QUARTZ ANTENNA FOR RADIO-FREQUENCY ION-SOURCE OPERATION

Radio-frequency (rf) driven multicusp ion sources developed at the Law rence Berkeley National Laboratory use an internal induction coil (ant enna) for plasma generation. The copper rf-antenna with a thin layer o f porcelain coating, which is presently used, cannot fully satisfy the increasing demands on source cleanliness and antenna lifetime under h igh power cw or pulsed operation in applications where water cooling i s not possible. A quartz antenna has been designed and operated in the multicusp ion source. It has been demonstrated that the overall perfo rmance of the new antenna exceeds that of the regular porcelain-coated antenna. It can be operated with a long lifetime in different dischar ge plasmas. The quartz antenna has also been tested at the Paul Scherr er Institute for cw source operation _at rf power higher than 5 kW. Re sults demonstrated that the antenna can survive under dense plasma dis charge operations. (C) 1998 American Institute of Physics.