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Title: Interaction of ICRF Fields with the Plasma Boundary in AUG and JET and Guidelines for Antenna Optimization

Abstract

W sputtering during ICRF on ASDEX Upgrade (AUG) and temperature rise on JET A2 antenna septa are considered in connection with plasma conditions at the antenna plasma facing components and E{sub parallel} near-fields. Large antenna-plasma clearance, high gas puff and low light impurity content are favorable to reduce W sputtering in AUG. The spatial distribution of spectroscopically measured effective W sputtering yields clearly points to the existence of strong E{sub parallel} fields at the antenna box ('feeder fields') which dominate over the fields in front of the antenna straps. The picture of E{sub parallel} fields, obtained by HFSS code, corroborates the dominant role of E{sub parallel} at the antenna box on the formation of sheath-driving RF voltages for AUG. Large antenna-plasma clearance and low gas puff are favorable to reduce septum temperature of JET A2 antennas. Assuming a linear relation between the septum temperature and the sheath driving RF voltage calculated by HFSS, the changes of the temperature with dipole phasing (00{pi}{pi}, 0{pi}{pi}0 or 0{pi}0{pi}) are well described by the related changes of the RF voltages. Similarly to the AUG antenna, the strongest E{sub parallel} are found at the limiters of the JET A2 antenna for all used dipole phasingsmore » and at the septum for the phasings different from 0{pi}0{pi}. A simple general rule can be used to minimize E{sub parallel} at the antenna: image currents can be allowed only at the surfaces which do not intersect magnetic field lines at large angles of incidence. Possible antenna modifications generally rely either on a reduction of the image currents, on their short-circuiting by introducing additional conducting surfaces or on imposing the E{sub parallel} = 0 boundary condition. On the example of AUG antenna, possible options to minimize the sheath driving voltages are presented.« less

Authors:
; ; ; ; ; ; ; ; ;  [1]; ;  [2]; ;  [3]; ; ;  [4];  [5];  [6]
  1. Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, Garching (Germany)
  2. CEA, IRFM, F-13108 Saint-Paul-lez-Durance (France)
  3. ERM-KSN EURATOM Association-Belgian State, Brussels (Belgium)
  4. EURATOM/UKAEA, Culham Science Centre, OX14 3DB, Abingdon (United Kingdom)
  5. Institute of Plasma Physics ASCR, Euratom Association, Za Slovankou 3, Prague (Czech Republic)
  6. Department of Electronics, Politecnico di Torino, Torino (Italy)
Publication Date:
OSTI Identifier:
21335688
Resource Type:
Journal Article
Journal Name:
AIP Conference Proceedings
Additional Journal Information:
Journal Volume: 1187; Journal Issue: 1; Conference: 18. topical conference on radio frequency power in plasmas, Gent (Belgium), 24-26 Jun 2009; Other Information: DOI: 10.1063/1.3273710; (c) 2009 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0094-243X
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ANTENNAS; ASDEX TOKAMAK; BOUNDARY CONDITIONS; ELECTRICAL FAULTS; FIRST WALL; HYPERFINE STRUCTURE; ICR HEATING; IMAGES; JET TOKAMAK; LIMITERS; MAGNETIC FIELDS; OPTIMIZATION; PLASMA; PLASMA IMPURITIES; PLASMA SHEATH; PLASMA WAVES; SPATIAL DISTRIBUTION; SPUTTERING

Citation Formats

Bobkov, V, Bilato, R, Braun, F, Dux, R, Giannone, L., Herrmann, A, Kallenbach, A, Mueller, H W, Neu, R, Puetterich, Th, Rohde, V, Colas, L, Goniche, M, Van Eester, D, Lerche, E, Jacquet, P, Mayoral, M -L, Monakhov, I, Krivska, A, Czech Technical University, Telecommunication Engineering Department, Prague, and Milanesio, D. Interaction of ICRF Fields with the Plasma Boundary in AUG and JET and Guidelines for Antenna Optimization. United States: N. p., 2009. Web. doi:10.1063/1.3273710.
Bobkov, V, Bilato, R, Braun, F, Dux, R, Giannone, L., Herrmann, A, Kallenbach, A, Mueller, H W, Neu, R, Puetterich, Th, Rohde, V, Colas, L, Goniche, M, Van Eester, D, Lerche, E, Jacquet, P, Mayoral, M -L, Monakhov, I, Krivska, A, Czech Technical University, Telecommunication Engineering Department, Prague, & Milanesio, D. Interaction of ICRF Fields with the Plasma Boundary in AUG and JET and Guidelines for Antenna Optimization. United States. doi:10.1063/1.3273710.
Bobkov, V, Bilato, R, Braun, F, Dux, R, Giannone, L., Herrmann, A, Kallenbach, A, Mueller, H W, Neu, R, Puetterich, Th, Rohde, V, Colas, L, Goniche, M, Van Eester, D, Lerche, E, Jacquet, P, Mayoral, M -L, Monakhov, I, Krivska, A, Czech Technical University, Telecommunication Engineering Department, Prague, and Milanesio, D. Thu . "Interaction of ICRF Fields with the Plasma Boundary in AUG and JET and Guidelines for Antenna Optimization". United States. doi:10.1063/1.3273710.
@article{osti_21335688,
title = {Interaction of ICRF Fields with the Plasma Boundary in AUG and JET and Guidelines for Antenna Optimization},
author = {Bobkov, V and Bilato, R and Braun, F and Dux, R and Giannone, L. and Herrmann, A and Kallenbach, A and Mueller, H W and Neu, R and Puetterich, Th and Rohde, V and Colas, L and Goniche, M and Van Eester, D and Lerche, E and Jacquet, P and Mayoral, M -L and Monakhov, I and Krivska, A and Czech Technical University, Telecommunication Engineering Department, Prague and Milanesio, D},
abstractNote = {W sputtering during ICRF on ASDEX Upgrade (AUG) and temperature rise on JET A2 antenna septa are considered in connection with plasma conditions at the antenna plasma facing components and E{sub parallel} near-fields. Large antenna-plasma clearance, high gas puff and low light impurity content are favorable to reduce W sputtering in AUG. The spatial distribution of spectroscopically measured effective W sputtering yields clearly points to the existence of strong E{sub parallel} fields at the antenna box ('feeder fields') which dominate over the fields in front of the antenna straps. The picture of E{sub parallel} fields, obtained by HFSS code, corroborates the dominant role of E{sub parallel} at the antenna box on the formation of sheath-driving RF voltages for AUG. Large antenna-plasma clearance and low gas puff are favorable to reduce septum temperature of JET A2 antennas. Assuming a linear relation between the septum temperature and the sheath driving RF voltage calculated by HFSS, the changes of the temperature with dipole phasing (00{pi}{pi}, 0{pi}{pi}0 or 0{pi}0{pi}) are well described by the related changes of the RF voltages. Similarly to the AUG antenna, the strongest E{sub parallel} are found at the limiters of the JET A2 antenna for all used dipole phasings and at the septum for the phasings different from 0{pi}0{pi}. A simple general rule can be used to minimize E{sub parallel} at the antenna: image currents can be allowed only at the surfaces which do not intersect magnetic field lines at large angles of incidence. Possible antenna modifications generally rely either on a reduction of the image currents, on their short-circuiting by introducing additional conducting surfaces or on imposing the E{sub parallel} = 0 boundary condition. On the example of AUG antenna, possible options to minimize the sheath driving voltages are presented.},
doi = {10.1063/1.3273710},
journal = {AIP Conference Proceedings},
issn = {0094-243X},
number = 1,
volume = 1187,
place = {United States},
year = {2009},
month = {11}
}