Assessment of a field-aligned ICRF antenna
Impurity contamination and localized heat loads associated with ion cyclotron range of frequency (ICRF) antenna operation are among the most challenging issues for ICRF utilization.. Another challenge is maintaining maximum coupled power through plasma variations including edge localized modes (ELMs...
| Main Authors: | , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | en_US |
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American Institute of Physics (AIP)
2014
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| Online Access: | http://hdl.handle.net/1721.1/88535 https://orcid.org/0000-0003-3234-8733 https://orcid.org/0000-0002-9518-4097 https://orcid.org/0000-0002-8753-1124 https://orcid.org/0000-0002-7841-9261 |
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| author | Wukitch, Stephen James Brunner, Daniel Frederic Ennever, Paul Chappell Garrett, Michael L. Hubbard, Amanda E. Labombard, Brian Lau, C. Lin, Yijun Lipschultz, Bruce Miller, D. Ochoukov, Roman Igorevitch Porkolab, Miklos Reinke, Matthew Logan Terry, James L. |
| author2 | Massachusetts Institute of Technology. Department of Physics |
| author_facet | Massachusetts Institute of Technology. Department of Physics Wukitch, Stephen James Brunner, Daniel Frederic Ennever, Paul Chappell Garrett, Michael L. Hubbard, Amanda E. Labombard, Brian Lau, C. Lin, Yijun Lipschultz, Bruce Miller, D. Ochoukov, Roman Igorevitch Porkolab, Miklos Reinke, Matthew Logan Terry, James L. |
| author_sort | Wukitch, Stephen James |
| collection | MIT |
| description | Impurity contamination and localized heat loads associated with ion cyclotron range of frequency (ICRF) antenna operation are among the most challenging issues for ICRF utilization.. Another challenge is maintaining maximum coupled power through plasma variations including edge localized modes (ELMs) and confinement transitions. Here, we report on an experimental assessment of a field aligned (FA) antenna with respect to impurity contamination, impurity sources, RF enhanced heat flux and load tolerance. In addition, we compare the modification of the scrape of layer (SOL) plasma potential of the FA antenna to a conventional, toroidally aligned (TA) antenna, in order to explore the underlying physics governing impurity contamination linked to ICRF heating. The FA antenna is a 4-strap ICRF antenna where the current straps and antenna enclosure sides are perpendicular to and the Faraday screen rods are parallel to the total magnetic field. In principle, alignment with respect to the total magnetic field minimizes integrated E∥ (electric field along a magnetic field line) via symmetry. Consistent with expectations, we observed that the impurity contamination and impurity source at the FA antenna are reduced compared to the TA antenna. In both L and H-mode discharges, the radiated power is 20–30% lower for a FA-antenna heated discharge than a discharge heated with the TA-antennas. Further we observe that the fraction of RF energy deposited upon the antenna is less than 0.4 % of the total injected RF energy in dipole phasing. The total deposited energy increases significantly when the FA antenna is operated in monopole phasing. The FA antenna also exhibits an unexpected load tolerance for ELMs and confinement transitions compared to the TA antennas. However, inconsistent with expectations, we observe RF induced plasma potentials to be nearly identical for FA and TA antennas when operated in dipole phasing. In monopole phasing, the FA antenna has the highest plasma potentials and poor heating efficiency despite calculations indicating low integrated E∥. In mode conversion heating scenario, no core waves were detected in the plasma core indicating poor wave penetration. For monopole phasing, simulations suggest the antenna spectrum is peaked at very short wavelength and full wave simulations show the short wavelength has poor wave penetration to the plasma core. |
| first_indexed | 2024-09-23T08:46:21Z |
| format | Article |
| id | mit-1721.1/88535 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T08:46:21Z |
| publishDate | 2014 |
| publisher | American Institute of Physics (AIP) |
| record_format | dspace |
| spelling | mit-1721.1/885352022-09-23T14:26:20Z Assessment of a field-aligned ICRF antenna Wukitch, Stephen James Brunner, Daniel Frederic Ennever, Paul Chappell Garrett, Michael L. Hubbard, Amanda E. Labombard, Brian Lau, C. Lin, Yijun Lipschultz, Bruce Miller, D. Ochoukov, Roman Igorevitch Porkolab, Miklos Reinke, Matthew Logan Terry, James L. Massachusetts Institute of Technology. Department of Physics Massachusetts Institute of Technology. Plasma Science and Fusion Center Wukitch, Stephen James Brunner, Daniel Frederic Ennever, Paul Chappell Garrett, Michael L. Hubbard, Amanda E. Labombard, Brian Lau, C. Lin, Yijun Lipschultz, Bruce Miller, D. Ochoukov, Roman Igorevitch Porkolab, Miklos Reinke, Matthew Logan Terry, James L. Impurity contamination and localized heat loads associated with ion cyclotron range of frequency (ICRF) antenna operation are among the most challenging issues for ICRF utilization.. Another challenge is maintaining maximum coupled power through plasma variations including edge localized modes (ELMs) and confinement transitions. Here, we report on an experimental assessment of a field aligned (FA) antenna with respect to impurity contamination, impurity sources, RF enhanced heat flux and load tolerance. In addition, we compare the modification of the scrape of layer (SOL) plasma potential of the FA antenna to a conventional, toroidally aligned (TA) antenna, in order to explore the underlying physics governing impurity contamination linked to ICRF heating. The FA antenna is a 4-strap ICRF antenna where the current straps and antenna enclosure sides are perpendicular to and the Faraday screen rods are parallel to the total magnetic field. In principle, alignment with respect to the total magnetic field minimizes integrated E∥ (electric field along a magnetic field line) via symmetry. Consistent with expectations, we observed that the impurity contamination and impurity source at the FA antenna are reduced compared to the TA antenna. In both L and H-mode discharges, the radiated power is 20–30% lower for a FA-antenna heated discharge than a discharge heated with the TA-antennas. Further we observe that the fraction of RF energy deposited upon the antenna is less than 0.4 % of the total injected RF energy in dipole phasing. The total deposited energy increases significantly when the FA antenna is operated in monopole phasing. The FA antenna also exhibits an unexpected load tolerance for ELMs and confinement transitions compared to the TA antennas. However, inconsistent with expectations, we observe RF induced plasma potentials to be nearly identical for FA and TA antennas when operated in dipole phasing. In monopole phasing, the FA antenna has the highest plasma potentials and poor heating efficiency despite calculations indicating low integrated E∥. In mode conversion heating scenario, no core waves were detected in the plasma core indicating poor wave penetration. For monopole phasing, simulations suggest the antenna spectrum is peaked at very short wavelength and full wave simulations show the short wavelength has poor wave penetration to the plasma core. United States. Dept. of Energy (DOE award DE-FC02-99ER54512) United States. Dept. of Energy (Fusion Energy Postdoctoral Research Program administered by ORISE) 2014-08-05T14:39:13Z 2014-08-05T14:39:13Z 2014 Article http://purl.org/eprint/type/JournalArticle http://hdl.handle.net/1721.1/88535 Wukitch, S. J., D. Brunner, P. Ennever, M. L. Garrett, A. Hubbard, B. Labombard, C. Lau, et al. “Assessment of a Field-Aligned ICRF Antenna” AIP Conference Proceedings, 1580, 73 (2014) p.73-80. https://orcid.org/0000-0003-3234-8733 https://orcid.org/0000-0002-9518-4097 https://orcid.org/0000-0002-8753-1124 https://orcid.org/0000-0002-7841-9261 en_US http://dx.doi.org/10.1063/1.4864504 AIP Conference Proceedings Creative Commons Attribution-Noncommercial-Share Alike http://creativecommons.org/licenses/by-nc-sa/4.0/ application/pdf American Institute of Physics (AIP) MIT web domain |
| spellingShingle | Wukitch, Stephen James Brunner, Daniel Frederic Ennever, Paul Chappell Garrett, Michael L. Hubbard, Amanda E. Labombard, Brian Lau, C. Lin, Yijun Lipschultz, Bruce Miller, D. Ochoukov, Roman Igorevitch Porkolab, Miklos Reinke, Matthew Logan Terry, James L. Assessment of a field-aligned ICRF antenna |
| title | Assessment of a field-aligned ICRF antenna |
| title_full | Assessment of a field-aligned ICRF antenna |
| title_fullStr | Assessment of a field-aligned ICRF antenna |
| title_full_unstemmed | Assessment of a field-aligned ICRF antenna |
| title_short | Assessment of a field-aligned ICRF antenna |
| title_sort | assessment of a field aligned icrf antenna |
| url | http://hdl.handle.net/1721.1/88535 https://orcid.org/0000-0003-3234-8733 https://orcid.org/0000-0002-9518-4097 https://orcid.org/0000-0002-8753-1124 https://orcid.org/0000-0002-7841-9261 |
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