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  • Articles  (8)
  • American Institute of Physics (AIP)  (8)
  • 1
    Electronic Resource
    Electronic Resource
    Ion temperature and plasma rotation velocity measurements using visible spectroscopy on TdeV : Proceedings of the 12th topical conference on high temperature plasma diagnostics (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 387-390 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A visible spectroscopic imaging system has been developed on Tokamak de Varennes (TdeV) that provides profile measurements of the ion temperature and plasma rotation velocity. Multiple poloidal and tangential chords were coupled to the entrance slit of a spectrometer equipped with a back-illuminated charge coupled device camera at its exit slit. The camera records spatially and spectrally resolved emission profiles with real time digitization and up to 70 ms/frame as temporal resolution. Line-integrated radiation from different ionization stages in the visible range (B V, C III, He II, and N IV) were chosen as representative of the plasma in their regions of maximum emission. Three types of plasma discharges are compared: ohmic and electron cyclotron resonance heated L and H modes. Preliminary results show that with an L–H transition, there is a 20%–30% increase of the ion temperature at midradius, without a pedestal and an increase of the toroidal velocity shear at r/a∼0.8. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149302
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  • 2
    Electronic Resource
    Electronic Resource
    Edge density profile measurements in TdeV using amplitude modulation reflectometry : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 990-993 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A single channel AM reflectometer, operating in the frequency range of 33.0≤f≤50.0 GHz, has been developed to provide edge electron density profiles on TdeV. The X-mode cut-off layer, covering densities ne≤1019 m−3 for 1.5 T operation, is used to measure a portion of the plasma edge region 0.9≤r/a≤1.2. Briefly, our design consists in launching a microwave beam amplitude modulated at 201 MHz. The reflected wave is detected and downconverted to 1 MHz to facilitate filtering and phase detection. Finally, a linear phase detector compares the phase of the resulting signal (1 MHz) with that of the reference source. The design and construction of the reflectometer will be described and preliminary results presented. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147733
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  • 3
    Electronic Resource
    Electronic Resource
    Measurements of edge density profiles on TdeV using the injection of laser-ablated lithium atoms : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 994-997 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An atom injector using laser blow off of lithium is installed on TdeV to obtain the radial edge profile of electron density near the throat of the top divertor. The profile is reconstructed from the emissivity of the LiI (2p 2P→2s 2S) transition at 670.8 nm. A short review of the diagnostic is given describing the experimental setup, the measurement procedures, and the density profile reconstruction method. Effects of plasma biasing on the edge electron density profile and the response of the edge profile to the line-average central electron density are shown to illustrate the diagnostic capabilities. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147734
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  • 4
    Electronic Resource
    Electronic Resource
    Multichannel submillimeter interferometer/polarimeter for TdeV (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 3428-3433 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An interferometer/polarimeter has been developed and tested for operation on the TdeV tokamak. The system operates at 393.6 μm on 7 channels equally spaced over the plasma diameter. The interferometer has operated routinely for six years and is used for density feedback control on TdeV, with very little supervision and maintenance. A sensitivity of 2.5×10−16 m−2 and a response time of 5 μs enables small density perturbations (Δn≥0.005n¯e) and fast transients to be resolved. With the appropriate choice of assumptions and boundary conditions, the system can supply credible electron density profiles together with their temporal evolution, using as isocontours the flux surfaces obtained from equilibrium calculations. When operated as a polarimeter, the system now routinely provides current-density profile measurements as well. Optical cross-talk between channels, identified as the main obstacle to the extension of the interferometer to polarimetry, was mastered using optical isolation techniques. The system can now resolve, on each chord, a Faraday rotation of 1.5 mrad, limited by vibration, cross-talk and deflection. Using a parametric approach, poloidal field and current-density profiles, as well as the axial safety factor and internal inductance of the discharge, are made available after each shot. The apparatus will be used for current-transport, MHD-equilibrium and current-drive studies on TdeV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144517
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  • 5
    Electronic Resource
    Electronic Resource
    Various divertor biasing configurations and improved divertor performance with biasing on Tokamak de Varennes (TdeV)* (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 1497-1502 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electrically insulated divertor plates are used on TdeV (Tokamak de Varennes) [18th EPS Conference on Controlled Fusion and Plasma Physics Berlin (European Physical Society, Petit-Lancy, 1991), Vol. 15C, Part I, pp. 1–141] to produce various biasing configurations, which can be decomposed into two basic modes. Plasma biasing, with a radial electric field Er in the scrape-off layer (SOL), is most promising for divertor applications. The Er field is produced with a particular divertor plate geometry, causing a nonambipolar radial current and a particle flow in the Er×BT direction, toward one of the divertors (the active divertor). The pressure and impurity retention in the active divertor are shown, in the Ohmic regime, to be strongly increased by biasing. He exhaust through this divertor is increased by a factor of almost 3 with modest biasing voltages and currents scalable to larger devices. Biasing also modifies the power repartition between the divertors, with the active divertor also receiving a larger fraction of the power.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870699
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  • 6
    Electronic Resource
    Electronic Resource
    Modification of the internal electric field by biasing of the divertor plates in the Tokamak de Varennes (TdeV) (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 3644-3654 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The radial electric field inside the separatrix has been deduced from spectroscopic measurements of impurities on TdeV (Tokamak de Varennes), using the reduced radial momentum balance and two neoclassical models [R. D. Hazeltine, Phys. Fluids 17, 961 (1974) and Y. B. Kim, P. H. Diamond, and R. J. Groebner, Phys. Fluids B 3, 2050 (1991)]. The results from all three models are in fair agreement. Furthermore, the electric field has been deduced using the same models both with and without biasing the divertor plates relative to the machine wall, showing an inward propagation of the effect of the biasing created in the scrape-off layer (SOL). Undeniably, the electric field has been modified well inside the separatrix (0.6(approximately-less-than)r/a(approximately-less-than)0.9), revealing the possibility of modifying the internal electric field by external means. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872260
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  • 7
    Electronic Resource
    Electronic Resource
    Density fluctuations and current penetration on a magnetized plasma column (1985)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 28 (1985), S. 554-559 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An experiment is described where an anomalously rapid current penetration is correlated with the appearance of strong fluctuations measured with a forward laser scattering technique. In this experiment, the current of a magnetized plasma column (5 eV, 1021 m−3) is reversed linearly on a time scale (μsec) much shorter than the classical time for current penetration toward the center of the column. Strong skin currents are observed to develop followed by a rapid current transport phase. The anomaly level of the current penetration is inferred from a comparison with numerical simulations. Simultaneously with the appearance of strong skin currents, we observe the onset of a large fluctuation level (ñe/ne∼1%) which persists for the duration of the anomalous current transport phase. The main contribution is from broadband fluctuations at low frequencies (a few MHz) and long wavelengths (a few mm). The nature of the fluctuations is not clear although a low level of ion-acoustic turbulence appears to be involved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865120
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  • 8
    Electronic Resource
    Electronic Resource
    Ion temperature measurement in a plasma column using pulsed CO2 collective scattering and heterodyne detection (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 1609-1614 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We describe a pulsed CO2 laser scattering experiment set up to measure the ion temperature of a magnetically stabilized arc plasma (ne(approximately-equal-to)1021 m−3, Te(approximately-equal-to)5 eV). Sensitivity and spectral resolution considerations led us to use heterodyne detection with a separate local oscillator and a multichannel rf frequency analyzer. The forward scattering angle is chosen to be 5° in order to match the expected ion feature spectrum to the receiver bandwidth and also to eliminate spontaneous fluctuations from the small-k larger-amplitude signal. Experimental scattering spectra illustrate the apparatus sensitivity to discharge current and gas mixture. Ion-acoustic resonances are resolved as well as the spectral signatures from various mixed ion species plasmas. The ion temperature appears to be determined to ±10% once Te and ne are known from other measurements. Applications to high temperature fusion plasmas are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.334479
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