short as 1 ms. Testing of the system is described; the total wavelength coverage is 40–130 nm with 0.37-nm spectral resolution; and the portion observable during a single plasma discharge has a bandwidth of 0.9 nm. The system has been calibrated by means of the atomic-branching-ratio method and is currently in operation as an impurity monitor.
Design and performance of cryogenic wafer prober
Authors: Kotani Seigo , Fujimaki Norio , Hasuo Shinya
Published: July 2002

This paper describes a probing system to test a wafer immersed in liquid helium. This system is intended to improve the following three functions in comparison with conventional systems: (1) measurement of fast rise-time electrical signals, (2) quick release of flux trapping with small loss of liquid helium, (3) facility in exchanging wafers. It was observed that signals with 2-ns rise time could transmit through the system, the release of flux trapping could be achieved in several minutes with negligible helium loss using a cryoinsert with a closable hole at its bottom, and wafers could be exchanged similarly.
Photoelectric inclination sensor
Authors: Kato Hisao , Kojima Masahiko , Hayashi Morihiko , Sasaki Shunji
Published: July 2002

A new photoelectric inclination sensor consisting of a light emitting diode (LED) spirit level mounted on a photodiode array is introduced. Light from the LED projects a bubble in the level and throws a shadow onto the surface of the array composed of four equivalent square-shaped diodes, isolated from each other by a cross on a wafer. When the transducer is kept horizontal, the area of the shadow in each diode is exactly equivalent. By taking the difference output positioned obliquely in the array, the water level in the two-dimensional plane is detected. This transducer detects the two-dimensional water level accurately, can be compact, and the response is fast.
Design parameters for differentially pumped rotating platforms
Authors: Columbia M. R. , Thiel P. A.
Published: July 2002

We have constructed a large differentially pumped platform for use in ultrahigh vacuum. The design utilizes spring-loaded Teflon seals to permit differential pumping between two horizontal stainless-steel disks. This allows the rotation of the upper disk and the items built into it directly inside a vacuum chamber while maintaining a pressure of 2×10−10 Torr. The following design parameters are discussed: conductance across the seals, deflection of the seals, rotational friction, and differential thermal expansion during bakeout.
Simple electronic device for position-sensitive detectors in VUV spectrometry
Authors: Chauvet G. , Brenac A. , Baptist R.
Published: July 2002

This paper describes a simple and low-cost electronic device which calculates the position of an incident VUV photon on a commercially available position-sensitive detector composed of two multichannel plates and a resistive anode. The readout method used consists of a position-time conversion during data acquisition and a subsequent transformation of the collected data by a personal computer (Apple IIe). Applications to VUV spectrometry in atomic physics, showing spectra of 400 Å width with a resolution of about 15 Å, bring out advantages and drawbacks of this system.
Extension to the 350-kV negative ion injector for the JAERI tandem accelerator
Authors: Minehara Eisuke , Yoshida Tadashi , Abe Shinichi , Kanazawa Shuhei , Tsukihashi Yoshihiro , Horie Katsuzo , Hanashima Susumu
Published: July 2002

An extension to the 350-kV negative ion injector for the JAERI tandem accelerator was constructed to minimize loss of the beam time due to changing and tuning the ion sources, and to improve substantially the reliability and personal safety in the accelerator operation. Performance during the first operation over three months is reported and discussed in comparison with the previous performance.
Circuit for extension of an interrupt input of a personal computer PC8001mkII
Authors: Matsuura Koichi , Yamasaki Tatsuo , Kishida Satoru , Taki Hiroyuki , Tsurumi Ichiro
Published: July 2002

A circuit is described which extends an interrupt input of a personal computer PC8001mkII to multiple interrupt inputs using a daisy-chain approach, where prioritized interrupts up to 128 levels may be available by providing additional wait states and an interrupt look-ahead circuit. The circuit presented in this note may be applied to other computers with some slight modifications.
Sample support rod for vibrating sample magnetometer with temperature control
Authors: Escorne M.
Published: July 2002

We report a sample support rod for use in a vibrating sample magnetometer which includes means for thermal contact and for temperature control. The magnetic susceptibility of the unit is 10−6 cgs (which corresponds to 0.01 emu at 10 kG).
Simple system for mapping magnetic field errors in tori
Authors: Bellan P. M.
Published: July 2002

A simple inexpensive electron beam/detector system is described. This system is capable of making vector maps of magnetic field errors over the minor cross section of toroidal plasma devices.
Fluorescence measurements of the M-band photon emission from a laser-irradiated gold disk
Authors: Phillion D. W. , Kauffman R. L. , Kornblum H. N.
Published: July 2002

Gold M-band x rays with energies above the sulfur K edge of 2.472 keV create sulfur Kα fluorescence with a quantum efficiency of 8.1%. The sulfur fluorescer was a 600×1500-μm rectangle about 1100 μm from the gold plate. It was 25 μm of C6H4S plastic shielded by 50 μm of beryllium. The absolute brightnesses of both the M-band spectrum and of the fluorescence line were measured by separate spectrographs. The spectrograph measuring the fluorescence did not have a direct line of sight to the hot gold. These measurements were made with 3512-Å laser light irradiating the gold plate for 1 ns over a number of intensities between 2×1014 and 1015 W/cm2.
Picosecond flash photolysis apparatus with high absorbance resolution
Authors: Ebbesen Thomas W.
Published: July 2002

A new picosecond flash photolysis apparatus is described which makes extensive use of fiber optics in the probing beam pathway. The apparatus is simple and easy to use. The absorbance resolution and accuracy are greatly enhanced and allow for quantitative determination of properties of transient species. The capability of the system is illustrated by determining the excited singlet state absorbance properties of erythrosine and rose bengal.
Superconducting rf cavity in a dc magnetic field
Authors: Benaroya R. , Shepard K. W.
Published: July 2002

A superconducting (SC) rf cavity has been operated in the presence of an external magnetic field up to 2.4 kG. Measurements on the 48.5-MHz cavity were performed at 4.2 K. The external field was produced by an unshielded 60-kG superconducting solenoid 5.8 cm from the cavity. No degradation of cavity Q was observed for fields on the outer surface of the cavity up to 1240 G. This result is consistent with no flux penetration of the cavity surface for fields up to the first critical field of niobium at 4.2 K, and shows that strong focusing elements with large fringing magnetic fields may be placed immediately next to Nb SC accelerating structures without causing performance degradation.
Design of the TFTR rf probe array (abstract)
Authors: Greene G. J. , Hosea J. C. , Wilson J. R. , Young K. M.
Published: July 2002

A new diagnostic, composed of an array of high-frequency magnetic probes, has been installed in TFTR for the study of waves driven by the ICRF heating antennas and waves generated spontaneously during ohmic and beam-heated discharges. The former is of interest because of the possibility of surface wave generation by the heating antennas, and the latter because emission spectra may be useful as a beam ion or fusion product diagnostic. The array consists of seven fixed probes positioned at various toroidal and poloidal locations in order to obtain information about the corresponding wavenumbers in the edge region. Each probe consists of two orthogonal loops oriented to measure Bφ and Bθ. The array utilizes single-turn loops with areas of 12 cm2 and carefully selected signal processing elements to achieve a usable bandwidth of 1–500 MHz. Reduction of electrostatic pickup is accomplished by differentially combining signals from both ends of a loop using a wideband hybrid junction and by using an alumina shield to reduce capacitive coupling. The system permits simultaneous observation of both the magnetic and electrostatic components of the probe signal, allowing verification of the rejection ratio in a particular experiment. Details of the diagnostic design and experimental plans are discussed. This work was supported by U. S. DOE Contract No. DE-AC02-76-CHO-3073.
Elliptical spectrograph/gated microchannel-plate detector for time-resolved spectral measurements in the x-ray region
Authors: Hammel B. A. , Ruggles L. E.
Published: July 2002

Time-resolved measurements from an elliptical crystal spectrograph are used to diagnose x-ray laser experiments on a gas puff Z pinch. The elliptical spectrograph (1.2-m working distance, eccentricity 0.9586) observes the 1-keV region, covering a range of λ/2d = 0.5 to 0.9. A thin filter (0.2 μm Al on 2 μm Kimfol) stretched across the spectrograph exit slit acts as a low-energy x-ray cutoff and as a vacuum window, allowing the detector to be at high vacuum regardless of the pressure in the experimental chamber. The detector consists of a seven-frame microchannel-plate intensifier system. A pulser is used to gate each of seven striplines on the microchannel plate, providing nanosecond resolution. With this instrument we are able to measure the pump radiation from the imploding plasma (Ne or Ar) and converter layer (Al), and to study the lasant ionization state (Ne-like Ni or Cu).
UV to soft-x-ray surveys using a compact, biplanar diode array
Authors: Armentrout C. J. , Geddes J. B. , Lee Ping , Canfield L. R.
Published: July 2002

Biplanar vacuum diodes, long used for the diagnostics of laser-produced plasmas, have also been used as spectroscopic survey instruments for magnetically confined plasmas. The compact seven-channel diode array, developed at KMS Fusion, provides broadband (ΔE/E≂1) channels of filtered cathodes to provide the spectral scan from 10 eV to about 5 keV (approximately 130 to 0.25 nm). Preliminary calibration results and calculations for a number of filters and cathodes are used to demonstrate that a satisfactory energy region may be obtained if an absorption edge of the cathode is below the mean energy of the desired channel and an absorption edge of the filter is above that energy. These devices are insensitive to neutron and gamma flux.
X-ray response of AlGaAs/GaAs radiation-hardened double-heterostructure photodiode compared to Si:p-i-n photodiodes
Authors: Anthes J. P.
Published: July 2002

Requirements for continuous operation of photodiodes in the presence of nuclear radiation has led to the development of a novel AlGaAs/GaAs photodiode. Device structure and semiconductor properties of this design were optimized to balance the need for photodetection at λ=820 nm against unwanted excess photocurrents induced by ionizing radiation. To achieve radiation hardness the photodiode employs a double-heterojunction device structure. The spectral response of this detector, 1 keV–10 MeV, may offer unique opportunities for use in high-temperature plasma diagnostics compared to typical bare Si:p-i-n x-ray photodiode characteristics. Application of this AlGaAs/GaAs detector in a fiber-optic link will be reviewed. Also, use of this detector in simple atomic-absorption-edge filtered x-ray detector channels is presented.
Measurements using tangentially viewing bolometers on TFTR
Authors: Bush C. E. , Schivell J. , Budny R. , Ellis R. A. , Goldston R. J. , McCune D. , Medley S. S. , Scott S. D. , Towner H. H. , Wieland R. M.
Published: July 2002

Co- and counter-viewing bolometers aimed along a common tangency chord are being used to study power losses due to charge exchange (CX) of fast ions in neutral beam injection (NBI) heated TFTR plasmas. For unidirectional injection, tangential bolometers oriented to view CX loss of circulating fast ions detect losses from the thermal target plasma (impurity radiation and CX) plus power due to the fast ion CX loss, whereas bolometers oppositely directed measure only the target plasma contribution. The difference between the two signals is a measure of the fast ion CX loss. Additional information is obtained by comparing the tangential bolometer signals with those of perpendicularly viewing bolometer monitors and arrays. The measurements are compared to results of the TRANSP code analysis.
Transparent data access in a multivendor, distributed data-acquisition and data processing system
Authors: Preckshot George G. , Butner David N. , Brown Michael D. , Meyer William H.
Published: July 2002

Location-independent data access methods are being developed at Lawrence Livermore National Laboratory to manage and use data acquired by a multivendor distributed laboratory computer network. An interprocess communication system (IPCS) is used to connect tasks which produce, manage, or use experimental data. These tasks may run on any of the computers in the network. A central database and database server maintain supervisory records of experimental activity and locations of data produced by the experiment. Data may be located in several subsidiary local databases, file systems, or tape archives. Data access requests, if they cannot be satisfied locally, are routed via the IPCS to database servers, which locate and retrieve (or store) the requested data. We describe the design details and give examples of the current implementation.
Menu-driven menu editor and associated menu system
Authors: Preckshot George G. , Butner David N.
Published: July 2002

A menu-style user interface has been developed at Lawrence Livermore National Laboratory (LLNL) for distributed control, data acquisition, and data processing. A graphical menu editor, which is itself the first application of the menu system, is used to construct or modify menu hierarchies. Unlike many menu systems, no code need be written to demonstrate a set of menus because there are no subroutine calls to make menus; developers need only write the code that performs the actions indicated by user menu picks. In addition to this rapid prototyping feature, the menu system is integrated with operating system asynchronous traps (in Unix, signals, and selects) so that it supports real-time user interfaces for control in a distributed computer system. UFrsi1
Operation of an E ∥ B end-loss ion spectrometer on the Tara tandem mirror
Authors: Casey J. A. , Horne S. F. , Irby J. H. , Post R. S. , Sevillano E. , Foote J. H.
Published: July 2002

An E ∥ B end-loss ion spectrometer from the Livermore TMX-U tandem mirror experiment was installed on Tara for high-resolution ion spectroscopy. This diagnostic contains parallel electric and magnetic fields, separating the masses and energies of the ions over 128 collector plates. The ion energy distribution nominally yields confining potentials and parallel ion temperatures. Additional experiments have diagnosed the resonance position of the central cell ion cyclotron heating, rf enhanced losses of high-energy sloshing ions in the axicell (‘‘plug’’), and observation of MHD instabilities at higher time resolution (20 kHz).
The DIII-D E∥B charge exchange diagnostic
Authors: Heidbrink W. W.
Published: July 2002

One of the neutral-particle spectrometers used on the Doublet III tokamak has been improved and modified for use as an active charge exchange diagnostic on the DIII-D tokamak. The spectrometer employs a He stripping cell, parallel E and B analyzer fields, and a microchannel-plate detector with 60 energy channels for each of two neutral-particle masses. Improvements to the diagnostic include better radio frequency and γ-ray shielding and complete instrumentation of all energy channels. Calibration results for H and D are similar to those reported previously. The instrument views across one of the DIII-D heating beams which can be modulated to provide local neutral doping. The analyzer is scanned shot to shot to measure neutrals with pitch angles between ∼5° and ∼110°.
Spatial distribution of fusion reactions by gamma-ray tomography
Authors: Moses K. G. , Sperling J. L. , Glassman A. J. , Trow J. R.
Published: July 2002

This article reports on the application of the minor branch of the D–T reaction, D2 +T3 =He5 +γ(16.7 MeV), as a diagnostic vehicle to determine the cross-sectional distribution of fusion reactions in a D–T burning plasma. Arrays of scintillation detectors, located circumferentially about the plasma, outside the reaction chamber, obtain line-integrated values of gamma-ray production along chords through the chamber. Tomographic techniques will be used to reconstruct the reacting profiles. A description of the tomographic system and reconstruction examples are presented.
A 1-mm collective scattering experiment for DIII-D (abstract)
Authors: Peebles W. A. , Burns S. , Doyle E. J. , Lehecka T. , Luhmann N. C. , Philipona R. , Rettig C.
Published: July 2002

A 1-mm collective scattering system is under construction for installation on DIII-D in May/June of 1988. The main objective of the experiment is to extend the recent TEXT work1 on the role of confinement damaging ηi modes to a more CIT/reactor relevant plasma with a divertor, H-mode, etc. In order to resolve these modes, which propagate in the ion-diamagnetic drift direction, both spatial resolution and a heterodyne detection capability are required. Spatial resolution will be obtained by operating at λ≊1 mm using both a twin frequency optically pumped FIR laser and a phase-locked carcinotron. One of the large midplane ports on DIII-D will be used to reflect a horizontal probe beam off the graphite tiles on the inner wall. This arrangement will allow for scattering angles of up to 18° from the plasma center. This work was supported by U.S. DOE Contract No. DE-FG03-86ER53225.
Two-dimensional horn imaging arrays (abstract)
Authors: Rebeiz Gabriel M. , Guo Yong , Stimson P. A. , Rutledge David B. , Kasilingan Dayalan P.
Published: July 2002

A two-dimensional horn imaging array has been demonstrated at 242 and 93 GHz. In this configuration, a dipole is suspended in a pyramidal horn, fabricated by an anisotropic chemical etch technique, on a 1-μm silicon-oxynitride membrane. This approach leaves room for low-frequency lines and processing electronics. Pattern measurements on a 1.45-λ imaging array agree well with theory, show no sidelobes, and a 3-dB beamwidth of 35° and 46° for the E and H planes, respectively. Application areas include a superconducting tunnel-junction receiver for radio astronomy and imaging arrays for real-time electron density mapping in fusion plasmas. Support for this project was provided by DOE contract DE-FG03-86-ER-53225 (subcontracted from U.C.L.A.).
Density profile reconstructions from 2-D interferometric data on Microtor using novel tomographic analysis techniques (abstract)
Authors: Howard J. , Doyle E. J. , Reibeiz G. , Savage R. L. , Peebles W. A. , Luhmann N. C.
Published: July 2002

Plasma tomographic reconstructions are subject to aliasing ambiguity as a result of the limited angular and radial sampling rates for the line-integrated data. The two-view interferometer installed on the Microtor tokamak yields unambiguous information, specifically, a collection of six low-order alias-free moments of the 2-D electron density distribution. The unspoiled coefficients can be related to physically intuitive quantities and so yield information pertinent to the equilibrium and dynamical behavior of the plasma column. Alternatively, they can be used as constraints for a maximum entropy reconstruction of the source to produce an image free of aliasing artifacts.
Current density profile determination via polarimetry
Authors: Nagatsu M. , Peebles W. A. , Luhmann N. C.
Published: July 2002

Extensive experimental and numerical studies have been performed to assess the feasibility of polarimeter systems to be installed on a number of devices. The systems employ an amplitude ratio technique similar to that of Soltwisch, with a 45° polarizer angle to divide probe beam equally between two mixer arrays. At present, a nine-channel system has been constructed to perform measurements of central q value and also the current density profile by scanning the entire system. Laboratory test results will be discussed together with installation plans. The system has the advantage that the amplitude ratio is very insensitive to ellipticity, which can be determined from the phase difference between equivalent detector signals. These properties make the polarimeter attractive, especially for high-field, high-density plasmas where the elliptization effects are large. In this case Ψp ≠const λ2∫neBpz.
Measurements of NBI and ion cyclotron range of frequency power deposition profiles using charge exchange spectroscopy
Authors: Ozaki T. , Kadota K. , Ogawa Y. , Fujita J.
Published: July 2002

Power deposition profiles of a heating neutral beam and/or an ion cyclotron range of frequency (ICRF) heating have been measured on the JIPP T-IIU tokamak. The deposition is obtained from the rise time of the ion temperature, which is measured from the Doppler broadening of C vi emission produced by charge exchange reaction between a neutral beam and a carbon impurity. The power deposition of ICRF has been found to be flatter than that of neutral beam injection (NBI). The thermal diffusivities are 4–5 times larger than the neoclassical values both in NBI and NBI+ICRF cases.
Field-dependent dipole matrix elements and their application to the calculation of plasma-broadened line profiles
Authors: Mancini R. C. , Hooper C. F.
Published: July 2002

We have computed field-dependent wavefunctions and dipole matrix elements for hydrogenic ions in the presence of a uniform electric field; we present the results for transitions connecting the ground and excited states. As an application we use these elements to compute Stark-broadened static line profiles and compare with similar ones that use field-independent matrix elements. The line-shape sensitivity to the use of field-dependent matrix elements is discussed.
Microvelocity sensor for instantaneous velocity determination
Authors: Zee R. H. , Jang B. Z. , Mount A. , Wang C. J.
Published: July 2002

A new microvelocity sensor unit was developed to measure the instantaneous velocity of a high velocity impactor during the penetration process. The concept of this device is based on the induced current generated in a coil due to the passage of a magnet. A special digital circuit was designed to yield a spatial resolution of better than 0.05 in. by eliminating the problem of signal overlap. The precise time delays obtained from these signals can be used to determine the slowing down or energy loss of a high-velocity projectile. The details of this sensor unit will be described and its resolution will be demonstrated. A light gas gun was used to propel aluminum projectiles to velocities up to 320 m/s. Energy loss of these high-velocity projectiles in composites reinforced with polyethylene, polyester, and graphite fabrics as well as pure Kevlar fabric was measured using this system. Results show that this microvelocity sensor is capable of identifying various energy-loss processes during the impact of high-velocity projectiles.
A novel interferometric liquid refractometer
Authors: Webb D. J. , Tatam R. P. , Jackson D. A.
Published: July 2002

We describe a novel form of liquid refractometer in which the optical length of a cavity containing the liquid is monitored interferometrically.
A simple mass spectrometry data system dedicated to fast atom bombardment mass spectrometry
Authors: Courcelle E. , Pratbernou F. , Prome J. C.
Published: July 2002

A high-performance data system has been designed using a Motorola 68000-based microcomputer running under a multitasking, real-time operating system. Data acquisition can be performed in the accumulation mode, thus increasing the signal-to-noise ratio. Operation with resolution 5000, over a large mass range [4000 atom mass units (amu)] can be achieved. The mass spectrometer must be calibrated before assigning one mass to each peak. The calibration is performed using data obtained with a known compound, with an interactive utility, so that the operator may control the search of reference peaks. The only requirement for a mass spectrometer to be used with this system is that it be equipped with a reproducible magnet, allowing for several consecutive spectra to be added without reducing the resolution.
A sensitive and inexpensive susceptometer for the study of high-temperature superconductors
Authors: Baker Roger C.
Published: July 2002

A moving-sample susceptometer based on a Hartshorn inductance bridge is described. This instrument makes it possible to measure magnetic susceptibility as a function of temperature. The lower limit of detection is approximately 50 parts per million of powdered YBa2Cu3Ox superconductor contained in a 5-mg sample, corresponding to approximately 10−6 emu/g. Measurements can be conducted in the 4.2–300 K temperature range. The apparatus can be built inexpensively of commonly available parts. Construction, operation, and possible applications are discussed.
Microwave photoconductivity scanning microscope studies of silicon surfaces
Authors: Schlichthörl G. , Beck G. , Lilie J. , Tributsch H.
Published: July 2002

The microwave photoconductivity scanning microscope (MPSM) is a new experimental tool for the space-resolved contact-free characterization of photoconductive materials. It allows the determination of the local photoconductivity down to a resolution determined by the width of the laser beam and the diffusion length of photogenerated carriers. The reflected laser light can be measured simultaneously, which allows one to correlate the microwave signals with the surface morphology and to correct them for the absorbed light intensity. Structural, mechanical, thermal, and chemical surface treatments of monocrystalline and polycrystalline silicon wafers have been performed to demonstrate the technical applications and the scientific value of the described experimental technique. For the first time a contact-free space-resolved characterization of a heterojunction between n-silicon and p-type polymeric film is presented. Possibilities and limitations of the technique are outlined.
Characteristics of optical components for soft x-ray microscopy and x-ray holography using an undulator radiation optical system (abstract)
Authors: Kakuchi Masami , Ozawa Akira , Ohkubo Takashi , Maezawa Hideki , Kagoshima Yasushi , Ando Masami
Published: July 2002

X-ray Fresnel zone plates and transmission gratings, have been fabricated using fine-focused electron-beam lithography and Ta-on-SiN x-ray mask fabrication technique. The optical components for x-ray microscopy and x-ray holography were evaluated in an undulator radiation system. Nanometer lithography using fine-focused electron-beam writing machines is now regarded as an important technology to create new devices on very small structures such as quantum wires or boxes and new scientific probe elements such as x-ray optical components. A new fabrication process of Ta-on-SiN x-ray mask1 for x-ray optical components has been established. Tantalum is used for the x-ray absorber, because of having approximately the same absorption coefficient as that of gold. A thin SiN film, which has a high transparency for soft x rays, acts as a membrane supporting the Ta-absorbing patterns. The fabricated zone plates have an outermost zone width of 0.25 μm with up to 2 mm diameter. The pitch width of the transmission grating is 0.4 μm with up to 1.0 mm2 area. Adopting a highly brilliant and highly coherent undulator2 synchrotron radiation, we have been developing its optical system to apply to x-ray microscopy and holography. An x-ray microscope system3 consists of two kinds of zone plates with different dimensions for imaging and focusing undulator radiation. The resolving power of this microscope system was evaluated by using resolution test charts, which have the same structure as x-ray optical components. A resolution limit of 0.3 μm was obtained, which is very close to Rayleigh’s limit of 0.25 μm for the outer-most zone width. We constructed a divided wave-front interferometer with x-ray transmission gratings, and estimated the dispersion of undulator radiation to be 1/20. The authors thank S. Aoki of Tsukuba University for his useful discussion on x-ray optics. The authors are also grateful for the help from T. Tamamura and H. Yoshihara, NTT for fabrication of x-ray components, and from Y. Toyoshima of the Photon Factory in undulator experiments, respectively.
New powder diffractometer for the Photon Factory
Authors: Ozawa Haruo , Uno Ryosei , Yamanaka Takamitsu , Morikawa Hideki , Ando Masami , Ohsumi Kazumasa , Nukui Akihiko , Yukino Ken , Kawasaki Tsutomu
Published: July 2002

A new powder diffractometer for the Photon Factory was designed and constructed in 1986. Its performance has been confirmed as follows: (1) it is capable of determining the wavelength of the Cu K edge as 1.380619±0.000012 A using NBS standard Si powder 640b, while the reported one is 1.38059 A; (2) the accuracy of monitoring the incident beam intensity was ±0.2%, which was estimated by the normalized integrated intensity; (3) the angle resolution of diffraction lines was comparable with that of SSRL; and (4) the sum of three Gaussians was the best profile function fitted for lines from NBS standard Si powder 640b.
A precision goniometer for the wiggler beamline station at the Photon Factory
Authors: Nakayama Kan , Tanaka Mitsuru , Kuroda Kazuaki
Published: July 2002

A vertical axis goniometer has been constructed for precision diffractometry on a multipole wiggler beamline at the Photon Factory. The goniometer permits angular increments of 0.02 arcsec in ±15° range by a stepping motor and 0.001 arcsec increments in ±10 arcsec range by a piezoelectric transducer. The goniometer is mounted on an antivibration system with horizontal resonant frequency of 0.6 Hz.
A versatile instrument for structural studies of interfaces in ultrahigh vacuum (abstract)
Authors: Clausnitzer M. , Pauly T. , Materlik G.
Published: July 2002

Structural studies of interfaces with synchrotron x-radiation (SXR) are presently carried out with several different methods which were developed in connection with SXR over the past decade: dynamical x-ray diffraction using standing wavefields (XSW), kinematical surface diffraction (KSD), Fresnel reflection (FR), and absorption spectroscopy (SEXAFS, SXANES). These methods can determine different, and often complementary parameters of a system such as short-/long-range order, relaxation relative to bulk, structure normal/parallel to surface, valence state of surface atoms, roughness of a buried interface, etc. Accordingly, these different principles have also been combined to form new methods such as diffraction of evanescent x rays during total external reflection (DEXTER) and reflection EXAFS (REFLEXAFS). It is, therefore, highly desirable to have the opportunity to study the same interface system with different methods. On the other hand, preparation of a system in ultrahigh vacuum requires in most cases expensive bulky equipment and time consuming techniques. These considerations call for a setup which provides different experimental options. We have, therefore, installed at the beamline ROEMO I at HASYLAB a versatile UHV system for interface studies. A sample can either be prepared inside a chamber with three Knudsen cells for MBE growth and standard equipment for cleaning, heating and surface characterization by RHEED, or inside a chamber for aggressive gases. The first one is installed outside the interlock area providing access also when the ROEMO beam is on and the second one inside the interlock area.

From either chamber the sample can be transferred into an analysis chamber at the ROEMO I station or into a transportable baby chamber. The analysis chamber can be used for measurements with standing waves, absorption spectroscopy and reflectivity measurements. Electrons are detected with a spherical analyzer and photons outside the vacuum through Be windows with a NaI detector for reflectivity and with a Si(Li) for scattered radiation. The baby chamber can be transported to other stations at HASYLAB which are equipped for kinematical surface diffraction and measure with high angular precision the intensity/angle correlation of many (often several hundred) different reflections. The baby chamber approach is used to avoid heavy and expensive diffractometer designs or sophisticated UHV angular feedthroughs. The baby chamber can also be used to measure with XSW, FR, and DEXTER. The performance of the system will be illustrated together with first results on different detection schemes.
Beamline 14B at Photon Factory: Precision x-ray optics experiment facility (abstract)
Authors: Ishikawa T. , Ando M. , Kikuta S.
Published: July 2002

The beamline 14B at Photon Factory is one of three branches of the 5T vertical superconducting wiggler beamline (BL14) at Photon Factory. This branch is used mainly for precision x-ray optics experiments and partly for commissioning a low-angle double-crystal spectrometer and a gas-phase scattering apparatus. A double-crystal fixed-exit monochromator was installed on this beamline; it has two offset positions, 200 and 500 mm. In order to avoid the leak of high-energy x rays from the monochromator chamber, the first crystal is shielded by lead with a rotatable 2θ window inside the vacuum chamber. A precision x-ray optics experiment facility consists of two vertical axis goniometers designed for the use of vertical polarization. Rough rotation (360° with the finest step of 3.24 arcsec) and fine rotation (within 6°, the finest step of 0.01 arcsec) are changed with a clutch. A rotary encoder with precision of 1.0 arcsec is equipped. A double-crystal aligner mounted on one of the precision goniometers is constructed to make another double-crystal arrangement. Combining the beamline double-crystal monochromator with this aligner, we can make a fixed-exit four-crystal monochromator of (+n,−n,−m,+m) setting, known as the high resolution x-ray optics in energy as well as momentum. Two independent microcomputer control systems are used for beamline monochromator and experimental facility. These two systems are connected by a serial communication (RS-232C) line via a software controlled line selector. This makes it quite easy for user-made equipment to control the beamline monochromator synchronously by its own control system. A low-angle double-crystal spectrometer was further constructed to characterize synthetic multilayers. This spectrometer consists of two ω-2θ goniometers mounted on x- (used for vertical axis) or xz- (used for horizontal axis) translation stage. These goniometers are mounted on independent carriers of a y-translation stage along the x-ray beam.