Towards the NBI Requirements at ITER: 20 A Negative Hydrogen Ion Beams for Up to 1 Hour at the ELISE Test Facility

The RF ion source test facility ELISE (Extraction from a Large Ion Source Experiment) operated at IPP is part of the R&D roadmap of the European ITER domestic agency F4E for the ITER neutral beam injection systems. ELISE is dedicated to demonstrate the ITER requirements in terms of extracted negative hydrogen densities (329 A/m2 H‾, 286 A/m2 D‾) at an electron-to-ion ratio of less than one for a source of the same width but only half the height of the ITER source (0.9 x 1 m2). Hence, at an extraction area of 0.1 m2 and considering the stripping losses an accelerated current of 20 A D‾ has to be demonstrated.  The low temperature plasma is generated by four drivers powered by two RF generators with 180 kW generator power each at a frequency of 1 MHz. At a source pressure of 0.3 Pa the negative ions are created predominately via the surface conversion process, i.e. the conversion of mainly atoms and positive ions at surfaces with a low work function, for which caesium is evaporated into the source. Stable beams have to be achieved up to 3600 s with a beam uniformity of better than 90%.

The developments and major steps at the ELISE test facility will be described in the talk addressing also the latest results and the major issues for long pulse operation. A brief outline of the next major steps within the European Neutral Beam Test Facility for the development of successful ITER NBI systems will be given as well.