RF sheath modeling of experimentally observed plasma surface interactions with the JET ITER-Like Antenna
Waves in the Ion Cyclotron Range of Frequencies (ICRF) enhance local Plasma-Surface Interactions (PSI) near the wave launchers and magnetically-connected objects via Radio-Frequency (RF) sheath rectification. ITER will use 20MW of ICRF power over long pulses, questioning the long-term impact of RF-e...
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| Format: | Article |
| Language: | English |
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Elsevier
2019-05-01
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| Series: | Nuclear Materials and Energy |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S2352179118301741 |
| _version_ | 1819225044998422528 |
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| author | A. Křivská V. Bobkov L. Colas P. Dumortier F. Durodié P Jacquet C.C. Klepper D. Milanesio G. Urbanczyk |
| author_facet | A. Křivská V. Bobkov L. Colas P. Dumortier F. Durodié P Jacquet C.C. Klepper D. Milanesio G. Urbanczyk |
| author_sort | A. Křivská |
| collection | DOAJ |
| description | Waves in the Ion Cyclotron Range of Frequencies (ICRF) enhance local Plasma-Surface Interactions (PSI) near the wave launchers and magnetically-connected objects via Radio-Frequency (RF) sheath rectification. ITER will use 20MW of ICRF power over long pulses, questioning the long-term impact of RF-enhanced localized erosion on the lifetime of its Beryllium (Be) wall. Recent dedicated ICRF-heated L-mode discharges documented this process on JET for different types of ICRF antennas. Using visible spectroscopy in JET ICRF-heated L-mode discharges, poloidally-localized regions of enhanced (by ∼2–4x) Be I and Be II light emission were observed on two outboard limiters magnetically connected to the bottom of the active ITER-Like Antenna (ILA). The observed RF-PSI induced by the ILA was qualitatively comparable to that induced by the JET standard, type-A2 antennas, for similar strap toroidal phasing and connection geometries. The Be II line emission was found more intense when powering the bottom half of the ILA rather than its top half. Conversely, more pronounced SOL density modifications were observed with only top array operation, on field lines connected to the top half of the ILA. So far the near-field modeling of the ILA with antenna code TOPICA (Torino Polytechnic Ion Cyclotron Antenna), using curved antenna model, was partially able to reproduce qualitatively the observed phenomena. A quantitative discrepancy persisted between the observed Be source amplification and the calculated, corresponding increases in E// field at the magnetically connected locations to the ILA when changing from only top to only bottom half antenna operation. This paper revisits these current drive phased and half-ILA powered cases using for the new simulations flat model of the ILA and more realistic antenna feeding to calculate the E// field maps with TOPICA code. Further, the Self-consistent Sheaths and Waves for Ion Cyclotron Heating Slow Wave (SSWICH-SW) code, which couples slow wave evanescence with DC Scrape-Off Layer (SOL) biasing, is used to estimate the poloidal distribution of rectified RF-sheath Direct Current (DC) potential VDC in the private SOL between the ILA poloidal limiters. The approach so far was limited to correlating the observed, enhanced emission regions at the remote limiters to the antenna near-electric fields, as calculated by TOPICA. The present approach includes also a model for the rectification of these near-fields in the private SOL of the ILA. With the improved approach, when comparing only top and only bottom half antenna feeding, we obtained good qualitative correlation between all experimental measurements and the calculated local variations in the E// field and VDC potential. |
| first_indexed | 2024-12-23T10:03:21Z |
| format | Article |
| id | doaj.art-c1f5da0626ce4c3598474f3a3c3acf0f |
| institution | Directory Open Access Journal |
| issn | 2352-1791 |
| language | English |
| last_indexed | 2024-12-23T10:03:21Z |
| publishDate | 2019-05-01 |
| publisher | Elsevier |
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| series | Nuclear Materials and Energy |
| spelling | doaj.art-c1f5da0626ce4c3598474f3a3c3acf0f2022-12-21T17:51:10ZengElsevierNuclear Materials and Energy2352-17912019-05-0119324329RF sheath modeling of experimentally observed plasma surface interactions with the JET ITER-Like AntennaA. Křivská0V. Bobkov1L. Colas2P. Dumortier3F. Durodié4P Jacquet5C.C. Klepper6D. Milanesio7G. Urbanczyk8Laboratory for Plasma Physics, ERM/KMS, 30 Avenue de la Renaissance B-1000, Brussels, Belgium; Corresponding author.Max-Planck-Institut für Plasmaphysik, D-85748 Garching, GermanyIRFM CEA, Cadarache F-13108 Saint Paul lez Durance, FranceLaboratory for Plasma Physics, ERM/KMS, 30 Avenue de la Renaissance B-1000, Brussels, Belgium; CCFE, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB, UKLaboratory for Plasma Physics, ERM/KMS, 30 Avenue de la Renaissance B-1000, Brussels, BelgiumCCFE, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB, UKOak Ridge National Laboratory, Oak Ridge, TN 37831-6169, USAPolitecnico di Torino, Corso Duca degli Abruzzi 24, I-10129 Torino, ItalyIRFM CEA, Cadarache F-13108 Saint Paul lez Durance, FranceWaves in the Ion Cyclotron Range of Frequencies (ICRF) enhance local Plasma-Surface Interactions (PSI) near the wave launchers and magnetically-connected objects via Radio-Frequency (RF) sheath rectification. ITER will use 20MW of ICRF power over long pulses, questioning the long-term impact of RF-enhanced localized erosion on the lifetime of its Beryllium (Be) wall. Recent dedicated ICRF-heated L-mode discharges documented this process on JET for different types of ICRF antennas. Using visible spectroscopy in JET ICRF-heated L-mode discharges, poloidally-localized regions of enhanced (by ∼2–4x) Be I and Be II light emission were observed on two outboard limiters magnetically connected to the bottom of the active ITER-Like Antenna (ILA). The observed RF-PSI induced by the ILA was qualitatively comparable to that induced by the JET standard, type-A2 antennas, for similar strap toroidal phasing and connection geometries. The Be II line emission was found more intense when powering the bottom half of the ILA rather than its top half. Conversely, more pronounced SOL density modifications were observed with only top array operation, on field lines connected to the top half of the ILA. So far the near-field modeling of the ILA with antenna code TOPICA (Torino Polytechnic Ion Cyclotron Antenna), using curved antenna model, was partially able to reproduce qualitatively the observed phenomena. A quantitative discrepancy persisted between the observed Be source amplification and the calculated, corresponding increases in E// field at the magnetically connected locations to the ILA when changing from only top to only bottom half antenna operation. This paper revisits these current drive phased and half-ILA powered cases using for the new simulations flat model of the ILA and more realistic antenna feeding to calculate the E// field maps with TOPICA code. Further, the Self-consistent Sheaths and Waves for Ion Cyclotron Heating Slow Wave (SSWICH-SW) code, which couples slow wave evanescence with DC Scrape-Off Layer (SOL) biasing, is used to estimate the poloidal distribution of rectified RF-sheath Direct Current (DC) potential VDC in the private SOL between the ILA poloidal limiters. The approach so far was limited to correlating the observed, enhanced emission regions at the remote limiters to the antenna near-electric fields, as calculated by TOPICA. The present approach includes also a model for the rectification of these near-fields in the private SOL of the ILA. With the improved approach, when comparing only top and only bottom half antenna feeding, we obtained good qualitative correlation between all experimental measurements and the calculated local variations in the E// field and VDC potential.http://www.sciencedirect.com/science/article/pii/S2352179118301741 |
| spellingShingle | A. Křivská V. Bobkov L. Colas P. Dumortier F. Durodié P Jacquet C.C. Klepper D. Milanesio G. Urbanczyk RF sheath modeling of experimentally observed plasma surface interactions with the JET ITER-Like Antenna Nuclear Materials and Energy |
| title | RF sheath modeling of experimentally observed plasma surface interactions with the JET ITER-Like Antenna |
| title_full | RF sheath modeling of experimentally observed plasma surface interactions with the JET ITER-Like Antenna |
| title_fullStr | RF sheath modeling of experimentally observed plasma surface interactions with the JET ITER-Like Antenna |
| title_full_unstemmed | RF sheath modeling of experimentally observed plasma surface interactions with the JET ITER-Like Antenna |
| title_short | RF sheath modeling of experimentally observed plasma surface interactions with the JET ITER-Like Antenna |
| title_sort | rf sheath modeling of experimentally observed plasma surface interactions with the jet iter like antenna |
| url | http://www.sciencedirect.com/science/article/pii/S2352179118301741 |
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