Lessons learned after three years of SPIDER operation and the first MITICA integrated tests

ITER envisages the use of 2+1 heating neutral beam injectors as part of the auxiliary heating and current drive system, to help demonstrate the desired goals during its various phases of operation. The 16.5 MW expected neutral beam power per injector is several notches higher than worldwide existing facilities. In order to enable such development, a Neutral Beam Test Facility (NBTF) was established at Consorzio RFX, exploiting the synergy of two test beds. SPIDER is dedicated to developing and characterizing large sources at relevant parameters in ITER-like conditions: source and accelerator located in the same vacuum where the beam propagates, electromagnetic interference of multiple radio-frequency (RF) antennas, RF-induced discharges on the outside of the source. Three years of experiments on SPIDER have indicated the necessary design modifications to enable full performances. The source is presently under one year shut down to incorporate such learnings. Parallelly, developments on MITICA, the full-scale prototype of the ITER NBI featuring a 1 MV accelerator, are underway including manufacturing of the beam source and the beam line components. Power supplies and auxiliary plants have been installed. Integration, commissioning and tests of the 1MV power supplies are essential for this first-ofkind system, unparalleled both in research and industry field. 1.2MV dc insulating tests of high voltage components were successfully completed. The integrated test to confirm 1MV output by combining invertor systems, DC generators and transmission lines extracted errors/accidents in some components. To realize a concrete system for ITER, phenomena have been addressed and solutions for the repair and the improvement of the system were developed. Hence, NBTF is emerging as a necessary facility effectively dedicated to identify issues and find solutions to enable successful ITER NBI operations in a time bound fashion. The lessons learned during the implementation on NBTF and future perspectives are here discussed.