bluuebunny/crossref_metadata_2025 huggingface dataset:
Geometrical and wave-optical phase-space matching between undulator radiation and grating monochromators
Authors: Miyahara Tsuneaki
Published: July 2002

Matching between undulator radiation and grating monochromators is discussed in terms of geometrical and wave optics. It is shown that slit diffraction plays an important role which is described by the relationship between observation and uncertainty of light. A design principle of an achromatic zone plate for undulator radiation is presented to obtain white radiation on the entrance slit.
Double-crystal monochromator for a PF 60-period soft x-ray undulator (abstract)
Authors: Ishikawa T. , Maezawa H. , Nomura M. , Ando M.
Published: July 2002

Since undulator light is sharply collimated itself, it can be effectively monochromatized by a perfect crystal. An x-ray double-crystal monochromator with a fixed exit has been designed and built for the use of undulator light from a 60-period undulator at Photon Factory (beamline 2A). Available Bragg angle ranges from 7° to 80°. Angle scan is made by means of a goniometer outside the vacuum chamber, with the finest step of 0.1 arcsec. Magnetic fluid is used as the vacuum seal of the feedthrough. The fixed exit beam position is kept by translating the second crystal along the two mechanical guides: one for normal and the other for parallel to the crystal surface. Adjustment of the parallelity of two crystals is made manually with flexible wires. Since a total power in the central coherent portion which is limited by a 1×1-mm2 slit is not so much, a stable operation is possible without cooling the crystal. Currently, InSb (111) reflection is used. The diffracting planes of the first cyrstal is 1° off from the surface and the second is the symmetric reflection. At its fifth harmonics, brilliant undulator light of approximately 1012 photons/s mm2 with 1-eV energy resolution is available (E=2 keV).
Experimental evaluation of thermal deformation effects of SiC mirror surfaces irradiated by undulator radiation
Authors: Maezawa Hideki , Sato Shigeru , Iijima Akio
Published: July 2002

Exposure tests were made on newly developed large-sized SiC mirrors made of recrystallized and sintered SiC substrates with a surface roughness of ≊5 Å (rms) using undulator radiation with a total power of up to 1 kW and central peak-power density of 400 mW/mm2. The mirrors withstood the long-term exposure even in a horizontal deflection arrangement. The maximum slope and swell of thermal deformation were observed as 13 mrad and ≊39 μm, respectively, and the surface temperature at the mirror center was raised up to ≊240 °C. No deterioration in quality was observed in the intensely irradiated area on the mirror surfaces.
A simple monochromator based on x-ray multilayer mirrors
Authors: Smith A. , Riedel C. , Edwards B. , Savage D. , Lai B. , Ray-Chaudhuri A. , Cerrina F. , Lagally M. G. , Underwood J. , Falco C.
Published: July 2002

A simple two-mirror monochromator based on multilayer films has been developed as a part of a reflectometer under construction at the University of Wisconsin Synchrotron Radiation Center. Measurements of the performance of this monochromator and the characterization of a typical component mirror have been made. At AlKα the monochromator has a peak transmission of 9%, which is 55% of the theoretical value. Its resolution, λ/Δλ, is 35.
Focusing of synchcrotron radiation by a multilayer-cylindrical tungsten-carbon Bragg reflector
Authors: Takenaka Hisataka , Muramatsu Yasuji , Takaoka Hidetoshi , Ishii Yoshikazu , Hashizume Hiroo
Published: July 2002

A curved Bragg reflector for focusing synchrotron radiation has been fabricated using a recently developed magnetron sputtering equipment. The Bragg reflector consists of alternate thin-film layers of  W and C deposited on a cylindrical substrate of 46 mm in radius of curvature, covering a 50×50-mm2 area. The focusing properties of the Bragg reflector were examined at beamline 15B of the Photon Factory. The focused beam intensity per unit area was six times higher than the unfocused beam, and the observed variations in beam size and shape with optical distances showed qualitative agreement with ray-tracing calculations.
Two-mirror device for harmonic rejection
Authors: Sainctavit Ph. , Petiau J. , Manceau A. , Rivallant R. , Belakhovsky M. , Renaud G.
Published: July 2002

A new mirror device has been implanted on the station EXAFS IV at LURE-DCI. This harmonic rejection assembly is made of two glass mirrors which ensure an output beam parallel to the entrance one. The characteristics of this efficient easy operating device have been measured and are discussed.
Beamline for the characterization of radiation transfer standards ranging from 200 to 2000 eV
Authors: Thornagel R. , Kühne M.
Published: July 2002

A novel soft x-ray beamline equipped with a specially designed Rowland circle monochromator has been installed at the laboratory of the Physikalisch-Technische Bundesanstalt (PTB) at the Berliner Elektronenspeicherring-Gesellschaft für Synchrotronstrahlung mbH (BESSY) for spectral radiant power determination of radiation sources and for spectral responsivity calibration of detectors in the photon energy range from 200 to 2000 eV. The mechanical and optical performances are presented, together with data on output flux and resolution of the monochromator.
Compact high flux photon beam position monitor
Authors: Johnson E. D. , Oversluizen T.
Published: July 2002

We have developed a new compact water-cooled beam position monitor for use at the NSLS X-13 Insertion Device Development beamline, currently fitted with a high-power, high-brightness soft-x-ray undulator. We describe the novel geometry of the monitor and present the results of tests which explore its sensitivity, stability, and linearity. These results were obtained on the NSLS Beamline Research and Development white light beamline, U14B, on the VUV ring and suggest that beam position monitors of this type might be adapted to other facilities with similar spectral characteristics.
Measuring devices at BESSY for stored beam currents ranging from 0.8 pA to 1 A
Authors: Ulm G. , Hänsel-Ziegler W. , Bernstorff S. , Wolf F. P.
Published: July 2002

The electron storage ring BESSY is a primary radiometric standard where the photon flux can be adjusted within a dynamic range of 12 orders of magnitude via the stored beam current IR. We describe the three different devices installed at BESSY to perform the measurement of the absolute beam current within the full range. Two toroidal dc beam current transformers are used in the range 0.5 mA<IR<1 A. The measurement of lower beam currents is based on monitoring the emitted white synchrotron radiation flux. If less than 1000 electrons are stored (IR<0.8 nA) then electron counting is performed. In the intermediate range (0.8 nA<IR<1 mA), IR is determined via windowless photodiodes which have been calibrated against the transformers and against the single electron measurements which allow a check of the linearity of the detectors. We report on the calibration procedure, on influences of changes of the source, and on the resultant uncertainties.
Insertion devices at the Photon Factory: Present status and future development (invited)
Authors: Kitamura Hideo , Yamamoto Shigeru , Kamada Susumu
Published: July 2002

Since the first operation of the Photon Factory ring in the beginning of 1982, we have constructed seven insertion devices of various types: a superconducting wavelength shifter; two undulators, including a multiundulator; two multipole wigglers; and two multipole wigglers for circularly polarized synchrotron radiation sources. The performances of those devices are summarized, and the possibilities of the use of the TRISTAN main ring as an advanced synchrotron radiation source are presented.
Wide range temperature compensated cryogenic scanning tunneling microscope
Authors: Burger Jurgen , Meepagala S. C. , Wolf E. L.
Published: July 2002

We describe a compact scanning tunneling microscope using piezoelectric bimorph elements to achieve a large scanning area of 20 μm2 at 4.2 K. This instrument provides inherent temperature compensation, compatibility with a high magnetic field environment, and a novel means of rough sample–tip (z) adjustment.
Performance of a high-energy-resolution, tender x-ray synchrotron radiation beamline (invited)
Authors: Cowan P. L. , Brennan S. , Jach T. , Lindle D. W. , Karlin B. A.
Published: July 2002

Beamline X-24A at the National Synchrotron Light Source was designed for optimal performance in the x-ray spectral region 500–5000 eV. This choice of energy range placed a number of constraints on the beamline design, requiring a crystal monochromator in a windowless UHV environment. Although this increased the complexity of the design, there were compelling scientific reasons for our desire to work in this range. In addition to tunability over the selected energy range, a primary goal was to obtain the highest possible energy resolution in the primary beam. We have achieved incident energy resolution significantly better than the typical core-level lifetime broadening for this energy range. This has permitted studies of processes that are not broadened by lifetimes, such as resonant scattering and back-reflection x-ray standing-wave effects. In addition to high resolution, it was designed to collect and focus as much flux as possible from the bending magnet source.
Three-axes sample manipulator for surface-science experiments in ultrahigh vacuum
Authors: Dai Y. , Li H. , Jona F.
Published: July 2002

Additions to commercially available manipulators are described which allow independent rotations of a sample in ultrahigh vacuum around three mutually perpendicular axes, as well as in situ adjustments of the sample orientation with respect to any of the three rotation axes. The additions allow also the interchange of three different samples in situ, with no need for breaking the vacuum in the experimental chamber. The modified manipulator has been successfully tested in experiments involving low-energy electron diffraction and photoemission with synchrotron light for either s or s-p polarization geometries.
Exploitation and development of particle beams at Culham Laboratory (invited)
Authors: Green T. S.
Published: July 2002

Particle beams have been developed at the Culham Laboratory for many years, mainly for application to the production of high-temperature plasmas. These developments included demonstration of fundamental plasma physics such as particle trapping, heating, and current drive coupled to continuous advances in the physics and technology of ion beam production and transport. This work reached its zenith in production of multimegawatt high-proton fraction sources for the neutral beam injectors for JET. A new initiative is now coming for the development of negative ion based injectors. This wide ranging base of physics and technology provided a springboard for exploitation of beams in areas other than fusion. The last few years have seen increasing R and D at Culham in areas such as space, defense, surface treatment, and implantation. The applications have ranged from beams of H+ or H− to Xe+, from currents of less than 1 mA to currents of amperes and from energies of 50 eV to energies of hundreds of kilovolts. This paper describes some examples of these activities and relates them to the physics and technology base. Future areas of interest are also discussed.
Generation of lithium ions for ion sources using the 670.8-nm resonant transition of lithium
Authors: Tisone G. C. , Bieg K. W. , Dreike P. L.
Published: July 2002

This article describes research on two methods of producing a 1-mm-thick singly ionized lithium plasma with an areal density up to 1×1016 cm−2. The first method relies on forming a 1-mm-thick layer of lithium vapor by ohmically pulse heating a thin film of a lithium bearing compound. The vapor is then ionized by a 670.8-nm laser light, the first resonant transition of lithium. Small scale experiments described here demonstrated average electron densities up to 5×1016 cm−3, using laser energy densities as low as 20 mJ/cm2 . The second method is direct heating, evaporation, and ionization of thin lithium bearing films on thermally insulating substrates using 670.8-nm laser light. The minimum tuned laser energy density for producing a plasma was 0.15 J/cm2 . These results are compared with measurements at other wavelengths and pulse lengths, and with models of the heating and ionization.
Formation of cathode plasma in a magnetically insulated high-current diode to generate negative hydrogen ions with current densities up to 200 A/cm2
Authors: Papadichev V. A. , Pikuz S. A. , Shelkovenko T. A.
Published: July 2002

High-power pulsed beams of neutral atoms may be useful for CTR as alternative ways to drive the target. They can be obtained by stripping high-current negative ion beams. Experiments are described on cathode plasma formation with sufficient negative hydrogen ion concentration to obtain H− current density up to 200 A/cm2. The plasma was formed by a surface discharge on a dielectric initiated by a bipolar prepulse or by laser illumination. It is shown that the electron current density flowing through the cathode plasma needs to be greater than 104 A/cm2 to create H− continuously in the outer region of the plasma and thereby produce H− current densities up to 200 A/cm2.
Plasma parameter characterization of a tandem multicusp ion source operating in H2 and D2
Authors: Mullan A. A. , Graham W. G.
Published: July 2002

The basic plasma parameters of a tandem multicusp ion source operating with hydrogen and deuterium gas have been measured and are compared. It is found that there is little variation in the electron temperature or electron energy-distribution function; however, both the electron density and plasma potential are consistently higher when operating with D2 rather than H2 gas. The experimental results are in general agreement with simple models of the discharge.
Hollow anode ion source
Authors: Miljević Vujo I.
Published: July 2002

A new type of cold cathode ion source, based on a hollow anode discharge in a magnetic field, is presented. The influence of the magnetic field is very strong: It is possible to considerably change the ion current by some slight changes of the magnetic field.
Analysis of the ion beam obtained from a small multicusp ion source
Authors: Langbein K. , Riehl G. , Klein H. , Leung K. N. , Walther S. R. , Keller R.
Published: July 2002

The small multicusp ion source developed at Lawrence Berkeley Laboratory (LBL) has been equipped with a low voltage ratio, single aperture extraction system. The influence of the potential of the plasma electrode and of a dipole filter field on the beam emittance are measured. A simple method to reduce hash is suggested. The aim of these investigations is to produce nitrogen ion beams with a high atomic ion fraction and a low emittance as required for a RFQ-accelerator, which will be built for ion implantation.
Superconducting 14-GHz ECRIS at Jülich
Authors: Beuscher H.
Published: July 2002

A two-stage electron cyclotron resonance source with a superconducting magnet system and a microwave frequency of 14.4 GHz for both plasma stages is in operation at the Jülich cyclotron since 1986. After same upgrading of the first plasma stage it can produce more than 1 μA of fully stripped Ne, 0.8 μ of 40Ar16+ and of 84Kr25+ ions in continuous wave operation.
An ECR ion source with high proton ratio
Authors: Ishii Shigeyuki , Amemiya Hiroshi
Published: July 2002

A highly ionized hydrogen plasma has been obtained by ECR in the minimum B field composed of an octupole and mirror fields. The beam current density extracted from it by a high voltage of 10 kV is 65 mA/cm2, while the saturation ion current density is 500 mA/cm2, and the ratio of the proton to the total components is as large as 0.9. Calculation based on particle balance equations explains the high proton ratio as well as the dependence of each ion component on the plasma parameters.
The effects on ion beam optics of a spherical aberration at the plasma boundary
Authors: Surrey E. , Holmes A. J. T.
Published: July 2002

Experimental data show that the minimum divergence of a positive helium ion beam does not occur at the beam perveance predicted by linear ion optics. A model is presented that introduces a third-order term into the ion optics equations, in the manner of a spherical aberration to the plasma boundary. Values of the aberration coefficient C are calculated from the data and it is shown that C∝(a/d)−1.9, where a/d is the aspect ratio of the accelerator. The contour of the plasma boundary is plotted and it is shown that the aberration leads to a flattening of the boundary at the extremes of the extraction aperture.
Inverse Poisson transformation and shot noise filtering
Authors: Qian Hong
Published: July 2002

A matrix method is introduced to invert the Poisson transformation that characterizes the effect of shot noise on optical measurements. This method offers the possibility of removing the effects of shot noise from these measurements. The theoretical limitations of the transformation and an algorithm for evaluation of the transformation matrix with maximal precision are discussed.
An ultrahigh vacuum scanning tunneling microscope for surface science studies
Authors: Zeglinski D. M. , Ogletree D. F. , Beebe T. P. , Hwang R. Q. , Somorjai G. A. , Salmeron M. B.
Published: July 2002

We describe the construction and operation of a scanning tunneling microscope designed in our laboratory that fits standard ultrahigh vacuum (UHV) systems as an add-on instrument. Sample motion is accomplished by electrical signals, eliminating mechanical feedthroughs. Samples are easily transferred to a modified Varian manipulator for heating and interfacing with other surface science techniques. In situ tip replacement and sample transfer in and out of the UHV system is also possible.
Autocorrelation and crossed-sightline correlation of ECE for measurement of electron temperature and density fluctuations on ATF and TEXT
Authors: Thomas C. E. , Gandy R. F.
Published: July 2002

The great stumbling block in the quest for fusion power using magnetic confinement devices is anomalous transport. It is conjectured that turbulent plasma fluctuations may be responsible for the degraded energy confinement observed in experiments. There exists a clear need for more detailed experimental studies of plasma microturbulence. A conceptual design is presented for a diagnostic to measure electron temperature and density fluctuations using electron cyclotron emission (ECE). The proposed ECE systems will employ autocorrelation and cross-correlation techniques to measure radiation from the Advanced Toroidal Facility (ATF) at Oak Ridge National Laboratory (ORNL) and also from the Texas Experimental Tokamak (TEXT) at the University of Texas. This set of experiments on a stellarator and a tokamak will allow a unique comparative study of the fluctuation physics in the two different magnetic configurations. This article presents the theoretical basis and conceptual design of the diagnostic.
Improvements in a chemiluminescent ozone analyzer for respiratory applications
Authors: Ben-Jebria Abdellaziz , Hu Shu-Chieh , Ultman James S.
Published: July 2002

The performance characteristics of a previously developed analyzer utilizing the homogeneous chemiluminescent reaction of ozone (O3) with a stoichiometric excess of 2-methyl-2-butene were improved with the eventual goal of measuring the distribution of O3 in a single human breath. By increasing the sampling flow from 200 to 400 mℓ/min and utilizing a combination of analog and digital filtering, it was possible to improve the signal-to-noise ratio at 0.5 ppm O3 from 5.5 to 28, the minimum detection limit from 0.02 to 0.01 ppm, the sensitivity from 1.5 to 2.3 na/ppm, and the 10%–90% step-response time from 200 to 100 ms. Humidity, temperature, and inlet gas composition interferences were also evaluated. While temperature and humidity have no influence on the analyzer output, the substitution of carbon dioxide for oxygen increased the analyzer sensitivity by 3.8% for each percent of CO2 that was present. Thus, provided that an appropriate correction for carbon dioxide is made, these improvements allow the instrument to monitor inhaled and exhaled O3 concentrations with a rapid dynamic response and over a broad range of physiologically relevant values.
MTX data acquisition and analysis computer network
Authors: Butner D. N. , Casper T. A. , Brown M. D. , Drlik M. , Meyer W. H. , Moller J. M.
Published: July 2002

For the MTX experiment, we use a network of computers for plasma diagnostic data acquisition and analysis. This multivendor network employs VMS, UNIX, and BASIC based computers connected in a local area Ethernet network. Some of the data is acquired directly into a VAX/VMS computer cluster over a fiber-optic serial CAMAC highway. Several HP-Unix workstations and HP-BASIC instrument control computers acquire and analyze data for the more data intensive or specialized diagnostics. The VAX/VMS system is used for global analysis of the data and serves as the central data archiving and retrieval manager. Shot synchronization and control of data flow are implemented by task-to-task message passing using our interprocess communication system. The system has been in operation during our initial MTX tokamak and FEL experiments; it has operated reliably with data rates typically in the range of 5 Mbytes/shot without limiting the experimental shot rate.
Technique for relating internal plasma shape to plasma current profiles in noncircular tokamaks
Authors: Powell E. T. , Kaita R. , Fonck R. J.
Published: July 2002

A tangentially viewing soft x-ray pinhole camera has been used to measure internal plasma shape on the PBX-M tokamak. While several methods of deriving the poloidal emissivity profile have been investigated, the most robust consists of a forward modeling technique which permits the inference of the internal shape, axial safety factor, and the current profile. Using poloidal flux measurements to constrain the external shape, equilibria are calculated for different values of q(0). The mapping of the x-ray emissivity to the internal poloidal flux value is obtained by Abel-inverting the x-ray image on the plasma midplane and assuming constant emissivity on a flux surface. Model camera images are then constructed and compared with the measured camera image. A least-squares fit of these models to the measured image produces an inferred value of q(0). The effects of noise have been examined, and the resulting uncertainty in q(0) can range from 0.1 to 0.3, depending on details of the experimental conditions.
Tokamak plasma diagnostics: Selected design studies (abstract)
Authors: Castracane J. , Saravia E. , Woo J. T. , Gutierrez A.
Published: July 2002

Progress in the magnetic fusion programs has driven and been driven by the development of sophisticated diagnostic systems. The application of state of the art technologies has resulted in major strides in detailed measurements of plasma characteristics. We present the details of design studies carried out to develop specialized instrumentation. For application to optical spectroscopy, a compact multichannel spectroscopic monitor is described. This instrument is designed for simultaneous observation of plasma emissions from a variety of spatial locations. The heart of the system is an optical filter mosaic and MCP/CCD array. Applications include impurity emission monitoring, particle inventory, and working gas fraction measurements in minority heating experiments. The second instrument includes a detector design for application to high time resolution measurements of electron cyclotron emissions. The system is based on arrays of slot-antennae/detectors manufactured on single semiconductor wafers. This millimeter-wave monolithic integrated circuit (MMIC) device can be tailored to detect radiation in the 50–300 GHz range typical of tokamak plasmas. Advantages include uniformity of detector response, spectral resolution without gratings, and high spatial resolution. Details of both designs will be discussed with emphasis on ranges of application in present and next generation machines.
Transport/hydrodynamic simulation of intense ion beam diagnostics (abstract)
Authors: Mehlhorn T. A. , Dukart R. J. , Haill T. A. , Nelson W. E.
Published: July 2002

Sandia is working towards igniting an ICF target using MJ-level ion beams focused to intensities of up to 100 TW cm2. The diagnostics used to confirm the achieved focal intensities and study the beam-target interactions are sensitive to variations in both ion energy and angle of incidence. Therefore, to properly simulate time-integrated and time-dependent diagnostics, a coupled transport/diagnostic model is required. Further, intense ion beams cause hydrodynamic response of the target material. We have been developing both a transport/diagnostic code, PICDIAG, and a coupled 1-D rad/hydro/CRE capability to study these effects. We will describe the models used as well as the results of recent simulations of intense beam-target experiments on PBFA II. This will include simulations of diagnostics utilizing Rutherford scattering, inner-shell x-ray generation, and nuclear activation, as well as shadowboxes. Comparison with experimental data will be emphasized. This work was supported by the U. S. Department of Energy under contract No. DE-AC04-76-DP00789.
Prompt gamma ray diagnostics of advanced fuel fusion plasmas
Authors: Cecil F. E. , Liu H. , Scorby J. C. , Medley S. S.
Published: July 2002

We summarize our recent measurements of the radiative capture of protons and deuterons at laboratory bombarding energies up to 180 keV by 6Li, 7Li, 9Be, and 11B. These measurements are used to calculate thermonuclear reactivities for the corresponding advanced fuel fusion plasmas for plasma temperatures up to kT=40 keV. Count rate estimates for the detection of these gamma rays using currently available gamma ray spectrometers are provided.
LANSA: A large neutron scintillator array for neutron spectroscopy at Nova (abstract)
Authors: Tietbohl G. L. , Cable M. D. , Nelson M. B. , Bennett C. E. , Mant G. , Deane D. J. , Connolly N. A.
Published: July 2002

A neutron spectroscopy system for use at Nova is currently under construction. It consists of 960 channels of neutron sensitive liquid scintillator detectors coupled to photomultiplier tubes. Each channel also has a discriminator, ADC, and TDC to allow measurement of neutron arrival time and pulse size. This facility will primarily be used to measure time-of-flight spectra for secondary and tertiary neutrons. Details of the detector design will be presented as well as a brief overview of the proposed use. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract No. W-7405-ENG-48.
Development of high-power millimeter and submillimeter wavelength collective Thomson scattering diagnostics for energetic ion measurements in tokamaks (abstract)
Authors: Machuzak J. S. , Rhee D. Y. , Woskov P. P. , Cohn D. R. , Myer R. C. , Bretz N. , Efthimion P.
Published: July 2002

High-power, large-angle (≳10°), collective Thomson scattering diagnostics can provide localized density and velocity distribution data of confined alpha particles, ICRH simulated alpha particles, and ions related to ICRH and neutral beam energy deposition. Millimeter-wave gyrotron systems are under development for TFTR and JET. Scattering with a submillimeter gyrotron is being investigated for Alcator C-Mod. Major design issues include plasma accessibility, scattering angle, orientation to magnetic field, spectra of non-Maxwellian velocity distributions, signal-to-noise ratio, refraction, electron cyclotron emission, and beam and viewing dumps.
Flash γ-ray detectors that operate at the tera rad/s level (abstract)
Authors: Sanford T. W. L. , Halbleib J. A. , Carlson G. A. , Beutler D. E. , Poukey J. W. , Mock R. C.
Published: July 2002

HERMES III is a 20 MV, 700 kA electron accelerator that produces an intense bremsstrahlung pulse for the study of nuclear radiation effects. We describe and characterize a Compton diode, scintillator photodiode, and Cerenkov photodiode detector that are designed to measure the radiation field of HERMES III. Our measurements and modeling show (1) that the Compton diode directly measures dose rate and is capable of linear operation up to 2.5×1012 rad/s in the near field of HERMES III, (2) the scintillator photodiode provides a sensitive measure of dose rate with high spatial resolution in the far field where dose rates are below 2×1011 rad/s, and (3) the Cerenkov photodiode can be used to place limits on the radiation pulse in the near field with high spatial resolution. We show that the measurements, when combined with the modeling, provide a powerful diagnostic for monitoring the flow of electrons at the bremsstrahlung target. This work was supported by the U. S. Department of Energy under contract DE-AC04-76DP00789.
X-ray and particle diagnostics of a high-density plasma by laser implosion (invited)
Authors: Nakai M. , Yamanaka M. , Azechi H. , Chen Y.-W. , Jitsuno T. , Katayama M. , Mima M. , Miyanaga N. , Nakaishi H. , Nakatsuka M. , Nishiguchi A. , Norreys P. A. , Setsuhara Y. , Takagi M. , Norimatsu T. , Yamanaka T. , Yamanaka C. , Nakai S.
Published: July 2002

A series of laser fusion implosion experiments of plastic hollow shell targets was performed by using the Gekko XII glass laser in order to achieve the required fuel areal density for ignition. Introducing random phase plates to improve illumination uniformity, high-density compression of more than 600 times deuterium liquid density has been achieved. The implosion dynamics and symmetry were observed with a spatially resolved x-ray streak camera and an x-ray multiframing camera. The three-dimensional emission profile of the laser-heated plasma was reconstructed from the x-ray images by use of computed tomography and was compared with the laser illumination profiles. The areal density of the imploded core was measured by the neutron activation of a silicon tracer, the secondary reaction method, and the knock-on proton method. Although the measured density and areal density were consistent with those from 1-D hydrodynamic simulation, experimental neutron yields were significantly lower than those predicted by the simulation for convergence ratios larger than 20. This suggests that better implosion uniformity is required to create a hot spark.
Experimental and numerical calibration of the neutron activation system on the FTU tokamak
Authors: Angelone M. , Batistoni P. , Bertalot L. , Esposito B. , Martone M. , Pillon M. , Podda S. , Rapisarda M. , Rollet S.
Published: July 2002

A benchmark experiment has been performed for the absolute calibration of the FTU tokamak neutron activation system with the purpose of comparing experimental and numerical absolute reaction rates. Indium samples have been activated by a 252Cf neutron source located on the torus axis at three different toroidal angles with respect to the irradiation ends. The same experimental arrangements have been simulated with the Monte Carlo neutron and photon transport code MCNP, in order to reproduce numerically the experimental results. The comparison was intended to assess the accuracy of the numerical simulation and of the modeling of the FTU device. The activation technique will be routinely used as a complementary method to the use of neutron counters for the determination of the absolute neutron yield. An agreement within 22% between experiment and calculation has been found, showing that the model used in MCNP provides an acceptable representation for FTU.
Neutron diagnostic experiment for Alcator C-Mod
Authors: Fiore C. L. , Granetz R. S.
Published: July 2002

The neutron production rate on Alcator C-Mod is expected to peak at 1×1016 n/s for the highest performance experimental pulses. Measurement of the total fusion yield is important for both assessing the experiment and for evaluation of radiological data. The neutron detectors must therefore be capable of accurate measurement over a wide operating regime (1011–1016 n/s from the source). This can be achieved with a series of fission detectors (U235 and U238), capable of operating in both a pulsed and current mode. Computer calculations optimizing the placement of these detectors and also the moderator design are detailed. Calibration of this system will be achieved using a Cf 252 source which will be moved on a track continuously around the major axis. It will also be placed discretely at a number of locations in the torus. MCNP calculations will complement the calibration data. Details of the experimental setup and calibration scheme will be presented.
Design study for a compact E ∥B particle spectrometer
Authors: Armentrout Charles J.
Published: July 2002

A design study is presented for a new, compact particle spectrometer. The device obtains energy and m/q analysis using parallel electric and magnetic fields in the same volume. The instrument differs from the current generation of spectrometers in that it is smaller and provides beam focusing in the energy direction. Focusing is due to 90° ion deflection which differs from the usual 180° deflection. A key feature of the design is that good energy resolution is obtained with broad incident beams with non-negligible divergence. A baseline design is presented to illustrate these features.
Instrumental aspects of extraordinary mode scattering on TFTR
Authors: Bretz N. , Nazikian R. , Bergin W. , Diesso M. , Felt J. , McCarthy M.
Published: July 2002

Initial results from extraordinary mode microwave scattering on TFTR show that the magnitude of density fluctuations approximately follows the mixing length prediction in both beam-heated and ohmic discharges and that the most important part of the k spectrum falls below k⊥ρs=0.5 at a scale unresolved in these measurements. These results are consistent with most scattering measurements done in the ordinary mode on smaller devices. We observe only electron diamagnetic spectral shifts in ohmic discharges while beam-heated discharges display a shift which depends on the sign of the toroidal flow velocity. The spatial resolution of the system inferred from ray tracing is consistent with the measured toroidal velocity profiles and measured spectral shapes. There are some limitations on our measurements caused by a relatively large ‘‘ghost’’ component in the low-frequency spectrum which cannot be identified with simple scattering from the crossing region of the incident and scattering antenna patterns. This component has some of the average features of scattering in the central region but does not have the frequency offset expected for drift waves and does not exhibit a Doppler shift when the plasma is rotating. We show that this ghost feature can be explained by non-Gaussian wings on the transmitting and receiving antennas which have a response to the high fluctuation levels at low values of k.
Motion of relativistic electrons through transverse relativistic plasma waves
Authors: Williams R. L. , Clayton C. E. , Joshi C. , Katsouleas T.
Published: July 2002

We examine computationally the interaction of a pulse of relativistic electrons that is injected perpendicular to the direction of propagation of a relativistic plasma wave. Such a study is useful for evaluating the feasibility of using transverse beam injection as a diagnostic of the amplitude of electric fields in a plasma wave, as well as for determining the suitability of using such waves as extremely short wavelength undulators for generating radiation from free electrons. We use 2D and 3D models which include the effects of transverse and longitudinal fields of the plasma wave, its finite size and electron beam emittance. We find that the change in the spot size of a short electron bunch as it traverses a relativistic plasma wave can indeed be a sensitive diagnostic of its local amplitude-width product.
Simulation of experimental data from the proposed C-Mod reflectometer
Authors: Irby J. H. , Stek P.
Published: July 2002

A six-channel, narrowband reflectometer is expected to go into operation on Alcator C-Mod during its first year of operation. Several programs have been developed to model the effects of both refraction and diffraction on the received signal. Results indicate that careful design and alignment will be necessary to avoid large variations in signal phase and amplitude caused by small variations in plasma position. Simulations of the effects of coherent fluctuations and driftwave turbulence on the echo indicate that both can in some cases degrade the localization of the reflection layer.
MHD magnetic fluctuation measurements using a heavy ion beam probe
Authors: Simcic V. J. , Connor K. A. , Crowley T. P. , Hickok R. L. , Schoch P. M. , Wootton A. J. , Yang X. Z. , Zhang Y. Z.
Published: July 2002

This paper describes a technique for measuring magnetic fluctuations using a heavy ion beam probe (HIBP) and presents the results of the first experiment to measure locally the internal magnetic structure of MHD modes in a hot, tokamak plasma. In these experiments on the TEXT tokamak, the toroidal position of the HIBP beam at the detector is used to measure the toroidal component of the magnetic vector potential fluctuations, Ãφ, at a localized position in the plasma. In an axisymmetric system a purely local measurement is possible. However, the detection method employed and the asymmetries in the tokamak introduce path effects. The importance of the path effects is estimated through numerical simulations of the experiment, and it is found that in this experiment the path effects are small throughout much of the plasma. In addition, toroidal asymmetries reduce the signal amplitude, but do not greatly distort the radial profile. The accuracy of the numerical simulations and detection technique is tested in a plasma with a known Ãφ, with agreement obtained to within 5%.
Neutral beam emission spectroscopy diagnostic for measurement of density fluctuations on the TFTR tokamak (abstract)
Authors: Paul S. F. , Fonck R. J.
Published: July 2002

A multichannel diagnostic for measuring low amplitude, long wavelength (k⊥ρi<0.5) density fluctuations along the outer half of the plasma has been installed on TFTR. It is based on observing fluctuations in the Hα fluorescence of a neutral heating beam due to collisional excitation from the plasma and impurity ions. Both radial and poloidal correlation lengths as short as 2–3 cm can be determined, with the spatial resolution limited primarily by the width and geometry of the three neutral beam sources. Optical fibers transmit the light from a 20-cm-diam vacuum window, reentrant mirror, and lens assembly to 16 interference filter/photomultiplier combinations located outside the radiation area. Initially, the fibers comprise a fixed 55-channel radial array and readily movable 10-channel vertical arrays which can be positioned at 27 radial locations. The filters are designed to accept the Doppler-shifted Hα emission from primary energy component of the neutral beam, and reject background lines and unshifted edge Hα. The measurable fluctuation amplitude (@ S/N=1) is limited to 0.5% over a 100 kHz bandwidth by the photon noise associated with the dc level of the beam emission. The contribution of impurities to the total beam fluorescence will be determined directly by measuring impurity density fluctuations using charge-exchange recombination emission from the n=8−7 C vi line at 5292 Å.
Fiber-optic temperature sensors for protective carbon tiles
Authors: Forman P. R. , Jahoda F. C. , Aksay E. R.
Published: July 2002

A new technology is emerging for making multiple temperature measurements with good spatial resolution on a single optical fiber. The germanium-doped fused silica fiber core is prepared by exposing short sections (4–6 mm) to interfering coherent UV laser light beams. This produces permanent gratings of selected spacings within the fiber core which reflect a very narrow band of light. This is done at several locations along the fiber producing multiple sensors each reflecting its own specific wavelength. One is free to choose the locations of these sensor elements. As the fiber sensor sections change temperature, the effective grating spacings change and reflect a slightly different wavelength. We demonstrate a few degree C resolution in the range 23–100 °C with our test, three–element sensor. We discuss the modifications necessary to apply such a device to measurements on the protective carbon tiles on CPRF/ZTH (coatings for higher temperatures, mounting sensors, vacuum compatibility, and feed through).
Measurement of the 2-D distribution of power loading on the TFTR bumper limiter during disruptions
Authors: Janos A. C. , Corneliussen M. , Fredrickson E. , McGuire K. M. , Owens K. , Ulrickson M.
Published: July 2002

Power loading on the first wall of a tokamak is an important issue in present research devices and in the design of future devices such as CIT and ITER. In particular, disruptions can deposit large amounts of power in localized areas which can then damage the wall or adversely affect operation. The plasma-facing wall in the Tokamak Fusion Test Reactor (TFTR) is covered in large part by a bumper limiter. This limiter extends the full 360° toroidally inside the vacuum vessel on the small-major-radius side, and ±60° poloidally with respect to the midplane. The TFTR tokamak has the unique feature that the bumper limiter is extensively instrumented with thermocouples. By carefully eliminating noise on the data from these sensors, we can now measure the heat deposition distribution for each discharge. We investigated disruptions due to operation at different operating limits such as (a) high density, (b) low qa, and (c) high beta poloidal (βp). It was found that while there were often common hot spots, different types of disruptions caused different heating patterns and heat loads on the bumper limiter. We also studied the heat distribution created by pulsed discharge cleaning and disruptive discharge cleaning. While originally intended to study disruptions, this new analysis tool has proven valuable for investigating other plasma phenomena such as blooms and detached plasmas, determining the heating effectiveness of various conditioning techniques such as pulsed discharge cleaning and disruptive discharge cleaning, and verifying and checking the alignment of the bumper limiter.
Proposal of infrared bolometry on Frascati tokamak upgraded
Authors: Apruzzese G. , Tonini G.
Published: July 2002

Bolometric diagnostics on fusion devices usually suffer from inadequate ;D performances: moderate S/N ratio, limited time and space resolution, radiation and neutron induced damage (particularly important for the next generation of fusion devices). A new bolometric system in which a blackened foil exposed to the plasma is monitored on its back side by an IR camera, is described. It is first demonstrated that the foil preserves, within a given time and space resolution, a linear relation between the incoming plasma radiation and the IR emission. Then the S/N ratio is derived as a function of the various system parameters. Representative values of resolution and S/N are computed for a realistic set of operational conditions.
Use of narrow bandpass optical filters in Zeeman polarimetry for poloidal field measurements on the Texas Experimental Tokamak (abstract)
Authors: Huang L. K. , West W. P. , Finkenthal M. , Yang X. Z. , Moos H. W.
Published: July 2002

Very narrow bandpass optical fibers have been used in Zeeman polarimetry of Li I 6708 Å line emission from a monoenergetic lithium beam as a spectral source makes the measurement well localized. Initial experimental results for measurements of q0 will be presented.
Infrared thermography system on DIII-D (abstract)
Authors: Petrie T. W. , Hill D. N. , Baptista J. , Brown M.
Published: July 2002

Six infrared cameras measure temperature changes on the protective graphite armor inside the DIII-D vacuum vessel. Simultaneous time-dependent temperature measurements are made on armor tiles located on the centerpost and divertor regions, and on both outboard limiters. The nearly complete poloidal coverage is useful in measuring both the plasma heat flux distributions inside the vessel and the plasma power balance. Spatial resolution of each camera system is ≲1 cm, while the minimum resolvable time is 125 μs. Data from the IR TV systems are recorded on video tape, and are post-processed serially, using an image processor with an AT-compatible microcomputer. The processing system controls all VCRs, interprets DIII-D timing pulses, digitizes video data in the predetermined regions of interest, averages digitized signals to reduce noise, and constructs data files which are then stored as part of the permanent shot record.
Design of a third-harmonic electron cyclotron emission diagnostic for ballooning mode fluctuations in PBX-M
Authors: Woskov P. P. , Kesner J. , Lane B. , Luckhardt S. , Machuzak J. S. , Rhee D. Y. , Cohn D. R.
Published: July 2002

A third-harmonic electron cyclotron emission diagnostic using ultrawide bandwidth (≊40 GHz) heterodyne receivers centered on 120 GHz with 14 channels per radial view is described for localized, long wavelength (5≲λ≲50 cm), fast time response (≊1 μs) fluctuation studies in the PBX-M tokamak. The optically gray emission signal will have a γñe/ne+(3/β)T̃e/Te dependence on temperature and density fluctuations where γ≤1 and 1≤β≤3 depending on local optical depth. Electron temperature fluctuation sensitivity is estimated to be 0.2%≤T̃e/Te ≤2.9% depending on local optical depth and fluctuation frequency in the 0.1–1 MHz range. Spatial resolution of approximately 3 cm radially and 5 cm vertically are estimated for 2 keV plasmas with low suprathermal electron emission.
A 12-channel polychromator for ECE measurement on FTU (abstract)
Authors: Tudisco O.
Published: July 2002

A 12-channel diffraction grating polychromator has been built to measure the plasma temperature at 12 different positions with a time resolution of 30 μs. The system allows us to exchange three different gratings in order to cover a larger frequency range. The normalized spectral range of each grating is about 0.37 and the total range of wavelength covered by the three gratings is from 0.6 to 1.7 mm. These wavelengths correspond to the second harmonic of electron cyclotron emission from 8 to 4 T. The resolving power of the channels ranges from 40 to 70. The frequency calibration has been performed using a Fourier transform interferometer and a high pressure mercury lamp as a source; the efficiency of low-pass filters, the frequency of each channel and their resolutions have been checked.
The PBX-M Thomson scattering system
Authors: LeBlanc B. , Bell R. , Dimock D. , Duperrex P.-A. , Felt J. , Palladino R. , Tolnas E.
Published: July 2002

The PBX-M Thomson scattering system is reviewed after its first 9 months of operation. The system measures Te(R) and ne(R) at 55 radial points on the horizontal midplane with a spatial resolution of ≤1.1 cm. The scattered light is collected by a Bouwers concentric mirror system and imaged onto 12-m-long fiber bundles. A composite entrance slit is used to optimize the system performance. The synchronization between the scattered light and detector gate is done via a laser-triggered spark gap. A penetration in the indentation coil allows the (ruby) laser beam to be dumped away from the plasma chamber. Other aspects of the system will be discussed.