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Abstract

RF heating in the ion cyclotron range of frequencies is impaired by a too large impurity production observed in all experiments. Analysis showed that a too large fraction of the power launched by the antenna inside the plasma vessel was not used to be transferred to (minority) ions and electrons. The first step was to optimize the power fraction absorbed by minority ions. This led to the concept of optimized antenna. But investigations showed that one should consider as well, the problem of really minimizing the power loss inside the plasma vessel, equal to: power launched by the antenna minus power dumped into the plasma particles, ions and electrons. Analysis of power deposition for monopole and quadrupole antenna was then making the quadrupole case less appealing, because in the monopole case almost all of the power launched by the antenna into the particles can be dumped especially as the plasma size is larger. As the coupling efficiency is larger for monopole, the total power absorbed in the plasma is larger than with a quadrupole, with modest impurity increase to be expected. However, a quadrupole antenna presents also interesting specific advantages, making a final choice between these two possibilities too premature.

Additional information

Authors: COTSAFTIS M CEA, FONTENAY-AUX-ROSES (FRANCE), CEA, FONTENAY-AUX-ROSES (FRANCE)
Bibliographic Reference: WRITE TO CEA, DEPARTEMENT DE RECHERCHES SUR LA FUSION CONTROLEE, MENTIONING REPORT EUR-CEA-FC-1288 EN, 1986
Availability: Can be ordered online
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