Scattering from ECRF waves

Abstract

There has heen considerable progress made in the heating of tokamak and mirror plasmas in the electron cyclotron range of frequencies (ECRF) due to the recent availability of high power millimeter wave gyrotrons. Both O-mode and X-mode heating studies have been performed using, outside and inside wave launching structures.(1,2) In Doublet-III, electron temperatures have increased from ≃ 1 keV to > 2 keV using 750 kW of 60 GHz heating power. Furthermore, in PDX electron temperature increases from ≃ 1.5keV to ≃ 3keV have been observed in the central plasma region with ≃ 80kW input power at 60 GHz. In addition, several interesting observations have also been made. First, the 60 GHz radiation that was transmitted through the plasma into the low field region was spectrally resolved. Satellites separated by the lower hybrid frequency were observed indicative of parametric decay. Second, the heating power was deposited locally and was therefore large compared to the ohmic heating power in the central region. This therefore resulted in steep temperature gradients over distances of only ≃ 10–15cm which can strongly affect the low frequency microturbulence.