A RAY TRACING STUDY OF ELECTRON CYCLOTRON RESONANCE HEATING IN TOKAMAK PLASMAS WITH A SUPERTHERMAL ELECTRON TAIL
We consider a tokamak plasma in which the distribution of electron velocities in the direction parallel to the magnetic field has a monotonically decreasing superthermal tail. A fully three-dimensional ray tracing code, which includes a realistic antenna pattern, toroidal effects, and refraction, is used to calculate the absorption of the extraordinary mode in the nonrelativistic limit away from perpendicular incidence. The ray tracing approach extends results previously obtained in slab geometry (3-8) to a more realistic configuration; it is also essential in dealing with strong refraction in high density plasmas. Our analytical model for the tail makes available a wide range of tail shapes and parameters. At low densities small tails (tail fraction <or=0.5%) can significantly affect wave absorption and energy deposition profiles. In a high density plasma where the fundamental cyclotron resonance is cut-off, tail electrons in the edge region can cause substantial absorption. The use of a gyrotron with frequency much less than the central electron cyclotron frequency with an outside launch position is confirmed as very effective in the presence of very few tail electrons (tail fraction approximately equal 0.5%).
Bibliographic Reference: WRITE TO THE LIBRARIAN, UKAEA, CULHAM LABORATORY, ABINGDON, OXON OX14 3DB (UK), MENTIONING REPORT CLM-P754, 1985
Record Number: 1989124099700 / Last updated on: 1987-01-01
Available languages: en