Influence of toroidal and vertical magnetic fields on Ion Cyclotron Wall Conditioning in tokamaks

Lyssoivan, A.; Sergienko, G.; Rohde, V.; Philipps, V.; Wassenhove, G. Van; Vervier, M.; Bobkov, V.; Harhausen, J.; Koch, R.; Noterdaeme, J.‐M.; Eester, D. Van; Freisinger, M.; Fahrbach, H.-U.; Reimer, H.; Kreter, A.; Hartmann, D.; Hu, J.; Weynants, R.; Gruber, O.; Herrmann, A.; Douai, D.; Bae, Y. D.; Esser, H. G.; Kwak, J.G.; Lerche, E.; Marchuk, O.; Mertens, V.; Neu, R.; Samm, U.; Scarabosio, A.; Schulz, Ch.; Wang, S.J.

doi:10.1016/j.jnucmat.2009.01.233

Cited by 17 publications

(11 citation statements)

References 5 publications

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“…In this regime, antenna coupling becomes sensitive to the radial location of the MC layer: the closer this layer is located to the antenna surface the higher the antennaplasma coupling. This coupling effect is more pronounced for the standard dipole-phasing operation (η/η 0 > 3) [36].…”

Section: Coupling Rf Power To Low-density Icwc Plasmasmentioning

confidence: 93%

“…This low pressure was imposed by JET operational constraints in order to avoid arcing inside the vacuum transmission line (VTL) as the VTLpressure is coupled to the torus pressure. To extend the ICWC plasma in vertical direction and push it down towards the divertor area, an additional vertical magnetic field B V between 3 and 30 mT in the 'barrel'-shaped configuration was also applied [36]. A schematic layout of the JET ICRF antennas and diagnostics involved in the ICWC experiment is shown in figure 14.…”

Section: Icwc Operational Windowmentioning

confidence: 99%

“…D + + H + , 4 He + + D + or 4 He + + H + . The effect was predicted from modelling with the TOMCAT full wave 1-D RF code [22] accounting for electron (collisional, Landau, TTPM) and ion (collisional, linear cyclotron at n = 1-3 harmonics) damping mechanisms, tested for the first time in JET [46] and further developed during ASDEX Upgrade ICWC experiments [36]. Generally, the FW may be non-propagating over the plasma cross-section except for the narrow conversion area located close to the fundamental ICR of the main plasma species, protons (ω = H + ) or deuterons (ω = D + ), depending on the ICWC scenario.…”

Section: Coupling Rf Power To Low-density Icwc Plasmasmentioning

confidence: 99%

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Simulation of ITER full-field ICWC scenario in JET: RF physics aspects

Lyssoivan¹,

Douai

Koch³

et al. 2012

Plasma Phys. Control. Fusion

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ITER as a superconducting fusion machine needs efficient wall conditioning techniques for application in the presence of the permanent high toroidal magnetic field for (i) reducing the in-vessel impurity content, (ii) controlling the surface hydrogen isotopic ratio and (iii) mitigating the in-vessel long-term tritium inventory build-up. Encouraging results recently obtained with ion-cyclotron wall conditioning (ICWC) in the present-day tokamaks and stellarators have raised ICWC to the status of one of the most promising techniques available to ITER for routine inter-pulse and overnight conditioning with the ITER main ICRF heating system in the presence of the permanent high toroidal magnetic field. This paper is dedicated to a milestone experiment in ICWC research: the first simulation of ICWC operation in an equivalent ITER full-field scenario and the assessment of the wall conditioning effect on the carbon wall in the largest present-day tokamak JET. In addition, we address in this paper the following topics: (i) an analysis of the radio frequency (RF) physics of ICWC discharges, (ii) the optimization of the operation of ICRF antennas for plasma startup and (iii) an outlook for the performance of ICWC in ITER using the ICRF heating system. Important operational aspects of the conventional ICRF heating system in JET (the so-called A2 antenna system) for use in the ICWC mode are highlighted: (i) the ability of the antenna to ignite the cleaning discharge safely and reliably in different gases, (ii) the capacity of the antennas to couple a large fraction of the RF generator power (>50%) to low-density (≈10 16 -10 18 m −3 ) plasmas and (iii) the ICRF absorption schemes aimed at improved RF plasma homogeneity and enhanced conditioning effect. Successful optimization of the JET-ICWC discharge parameters

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Section: Coupling Rf Power To Low-density Icwc Plasmasmentioning

confidence: 93%

Section: Icwc Operational Windowmentioning

confidence: 99%

Section: Coupling Rf Power To Low-density Icwc Plasmasmentioning

confidence: 99%

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Simulation of ITER full-field ICWC scenario in JET: RF physics aspects

Lyssoivan¹,

Douai

Koch³

et al. 2012

Plasma Phys. Control. Fusion

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“…Although the antenna-plasma coupling during ICWC at high cyclotron harmonics (HCH, at BT = 0.23T) has been observed to be better than that in the fundamental MC scenario (at BT = 2.3T), the latter might benefit from the IC generation of fast ions [2]. Although the antenna-plasma coupling during ICWC at high cyclotron harmonics (HCH, at BT = 0.23T) has been observed to be better than that in the fundamental MC scenario (at BT = 2.3T), the latter might benefit from the IC generation of fast ions [2].…”

Section: Discussionmentioning

confidence: 99%

“…Although application of a stationary (By = 0.01-0.03T « BT) vertical and oscillating poloidal Bp (vertical + radial) magnetic field, during RF discharge at BT = 2.3T, demonstrated effective and promising results for wall conditioning [2], antenna coupling could not be improved in this condition (Fig.l). This effect could be attributed to the asymmetric (to equatorial plane) location of the partially shielded poloidally polarized ICRH antennae in TEXTOR which remain insensitive to the expansion of plasma in presence of By [2].…”

Section: Influence Of Stationary and Rotating Magnetic Fields On Antementioning

confidence: 99%

Study of TEXTOR ICRF Antenna Coupling in the ICWC Mode of Operation

Paul¹,

Lyssoivan²,

Koch³

et al. 2009

AIP Conference Proceedings

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Ion Cyclotron Wall Conditioning (ICWC) discharges, in pulsed-mode operation, were carried out in TEXTOR to simulate a scenario of ITER wall conditioning at half-field. The ICWC discharges were performed in a continuous Helium flow with adjunction of molecular Hydrogen, puffed after the ICRF ignition thus achieving better antenna coupling in the Mode Conversion scenario with improved ICWC performance. Reproducible generation of ICRF plasmas and reliable wall conditioning, after proper wall preloading with Deuterium glow, were achieved by coupling the RF power at 29MHz from one or two ICRF antennas at different toroidal magnetic fields (different cyclotron harmonics). The antenna coupling properties were analyzed in relation to wall conditioning output (removal rates) for selected marker masses. Present study of ICWC at low and high power density per particles (at different gas pressures) emphasizes on the efficiency of the application of stationary, oscillating or rotating poloidal magnetic field. These experimental results will be compared with the predictions of a 0-D RF plasma production model.

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