ICRF plasma production in TEXTOR-94

This paper gives an overview of ICRF plasma production in TEXTOR-94 using the present two double loop antennas, one with and one without Faraday screen, for start-up of OH discharges and conditioning / coating of the vessel. The results show that He-plasma with density up to ne0≈3×1012 cm−3 is reliably produced at the standard ICRH frequency (f=32.5 MHz) in a wide range of toroidal magnetic field BT=0.20–2.25 T (2ωci⩽ω⩽20ωci), gas pressure pHe=1×10−5−1×10−3 mbar and total RF power at generators up to PRF=2×600 kW in the best cases. In addition, H-, D-plasmas and multi-ion species plasmas (mixture of He and SiD4 up to 70%) were produced. The screenless antenna gives the largest RF power contribution, the coupling increases with pressure and by lowering BT. This novel RF technique recently allowed reliable and reproducible ICRF assisted low voltage start-up and efficient ICRF wall conditioning in between normal OH discharges in TEXTOR-94.