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  • 1
    Electronic Resource
    Electronic Resource
    Electron density profile measurement with a heavy ion beam probe : Proceedings of the 9th topical conference on high temperature plasma diagnostics (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4571-4573 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The feasibility of electron density profile measurements using a heavy ion beam probe in high-temperature plasmas has been demonstrated earlier [J. Schwelberger et al., Bull. Am. Phys. Soc. 36, 2292 (1991); Yu. N. Dnestrovskij et al., Sov. J. Plasma Phys. 12, 130 (1986)]. Two algorithms were developed to obtain density profiles from the heavy ion beam probe on the Advanced Toroidal Facility (ATF). A comparison of the algorithms is presented with a detailed study of the errors involved in the measurements. The errors can be due to uncertainties in cross sections, electron temperature, the line average density measurement, and the ion trajectory calculations. The heavy ion beam probe density profile measurement is not very susceptible to errors as long as the electron temperature stays above 30 eV. If the electron temperature is below this value, a small uncertainty in the temperature introduces a large error in the density. Also, important for a good density profile measurement is the calculation of the correct ion trajectories. Examples of density profiles are shown for ECH plasmas on ATF together with a detailed error analysis. The heavy ion beam probe results are in good agreement with multichannel far-infrared laser interferometry and Thomson scattering results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143671
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  • 2
    Electronic Resource
    Electronic Resource
    Long pulse experiments on the Advanced Toroidal Facility (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 2435-2439 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Advanced Toroidal Facility (ATF) [Fusion Technol. 10, 179 (1986)] is the world's largest stellarator. It was designed and built to demonstrate high beta, steady-state operation in a toroidal confinement system. During its final operating period ATF achieved pulse lengths of over one hour (4667 s). The objectives of these experiments were (1) investigation of plasma performance at times that are long compared to the plasma/wall equilibrium time; (2) determination of plasma control and wall conditioning techniques; and (3) adaptation of plasma diagnostic and data acquisition systems to long-pulse operation. Other experiments have also extended earlier studies of dimensionless-parameter plasma confinement scaling. By employing two discrete electron cyclotron heating (ECH) frequencies (28 and 35 GHz), and by simultaneously modulating the ECH power, magnetic field, and plasma density, it has been possible to maintain fixed plasma beta and collisionality while modulating the normalized gyroradius. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871267
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  • 3
    Electronic Resource
    Electronic Resource
    Transient effects of ionizing and displacive radiation on the dielectric properties of ceramics (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 2920-2933 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A resonant cavity technique was used to measure the dielectric constant and loss tangent of ceramic insulators at a frequency near 100 MHz during pulsed fission reactor irradiation near room temperature. Tests were performed on single crystal and several different grades of polycrystalline Al2O3, MgAl2O4, AlN, and Si3N4. Lead shielding experiments were performed for some of the irradiations in order to examine the importance of gamma ray versus neutron irradiation effects. With the exception of AlN, the dielectric constant of all of the ceramics decreased slightly (〈0.2% change) during the pulsed fission reactor irradiation. The dielectric constant of AlN was observed to slightly increase during irradiation. Significant transient increases in the loss tangent to values as high as 6×10−3 occurred during pulsed reactor irradiation with peak ionizing and displacements per atom (dpa) radiation fields of 4.2×104 Gy/s and 2.4×10−6 dpa/s, respectively. The loss tangent measured during irradiation for the different ceramics did not show any correlation with the preirradiation or postirradiation values. Analysis of the results indicates that the transient increases in loss tangent are due to radiation induced increases in the electrical conductivity. The loss tangent increases were proportional to the ionizing dose rate in all materials except for AlN, which exhibited a dose rate exponent of ∼1.6. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361288
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  • 4
    Electronic Resource
    Electronic Resource
    Two-dimensional Thomson scattering system for ATF (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 1816-1818 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A two-dimensional Thomson scattering system is being designed for the Advanced Toroidal Facility (ATF) torsatron experiment. This system will provide electron temperature and density measurements at 15 points along a vertical chord with each shot from a two-dimensional Te and ne map of an ATF toroidal cross section can be obtained. The horizontal Thomson scattering viewing port is offset by 15° toriodally from the ports passing the vertical laser beam. Translating and rotating mirors will be used to relay light from the viewing port to the collection lens. This makes it possible to scan horizontally, view as much of the vertical laser beam as possible, and to use a fixed focal length, fixed position lens. Three sets of spectrometers optimized to three temperature ranges will be used. At the output of each spectrometer, dispersed light will be detected by an array of five, seven, or eight photomultiplier tubes, depending on the temperature range of the spectrometer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139138
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  • 5
    Electronic Resource
    Electronic Resource
    Possible integrated diagnostic set for ion cyclotron heating for the tokamak physics experiment (TPX) (abstract)a) : Proceedings of the tenth topical conference on high temperature plasma diagnostics (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 866-866 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Heating and current drive with ICRF is one of the major missions of TPX and is crucial to its success. In contrast to the integrated nature of core diagnostic programs, diagnostics that measure ICRF propagation and edge interactions are often assigned lower priority, have not been included in the base diagnositics set, or were included as upgrades. This can result in an incomplete and unoptimized set of measurements. Thus it is important that an integrated set of diagnostics (engineered along with the antenna design), capable of fully diagnosing the interaction, propagation, and absorption of the ICRF be available for TPX. The parameters of interest include: coupling of the ICRF antenna to the plasma, launched spectrum, wave propagation, edge plasma interactions, electron heating, and current drive, and fast ion power deposition and losses. The diagnostic set should be designed so it can be upgraded for control of loading and spectrum by providing feedback information for adjusting phase, power level, fuel gas injection, and plasma position. The proposed set focuses on wave propagation, launched spectrum, absorption, and measuring and comparing the plasma edge properties in the near vicinity of the antenna with that measured at a large toroidal distance from them; thus many would be installed as toroidally separated indentical sets. In addition to the planned core diagnostic set, the ICRF specific diagnostics proposed for TPX include: edge density reflectometers, RF fluctuation reflectometers, fixed and moveable Langmuir probes, visible and IR cameras with spectroscopic line filters, rf magnetic loop probes, local ion energy analyzer, direct ion loss detectors, charge exchange analyzers, fast response ECE, and edge temperature ECE. The anticipated approach is one in which individual diagnostics could be provided by industry, universities, or laboratories but overall coordination, driven by specific ICRF issues, would be required. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146425
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  • 6
    Electronic Resource
    Electronic Resource
    Differential-phase reflectometry for edge profile measurements on Tokamak fusion test reactor : Proceedings of the tenth topical conference on high temperature plasma diagnostics (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 863-865 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Edge electron density profile measurements, including the scrape-off layer, have been made during ion cyclotron range of frequency (ICRF) heating with the two-frequency differential-phase reflectometer installed on an ICRF antenna on the Tokamak fusion test reactor (TFTR). This system probes the plasma using the extraordinary mode with two signals swept from 90 to 118 GHz, while maintaining a fixed-difference frequency of 125 MHz. The extraordinary mode is used to obtain density profiles in the range of 1×1011–3×1013 cm−3 in high-field (4.5–4.9 T) full-size (R0=2.62 m, a=0.96 m) TFTR plasmas. The reflectometer launcher is located in an ICRF antenna and views the plasma through a small penetration in the center of the Faraday shield. A 26-m-long overmoded waveguide run connects the launcher to the reflectometer microwave electronics. Profile measurements made with this reflectometer system will be presented along with a discussion of the characteristics of this differential phase reflectometer and data analysis. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146187
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  • 7
    Electronic Resource
    Electronic Resource
    In situ dye laser calibration for Thomson scattering diagnostics (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 1464-1466 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The standard laser Thomson scattering calibration technique involves the convolving of density and wavelength response calibrations. This usually includes an in situ Rayleigh scattering from neutral gas for an absolute density calibration at the laser wavelength. In addition, a spectral calibration (i.e., a National Bureau of Standards traceable lamp and white reflective plate) is required to determine the relative wavelength channel responses for the combination of collection optics, spectrometers, and associated detectors. This technique involves a considerable amount of time and effort in two-dimensional scattering systems because of the number of spectrometers/detectors and the large range of scattering and collection angles. An alternative technique employing a nominal 40-mJ, small-divergence tunable dye laser substituted into the Thomson scattering laser beam path is proposed. Rayleigh scattering (from ∼10-Torr H2) measurements are made at a high repetition rate (1–10 Hz) while the dye laser output wavelength is scanned. This includes in one step the in situ density and channel response calibrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139689
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  • 8
    Electronic Resource
    Electronic Resource
    ECE diagnostic for ATF (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 1614-1616 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Electron cyclotron emission (ECE) from the Advanced Toroidal Facility (ATF) torsatron will allow measurement of plasma electron temperature. For low-field operation (0.95 T) the second harmonic is cut off at a relatively low density; therefore, third-harmonic emission from 67 to 83 GHz is used to yield central electron temperatures. At high-field operation (1.9 T) second-harmonic emission from 82 to 114 GHz is optically thick and can provide Te(r) information. A vertical view of the saddle-point geometry of the ATF mod B spatial contours provides a line of sight along which the mod B contours are symmetric with respect to flux surfaces. A single horn–lens viewing beam system with a vertical view is designed to cover the entire 67–114-GHz range, providing a spot size on the order of 6 cm. Radiation will be delivered to one of three waveguide mixers by C-band waveguide. Each of the three mixers covers a 16-GHz segment of the emission spectrum, downconverting it to the 2–18-GHz intermediate-frequency band, where it is processed by a 16-channel array of bandpass filters, providing 1-GHz frequency resolution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140163
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  • 9
    Electronic Resource
    Electronic Resource
    Multiple-frequency electron-cyclotron heating of hot-electron rings in a bumpy torus (1985)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 28 (1985), S. 1932-1936 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The use of multiple-frequency microwave power for electron-cyclotron heating significantly increased the ring stored energy in the SM-1 simple mirror device. Multiple-frequency electron-cyclotron heating (MFECH) was used on the ELMO Bumpy torus (EBT) in an effort to increase its hot-electron beta. No substantial improvement in the ring parameters was observed in a series of two-frequency ECH experiments, with frequency separations up to 90 MHz, in contrast to the dramatic improvement found in the axisymmetric SM-1 experiment. The toroidal canting of the EBT mirror sectors introduces asymmetries that destroy the superadiabatic behavior of the energetic electrons, reduce microwave heating efficiency, and produce additional ring losses. These effects qualitatively explain the different multiple-frequency heating results obtained in EBT and SM-1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.864937
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  • 10
    Electronic Resource
    Electronic Resource
    Electron confinement in a bumpy torus without the influence of hot-electron rings—"Ring killer'' experiment (1985)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 28 (1985), S. 2848-2856 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The ELMO Bumpy Torus (EBT) [Plasma Physics and Controlled Nuclear Fusion (IAEA, Vienna, 1975), Vol. II, p. 141] normally has an energetic electron ring in each of its 24 mirror sectors. The original intention of using this hot-electron population was to provide an average local minimum in the magnetic field (through its diamagnetism) to stabilize the simple interchange and flute modes, which otherwise are theoretically inherent in a closed-field-line bumpy torus. To study the confinement properties of a bumpy torus without the influence of hot-electron rings, a water-cooled stainless steel limiter in each mirror sector was extended into the plasma to the ring location; this eliminated the hot-electron ring population. These limiters were aptly named "ring killers.'' Electron temperature, density, space potential, and plasma fluctuations have been measured during the ring killer experiment and are compared to standard EBT operation. The results of these experiments indicate that the hot-electron rings in EBT do enhance the core plasma properties of EBT and do, in fact, reduce plasma fluctuations; however, these improvements are not large in magnitude. These measurements and recent theoretical models suggest that simple interchange/flute modes are stabilized, or fluctuation levels reduced, well before that condition is obtained for average minimum-B stabilization. Several possible mechanisms for this stabilization are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865205
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