NONLINEAR MODE COMPETITION BETWEEN UNSTABLE DRIFT WAVES IN AN RF HEATED RING DISCHARGE

The nonlinear wave-wave interaction between unstable drift modes of di fferent wave numbers existing in an rf heated, magnetized plasma is st udied experimentally by means of capacitive probe measurements during the evolution of the discharge towards steady state. The results are c ompared with theoretical calculations. Special interest is attached to the unstable growth of multiple modes arising out of the noise level, where strong suppressive interaction between different modes is obser ved, finally leading to a single mode spectrum.