Characterisation of electron cyclotron wall conditioning plasma in ASDEX Upgrade
Year of publication
2023
Authors
Wauters, T.; Buermans, J.; Cavalier, J.; Huett, E.; Ragona, R.; Svoboda, J.; Bobkov, V.; Griener, M.; Jacobsen, A. S.; Kallenbach, A.; Likonen, J.; Loarer, T.; Lunt, T.; Nielsen, S. K.; Pitts, R. A.; Ricci, D.; Rohde, V.; Stober, J.; Schneider, P.; Usoltseva, M.; EUROfusion MST1 Team
Show moreAbstract
<p>Electron cyclotron wall condition (ECWC) discharges are characterised in ASDEX Upgrade with full tungsten plasma facing components and X2 polarised waves launched from the equatorial ports, relevant to ECWC conditions in ITER Pre-Fusion Power Operation phase 1. The characterisation of the deuterium plasmas is based on experimental inputs such as electron density measurements, in-vessel pressure measurements, poloidal field maps obtained from the measured coil currents, as well as advanced tomographic methods on camera images filtered at the hydrogen Balmer lines. TOMATOR-1D simulations and collective Thomson scattering radiometer spectra complement the findings. The cold, high density and partially ionized toroidal plasmas show significant levels of stray radiation. The measured radiation includes waves at half of the gyrotron frequency suggesting the occurrence of parametric decay instabilities at 2nd harmonic upper hybrid resonance that locates at the low field side of the resonance. A displacement of the plasma emission along the resonance layer is observed at higher discharge power in discharges with a vertical poloidal magnetic field only. By optimizing the poloidal field pattern, along with the location of the electron cyclotron heating (ECH) resonance, the strongest surface interaction regions for the charged particles can be controlled. Directing plasma flux to inner wall surfaces, and same for the inner divertor apron, is found less effective in ASDEX Upgrade due to magnetic mirror effects and outward convective flows. Modeling however predicts the presence of an intense and uniform flux of low energy atoms produced at the ECH absorption layer that may be effective for conditioning the high field side surfaces after use of the disruption mitigation system.</p>
Show moreOrganizations and authors
VTT Technical Research Centre of Finland Ltd
Likonen J.
Publication type
Publication format
Article
Parent publication type
Journal
Article type
Original article
Audience
ScientificPeer-reviewed
Peer-ReviewedMINEDU's publication type classification code
A1 Journal article (refereed), original researchPublication channel information
Journal
Volume
63
Issue
6
Article number
066018
ISSN
Publication forum
Publication forum level
2
Open access
Open access in the publisher’s service
Yes
Open access of publication channel
Partially open publication channel
License of the publisher’s version
CC BY
Self-archived
No
Other information
Fields of science
Materials engineering
Keywords
[object Object],[object Object],[object Object],[object Object],[object Object]
Language
English
International co-publication
Yes
Co-publication with a company
No
DOI
10.1088/1741-4326/acc674
The publication is included in the Ministry of Education and Culture’s Publication data collection
Yes