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Abstract

CURRENT DRIVE BY ELECTRON CYCLOTRON (EC) WAVES FOR OPERATING A STEADY STATE TOKAMAK REACTOR WAS STUDIED BY GENERATING A NET TOROIDAL CURRENT, BY A HEATING PROCESS WHICH IS ESSENTIALLY PERPENDICULAR TO THE TOROIDAL DIRECTION. IN THE LIMIT OF A HOMOGENEOUS MAGNETIC FIELD CONFIGURATION, THIS PROCESS CAN BE AS EFFICIENT AS DIRECT PARALLEL HEATING. IN A TOROIDAL SYSTEM ELECTRON TRAPPING IMPOSES A STRINGENT LIMIT TO ITS EFFICIENCY. THE CASE IS SIGNIFICANT WHEN WAVE ABSORPTION IS AT DOWN SHIFTED FREQUENCIES (WHEN THE WAVE FREQUENCY IS BELOW THE EC FREQUENCY) AND AT HIGH POWER LEVELS. TWO METHODS FOR MINIMIZING THIS LIMITATION WERE INVESTIGATED: I) MOVING THE ABSORPTION REGION TO THE INBOARD SIDE OF THE MAGNETIC SURFACE) COMBINING EC AND LOWER HYBRID (LH) WAVES. TO EVALUATE THE CURRENT DRIVE EFFICIENCY FOR REALISTIC WAVE POWER LEVELS, THE TIME-DEPENDANT BOUNCE-AVERAGED QUASILINEAR/FOKKER-PLANCK EQUATION WAS SOLVED USING A 2-D FOKKER-PLANCK CODE. THE CASE OF EXTRAORDINARY (X) MODE ABSORBED AT LOW WAVE FREQUENCY WAS CONSIDERED FOR LOW AND HIGH WAVE POWER. MOVING THE ABSORPTION REGION WAS INEFFECTIVE IN ENHANCING THE CURRENT DRIVE EFFICIENCY, BECAUSE OF THE INTERPLAY OF QUASILINEAR AND TOROIDAL EFFECTS AT HIGH WAVE POWER. COMBINATION WITH LH WAVES CAN BE EFFICIENT IN MINIMIZING THE NEGATIVE IMPACT OF ELECTRON TRAPPING.

Additional information

Authors: GIRUZZI G FOM-INSTITUUT VOOR PLASMAFYSICA "RIJNHUIZEN", NIEUWEGEIN, NL, FOM-INSTITUUT VOOR PLASMAFYSICA "RIJNHUIZEN", NIEUWEGEIN, NL
Bibliographic Reference: PAPER PRESENTED: 15TH EUROPEAN CONFERENCE ON CONTROLLED FUSION AND PLASMA HEATING, DUBROVNIK/YU, MAY 16-20, 1988, AVAILABILITY: CEC-LUXEMBOURG, DG XIII/A2, BP 1907, MENTIONING PAPER ORA 33965 E
Availability: Can be ordered online
Record Number: 1989126228600 / Last updated on: 1989-04-01
Category: PUBLICATION
Available languages: en