Diagnostics for high power beams

A review will be presented of the most common and recently developed diagnostics used to characterize high power particle beams in fusion experiments. In particular, diagnostics will play a key role in assessing the demanding specifications of the heating neutral beam injectors of the ITER experimental fusion reactor. ITER requires delivering to the plasma a total power of 33 MW up to one hour in a stationary condition by two heating neutral beam injectors (HNB). This level of power is provided by negative ion beams generated by an RF source and accelerated at 1 MeV [1]. The HNB specifications have never been simultaneously achieved so far and therefore a development programme has started to demonstrate the feasibility of a prototype injector and to optimize its performances: it comprises SPIDER, a 100 kV negative hydrogen/deuterium RF source, full size prototype of the HNB source, and MITICA, a prototype of the full HNB [2]. The mission of this programme is to guarantee reliable and efficient operation of HNB on ITER, where it will be impossible to have a direct view of the plasma in the source and of the beam in the injector, but a much reduced set of diagnostics will be available, mainly thermocouples. The diagnostics to be installed on SPIDER and MITICA are therefore essential to qualify and optimize the HNB for ITER. Sufficient instrumentation has then been included in each component to monitor its performance within the design envelope, to alert plant operators of the onset of operation outside design margins and to monitor source and beam characteristics to improve the injector performance [3]. This work was set up in collaboration and financial support of F4E. [1] R. Hemsworth et al., Nuclear Fusion, 49, 045006 (2009) [2] P. Sonato et al., AIP Conference Proceedings, 1515, 549-558 (2013) [3] R. Pasqualotto et al., Review of Scientific Instruments, 83, 02B103 (2012)