Speaker
Description
MITICA, the full-size ITER heating neutral beam (HNB) injector prototype, is under construction in the ITER Neutral Beam Test Facility (NBTF) at Consorzio RFX. MITICA is based on an RF negative ion source, producing a 40A deuterium beam accelerated to 1 MeV; the beam is then gas neutralized with 60% efficiency, the residual ions are electrostatically removed, and it is finally dumped on a water cooled calorimeter. MITICA is required to validate the design and demonstrate the performance of ITER injectors: operate in stationary conditions for up to one hour, with low divergence, 3-7 mrad, intensity uniformity better than 10%, and low co-extracted electron fraction e¯ /D¯<1.
On SPIDER, the 100 kV full size prototype of the HNB RF source in NBTF, a complete set of diagnostics is proving to be essential to characterise the plasma in the source and the beam, also to understand the complex behaviour of the system especially in the first years of operations when different kind of anomalies were affecting the performance and required deep investigation. Similarly on MITICA we are expecting the need to have a comprehensive range of measurements, especially for the key parameters like beam uniformity and divergence, but in general to assist in the operation. Most of these diagnostics will not be available on the ITER HNB, equipped mainly with thermocouples, because of the restricting ITER requirements and the reduced accessibility. MITICA will then represent the best bench test for the solutions considered for HNB thermocouples and their layout, e.g. fixation methods, cabling, connectors and feedthroughs.
This contribution, starting with a summary of diagnostics impact on operation understanding in SPIDER, will provide an overview of MITICA diagnostics (thermo-mechanical sensors, electrostatic probes, source and beam spectroscopy, beam imaging and tomography), a description of their current design, the status of procurements and some solutions that can be reproduced also in the ITER HNBs.
