Technical overview and first results of the half-size ITER NNBI source

IPP Garching is currently developing a radio frequency (rf) driven ion source for the ITER negative ion neutral beam injection (NNBI) as an alternative to the presently foreseen filament source. The rf source has demonstrated the ITER requirements concerning negative ion current and electron/ion ratio at the required source pressure for small pulse length and small extraction area. The next goals are the extension to long pulses and large area sources at two further test facilities. The negative ion source at RADI – the test bed is located at the place of the former Wendelstein 7 AS RADIal Injector and uses some of its components – has roughly half the size of the ITER source and is therefore called the half-size source. It was recently commissioned at the IPP Garching. RADI is devoted to demonstrate the required plasma homogeneity of a large rf driven source, to test an ITER relevant rf circuit and to show the scalability of the IPP rf source. Having no large area extraction the source performance will be demonstrated with an extensive diagnostic and modeling program. This paper will present the results of the first plasma discharges and describe the main technical features of RADI.