The Ipp Rf Source: A High Power, Low Pressure Negative Ion Source For The Neutral Beam Injection System Of Iter

IPP Garching has successfully developed a RF driven negative ion source for the ITER neutral beam injection system. The RF source was chosen recently as the reference source for ITER due to its in principle maintenance-free operation. Current densities of 330 A/m(2) and 230 A/m(2) have been achieved for hydrogen and deuterium, respectively, at a pressure of 0.3 Pa and an electron/ion ratio of less than 1 for a small extraction area (7.0x10(-3) m(2)) and short pulses (< 4 s). The development concentrates now on extending the pulse length and extending the size of the source on two dedicated test facilities. The pulse length can be extended up to one hour at the long pulse test facility having an extraction area of 0.02 m(2). The large source test facility is equipped a large RF source with the width and half the height of the ITER beam source in order to demonstrate the homogeneity of a large RF plasma. The paper will give a short overview on the results achieved at the three test facilities of IPP; the underlying physical mechanisms are discussed with an emphasis on electron suppression.