Isotope exchange by Ion Cyclotron Wall Conditioning on JET

Wall conditioning is essential in tokamak and stellarator research to achieve plasma performance and reproducibility. This paper presents an overview of recent conditioning results, both from experiments in present devices and modelling, in view of devices with superconducting coils, with focus on W7-X, JT-60SA and ITER. In these devices, the coils stay energised throughout an experimental day or week which demands for new conditioning techniques that work in presence of the nominal field, in addition to the proven conditioning methods such as baking, glow discharge conditioning (GDC) and low-Z wall coating through GDC-plasma, which do not work under such condition. The discussed techniques are RF conditioning without plasma current, both in the ion cyclotron and electron cyclotron range of frequencies, and diverted conditioning plasmas with nested magnetic flux surfaces.

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“…equations in section 2.2). Removal dependencies on coupled power, discharge pressure and plasma density are described in [63].…”

Section: Fuel Recovery By Icwcmentioning

confidence: 99%

Wall conditioning in fusion devices with superconducting coils

Wauters¹,

Borodin

Brakel

et al. 2020

Plasma Phys. Control. Fusion

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“…Numerous experiments evidenced the effectiveness of ICWC, demonstrating (i) recovery of sustained ohmic breakdown and density control after disruptions (realised e.g. on Tore Supra [56]) and after severe impurity exposure (evidenced in TEXTOR [57]), (ii) full change-over of the isotopic ratio of the JET ITER-like wall [58], (iii) full depletion of the Tungsten ASDEX-Upgrade wall from deuterium by He-ICWC [59] (iv) higher density, temperature and purity of the main plasma in the U-3M stellarator after ICWC performance [60].…”

Section: Icrf Assisted Plasma Start-up and Wall Conditioningmentioning

confidence: 99%

Ion cyclotron resonance heating scenarios for DEMO

Eester¹,

Lerche²,

Ragona³

et al. 2019

Nucl. Fusion

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The present paper offers an overview of the potential of ion cyclotron resonance heating (ICRH) or radio frequency (RF) heating for the DEMO machine. It is found that various suitable heating schemes are available. Similar to ITER and in view of the limited bandwidth of about 10M Hz that can be achieved to ensure optimal functioning of the launcher, it is proposed to make core second harmonic tritium heating the key ion heating scheme, assisted by fundamental cyclotron heating 3 He in the early phase of the discharge; for the present design of DEMO-with a static magnetic field strength of B o = 5.855T-that places the T and 3 He layers in the core for f = 60M Hz and suggests to center the bandwidth around that main operating frequency. In line with earlier studies for hot, dense plasmas in large-size magnetic confinement machines it is shown that good single pass absorption is achieved but that the size as well as operating density and temperature of the machine cause the electrons to absorb a non-negligible fraction of the power away from the core when core ion heating is aimed at. Current drive and alternative heating options are briefly discussed and a dedicated computation is done for the traveling wave antenna, proposed for DEMO in view of its compatibility with substantial antenna-plasma distances. The various tasks that ICRH can fulfill are briefly listed. Finally, the impact of transport and the sensitivity of the obtained results to changes in the machine parameters is commented on.

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“…The most suitable ICRF frequency for current drive is 50 MHz or 80 MHz [6]. Moreover, ICRF heating can be used for ion cyclotron wall conditioning and plasma startup [7], core impurity control [8] and sawtooth control/pacing [9,10]. Thus, ICRF is a promising and versatile heating method for DEMO.…”

Section: Emc3-eirene Modeling Of Edge Plasma To Improve the Icrf Coup...mentioning

confidence: 99%

EMC3-EIRENE modeling of edge plasma to improve the ICRF coupling with local gas puffing in DEMO

et al. 2018

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We report the first 3D EMC3-EIRENE simulations of scrape-off layer (SOL) plasma in DEMO. EMC3-EIRENE is a 3D edge plasma fluid and neutral particle transport code. Effects of local gas puffing on the SOL density and Ion Cyclotron Range of Frequencies (ICRF) power coupling have been studied. A pure deuterium is simulated and the puffing/fueling gas is deuterium gas. The investigated gas puffing cases include the divertor, top, midplane and antenna gas puffing. The ICRF antenna is toroidally 360 o distributed and poloidally located in the outer top of the vessel. The results show that toroidal distributed but poloidal localized antenna gas puffing increases the density in front of the antenna most significantly while top or midplane gas puffing increases this antenna density to a moderate level. Influences of gas puff rate and particle transport parameters on the SOL density are investigated. The parameter scans indicate that the shift of the fast wave cutoff density position to the antenna depends almost linearly on the total gas puff rate. To achieve a significant antenna density increase, the antenna gas puff rate should be at the level of 1.8 × 10 23 el/s (i.e. 1.0 × 10 22 el/s per tokamak segment). As the total gas puff rate increases to 4.0 × 10 23 el/s, the evanescent layer of the fast wave (with k || = 2 m-1) almost vanishes. Moreover, it is found that antenna gas puffing reduces the local power flux to the main chamber wall near the gas valve due to a local decrease of the SOL temperature.

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Isotope exchange by Ion Cyclotron Wall Conditioning on JET

Cited by 18 publications

References 12 publications

Wall conditioning in fusion devices with superconducting coils

Wall conditioning in fusion devices with superconducting coils

Ion cyclotron resonance heating scenarios for DEMO

EMC3-EIRENE modeling of edge plasma to improve the ICRF coupling with local gas puffing in DEMO

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