ANTENNA OPTIMIZATION FOR ALFVEN WAVE HEATING
Antenna optimization studies for radio-frequency coupling to the Alfven waves is carried out using a self-consistent, three-dimensional, fully analytic, Faraday shielded, periodic loop antenna model. The antenna characteristics (the loading resistance R, the reactance X, the quality factor Q, and the efficiency eta-A) are investigated over a wide range of parameters using the ASDEX UPGRADE parameters as reference. With proper care it is possible to obtain an experimentally acceptable loading of R about 1O MEGA with an attendent Q about 20 under optimal conditions. The required conditions consist of (i) locating the singular Alfven layer at about two-thirds the plasma radius, and (ii) the adjacent antenna separation along the toroidal direction is of the order of the plasma radius. This implies using a toroidal wave number n about 8, for the ASDEX UPGRADE case. The extensive results presented here should facilitate the antenna design for Alfven wave heating in most existing as well as projected machines. By scaling the linear dimensions of the ASDEX UPGRADE it is shown that the Alfven wave heating continues to be an attractive alternative even for plasmas of thermonuclear dimensions. Due to the changing plasma conditions during the radio-frequency heating phase, dynamic impedance tracking may become necessary. Methods for maintaining an efficient coupling under these conditions through the phase control of a dense cluster array antenna, resembling the lower-hybrid grill coupler, is suggested.
Bibliographic Reference: WRITE TO MAX-PLANCK-INSTITUT F41VUR PLASMAPHYSIK, 8046 GARCHING BEI MUENCHEN (GERMANY), MENTIONING REPORT IPP 4/228, 1986
Record Number: 1989125020600 / Last updated on: 1987-02-01
Available languages: en