Propagation and Absorption of ECR Waves in a Low Temperature Toroidal Plasma of Small Size and Magnetic Field

Abstract

The propngntion nnd nbsorption of ECR wnves in n toknmnk plasma with sm;ill size and low values of the elertron temperature and the toroidal mngnetic field is studied numerically. The cold plasma dispersion equation is solved and my tracing calculations are prformcd to find thc nccessibility conditions nnd the optimal tingle of wnve launching for maximal ECR absorption.Absorption coefficients nre computed in the high density approximation. In troduc t,ionAs it has been shown by analizing the power balance of a tokamak type plasriia it is not possible to obtain t hernionuclenr ignition by mere ohniic heating. Therefore various scheiires have been developed in the last years in view of auxiliary heating of hot plasmns. Among them the methods based on launching of high power microwaves in the tokamak plasma showed to be very efficient. Progress in this field is related on one hand to the development of high power techniqurs of generation, transmission and launching of niicrowaves and on the other hand to a n extensive theoretical work elucidating the niechanimis of the energy transfer from the electromagnetic field to t,he plasma.Wave injection near the electron cyclot.ron resonance (ECR) frequency has been theoreticly stidied [ 1-81 and successfully applied to heat the plasiila in varioris toroiclal devices as TM-3, T-10, ISX-B, TFR, PLT, WT-1, ,JIPPT-11, JFT-2, Tosca etc. [9-191. The heating efficiences are of 5-7 eV/kW by using the extraordinarl\. oscillation nrode (with elliptical polarization perpendicrilar to the toroitlnl inagnct ic field) and of 2-4 eV/kW for the ordinary oscillation mode (with linenr polarization parnllcl t o the 1i1ag-nntic field). The ternperatlire growth is of 40--609/, (from 1,5 keV to 2,3 kc\-in T-10, 0,fi to 1 krV in JFT-2, 0,7 to 0,9 keV in Tosca, 0,8 to 1,3 keV in ISX-I3 etc.). The prtwnee of nn ECR wave in the plasma seems to be harmleas from the point of vien Wlierens in tokaniaks of sufficiently great tliniensions, a high teriiperntrire plasiirii itlap absorb conipletely the incident energy arid 1000/, cfficiencies of energy transfer are obtained without iiiajor difficulties, the heating rates have less encorrraging values for plasmas of modest sizes and temperatures; Good efficiencies niay be obtained in