Experimental study of parametric instabilities driven by finite-extent lower-hybrid waves

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Abstract
The lower-hybrid wave is an attractive candidate for the supplemental heating of Tokamak plasmas because of its engineering advantages in a reactor environment. It is estimated that 50 MW of supplementary r.f. heating power will be required to ignite a DT fusion reactor. At this power level the linear theory for lower-hybrid waves may be invalid, and one is forced to consider possible non-linear effects such as parametric instabilities. The authors present experimental results on the parametric decay of the lower-hybrid 'pump' wave into another lower-hybrid wave and a non-resonant 'quasi-mode', that is, a wave which is not a normal mode of the plasma.