ECRH sustained breakdown plasmas in RTP

The future research programme of the Rijnhuizen Tokamak Project RTP will concentrate on the study of transport mechanisms in strongly auxiliary heated tokamak plasmas. An Electron Cyclotron Resonance Heating (ECRH) system which can comprise up to three 60 GHz, 200 kW, 100 ms gyrotrons will supply the additional heating power. ECRH is also attractive for starting-up tokamak plasmas. This paper deals with experimental results on plasmas produced and sustained by sole ECRH power. It appears that during the ECH pulse, with the RF power launched perpendicular to the magnetic field from the lower field side, a weak plasma current (Ip<2 kA) flows in RTP. Suchlike currents were observed earlier in various devices, and for diverse experimental parameters will be described for 60 GHz irradiation. The ECH power ranges up to 200 kW, and the pulse lengths are up to 100 ms. The studies should yield the best scenario for low-voltage tokamak start-up. (author) 7 refs., 8 figs