29th Symposium on Fusion Technology (SOFT 2016)

P4.037 ITER-like antenna for JET first results of the advanced matching control algorithms

8 Sep 2016, 14:20

1h 40m

Foyer 2A (2nd floor), 3A (3rd floor) (Prague Congress Centre)

Board: 37

Poster B. Plasma Heating and Current Drive P4 Poster session

Speaker

Frederic Durodie` (Laboratory for Plasma Physics)

Description

The ITER-like Antenna (ILA) [1] for JET is a 2 toroidal by 2 poloidal array of Resonant Double Loops (RDL). It featurs in-vessel matching capacitors feeding RF current straps in Conjugate-T (CT) manner, a low impedance quarter-wave impedance transformer and a service stub allowing hydraulic actuator and water cooling services to reach the aforementioned capacitors. A 2^ndnd stage phaseshifter / stub matching circuit allows to match the chosen conjugate-T working impedance to 30Ω. Toroidally adjacent RDLs are fed from a 3dB hybrid splitter. The assessment of the ILA results (2008-2009) identified that achieving routine full array operation required a better understanding of the RF circuit, tighter calibrations of RF measurements and last but not least a feedback control algorithm for the 2^ndnd stage matching. The matching and phasing of the array is controlled by 22 feedback loops actuating the 8 matching capacitors, the 4 second stage phase shifters and 4 stubs, the 4 Main Transmission Line (MTL) phase shifters and the 2 phases with respect to a reference of the generators feeding the upper and lower half array through 3dB hybrid combiner-splitters. The circuit was extensively simulated [2] allowing to develop an algorithm which drives the 2^ndnd stage matching circuit components, phase shifter and stub, to optimal locations with respect to the measured remaining VSWR excursions due to ELMs. The paper focusses on the new additional matching algorithms and assesses their performance. [1] F. Durodié et al., Plasma Physics and Controlled Fusion 54, 074012+ (2012), ISSN 0741-3335, URL http: //dx.doi.org/10.1088/0741-3335/54/7/074012. [2] F. Durodié et al.,AIP Conf. Proc. 1689, 070013 (2015); http://dx.doi.org/10.1063/1.4936520 *See the Appendix of F. Romanelli et al., Proceedings of the 25th IAEA Fusion Energy Conference 2014, Saint Petersburg, Russia