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Your search keyword '"Brémond, S."' showing total 5 results
Start Over Author "Brémond, S." Topic ion cyclotron resonance spectrometry
5 results on '"Brémond, S."'

1. Modelling of Ion Cyclotron Wall Conditioning plasmas.

Author

Douai, D., Wauters, T., Lyssoivan, A., Marchuk, O., Wünderlich, D., Brémond, S., Lombard, G., Mollard, P., Pegourié, B., and Van Oost, G.

Subjects
ION cyclotron resonance spectrometry, PLASMA gases, FUSION reactors, POINT defects, TOROIDAL magnetic circuits, PLASMA injection, ELECTRON impact ionization
Abstract

Ion Cyclotron Wall Conditioning (ICWC) is envisioned in ITER to clean the wall from impurities, to control the wall isotopic ratio and the hydrogen recycling in the presence of the toroidal magnetic field. Various experiments and modelling are advancing to consolidate this technique. In this contribution the modeling of ICWC is presented, which can be divided in two parts: plasma description and plasma wall interaction. Firstly a 0D plasma model, based on a set of energy and particle balance equations for Maxwellian Hydrogen and Helium species, is presented. The model takes into account elementary collision processes, coupled RF power, particle confinement, wall recycling, and active gas injection and pumping. The RF plasma production process is based mainly on electron collisional ionization. The dependency of the plasma parameters, the Hydrogen and Helium partial pressures and neutral or ionic fluxes on pressure and RF power are quantitatively in good agreement with those obtained experimentally on TORE SUPRA. Secondly an extension of the 0D model including the description of the wall interaction is presented and compared to TORE SUPRA multi-pulse ICWC discharges. [ABSTRACT FROM AUTHOR]

Published
2011
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2. Ion Cyclotron Wall Conditioning Experiments on Tore Supra in Presence of the Toroidal Magnetic Field.

Author

Wauters, T., Douai, D., Brémond, S., de la Cal, E., Lombard, G., Lyssoivan, A., Pegourié, B., Tsitrone, E., Van Schoor, M., and Van Oost, G.

Subjects
ION cyclotron resonance spectrometry, MAGNETIC fields, GLOW discharges, TRITIUM, PHYSICS experiments
Abstract

Wall conditioning techniques applicable in the presence of the high toroidal magnetic field will be required for the operation of ITER for tritium removal, isotopic ratio control and recovery to normal operation after disruptions. Recently ion cyclotron wall conditioning (ICWC) experiments have been carried out on Tore Supra in order to assess the efficiency of this technique in ITER relevant conditions. The ICRF discharges were operated in He/H2 mixtures at the Tore Supra nominal field (3.8 T) and a RF frequency of 48 MHz, i.e. within the ITER operational space. RF pulses of 60 s (max.) were applied using a standard Tore Supra two-strap resonant double loop antenna in ICWC mode, operated either in π or 0-phasing with a noticeable improvement of the RF coupling in the latter case. In order to assess the efficiency of the technique for the control of isotopic ratio the wall was first preloaded using a D2 glow discharge. After 15 minutes of ICWC in He/H2 gas mixtures the isotopic ratio was altered from 4% to 50% at the price of an important H implantation into the walls. An overall analysis comparing plasma production and the conditioning efficiency as a function of discharge parameters is given. [ABSTRACT FROM AUTHOR]

Published
2009
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3. ICRF physics aspects of wall conditioning with conventional antennas in large-size tokamaks

Author

Lyssoivan, A., Koch, R., Douai, D., Noterdaeme, J.-M., Philipps, V., Rohde, V., Schüller, F.C., Sergienko, G., Van Eester, D., Wauters, T., Blackman, T., Bobkov, V., Brémond, S., Brezinsek, S., de la Cal, E., Dumont, R., Garcia-Munoz, M., Gauthier, E., Graham, M., and Jachmich, S.

Subjects
*ANTENNAS (Electronics), *TOKAMAKS, *ELECTRIC heating, *ION cyclotron resonance spectrometry, *ELECTRIC discharges, *MIXTURES, *ABSORPTION, *ELECTRONIC excitation
Abstract

Abstract: This paper focuses on a study of the principal operation aspects of standard ICRF heating antennas in the ion cyclotron wall conditioning (ICWC) mode: (i) ability of the antenna to ignite the cleaning discharge safely and reliably in different gases including those most likely to be used in ITER – He, H2, D2 and their mixtures, (ii) the antenna capacity to couple a large fraction of the RF generator power (>50%) to low density (∼1016–1018 m−3) plasmas and (iii) the RF power absorption schemes aimed at improved RF plasma homogeneity and enhanced conditioning effect. The ICWC discharge optimization in terms of RF plasma wave excitation/absorption resulted in successful simulation of the conditioning scenarios for ITER operation at full field (JET) and half-field (TEXTOR, TORE SUPRA, ASDEX Upgrade). [Copyright &y& Elsevier]

Published
2011
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4. Recent results on Ion Cyclotron Wall Conditioning in mid and large size tokamaks

Author

Douai, D., Lyssoivan, A., Philipps, V., Rohde, V., Wauters, T., Blackman, T., Bobkov, V., Brémond, S., Brezinsek, S., Clairet, F., de la Cal, E., Coyne, T., Gauthier, E., Gerbaud, T., Graham, M., Jachmich, S., Joffrin, E., Koch, R., Kreter, A., and Laengner, R.

Subjects
*ION cyclotron resonance spectrometry, *TOKAMAKS, *PERMANENT magnets, *TOROIDAL magnetic circuits, *DISRUPTIVE innovations, *NUCLEAR engineering
Abstract

Abstract: Wall conditioning techniques applicable in the presence of permanent toroidal magnetic field will be required for the operation of ITER, in particular for recovery from disruptions, vent and air leak, isotopic ratio control, recycling control and mitigation of the tritium inventory build-up. Ion Cyclotron Wall Conditioning (ICWC) is one of the most promising options and has been the subject of considerable recent study on current tokamaks. This paper reports on the findings of such studies performed on European tokamaks, covering a range of plasma-facing materials: TORE SUPRA, TEXTOR, ASDEX Upgrade and JET. [Copyright &y& Elsevier]

Published
2011
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5. Isotope exchange experiments on TEXTOR and TORE SUPRA using Ion Cyclotron Wall Conditioning and Glow Discharge Conditioning

Author

Wauters, T., Douai, D., Lyssoivan, A., Philipps, V., Brémond, S., Freisinger, M., Kreter, A., Lombard, G., Marchuk, O., Mollard, P., Paul, M.K., Pegourié, B., Reimer, H., Sergienko, G., Tsitrone, E., Vervier, M., Van Wassenhove, G., Wünderlich, D., Van Schoor, M., and Van Oost, G.

Subjects
*PHYSICS experiments, *TOKAMAKS, *ION cyclotron resonance spectrometry, *GLOW discharges, *MIXTURES, *IONIZATION (Atomic physics), *NUCLEAR engineering
Abstract

Abstract: This contribution reports on isotope exchange studies with both Ion Cyclotron Wall Conditioning (ICWC) and Glow Discharge Conditioning (GDC) in TEXTOR and TORE SUPRA. The discharges have been carried out in H2, D2 (ICWC and GDC) and He/H2 mixtures (ICWC). The higher reionization probability in ICWC compared to GDC, following from the 3 to 4 orders of magnitude higher electron density, leads to a lower pumping efficiency of wall desorbed species. GDC has in this analysis (5–10) times higher removal rates of wall desorbed species than ICWC, although the wall release rate is 10 times higher in ICWC. Also the measured high retention during ICWC can be understood as an effect of the high reionization probability. The use of short RF pulses (∼1s) followed by a larger pumping time significantly improves the ratio of implanted over recovered particles, without severely lowering the total amount of removed particles. [Copyright &y& Elsevier]

Published
2011
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