An Experimental Study of Waveguide Coupled Microwave Heating with Conventional Multicusp Negative Ion Source

摘要

Negative ion production with conventional multicusp plasma chambers utilizing2.45 GHz microwave heating is demonstrated. The experimental results wereobtained with the multicusp plasma chambers and extraction systems of theRFdriven RADIS ion source and the filament driven arc discharge ion sourceLIISA. A waveguide microwave coupling system, which is almost similar to theone used with the SILHI ion source, was used. The results demonstrate that atleast one third of negative ion beam obtained with inductive RF-coupling(RADIS) or arc discharge (LIISA) can be achieved with 1 kW of 2.45 GHzmicrowave power in CW mode without any modification of the plasma chamber. Theco-extracted electron to H^- ratio and the optimum pressure range were observedto be similar for both heating methods. The behaviour of the plasma impliesthat the energy transfer from the microwaves to the plasma electrons is mainlyan off-resonance process.