bluuebunny/crossref_metadata_2025 huggingface dataset:
Backward Compton scattering for probing electric fields in a plasma
Authors: Clayton C. E. , Joshi C.
Published: July 2002

A new method is suggested for probing ultrahigh electric fields associated with relativistic plasma waves in high-density plasmas. A relativistic electron beam and an intense photon beam are collided inside the plasma. In the absence of any perturbing fields, the electrons Compton scatter some of the photons. In the backward direction, the frequency of the scattered radiation is roughly 4γ2ω0 with a frequency spread of ∼2(Δγ/γ). When strong electric fields are present, some of the electrons are accelerated and others are decelerated. This leads to broadening of the Compton-scattered spectrum. An experiment designed to probe coherent longitudinal electric fields of a beat-excited plasma wave will be described. This technique has the potential to give time-resolved information about relativistic wave particle interaction.
Software systems for processing and analysis at the NOVA high-energy laser facility
Authors: Auerbach J. M. , Montgomery D. S. , McCauley E. W. , Stone G. F.
Published: July 2002

A typical laser interaction experiment at the NOVA high-energy laser facility produces in excess of 20 Mbytes of digitized data. Extensive processing and analysis of this raw data from a wide variety of instruments is necessary to produce results that can be readily used to interpret the experiment. Using VAX-based computer hardware, software systems have been set up to convert the digitized instrument output to physics quantities describing the experiment. A relational data-base management system is used to coordinate all levels of processing and analysis. Software development emphasizes structured design, flexibility, automation, and ease of use.
Thomson scattering in the Tara tandem mirror central cell
Authors: Casey J. A. , Irby J. H.
Published: July 2002

A Thomson scattering experiment is under construction for the central cell of the Tara tandem mirror. This experiment has been designed to measure electron temperature and density at densities as low as 3×1011 cm−3. The measurement is made at a single time point per shot using a Holobeam 10-J Q-switched ruby laser, folded back for two passes through the scattering volume. Detection is at 90° with f/5 optics. The optical table is mounted on linear bearings with a 10-in. stroke, so that the radius of the scattering volume may be changed from shot to shot. Novel features of the experiment include a high-throughput (>25%) commercial triple-grating polychrometer using holographic gratings, and a directly coupled ten-channel microchannel plate photodetector array.
Optical method for measuring uniform thickness of the order of 10 μm–1 mm of transparent solid and liquid films
Authors: Ohyama Tetsuya , Mori Yasuhiko H.
Published: July 2002

An optical-interference method is proposed for measuring the thickness of ‘‘fairly thick’’ films of transparent (or weakly absorbing) solid materials or liquids. It uses a laser beam with an incident angle, on the subject film, changing with time, causing an alternation of constructive and destructive interferences of beams reflected, respectively, at upper and lower surfaces of the film. The total irradiance of the beams interfering with each other is continuously detected and recorded. From the number of periodical changes of the irradiance during the change of the incident angle over a specified range we can readily calculate the thickness of the film. A simple apparatus has been designed and constructed to realize this method. It has been shown that the method is applicable to measurements of thicknesses of both solid and liquid films, provided the films are kept stationary enough.
Design and calibration of the JET neutral particle analyzer
Authors: Bartiromo R. , Bracco G. , Brusati M. , Grosso G. , Mantovani S. , Tilia B. , Zanza V.
Published: July 2002

The neutral particle analyzer with energy and mass selection capability built for JET is described. The analyzer is able to detect in the same shot both H atoms from 0.3 to 320 keV and D atoms from 0.15 to 160 keV. In order to optimize the ion optics of the analyzer an oblique entrance in the magnet has been chosen. An ion trajectory code shows that in this way a good mass separation and a high efficiency can be achieved. The problems inherent in the analyzer calibration for a wide energy range are discussed, and the calibration procedure is described. In conclusion, the calibration results obtained with five analyzers are presented, together with theoretical consideration on ion optics and atomic processes, which have enabled us to write a simple interpolation formula for the experimental data.
Pulsed excimer (KrF) laser induced crystallization of PbZr0.44Ti0.56O3 amorphous films
Authors: Lu X. M. , Zhu J. S. , Hu W. S. , Liu Z. G. , Wang Y. N.
Published: July 2002

Amorphous PZT thin films 600 nm thick were rf sputtered from a PbZr0.44Ti0.56O3 ceramic target with excess PbO onto glass substrates maintained at room temperature. After irradiation with a 248 nm KrF pulsed excimer laser with a power density of 2.3×107 W/m2 at a frequency of 50 Hz and a pulsed width of 30 ns for 2 min, the films crystallized into the PZT perovskite structure to a depth of about 120 nm. Comparisons of this work with PZT crystallization obtained from a traditional oven and 488 nm Ar+ laser postdeposition treatments are also given.
Hydrogen particle diagnostic based on Pd-MOS diode arrays
Authors: Bastasz Robert , Hughes Robert C.
Published: July 2002

The reverse-bias current through a Pd-MOS diode changes when hydrogen is present at the diode interface and this effect provides the bias for a solid-state detector to monitor the flux and energy of hydrogen particles emanating from a beam or plasma. The addition of a coating atop the Pd forms a high-pass energy filter and an array of coated Pd-MOS diodes can function as a compact, hydrogen-specific, energy spectrometer. The response characteristics of an Au-coated Pd-MOS diode array have been measured using a low-energy hydrogen ion source. The array has several desirable characteristics for energetic hydrogen detection. Its response is dosimetric, it discriminates between hydrogen irradiations at different energies, and it can be regenerated by heating briefly to 100–200 °C. These properties make Pd-MOS diode arrays attractive candidates for remote plasma-edge flux and energy monitors in fusion devices.
Photoconducting x-ray detectors for Z-pinch experiments
Authors: Spielman R. B. , Hsing W. W. , Hanson D. L.
Published: July 2002

We have used GaAs and GaAs:Cr photoconducting detectors (PCDs) to measure the absolute x-ray output from 1 to 10 keV from Z-pinch plasma radiation sources. We calibrated the detectors over the spectral range of 900–3000 eV and found the spectral response to be constant to within the accuracy of the measurements. The flat spectral response, increased sensitivity (compared with bolometers), and good time response of the PCDs, coupled with their reliability and long lifetimes, have allowed us to acquire absolute x-ray data of significantly higher quality than possible with resistive bolometers or x-ray diodes (XRDs). An added attraction of PCDs is their smooth saturation at high incident x-ray fluxes. Unlike other types of electrical x-ray detectors, this feature allows a PCD to operate over a wide range of incident x-ray powers (10–104 W/cm2 ). We present results from gas puff Z-pinch experiments on Proto-II and Supermite comparing PCD, XRD, and resistive bolometer performance.
Species and divergence measurements on the TFTR diagnostic neutral beam
Authors: Gammel G. , Fonck R. J. , Roquemore A. L. , Schilling G.
Published: July 2002

The ion source of the TFTR diagnostic neutral beam utilizes a magnetic cusp bucket from a PLT source modified with an internal rf antenna in place of filaments. The species mix of the beam has been measured after the neutralizer as a function of several parameters in two ways: spectroscopically and by an electrostatic charge exchange analyzer. Source and neutralizer gas feeds (both hydrogen) were varied. Some measurements were made with the bending magnet alternately on and off to obtain neutralizer efficiency for each component. Accelerator current was varied, at fixed acceleration voltage and gas feed rate, by varying rf power to the antenna. Relative beam divergence during this scan was monitored by both diagnostics, and an absolute divergence was obtained from a spectroscopic profile scan.
Intense ion beam Kα measurements on PBFA-II
Authors: Maenchen J. , Mehlhorn T. A. , Wenger D. F. , Leeper R. J. , Johnson D. J. , Lockner T. R.
Published: July 2002

Inertial confinement fusion research efforts at Sandia National Laboratories center on generating and focusing high-intensity light ion beams on the Particle Beam Fusion Accelerator PBFA-II. A time-integrating three-frame ion beam spatial monitor was developed for these experiments to determine proton and lithium ion beam uniformity and orbit characteristics by imaging the ion-induced Kα line radiation. The three views of the ion beam are made off axis in three diode quadrants at a 3.8-cm radius. This spatial monitor, in conjunction with other beam diagnostics, allows experimenters to determine the high-voltage focusing characteristics of the ion diode.
Design and performance characteristics of the radiation shield developed for the TFTR charge exchange diagnostics
Authors: Roquemore A. L. , Medley S. S. , Scott S. D.
Published: July 2002

The high source strength of 2.45-MeV neutrons (∼1.2×1016 n/s) and neutron-induced gamma rays produced by the Tokamak Fusion Test Reactor (TFTR) have substantially degraded the performance of many diagnostics. In particular, data obtained by the charge exchange neutral analyzer (CENA) were seen to degrade at modest production levels of ∼1015 n/s. To reduce the radiation-induced noise to acceptable levels, massive shielding was required. A design and cost-effectiveness study was performed for the TFTR CENA which showed that a double-layered enclosure consisting of a 10-cm-thick inner housing of lead surrounded by a 23-cm-thick layer of 1.0% borated polyethylene was required to reduce the neutron and gamma noise level by two orders of magnitude. This design was recently implemented on TFTR and was shown to perform as predicted. The details of the enclosure will be presented and the contributing factors that led to the choice of this particular design will be reviewed.
High-resolution time-of-flight mass spectrometers: Part I. Effects of field distortions in the vicinity of wire meshes
Authors: Bergmann T. , Martin T. P. , Schaber H.
Published: July 2002

Field distortions in the vicinity of wire meshes can change the direction of passing ions. Small deflection angles of ions passing through wire meshes in the reflector can reduce the mass resolution of time-of-flight mass spectrometers. We calculate these effects.
Automatic alignment correction system for an ellipsometric monitor
Authors: Hayashi Yasuaki
Published: July 2002

A simple method of alignment correction and evaluation of incidence-angle change for a laser ellipsometric monitor is presented. Once the alignment is out of order after accurate adjustment, it is corrected by an automatic alignment correction system. The system moves an analyzer assembly with a X-Z translation stage so as to adjust the center of the entrance aperture to the reflected laser light from a specimen. Incidence-angle change is evaluated from the length of the movement. Performance of the system has been tested and the result was that the error was not more than 0.01° for an incidence-angle change and 0.1° for ψ and Δ.
Spectral quantum efficiencies of semiconductor photodiodes in the far ultraviolet region
Authors: Saito T. , Katori K. , Nishi M. , Onuki H.
Published: July 2002

The spectral quantum efficiencies and reflectances of p-i-n-type Si photodiodes and a Schottky-type GaAsP photodiode were measured in the wavelength region between 105 to 300 nm. These results are compared with an optical model using complex refractive indices. The spectral relative external quantum efficiencies are well interpreted within the model by assuming that the production energy of an electron-hole pair, ε, is wavelength independent. It is suggested that surface recombination of minority carriers occurs in some devices. The internal quantum efficiency for the GaAsP photodiode is shown to be constant in the photon energy range below about 5.4 eV. The recombination loss and the ε value are separately estimated.
Attempt at LSI pattern demagnification by Bragg reflection
Authors: Nishino J. , Morigami M. , Harada M. , Terakado S. , Kobayashi S. , Fujiwara S. , Kaneda K. , Goto T. , Shimizu R. , Suzuki S. , Maezawa H. , Ando M.
Published: July 2002

A new method for pattern reduction in the x-ray region is proposed. In its principle was used the asymmetric Bragg reflection giving the different beamwidth in the reflected beam from the incident one. Light from an undulator line (BL-2) at the Photon Factory was used to obtain highly spatially resolved replication in reasonably short exposure time. Performed was one-dimensional demagnification of a pattern with a ratio of 1/4 in the following condition: Si 111 reflection was used where the offset angle α from the surface is 22° and the wavelength λ was 3.5 λ, which is available from the 7th harmonic of the undulator radiation. The submicron scale resist pattern was resolved.
Prospective nonlithographic applications of a synchrotron radiation source for deep-etch lithography
Authors: Moser H. O. , Ehrfeld W.
Published: July 2002

It is pointed out that the performance of superconducting storage ring synchrotron radiation sources designed for deep-etch lithography like the source KSSQ planned at Karlsruhe is much superior to that of typical thin film lithography sources and comes close to that of first and second generation synchrotron radiation sources. Therefore, the range of applications of such machines exceeds the original design goal by far and includes many of the important synchrotron radiation methods based on diffraction, absorption, and fluorescence excitation, as well as foreseeable production methods. Thus, these machines may become a new class of sources of their own.
Parameters of exposure equipment for SOR x-ray lithography (abstract)
Authors: Oertel H.
Published: July 2002

The potential of x-ray lithography makes it a promising method to fulfill the demands of ultralarge-scale integration (ULSI) device fabrication. The main advantages compared to competing lithographic methods are simple shadow printing exposure arrangement, large field size, the excellent resolution down to approximately 150-nm pattern size, high depth of focus, process latitude, and low sensitivity against wafer topography and against dust particles. An increasing worldwide activity can be observed to solve the remaining problems: the small source for production environment, the 1:1 x-ray mask with high quality concerning positioning and linewidth, the x-ray stepper with large throughput and accurate alignment strategy, and a quick repair system for subhalf micron defects. The high sensitive x-ray resist will probably be available in the near future. At Fraunhofer-Institute für Mikrostrukturtechnik (IMT) in Berlin there is an exposure instrumentation under construction, consisting of the race-track compact storage ring COSY, the beamline, and the x-ray stepper XRS 200 from Suss Company. This contribution presents an investigation of choosing the parameter of the above mentioned setup to ensure high-throughput requirements. Experimental results based on experiments at BESSY and theoretical results obtained by means of the simulation program x-ray lithography modeling and simulation (XMAS) are presented concerning, e.g., resolution and transfer of defect particles.
Towards high-resolution spectroscopy and dynamics studies in complex multi-ionized molecules
Authors: Besnard-Ramage M. J. , Morin P. , Lebrun T. , Nenner I. , Hubin-Franskin M. J. , Delwiche J. , Lablanquie P. , Eland J. H. D.
Published: July 2002

New experimental developments for high-resolution spectroscopy and dynamics studies of complex multi-ionized molecules are presented. Using photoion-photoion coincidence measurements in the doubly ionized C6F6 (hexafluorobenzene) molecule obtained with a conventional time-of-flight spectrometer and the ACO storage ring as an example, we demonstrate the importance of improving (i) the light source by using the new storage ring Super-ACO, (ii) the detection mode by using the photoelectron-photoion-photoion coincidence method, and (iii) the mass resolution of the spectrometer by constructing a reflectron time-of-flight mass spectrometer.
Investigations of resolution degradation due to scattering in a long focal length monochromator
Authors: Hansen Roger W. C. , Pruett Charles H. , Salehzadeh Amir , Wallace Daniel J.
Published: July 2002

Scattering of light by optical surfaces causes broadening of focused images and can limit the resolution of monochromators and other optical systems. This problem is most troublesome in the vacuum ultraviolet and x-ray region of the spectrum with long focal length, high resolution instruments. The resolution of a 4-m normal-incidence monochromator was found to be limited by scattering due to damaged replica grating surfaces. The effect of scattering on resolution was documented by scanning the zero-order peak with detectors sensitive to different wavelengths of light. In one case a scan of zero order with a visible sensitive photomultiplier tube gave a linewidth of 0.05 Å. The same image scanned with a gold diode detector which is sensitive below 1100 Å gave a peak width of 0.39 Å. Microscopic examination and knife-edge bench tests of the gratings provided additional evidence that this problem was caused by scattering. It is suggested that use of image scans at different wavelength could be used as a simple test of mirror or grating performance at shorter wavelengths where scattering is a more severe problem.
On the phase-space description of synchrotron x-ray beams (abstract)
Authors: Suortti P. , Freund A. K.
Published: July 2002

Simple graphic methods for illustrating the transformation of x-ray beams by optical elements such as mirrors, monochromators, and slits are very helpful tools when optimizing synchrotron radiation experiments. They provide guidelines for matching the optical components to the source and to the experiment, and for checking the physical meaning of the more detailed results obtained by subsequent ray-tracing calculations. Phase-space diagrams have been used extensively to describe synchrotron radiation experiments by plotting an angular variable against a positional one with the possibility to add the energy in a third dimension. For neutron scattering, the traditional method consists in parallel representations, in reciprocal and in real space, that can also be considered as another kind of phase-space diagram. In this paper, we show the specific advantages and the complementary character of the above diagrams. The representation of several optical elements and their effect on beam transformation is given first individually and then for some arrangements of two or more beam-defining devices. Finally, a beamline is described and optimized as a demonstration of the usefulness and the limits of these graphic methods.
Electron beam and magnetic field mapping techniques used to determine field errors in the ATF torsatron
Authors: Colchin R. J. , Anderson F. S. B. , England A. C. , Gandy R. F. , Harris J. H. , Henderson M. A. , Hillis D. L. , Kindsfather R. R. , Lee D. K. , Million D. L. , Murakami M. , Neilson G. H. , Saltmarsh M. J. , Simpson C. M.
Published: July 2002

The beam from an electron gun was used to trace flux surfaces in the Advanced Toroidal Facility (ATF) torsatron. The ATF magnetic field was run steady state at 0.1 T, and the electron beam was detected optically with an image-intensified, solid-state camera when it impinged on a phosphor-coated screen. Closed flux surfaces and islands at several low-order resonances were observed. The largest island, located at the ι= 1/2 surface, was from 5 to 6 cm in width, and its presence implied the existence of magnetic field errors. To determine if these error fields could be traced to small misalignments of the magnetic coils, a device capable of accurately measuring the radial and vertical magnetic field components of individual coil sets was placed in the center of ATF. This device allowed for a determination of the precise location of each of the coils that make up the ATF coil set. No significant coil misalignments were found. A further investigation of the coil configuration led to the identification of dipole fields in the helical field coil leads as the source of the field errors. The techniques developed in making these measurements are described in the text.
Low dead volume piezoelectric valve
Authors: Marinescu Dan
Published: July 2002

By using a capillary tube as both seat and exit duct in a commercial piezoelectric valve, the outlet dead volume is reduced by more than three orders of magnitude. The described modification also makes a separation between the gas flow and the actuator chamber which considerably extends the choice of working gases.
Infrared real-time-normalized photopyroelectric measurements of crystalline germanium: Instrumentation and spectroscopy
Authors: Christofides Constantinos , Mandelis Andreas , Ghandi Kamyar , Wagner Robert E.
Published: July 2002

An infrared photopyroelectric spectrometer with real-time spectrum normalization capability measurements has been optimized and used for the spectroscopy of crystalline Ge, performed as a function of wavelength (1700–1960 nm) and modulation frequency (0.5 to 400 Hz), to determine the optical absorption and nonradiative quantum efficiency spectra. High-modulation-frequency (thermally thick limit: f > 40 Hz) data yielded the optical absorption-coefficient spectrum, while at low modulation frequency (thermally thin limit: f<15 Hz) the nonradiative quantum efficiency spectrum was obtained self-consistently by substitution of the experimental optical absorption coefficient spectrum to the thermally thin limit photopyroelectric theory. The experimental results will be discussed in the light of an existing photopyroelectric model [A. Mandelis and M. M. Zver, J. Appl. Phys. 57, 4421 (1985)] and in terms of well-established semiconductor germanium physics.
Neutron calibration techniques for comparison of tokamak results (abstract)
Authors: Strachan J. D. , Adams J. M. , Barnes Cris W. , Batistoni P. , Bosch H.-S. , Brzosko J. S. , England A. C. , Fiore C. L. , Granetz R. S. , Hendel H. W. , Hoenen F. , Jarvis O. N. , Jassby D. L. , Ku L. P. , Liu P. , Martin G. , McCauley S. , Motley R. W. , Nishitani T. , Robouch B.V. , Saito T. , Sasao M. , Stav R. D. , Taylor P. L.
Published: July 2002

A workshop on 1–3 August 1989 reviewed the techniques, uncertainties, and experiences of neutron calibration on PLT, TFTR, JET, Tore Supra, JT-60, JIPPT-IIU, Alcator C-Mod, ATF, FT, ASDEX, Textor, and DIII-D. In the summary session, the workshop participants discussed possible consensus neutron calibration techniques appropriate to D-D plasmas in tokamaks. The application of such techniques would facilitate a more accurate comparison of neutron yields from different devices, and also allow new calibration techniques to relate their precision to a reference value. General agreement was reached on the suitability of two techniques: (1) a 252Cf source calibration of epithermal neutron detectors, and (2) threshold neutron activation of Ni foils placed vertically above or below the plasma. This paper will present details on detector positioning, neutron transport calculations, and interlab normalization needed to accomplish the standardized calibration using a Cf neutron source.
Proof-of-principle test of a Thomson scattering alpha particle diagnostic (abstract)
Authors: Hutchinson D. P. , Richards R. K. , Hunter H. T. , Bennett C. A.
Published: July 2002

A CO2 laser Thomson scattering diagnostic is being developed for the measurement of high-energy alpha particles in a burning plasma. To evaluate the system, a proof-of-principle test is presently in progress. The goal of the experiment is to perform small-angle scattering measurements on a nonburning plasma in the Advanced Toroidal Facility (ATF). In the absence of fusion-product alpha particles, measurements are being made on the smaller scattered signal from the background electrons in the plasma. Preliminary results, indicating receiver calibration and stray light measurements, and calculations of expected scattered power based on measured density and temperature profiles in ATF will be presented. This research was sponsored by Office of Fusion Energy, U. S. DOE, under contract No. DE-AC05-84OR21400 with Martin Marietta Energy Systems, Inc.
Constraints on escaping alpha particle detectors for ignited tokamaks (abstract)
Authors: Zweben S. J. , Boivin R. , Liew S. L. , Owens D. K. , Strachan J. D. , Ulrickson M.
Published: July 2002

Several modifications to existing escaping alpha scintillation detectors in TFTR will be needed before they could be used on ignited tokamaks such as CIT or ITER. The main difficulties are the large heat flux at the desired detector locations and the accumulated radiation damage to the scintillator itself. Constraints imposed by these problems can probably be overcome by using remotely movable (and removable) detectors.
Test particle diagnostics for high-temperature plasmas (abstract)
Authors: Skiff F. , Boyd D. A.
Published: July 2002

A new type of tagging diagnostic which employs ballistic modes to follow particle orbits is introduced. ‘‘Vlasov tagging’’ is accomplished by the selective excitation of small amplitude ballistic modes either by the resonant Landau or cyclotron resonant absorption of incident waves or by spatially localized nonresonant nonlinear interactions. Subsequent detection of ballistic modes may be accomplished by laser fluorescence (for ions) or by changes in the transmission of a probe beam. Results demonstrating ion Vlasov tagging will be presented. Electron Vlasov tagging appears most attractive by means of the cyclotron resonance. Transmission measurements with a search beam may be made at the harmonics. Vlasov tagging may be used to directly measure transport in both velocity and coordinate space.
Quantitative measurement of the stress transfer function in nickel/polyimide thin film/copper thin film structures
Authors: Schadler L. , Noyan I. C.
Published: July 2002

The stress transfer behavior in multilayer thin film structures (nickel/polyimide/copper) was measured using x-ray stress analysis. Copper was deposited in various line lengths, and the stress/strain transferred from a loaded Ni substrate to the Cu thin film was measured as a function of line length. It was found that there is incomplete strain transfer from one layer to another, and that the shape of the stress transfer function is similar to that predicted by the shear lag model.
Feasibility study of bulk ion temperature measurements on JET by means of collective scattering of gyrotron radiation
Authors: Orsitto F.
Published: July 2002

The proposed JET fast ion and alpha particle diagnostic, based on collective scattering of gyrotron radiation, will also give information about bulk plasma ion velocities. Results of calculations for impure deuterium plasmas are presented which indicate that good signal-to-noise ratios will be achieved in recording the bulk ion feature. The effects of magnetic field, turbulence, and multimode gyrotron radiation are considered briefly.
Ion temperature measurements by means of Rutherford scattering at TEXTOR
Authors: van Blokland A. A. E. , Barbian E. P. , Grimbergen T. W. M. , Oyevaar Th.
Published: July 2002

Rutherford scattering of neutral particles from a diagnostic beam is a method for local and time-resolved measurements of the ion temperature. Energetic helium atoms are injected into the plasma and become elastically scattered by plasma ions. Energy and momentum conservation determine the energy distribution of the scattered particles. The ion temperature can be deduced from the width of this distribution. This paper deals with the Rutherford scattering diagnostic which has been recently installed at TEXTOR. The diagnostic consists of two main components: a monoenergetic probing beam (He, 35 keV, 10 mA) injected into the plasma and a time-of-flight analyzer for the determination of the energy of scattered particles. The scattering angle can be adjusted in the range from 3° to 8°.
X-ray imaging of impurity transport (abstract)
Authors: Petrasso R. D. , Wenzel K. W.
Published: July 2002

The last decade has seen increasing application of x-ray imaging arrays for the quantitative study of impurity transport in magnetically confined plasmas. This is partly a result of their high spatial (≲1 cm) and temporal resolution (≲1 μs) as well as reasonably accurate (optically thin) models of the plasma x emissions. We briefly review some of these results, some near-term applications, and x-ray detector modifications needed for the imaging of high-temperature plasmas (≥5 keV). This work was supported by U.S. Department of Energy contract No. DE-AC02-78ET51013.
Development of a metallic shield for the TFTR rf probe diagnostic
Authors: Greene G. J.
Published: July 2002

The ceramic shields covering rf probes located on the bottom of the TFTR vessel sustained damage even after 3 cm retraction from the plasma, while those located on the top of the vessel remained unharmed after two years of exposure. New, metallic, optically opaque shields to replace the ceramics were developed, tested, and installed at two locations. The double-layer, slotted shield was designed to maximize rf transparency to both transverse components of the incident field. rf characteristics are presented, and thermal and stress considerations are discussed.
Measurement of tokamak poloidal field by spectroscopic observation of a neutral helium beam
Authors: Jobes F. C. , Redi M. H. , Roquemore A. L. , Schilling G. , Stratton B. C. , Synakowski E. J.
Published: July 2002

The pitch angle of the magnetic field of a tokamak can be determined by observing the light emitted by He+ ions injected into the plasma by a perpendicular He0 beam. These ions will orbit in small circles near the ionization point. The observed spectrum of a He ii line (4686 Å) has a very wide and distinctive shape; the width of the spectrum depending only upon the particle velocity and the geometry of the view point. The geometry depends upon both the pitch of the poloidal field and the choice of observation point. Preliminary observations of a 60 keV He0 beam show that the above effect indeed exists, and is intense enough to be seen all the way into the center of the plasma (even in a helium plasma), and that pitch measurements derived from the observed widths in the outer part of the plasma agree with the pitch derived from magnetic measurements of q(a).
Impulse generation by superintense ultrashort laser pulses as an energy absorption diagnostic (abstract)
Authors: Harrach Robert J.
Published: July 2002

Impulse generation by superintense (I≳1016 W/cm2) ultrashort-duration (τ≲100 fs) laser pulses interacting with solid targets in vacuum, and the possible diagnostic utility of impulse or shock pressure measurements in this regime, are examined by means of computations and simple theory. Easily observable impulse levels, up to several hundred dyne s/cm2, should be attainable with present lasers. However, the anticipated rapid attenuation of these high-pressure, short-duration shocks in propagating through the target material will pose a significant challenge for target design. When combined with other diagnostic information (e.g., pulse reflectivity, ablation plasma properties, and plasma radiation emission) and a comprehensive modeling capability, we show that impulse or shock pressure data can clarify the laser/target interaction physics, especially regarding the energy absorption efficiency and depth, and the rate energy diffuses into the target during the brief irradiation time. This work was supported by U.S. DOE under contract W-7405-ENG-48 by LLNL.
Text-upgrade 2 MeV heavy ion beam probe (abstract)
Authors: Ouroua A. , Hickok R. L. , Crowley T. P. , Connor K. A. , Lewis J. F. , McLaren P. E. , Schatz J. G. , Schwelberger J.
Published: July 2002

A unique 2 MeV heavy ion beam probe diagnostic system, presently under construction, with two injection lines and two energy analyzers will be used to measure the space potential as well as density, electrostatic (and possibly magnetic) fluctuations, and average wave numbers in the TEXT upgrade tokamak. The capabilities of the 2 MeV beam include a good penetration of the TEXT-U magnetic fields (up to 2.2 T) and access to most of the plasma cross section (90%) including all null points (during divertor operations), the top, bottom, and outside edges. We plan to use parallel plate electrostatic energy analyzers which require that 400 kV be held on a large electrode across a 20 cm vacuum gap. Feasibility tests of such analyzers are under way. Progress of construction and testing of different parts of the system are reported. A description of the 2 MeV heavy ion beam probe system and a discussion on the measurements to be performed will be presented. This work was supported by DOE.
Neutral beam probe for edge plasma analysis in tokamaks (abstract)
Authors: Saravia E. , Castracane J. , Woo J. T.
Published: July 2002

A neutral beam diagnostic system has been designed to do simultaneous space potential and density measurements in the tokamak plasma edge to complement existing probe diagnostics. Rapid radial profiles are possible by computer control of the energy and the injection angle of the neutral beam. A particular application under consideration is the Tokamak de Varennes, which is presently being upgraded to operate either as a limiter or as a divertor machine. In this application, an ion gun is used to produce a Tl+1 beam that can be steered radially and toroidally to scan the plasma edge. The ion beam is neutralized downstream in a charge-exchange cell and the resulting Tl neutral beam is injected through a side port into the plasma. Singly charged Tl ions produced in the plasma exit through a top port of the tokamak and are collected by an electrostatic energy analyzer. Numerical simulations of the trajectories show that beam energies between 40 and 55 keV are sufficient to probe the plasma edge radially from 23 to 29 cm with a few millimeters resolution. The use of a neutral beam allows measurements in a tokamak edge plasma with BT∼1.0 T with a reduction in beam energy by more than a factor of 3 compared to the use of ion beams. Details of the beam probe hardware and the Tokamak de Varennes application are presented.
Biased probe for plasma diagnostics in spherical electrostatic inertial plasma confinement
Authors: Gu Y. B. , Miley G. H.
Published: July 2002

The biased probe, as a unique extension of the Langmuir probe, offers several advantages in measuring the charged-particle flux versus position in a beam-dominated plasma such as encountered in the spherical electrostatic inertial confinement (SEIC) device. The probe operates in a non-Maxwellian and locally non-neutral plasma, where the Debye length is large compared to the probe itself. Its conical particle acceptance extension minimizes the measurement error caused by the distortion of the SEIC potential structures. Either the ion or electron flux can be measured using the proper bias on its inner collecting element.
Extreme ultraviolet amplifier experiments at the LLNL Nova two-beam facility (abstract)
Authors: Shimkaveg G.
Published: July 2002

We present the results of our most recent experiments on extreme ultraviolet (XUV) and soft x-ray amplifiers conducted at LLNL’s Nova laser two-beam facility. Of particular interest are high-Z nickel-like amplifiers which have demonstrated gain at photon energies above the carbon K edge, sub-Doppler-resolution spectra of amplified lines from long selenium amplifiers, absolutely timed streaked XUV and x-ray spectra from germanium amplifiers at a variety of L-shell ionization states, and gain measurements from neon-like silver amplifiers. The array of spectroscopic instruments utilized in these experiments will be described in detail. This work was performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under contract W-7405-ENG-48.
High-speed photoconductive device development for laser fusion experiments on Phebus facility (abstract)
Authors: Bourgade J.-L. , Garconnet J-P. , Nail M. , Cuzin M.
Published: July 2002

The goal of laser fusion experiments conducted with the most powerful European laser Phebus is to study deuterium tritium mixture implosions close to thermonuclear conditions. For this purpose we develop very high speed (less than 100 ps) photoconductive devices able to measure the time behavior of the thermonuclear neutron burst or x-ray emission. Some test results on these specific detectors will be presented.
Resolution limits of transmission diagnostics due to nonlocal wave absorption
Authors: Kirkwood R. K.
Published: July 2002

The resonance between wave phase velocity and particle momentum used in electron cyclotron diagnostics requires that particles travel a distance in the wave field. It is shown that gradients in wave number consistent with the geometric optics limit can cause a substantial broadening of this resonance and a technique for calculating absorption in this case is developed. The result is a fundamental limit to the resolution in momentum space attainable with these techniques which is calculated for a recent wave transmission experiment.
A new method for estimating and identifying systematic error in Thomson scattering diagnostics
Authors: Fajemirokun H. , Gowers C. , Nielsen P. , Salzmann H. , Hirsch K.
Published: July 2002

A method has been developed to identify and estimate systematic error in the calibration of Thomson scattering systems. The basis of the technique is an iterative recalculation of electron temperature using successively more self-consistent calibrations. A computational method was developed to calculate from a large dataset a calibration correction factor for each channel. The correction factor was then applied and the fitting routine rerun on the whole dataset with the new calibration factors. The resulting frequency distribution of chi-squared values was close to the theoretical distribution while the calculated electron temperatures were changed by only 1 to 2%. The technique succeeded in identifying and quantifying errors in a dataset known to be of poor quality.
Real-time density computer for two-color interferometers
Authors: Innocente P. , Martini S. , Corradi G. , Fadin G. , Fasoli C. , Garonzi G.
Published: July 2002

An electronic circuit has been developed which performs real-time density computation on the quadrature phase signals of the two-color CO2 interferometer for the RFX experiment. Cartesian to polar coordinate conversion is obtained by a look-up table, and a ‘‘phase fine tuning’’ table allows us to introduce corrections to the systematic phase nonlinearity errors of the interferometer, by which the overall accuracy of the diagnostic is made better than 1°, equivalent to a line density of 6×1017 m−2 for a CO2 system. The phase total range is ±512 fringes and the maximum allowed rate of change is 125×103 m−2 s−1 equivalent to a density rate of change of 2×1025 m−2 s−1. A real-time signal proportional to the plasma density to be used for density feedback is provided by a 50 kHz, 12 bit converter. The system is a triple width CAMAC module and the two-color wavelength ratio is remotely programmable as a 20 bit constant, hence it is suitable in general for any two-color interferometer. The density data are also stored with a sampling rate of 10–250 kHz in a 128 K×24 bit memory buffer, which is interfaced via a CAMAC bus to the data acquisition system.
Advanced CCD imager technology for use from 1 to 10 000 Å
Authors: Twichell J. C. , Burke B. E. , Reich R. K. , McGonagle W. H. , Huang C. M. , Bautz M. W. , Doty J. P. , Ricker G. R. , Mountain R. W. , Dolat V. S.
Published: July 2002

We have developed a low-noise, high-sensitivity charge-coupled-device (CCD) technology for imaging applications extending from the soft x-ray (1 Å) to the near-infrared (10 000 Å) regimes. We have also developed a fabrication technology for making back-illuminated versions of these devices with quantum efficiencies as high as 90% from 5000 to 7000 Å. Our efforts have focused on two devices, a 64×64 pixel back-illuminated imager with two output ports that operates at 2000 frames per second with 23 electrons read noise, and a larger device, with 420×420 pixel format, designed for lower frame rates with noise as low as 1.5 electrons and used at visible, UV, and x-ray wavelengths. Applications to plasma diagnostics include Thomson scattering and high-frame-rate imaging in the visible, as well as x-ray imaging and bolometry.
Calibration of bremsstrahlung prefogged Kodak RAR 2492 film
Authors: Gorzen D. F. , Armentrout C. , Burek A. , Bird R. , Geddes J. , Gerber G. , Rockett P. D.
Published: July 2002

High-energy background radiation from PBFA II at Sandia National Laboratory introduces uncertainty regarding the effect of background fogging on the sensitivity of the x-ray film at soft x-ray energies. We have performed a calibration to determine how the sensitivity of the Kodak RAR 2492 film is affected by high-energy background radiation. To simulate the background radiation the film was fogged to various densities using a 10 keV bremsstrahlung spectrum. The film was then exposed to soft x-ray emission lines of Al Kα and Ti Kα selected by Bragg reflection from an electron bombardment source. The intensity of the x-ray flux was continuously monitored with a Si(Li) detector to eliminate error due to drift of the x-ray source’s intensity. A microdensitometer with matched objectives was used to find the specular density of the exposed film. The results of the calibration are presented in the form of D vs log l for the various densities of the bremmstrahlung prefog exposures.
Space- and time-resolved McPIGs for multiterawatt Z-pinch spectroscopy
Authors: Nash T. , Deeney C. , LePell P. D. , Prasad R. , Krishnan M.
Published: July 2002

A microchannel plate intensified grazing incidence spectrometer (McPIGs) produces three spatially resolved 10 ns time frames of XUV spectra emitted by multiterawatt Z pinches. As Z pinches are copious radiators at these wavelengths, the McPIGs is well suited to diagnose these plasmas. Data obtained in the course of research on plasma radiation sources and x-ray lasers will be presented, where the time-resolved spectra are radially resolved to give radial line profiles and to measure Doppler splitting as a velocity diagnostic.
Test of an anomalous electromagnetic effect
Authors: Bartlett D. F. , Maglic Steven
Published: July 2002

Sansbury has suggested and measured a new electromagnetic attraction between a current and a static charge. We have searched in vain for this interaction. The sensitivity of our measurement is roughly 5 times higher than that of the experiment in which the effect was originally seen.
Temperature-compensated composite thin-film resistors
Authors: Steinbrüchel Ch. , Razborsek A.
Published: July 2002

A method for producing temperature-compensated thin-film resistors is described that involves a conductor with negative temperature coefficient of resistance (TCR) partially overlayed by another conductor with positive TCR. The temperature dependence of the resistance of the composite film is evaluated to second order in temperature. It is found that when the geometry and the materials parameters of the composite film are chosen such that the first order TCR is zero, the second-order coefficient is not negligible for temperature variations of practical importance. The model predictions are in good agreement with experimental results using TaN and Ni as the two conductors, in which case the second-order coefficient turns out to be about 5×10−7 °C2. This also means that a first-order TCR of zero can only be achieved at a specified temperature.
Accessory for high-sensitivity spectrometry of strongly absorbing and air-sensitive liquid samples under vacuum
Authors: Lunelli Bruno
Published: July 2002

A simple accessory of a previously reported optical absorption cell allows some operations on the sample, and spectrometric measurements with the cell and sample under vacuum to be performed. It enables one to handle extremely air-sensitive specimens, and to get easily and reproducibly liquid films of thickness down to 6 μm. Consequently it is possible to record the entire IR spectrum of a solute in a single solvent and to use very strongly absorbing solvents, water included.
High-precision optical reflectometer for the study of semiconductor materials and structures
Authors: Bell M. I. , McKeown D. A.
Published: July 2002

The design and performance of a high-precision optical reflectometer are described. This instrument has been optimized for measuring the specular reflectivity of thin films and multilayer structures of interest in semiconductor technology. Its design emphasizes high spectral and spatial resolution, photometric accuracy, and stray light rejection. Use of a spectrometer drive linear in wavenumber (energy) and a flexible data acquisition system facilitates data analysis. The performance of the reflectometer is demonstrated using a set of specimens consisting of silicon-dioxide layers on silicon substrates for which the oxide thicknesses had been determined by ellipsometry. Excellent agreement is obtained between the thicknesses derived from the reflectivity spectra and those determined ellipsometrically.
A data acquisition and display system for spin-polarized scanning electron microscopy (spin SEM)
Authors: Matsuyama Hideo , Koike Kazuyuki
Published: July 2002

A new data-acquisition and display system has been developed for magnetic domain observation using spin-polarized scanning electron microscopy. The system is composed of 32 frame memories (512×512×16 bit), an image processor with two high-speed digital signal processors, and a 1280×1024 pixel color monitor. It has the following capabilities: electron probe scanning control; high-speed (21 s/512×512 pixel image) computing and recording of two components (Px, Py) of secondary-electron spin polarization; computing and displaying the averaged Px and Py obtained with repetitive scanning; domain image formation for an arbitrary component from (Px,Py) data (8 s/512×512 pixel image); variable speed scanning to obtain a homogeneous quality image in minimum time, even when secondary-electron intensity varies due to surface inclination; two-dimensional display of polarization vector distribution; and angle image of the magnetization direction in both black and white and color representation.