bluuebunny/crossref_metadata_2025 huggingface dataset:
Fiber-optic control of the ZT-P experiment
Authors: Caudill L. D. , Chandler G. I. , Hall C. R. , Trujillo J. F.
Published: July 2002

The computer control system for the ZT-P experiment has been implemented using a fiber-optic link in all 161 control signal paths. Four classes of control signals are used in this design. These are (a) digital-out, an on–off signal from computer to machine actuator, (b) digital-in, an on–off signal from machine sensor to computer, (c) analog-out, a 0–10-V analog signal from computer to machine actuator, (d) analog-in, a 0–1-mA analog signal from machine sensor to computer. The digital-in and the digital-out class of signals require no control power at the machine. The analog-out and the analog-in class of signals use available machine power for control. This unique power arrangement and the use of fiber-optic links totally isolate the electrically noisy machine areas from the sensitive electronics in the computer control. Advantages of this system including low cost, small size, personnel safety, and ease of maintenance and modification are discussed.
Development of a plasma-fluctuation diagnostic software tool
Authors: Hong J. Y. , Powers E. J. , Ritz Ch. P.
Published: July 2002

This paper describes a software package that will ultimately be made available to the entire magnetic fusion energy community and which may be used to analyze and interpret linear and nonlinear fluctuation data generated by a wide variety of plasma diagnostics such as, for example, probes, scattering systems, and beams. The software tool is divided into two basic parts: mathematical/statistical programs and applications programs. The mathematical/statistical programs will be further subdivided into those suitable for stationary and nonstationary data. The stationary data package will include bispectral analysis, a very powerful tool in the analysis of nonlinear data. Application programs will include fluctuation-induced particle transport, two-point estimates of S(k, ω), three-wave coupling coefficients and energy cascading, and nonlinear digital filters. Both the prototype plasma-fluctuation diagnostic software tool and plans for the complete software package will be described. This work was supported by the U.S. DOE Contract No. DE-AC05-85ER80251.
Grating spectrometer installation for electron cyclotron emission measurements on the DIII-D tokamak using circular waveguide and synchronous detection
Authors: Lohr John , Jahns Gary , Moeller Charles , Prater Ron
Published: July 2002

The grating spectrometer installation on the DIII-D tokamak uses fundamental circular waveguide propagating the TE11 lowest-order mode followed by oversized circular guide carrying the low-loss TE01 mode. The short section of fundamental guide permits use of an electronic chopper operating at 100 kHz for both calibration and plasma operation. By using ac-coupled amplifiers tuned to the chopping frequency, the background signal generated in the indium antimonide detectors by neutrons and x rays is automatically subtracted and the system noise bandwidth is reduced. Compared with a quasi-optical system, the much smaller fundamental horn and front-end waveguide allow the waveguide system to be located outside a gate valve. With this configuration the entire waveguide run, including the actual horn and vacuum window used during plasma operations, can be included in the calibration setup.
Feasibility study of using the TFTR Thomson scattering system for q profile measurements
Authors: Brizard A. , Grek B. , Leblanc B. , Johnson D.
Published: July 2002

The results of a study made to determine the possibility of using the tokamak fusion test reactor (TFTR) Thomson scattering system to measure the direction of the local magnetic fields in a tokamak plasma are presented. We find that it should be possible to measure the q profile for q<1.3 and minor radius <40 cm, with an accuracy of less than 5%.
Use of the Kalman filter in signal processing to reduce beam requirements for alpha-particle diagnostics
Authors: Cooper William S.
Published: July 2002

In principle, a probing beam of neutral atoms can be used to measure the velocity distribution of fast alpha particles confined in an ignited fusion plasma. In this article we discuss beam modulation techniques and a compatible signal processor based on a Kalman filter that together can provide, in one hypothetical case, a reduction of a factor of 10 in the beam current required, as compared with that required for a straightforward measurement with a dc beam.
Data acquisition and display in space-plasma physics (invited)
Authors: Williams D. J.
Published: July 2002

Studies of the behavior of space plasmas and their interactions require the acquisition and display of voluminous amounts of data. The basic data set required consists of ac and dc magnetic and electric fields and the three-dimensional distribution functions for ions and electrons. The frequency, energy, and intensity ranges for these data span many decades and present a challenge to the observer to identify and understand the systematics of the data set as a whole. The data are used to characterize the plasmas encountered and their dependence on both external and internal parameters. This requires data displays which encompass long time intervals and which allow one to distinguish readily between various plasma regimes. The data also are used to study the microphysics of the ambient plasmas and their interactions. Here displays are required to show details of the spatial and temporal evolution of the data set over short time periods. We present and discuss several techniques used in space-plasma physics to display these large amounts of data for effective and efficient analysis and study.
Time-resolved 14-MeV neutron detector for triton confinement studies
Authors: Smith J. R. , Fisher R. K. , Leffler J. S. , Newman D. E.
Published: July 2002

Previous measurements of triton burnup in deuterium tokamak plasmas show an anomalously small burnup for low-q discharges with significant magnetohydrodynamic activity. This may have important implications for alpha particle burnup in a fusion reactor. By developing a detector capable of time-resolved 14-MeV neutron measurements, it should be possible to separate triton confinement and slowdown anomalies. We are testing lithium-free glass scintillators which would observe 14-MeV neutrons through prompt 28Si(n, p) 28Al reactions. These detectors are not sensitive to the much larger 2.5-MeV neutron background and should also have less sensitivity to the large thermal neutron background when compared to conventional 6Li-depleted glasses. Measurements of detector sensitivity to signal and potential background sources are being performed using a 14-MeV neutron source and radioactive sources. The expected signal behavior under various DIII-D plasma and beam conditions will also be presented.
Zone-plate imaging of neutrons emitted from a laser fusion target
Authors: Lerche R. A. , Lane S. M. , Hawryluk A. M. , Ceglio N. M.
Published: July 2002

Zone-plate coded imaging techniques are routinely used to image nonpenetrating emissions from laser fusion targets. Only highly penetrating radiations like 14-MeV neutrons will escape the dense compressed core region of future targets to provide information about the burn region. A zone plate for 14-MeV neutrons must be several centimeters thick to produce adequate modulation in the coded image. Computer modeling of zone-plate systems show that a thick, tapered zone plate acts like a thin zone plate for points within its field of view and depth of field. Equations developed for thin zone-plate systems that describe quantities such as planar and tomographic resolution may be applied to thick zone-plate systems. System simulations of a 100-zone, 5-cm-thick zone plate with 5-μm outer zone width constructed of alternating layers of gold and aluminum produce images with 10-μm resolution. The source strength required to image a 20-μm-diam source is 100 to 1000 times less than that needed with an equivalent pinhole system. Work performed under the auspices of the U.S. DOE by the LLNL under Contract No. W-7405-ENG-48.
TFTR edge Thomson scattering system
Authors: Johnson D. , Grek B. , Dimock D. , Palladino R. , Tolnas E.
Published: July 2002

A system is under construction which will make use of the laser and collection optics of an existing multichannel Thomson scattering system on the tokamak fusion test reactor (TFTR). A scanning sampling mechanism will divert signal from a 10-cm segment of the radial-beam path to a spectrometer–detector system which is optimized for low temperatures and densities. In the absence of stray laser light and background plasma light the system will be capable of measuring temperatures down to 3–5 eV at 1–3×1011 cm−3 minimum densities.
Development and testing of a space-flight dilatometer/reactor
Authors: Sudol E. D. , El-Aasser M. S. , Micale F. J. , Vanderhoff J. W.
Published: July 2002

A stainless-steel piston cylinder dilatometer (volume ∼100 cm3), designed for use in microgravity, was tested and modified for the purpose of obtaining the polymerization kinetics of monodisperse polystyrene latexes, as well as the latexes themselves. A low-speed, oscillatory agitation (10 rpm, 30° arc per cycle) and redesigned stir paddle were selected for the low shear requirements of the microgravity experiments. Conversion histories accurate to within 2% were obtained after apparatus modification and procedural changes were implemented.
Characteristics of a compact microwave ion source
Authors: Walther S. R. , Leung K. N. , Kunkel W. B.
Published: July 2002

A small microwave ion source has been fabricated from a quartz tube with one end enclosed by a two-grid accelerator. The source is also enclosed by a cavity operated at a frequency of 2.45 GHz. Microwave power as high as 500 W can be coupled to the source plasma. The source has been operated with different geometries and for various gases in a cw mode. For hydrogen, ion current density of 200 mA/cm2 with atomic species concentration as high as 80% has been extracted from the source. It has been demonstrated that low-energy oxygen ion beams can also be extracted from the source. Beam-energy spread has been measured to be less than 1 eV.
Escape factors for Stark-broadened line profiles
Authors: Mancini R. C. , Joyce R. F. , Hooper C. F.
Published: July 2002

Escape factors for upper and lower limits to the source function appropriate for spherical geometry have been evaluated using a set of Stark-broadened line profiles, computed with different approximations, for the Ly-∝ line of Ar xviii. The method used to compute the escape factors, which is based on a general formalism, can be applied to any kind of line profile and is suitable for any geometry. The escape factor is expressed as an integral over the frequency of a functional of the line profile; hence our treatment highlights its dependence on the line profile. Comparisons are made with previous calculations that used Holtsmarkian line profiles and significant differences are noted. This work has been submitted for publication to J. Phys. B (London). This work was supported by the U.S. DOE Grant No. DEA508-833PP-40177.
Sample transfer system for surface studies in wide pressure range (10−7–106 Pa)
Authors: Ichikawa Shinichi , Wilson Mahlon S.
Published: July 2002

An inexpensive sample transfer system suitable for surface studies with in situ prepared model catalysts is described. Experiments from ultrahigh vacuum to 10 atm and 50-cm travel with negligible pressure spikes were made possible by the use of double-seal glands with spring-loaded Teflon O-rings and a guided rotational transport rod.
Microprocessor-based data-acquisition system
Authors: Umeagukwu Charles I. , Peters Walter H. , Dickerson John R.
Published: July 2002

This article describes the development of an automated microprocessor-based data-acquisition system and, in particular, the use of an inexpensive microcomputer to automate an acoustic experiment. Specifically, it explains the use of a Motorola MC6801 in the single-chip mode to control a rather complex experimental process. The system is configured to provide for automated, two-dimensional data acquisition of ultrasonic transmissibility through a specimen surface. Results to evaluate the accuracy and the performance of the system with known analytical predictions will be presented.
Transient local magnetic field measurement in a bumpy torus by rapid-frequency-scan laser spectroscopy
Authors: Honda Chikahisa , Maeda Mitsuo , Yokoo Masakazu , Muraoka Katsunori , Akazaki Masanori , Kadota Kiyoshi , Hosokawa Minoru , Iguchi Harukazu , Takita Yasuyuki , Takahashi Chihiro , Fujiwara Masami , Fujita Junji
Published: July 2002

A new technique for local magnetic field measurement in a bumpy torus NBT-1M (which is a magnetic plasma confinement device) has been developed using a rapid-frequency-scan (RAFS) laser system combined with sodium atomic beam probing. The RAFS laser beam excites the sodium D1 transition in the plasma cavity, and the Zeeman pattern is determined with laser fluorescence spectroscopy in a single laser shot. From the Zeeman splitting, the transient magnetic field distribution in the plasma, produced by electron cyclotron resonance heating (ECH), is measured with an accuracy of ±3.2%, a spatial resolution of 5 mm, and a temporal resolution of 5 μs.
Extraction of secondary electrons in a newly proposed immersion lens
Authors: Shao Zhifeng
Published: July 2002

An analysis is given of a symmetric secondary electron extraction system suitable for use in a newly proposed immersion lens. The detailed behavior of secondary electrons in the combined electrostatic and magnetic field is presented. Numerical results show that this extraction system imposes very small effects on the primary electrons yet retains a high collection efficiency on secondary electrons, so that the advantages of the low aberration immersion lens can be fully utilized.
Design operation and test of a light gas gun in a developing country
Authors: de Icaza M. , Renero C. , Prieto F. E.
Published: July 2002

A detailed description is given of the light gas gun designed, machined, and operated at the National University of Mexico. Emphasis is made on the difficulties to be faced in a developing country to construct this kind of experimental facility, as well as on the solutions given. In particular, the barrel is made of 15 interlocking sections, each one as long as could be machined and honed in the available lathes in our country. These sections are conically tapered inside to allow the projectile to move from one section to the next without being shaved or deformed. The double diaphragm type breech has a working pressure of 40 MPa, the length of the barrel is 12.7 m and its bore is 75 mm. We indicate how to maximize the bursting cross section of the diaphragms, because this increases the projectile velocity. The projectile mass may be chosen between 0.5 and 2 kg, and the maximum projectile velocity may be as high as 1200 m/s. The gas gun performances are presented and, as a final remark, we comment on what we would change if we were to construct another gun.
A combustion facility for high-pressure flame studies by spectroscopic methods
Authors: Carter Campbell D. , King Galen B. , Laurendeau Normand M.
Published: July 2002

We have developed a high-pressure combustion facility that includes the following: (1) a pressure vessel constructed from standard stainless-steel piping components; (2) an internal x-y burner translation system employing inexpensive stepper motors and translation mechanisms; (3) two flat-flame burners; and (4) an electronic gas delivery system, which is interfaced to a microcomputer. The facility is designed for study of high-pressure flames by spectroscopic methods and should also aid in the development of spectroscopic tools for high-pressure combustion environments.
A heat transfer study for beamline components in high-power wiggler and undulator beamlines. Part I. Beam stops (invited)
Authors: Bedzyk M. J. , Keeffe M. J. , Schildkamp W. , Shen Q.
Published: July 2002

The heat transfer capabilities of beam stops in CHESS wiggler and undulator beamlines is described. The thermal analysis for the design of these crucial in-vacuum beamline components is based on the use of a finite element analysis computer calculation and experimental heat loading tests.
A source for producing alkali ion beams for low-energy surface scattering spectroscopies
Authors: Peale D. R. , Adler D. L. , Litt B. R. , Cooper B. H.
Published: July 2002

We present the design and performance of an alkali ion source which is the injection stage of an ion beam system for surface scattering experiments in the range of 10 eV to 10 keV. In order to maximize emitter lifetimes, emphasis was placed on obtaining low phase space beams which minimize current losses in later stages of the optics. The source is based on a commercially available solid state β-eucryptite emitter, uses two stages of extraction for independent control of extracted current and final beam energy, and has a modified Pierce confinement electrode to control space charge spreading inside the source. Results of computer ray tracing are included to illustrate the operation of this source. Tests with K+ ions at 500 eV have produced beams which, in the range of 600–700 nA, were space-charge limited in transport through the remainder of the system. Beam currents measured more than 1 m downstream of the source are nearly independent of the emitter surface temperature over a range of 1023 to 1142 °C. Emitter lifetimes in excess of 200 h have been obtained. Using this source and our beamline optics, we have produced at the sample position low phase space beams ranging in energy from 10 eV to several kiloelectron volts.
A microcomputer-based solid-state nuclear track image analyzer
Authors: Chou H. P. , Shen H. J. , Song S. J.
Published: July 2002

A microcomputer-based image processing system has been developed to use with solid-state nuclear track detectors for number counting, area measurement, and location identification. The image digitizer is designed to interface with a microcomputer and a standard black and white TV camera for data acquisition. A spatial dependent segmentation algorithm is proposed for track identification under nonuniform illumination and the low track-pixel population conditions. The system has been tested using Lexan samples irradiated by a Cf-252 spontaneous fission source. The counting accuracy is approximately 3% with a long term stability of 5%. Efficiency calibration was performed using samples with track densities up to 104/mm2. Results indicate that the proposed track identification scheme tends to reduce the track overlap effect and the system behaves as a nonparalyzable counting system. For track densities below 3000/mm2, either a paralyzable or a nonparalyzable counter model can be established with an accuracy better than 0.5%. For track densities below 1500/mm2, the track registration efficiency is in good agreement with manual counting results.
Prediction of optical disk tracking servo signals from surface microtopography measured by scanning tunneling microscopy
Authors: Best M. E. , Karis T. E. , Logan J. A. , Lyerla J. R. , Lynch R. T. , McCormack R. P.
Published: July 2002

Scanning tunneling microscopy (STM) was employed to measure the three-dimensional surface topography of radial servo grooves etched in a glass substrate. The effect of groove depth (nominal values of 20, 40, and 70 nm) on tracking servo signals at a track pitch of 1.6 μm is examined. Using an optical disk tester, three groove related signals were measured for each groove depth: the on-track signal ratio, cross-track ratio, and the push-pull ratio. In a key feature of this study, scalar diffraction theory was used to calculate the groove related signals from the STM profiles and the beam profile of the optical disk tester. The calculated groove related signals were found to be in nearly quantitative agreement with those measured with the disk tester.
ac detection of secondary photoelectrons
Authors: Ruckman M. W. , Qiu S. L. , Strongin Myron
Published: July 2002

A current channeltron whose anode is biased at positive high voltage is used in conjunction with a lock-in amplifier to measure secondary photoelectron emission. The detector has good sensitivity, noise rejection, and produces surface x-ray absorption fine structure (XAFS) spectra with low noise-to-signal ratios. The need to modulate the photoelectron emission current can be exploited to limit the detection of photoelectrons to the sample.
Spectrophotometer design for the characterization of coated optical components
Authors: LaDelfe Peter C. , Stahl D. B.
Published: July 2002

The spectral transmittance and reflectance of an optical component, especially one with an interference coating, is severely dependent on angle of incidence and polarization. We report here on the design of an instrument which provides accurate, direct measurement of the spectral response of coated components at arbitrary angles of incidence.
Front contact electroreflectance: An alternative technique for semiconductor optical studies
Authors: Giordana Adriana , Glosser R.
Published: July 2002

An alternative form of application of an electric field to semiconductors so as to provide electroreflectance modulation is presented. Two metallic contacts, a large ring-shaped one enclosing a small transparent one, are deposited on the specimen surface and connected to the two leads of a signal generator. Results from a highly doped n-type silicon bulk and from an undoped 4000 nm silicon film on sapphire demonstrate that this technique yields spectra equivalent to traditionally performed electroreflectance or photoreflectance. We also show that electroreflectance response can be obtained with a current generator connected across a single metal contact.
Enhanced ECR ion source performance with an electron gun
Authors: Xie Zuqi , Lyneis C. M. , Lam R. S. , Lundgren S. A.
Published: July 2002

An electron gun for the advanced electron cyclotron resonance (AECR) source has been developed to increase the production of high charge state ions. The AECR source, which operates at 14 GHz, is being developed for the 88-in. cyclotron at Lawrence Berkeley Laboratory. The electron gun injects 10 to 150 eV electrons into the plasma chamber of the AECR. With the electron gun the AECR has produced at 10 kV extraction voltage 131 e μA of O7+, 13 e μA of O8+, 17 e μA of Ar14+, 2.2 e μA of Kr25+, 1 e μA of Xe31+, and 0.2 e μA of Bi38+. The AECR was also tested as a single stage source with a coating of SiO2 on the plasma chamber walls. This significantly improved its performance compared to no coating, but direct injection of electrons with the electron gun produced the best results.
Apparatus for i
n s
i
t
u measurement of surface magnetic moments prepared in UHV
Authors: Youm D. , Starr A. , Armstrong J. , Schultz S.
Published: July 2002

An apparatus for making in situ measurements of the magnetic moment of submonolayer through multimonolayer samples deposited in a UHV chamber is described. The UHV chamber is designed to be used with a commercial SQUID magnetometer with a sensitivity of ∼10−8 emu. The component of magnetic moment parallel to the sample surface may be measured over the temperature range 4–400 K and for magnetic fields (applied parallel to the surface) up to 5 T. A thin re-entrant metal tape is used both as an initial substrate for the deposition of any desired films, and as the means of transporting the deposited sample from the evaporation and evaluation regions of the vacuum chamber to the SQUID analysis region. Some results for Fe evaporated on polycrystalline Ag films are presented.
Synchronous pulse generator encompassing a wide range of time scales
Authors: Candela D. , McAllaster D. R.
Published: July 2002

A digital pulse generator has been developed that produces outputs synchronous with a 400-MHz master clock. Fifteen independent outputs may assume an arbitrary sequence of up to 2048 successive output states. The duration of each output state may be varied from 330 ns to several hours, with uniform 10-ns resolution. The generator has a new, simplified architecture that is easily programmed and requires a minimal amount of high-speed logic. The circuit was constructed in a commercially available CAMAC prototyping module.
Laser-driven electron ionization for a VUV photoionization time-of-flight mass spectrometer
Authors: Boyle J. G. , Pfefferle L. D. , Gulcicek E. E. , Colson S. D.
Published: July 2002

The modification of a VUV photoionization time-of-flight mass spectrometer (TOF-MS) to accommodate pulsed electron ionization is described. Utilizing a selected wavelength from a UV or VUV laser, structurally important fragment ions can be created for mass analysis. Data are straightforwardly obtained with only minor modifications to the experimental apparatus. The electron energy is continuously adjustable, thereby allowing the extent of fragmentation to be controlled. Observed fragmentation patterns are quantitatively similar to conventional electron ionization. Performance using UV or VUV radiation as the photoelectric driver is adequate to perform pulsed electron ionization on a time scale compatible with TOF-MS.
Constant frequency pulsed phase-locked-loop instrument for measurement of ultrasonic velocity
Authors: Yost William T. , Cantrell John H. , Kushnick Peter W.
Published: July 2002

A new instrument based on a constant frequency pulsed phase-locked-loop (CFPPLL) concept has been developed to accurately measure the ultrasonic wave velocity in liquids and changes in ultrasonic wave velocity in solids and liquids. An analysis of the system shows that it is immune to many of the frequency-dependent effects that plague other techniques including the constant phase shifts of reflectors placed in the path of the ultrasonic wave. Measurements of the sound velocity in ultrapure water are used to confirm the analysis. The results are in excellent agreement with values from the literature, and establish that the CFPPLL provides a reliable, accurate way to measure velocities, as well as for monitoring small changes in velocity without the sensitivity to frequency-dependent phase shifts common to other measurement systems. The estimated sensitivity to phase changes is better than a few parts in 107.
Measurement of velocity of particles in a dense suspension by cross correlation of dual laser beams
Authors: Zhu C. , Slaughter M. C. , Soo S. L.
Published: July 2002

This note deals with measurement of local average velocity of a particle cloud in an air suspension by cross correlation of two attenuated laser beams.
Measurement of microdisplacements by machine vision photogrammetry (DISMAP)
Authors: Franke E. A. , Wenzel D. J. , Davidson D. L.
Published: July 2002

An image processing system is described for use in micromechanics research on materials, such as for determining the displacements and strains surrounding crack tips. This vision system is a machine implementation of the stereoimaging technique that was developed for making submicron measurements of displacements under high resolution conditions. It uses a Cognex 2000 image processing system, cameras to obtain digital images from analog photographs, a graphics display terminal and track ball for operator interaction with the system, and a video display monitor for display of the measured displacements. Displacements are sent directly to an associated VAX that computes strains and permits their graphical display. The system is described in detail and examples of its use in micromechanics research are given.
High-resolution, high-sensitivity ac calorimeter
Authors: Bednarz Grzegorz , Millier Brian , White Mary Anne
Published: July 2002

A high-resolution, high-sensitivity, automated ac calorimeter capable of heat capacity measurements on very small samples (m<20 mg) with a temperature resolution of a few mK in the ac mode is described. This calorimeter also can be operated in the relaxation mode to provide absolute heat capacity values with precision and accuracy of around 2%. A microprocessor was employed to generate a stable oscillatory heating signal and to control the heater power, in order to improve the sensitivity of the measurement over other designs. A new very sensitive and miniature temperature probe (a film flake of a thermistor material), which increased measurement resolution and minimized the heat contribution of the addenda, also was used. This calorimeter was tested by measuring the heat capacity of gadolinium over its ferromagnetic phase transition. The results agree well with the literature data giving, however, substantially better resolution of the heat capacity in the critical region.
Characteristics of UHV stepping motors
Authors: Domeki Hideo , Satomi Hirofumi , Kusunoki Isao
Published: July 2002

Characteristics of an ultrahigh vacuum (UHV) stepping motor have been examined for practical use. The temperature rise of the motor in the energized-and-rest condition was measured as a function of the coil current. The result showed that it is approximately proportional to the electric power fed to the coil. The outgassing from the motor increased significantly at temperatures above 100 °C. The components of the released gas were the usual species in vacuum such as H2, H2O, CO, CO2, and hydrocarbons. Initially a small amount of NH3 was also observed at temperatures higher than 150 °C. This gas might originate from a small amount of the epoxy resin used for bonding the rotor and the permanent magnets. It decreased rapidly during the test operation. In the running mode, the outgassing of H2, CH4, H2O, CO, and CO2 increased with the revolution rate. The amount of the H2 released from the motor with the silver-ion plated ball bearings was larger than that with the MoS2 coated ball bearings. The lifetime of the MoS2-coated ball bearings was longer than that of the Ag ion plated ones.
Paralyzable and nonparalyzable deadtime analysis in spatial photon counting
Authors: Sharma A. , Walker J. G.
Published: July 2002

Inherent in particle and photon-counting systems is a deadtime period that affects the measured counting distribution. The effects of deadtime on counting distributions in single-channel detectors have been extensively studied. These results, however, are not generally applicable to two-dimensional detectors which measure both spatial and temporal photon event coordinates. Deadtime is attributed to the finite recovery characteristics (which include adjacency effects) in the microchannel plate intensifier part of the system and this process is modeled by introducing concepts of a temporal deadtime extending over a rigid or variable spatial dead area. Novel theoretical analyses are presented to predict the effect of paralyzable and nonparalyzable deadtime on the reduced mean count rate in a 2D imaging array. In the limits where the system resembles a one-dimensional detector, the analytic expressions agree exactly with previously published results. The accuracy of the analyses is examined by comparison with computer simulations. The paralyzable analysis is shown to be accurate at all count rates. The accuracy of the nonparalyzable analysis is excellent over count rates relevant in practical situations, but is in general count rate dependent. An inversion procedure is proposed which is applicable to both the paralyzable and nonparalyzable cases. This procedure allows an ‘‘ideal’’ incident image to be estimated by correcting for deadtime losses in the ‘‘measured’’ image. Computer results are presented which demonstrate the effectiveness of this inversion method and thus illustrate an important practical application of the work.
Undulator-radiation-excited x-ray fluorescence analysis system for light elements
Authors: Muramatsu Yasuji , Oshima Masaharu , Shoji Takashi , Kato Hiroo
Published: July 2002

An undulator-radiation-excited x-ray fluorescence analysis system for light elements has been developed and tested on the 26-period multipole wiggler/undulator beamline at the Photon Factory. An entrance-slitless optics with a variable-spacing grating was devised for a fluorescent x-ray dispersion system to achieve spectroscopic analysis with high efficiency and high resolution. Both soft x-ray emission (SXE) spectra and x-ray absorption near-edge structure (XANES) spectra with fluorescent x-ray detection were obtained by this system, taking advantage of the high brightness and quasimonochromatic character of the incident undulator beam. The analysis system was evaluated by measuring the B Kα SXE and fluorescence XANES spectra of B, BN, and B2O3.
MIT fusion γ-ray diagnostic development
Authors: Wenzel K. W. , Petrasso R. D. , Lo D. H. , Li C. K. , Coleman J. W. , Lierzer J. R. , Hsieh E. , Bernat T.
Published: July 2002

In conjunction with γ-ray diagnostic development for the NOVA Upgrade and Alcator C-MOD experiments, we have assembled a comprehensive set of absolutely calibrated γ-ray sources and several γ-ray detectors. These tools will be used in characterizing and calibrating new γ-ray diagnostic systems as they are assembled. The γ-ray sources comprise both radioisotopes and nuclear reactions. The latter are generated in the MIT Cockcroft–Walton fusion-product generator. The detectors include several ‘‘standard’’ NaI(Tl) scintillators and a high-resolution germanium detector. This paper briefly discusses the diagnostics planned for NOVA Upgrade and Alcator C-MOD. In addition it describes the γ-ray sources and detector characterizations we have performed in the laboratory.
Ion-beam-modified polyimide as a novel temperature sensor: Fundamental aspects and applications
Authors: Xu Dong , Xu Xinglong , Zou Shichang
Published: July 2002

A series of polyimide films irradiated by 170 keV N+ and 120 keV B+ with controlled and related implantation conditions were investigated with respect to their microstructures in modified layers, as well as their application prospects as temperature sensors. The sensitivities and sensitive ranges of these functional materials were correlated with the implantation conditions in terms of the Raman spectroscopic results. This well-defined relationship was interpreted with perspectives of ion beam microstructural modification, which provides a deeper insight into the fundamental aspects for the synthesis of temperature-sensitive materials out of polyimide precursor. It seems that greater irradiation dose, stronger beam current density, and higher target temperature constitute a set of favorable conditions for the fabrication of temperature sensors with a comparatively broad sensitive scope.
Modular enthalpy probe and gas analyzer for thermal plasma measurements
Authors: Swank W. D. , Fincke J. R. , Haggard D. C.
Published: July 2002

The enthalpy or calorimetric probe is a water-cooled stagnation/sampling probe for studying the temperature, velocity, and composition of hot-gas flow fields. In order to derive the thermodynamic properties of complex flow fields such as plasma arc jets or high-velocity oxygen fuel jets, the specie concentration must be known accurately. To this end a differentially pumped quadrapole mass spectrometer has been integrated with a fully automated enthalpy probe system. An inexpensive modular probe is described along with the system and its theory of operation. Calibration and error are also discussed. Typical results are presented for the system operating in an argon/helium plasma arc jet in atmospheric pressure air. The maximum temperature measured is 13434 K on the center line of the jet, 5 mm from the exit, with a corresponding velocity of 1295 m/s. The utility in integrating the mass spectrometer to the enthalpy probe system is not only an accurate measurement of the gas mixture components for obtaining the correct property information, but also valuable information can be obtained about demixing diffusion and chemical reaction taking place in the plasma plume. The relative amount of argon to helium is shown to deviate from the nominal mixture by as much as 40% at the center of the plume.
Fast lithium-beam spectroscopy of tokamak edge plasmas
Authors: Wolfrum E. , Aumayr F. , Wutte D. , Winter HP. , Hintz E. , Rusbüldt D. , Schorn R. P.
Published: July 2002

Plasma-wall interaction and impurity transport processes in the outermost region of magnetically confined hot plasmas (the so-called plasma edge) must be well understood for successful development of future thermonuclear fusion reactors. To this goal, sufficiently detailed edge plasma diagnostics are in great demand. By injecting a fast Li beam into the edge plasma region, a great number of information can be obtained with excellent space and time resolution. This so-called Li-beam plasma spectroscopy gives access not only to edge plasma density profiles from the collisionally excited Li atoms, but also to the impurity concentration and temperature profiles via line emission induced by electron capture from the injected Li atoms by the impurity ions. Full utilization of all capabilities requires a reliable data base for the atomic collision processes involving injected Li atoms and plasma constituents (i.e., electrons, hydrogen ions, and relevant impurities in their various charge states), since a precise modeling of Li beam attenuation and excited-state composition has to be made for evaluating desired plasma properties from the related spectroscopical measurements. The most recent methodical improvement permits a fully consistent determination of absolute edge plasma density profiles by measuring only relative LiI line emission profiles. This is of special interest for investigating rapid edge plasma density fluctuations in connection with, e.g., ELMs, L-H mode transition, turbulence or edge cooling by impurity injection. This paper describes the capabilities of Li-beam edge plasma spectroscopy by way of illustrative examples from measurements at the tokamak experiment TEXTOR.
Diamond film synthesis in low-pressure premixed methane-oxygen flames
Authors: Kim J. S. , Cappelli M. A.
Published: July 2002

We present the successful demonstration of diamond film synthesis in low-pressure premixed methane-oxygen flames. Experiments are performed in a low-pressure flat-flame facility that has been employed previously to study diamond synthesis in premixed acetylene-oxygen and ethylene-oxygen flames. The quality of the diamond films deposited is comparable to that deposited using these other flames, and the growth rate is approximately 0.2–0.3 μm/h; some factor of 10 less than acetylene-oxygen flames and one-third of that obtained for ethylene-oxygen flames. However, carbon conversion efficiencies are remarkably similar, since the cold gas velocities used here are substantially less, because of the lower burning velocities. The equivalence ratios employed in these methane-oxygen flames are in the 1.8–2.0 range. These values correspond to C:O ratios that are substantially lower than those that have been used to grow good quality diamond in acetylene-oxygen and ethylene-oxygen flames at low and atmospheric pressure. General observations suggest that the quality is only slightly sensitive to changes in equivalence ratios and very sensitive to substrate temperature. Uniform diamond films over areas of about 5.5 cm2 are deposited with substrate temperatures of approximately 900 °C.
Mass and charge selection of pulsed ion beams using sequential deflection pulses
Authors: Sung M. M. , Al-Bayati A. H. , Kim C. , Rabalais J. W.
Published: July 2002

A method of preparing ion beams of known mass and charge for time-of-flight scattering and recoiling spectrometry (TOF-SARS) using sequential deflection pulses (SDP) has been developed. A double-pulsing sequence is described in which the first pulse is used to create ion pulses and the second pulse, triggered after a suitable delay, allows only the species of interest to be transmitted to the target. A mass resolution of m/Δm=3–5 was achieved with the present system, eliminating the need for conventional mass resolution devices when high mass resolution is not required. Examples of the direct separation of Ar+ and Ar2+ ions from an ion beam and separation of Ar+ and Ar2+ scattering and recoiling spectra from an indium phosphide (InP) surface are provided.
Gas distribution effects on electron cyclotron resonance deposition reactions
Authors: Orloff Glennis J. , Hurst James H.
Published: July 2002

The ability to produce high quality films in an electron cyclotron resonance reactor is dependent on the gas distribution system. In an effort to understand gas distribution effects, a variety of gas ring injection systems were implemented during silicon nitride growth. Film refractive index, uniformity, and stress were used to gauge each gas distribution system. As a result, we have demonstrated that evenly distributed gas injection systems are the most desirable producing uniform films. Film thickness uniformity was significantly influenced by the design of the gas ring as well as the gas flow. Theoretical models supported the observed results and identified desirable properties for gas ring distribution systems.
Electron temperature measurement of Ba photoplasma by using an electrostatic probe
Authors: Furtlehner J. P. , Blanchet A. , Leloutre B.
Published: July 2002

We study experimentally and theoretically the time evolution of the electron temperature Te of a photoionized barium vapor which expands freely into a vacuum. Using the gas dynamics fundamental equations and assuming the plasma expansion to be adiabatic, a model is built and analytical expressions are derived for the electron and ion temperatures, velocity, and density time evolutions. The experimental apparatus consists essentially of a vacuum chamber, a Joule effect furnace which produces the Ba vapor. A cylindrical plasma created between the two vertical plates is produced by two-step ionization of the vapor. The electron temperature is measured with a cylindrical electrostatic probe biased by a slowly variable voltage ramp. The current-voltage curve is built step by step with a boxcar averager. The results involve different parameter variations like vapor density or sampling time of the probe current for studying the time evolution of electron temperature. Finally, it was found that the adiabatic cooling model agrees well with the experimental electron temperature evolution, but was limited below 0.025 eV by the Langmuir probe accuracy.
Readily constructed modular polarization-emission scanning spectrometer
Authors: Wallin Sten A. , Schreiner Anton F. , Knopp James A. , Barnes N. Randy
Published: July 2002

A modular polarization spectrometry system for the measurement of the degree of polarization (linear or circular) of luminescence intensity is described. It is based on polarization modulation with a photoelastic modulator and two lock-in amplifiers for signal recovery. Interfaced to the spectrometer is a microcomputer configured with CRT monitor, disk drive, and digital printer to provide system control and to permit digital data storage and data manipulations such as multiple scan averaging and averaged background subtraction. The system described is capable of measuring linearly polarized emission, linearly polarized excitation luminescence, and circularly polarized emission spectra. The modular design also allows the spectrometer to be rapidly and easily modified for the measurement of circular dichroism, magnetic circular dichroism, or magnetic circularly polarized emission. The system performance is demonstrated.
An instrumentation assembly for studying operational behavior of thermal gradient programmed gas chromatography
Authors: Rubey Wayne A.
Published: July 2002

Extensive laboratory experiments and measurements are required for the operational evaluation and optimization of thermal gradient programmed gas chromatography (TGPGC). To accommodate these numerous laboratory investigations, an instrumentation assembly has been designed and constructed which possesses the needed built-in experimental flexibility or adaptability. This system has been configured to test a variety of column sheath assembly designs and their associated open tubular separation columns. It is also used for performance testing many other special TGPGC components, including devices needed for the different types of sample introduction. The major application area of TGPGC is the rapid analysis of complex organic mixtures which cover a broad volatility range. Consequently, this system has been designed to permit exploratory investigations over a temperature range of −100 to 500 °C, while using programmed flows of a variety of inert transport gases. With the use of this instrumentation assembly, operational data and performance assessments can systematically provide the information needed to optimize and spatially compact this different analytical chromatographic procedure.
A noncontact cryogenic microwave measurement system for superconducting device characterization
Authors: Findikoglu Alp T. , Nakamura T. , Tokuda H. , Iiyama M.
Published: July 2002

A noncontact cryogenic microwave measurement system has been developed for the characterization of passive and active superconducting devices by means of an unloaded quality factor measurement technique. The measurement system was designed specifically for the characterization of planar thin film resonant structures as a function of temperature (4–300 K), frequency (100 MHz–26.5 GHz), and dc voltage bias (≤100 V). It has been used for basic device studies of novel active superconducting lumped components made of metal-oxide superconductor/insulator heterostructures.
A small-area high-T
c superconducting bolometer with Y-Ba-Cu-O thin film
Authors: Li Xizhi , Shi Xiangqing , Wang Li , Li Shuqin , Qi Yizhi , Yang Bingchuan , Wang Xiaoping , Shi Dongqi
Published: July 2002

A small-area high-Tc superconducting bolometer with a dense YBCO meander wire on a (100) Zr(Y)O2 substrate has been tested at λ=1.5 μm using a diode laser as the radiation source. The infrared power absorbed by the bolometer was calibrated using a dc infrared substitution method. Responsivities of hundreds of V/W with a millisecond response time were obtained at a temperature of 86.5 K in the modulation frequency range of 10–3000 Hz. A minimum noise equivalent power of 6×10−11 W/Hz1/2 was measured at 1000 Hz. The experimental results are compared with those obtained from a thermal analysis of the substrate-supported microbolometer. No nonbolometric effect was distinguished.
Measurement of some parameter on MEVVA ion source
Authors: Zhou F. S. , Wu X. Y. , Zhou F. , Zhang H. X. , Zhang X. J.
Published: July 2002

The charge density and the charge state distribution of ions extracted from metal vapor vacuum arc ion source have been measured by single, double probe, and time of flight systems, and the ion beam density distributions near the extracting electrode have been measured with and without a cusped magnetic field in order to improve the performance of ion beams. The charge state distributions as a function for many operational cathode materials were investigated.
14 GHz ECR operating and development at GSI
Authors: Schulte H. , Bossler J. , Schennach S. , Wolf B.
Published: July 2002

A 14 GHz Caprice ECR ion source is now in operation at the high charge state injector of the Unilac accelerator. Ions with charge to mass ratio ≥0.117 can be accelerated. Performance of the source with Uranium 28+ will be presented. A rebuilt ECR ion source similar to the Caprice operates at a test bench in order to investigate metal ion production and the afterglow operation mode.