Lower hybrid heating in high density discharge in FT

This paper deals with the results of the experiment of plasma heating by 8 GHz LH waves carried out on the Frascati Tokamak. The main purpose of the experiment is the investigation of the possibility of heating a high density plasma with LH waves. The coupling properties of the 8 GHz LH waves to the plasma are very good. A power density as high as 10 KW/cm2 is routinely injected into the plasma with reflection coefficent of ∼ 15%. In the explored range of densities no evidence of density limit has been observed. As far as the heating results are concerned a RF power of 200 kW has been injected in two target plasmas of different densities. At low density (ne=3.5x1013 cm-3) the observed phenomenology is very similar to the one observed in a previous experiment with 2.45 GHz. At higher density ne=1014 cm-3 well above the 2.45 GHz density limit, the RF power. On the other hand the analysis of electron cyclotron emission spectra shows that faster electrons, corresponding to less accessible values of n are suppressed more strongly than the slower ones as the density is increased. The results on accessibility and those on plasma heating indicate that also the inaccessible part of the spectrum contribute effectively to plasma heating