Progress in the MITICA beam source design

In the framework of the development of the ITER Heating Neutral Beam (HNB) system, a test facility is planned to be built in Padova. Two experimental devices are foreseen: SPIDER is a full size plasma source with low voltage acceleration (100 kV) and MITICA is a full size ITER HNB injector at full beam power (1 MV). Design activities for all MITICA components are being carried out in collaboration among ITER Organization, F4E, JAEA and the European involved Association within the framework of F4E contracts. Under the F4E-2009-GRT-032 Grant, the design of the MITICA Beam Source was deeply revised with respect to the previous activities carried out up to 2008 under EFDA tasks. Several inputs and requirement changes were taken into account: o The final choice of the accelerator configuration restored the Multi Aperture Multi Gap (MAMuG) option with respect to the SINgle GAP (SINGAP) one; this led to recalculation of optics and re-assessment of power deposition and mechanical verification. o Some relevant features of SPIDER ion source were also transferred and integrated in the MITICA ion source. o Updated requirements by ITER Organization on minimum distances between parts at different voltage led to modification in the geometric configuration of the overall assembly and of critical areas at -1 MV. o New numerical methods for electrostatic verification were set up and implemented to tackle this critical aspect. In the paper the major design choices and revisions are presented, together with the main results of numerical analyses carried out in order to assess the electrostatic behavior of the source.