Custom silicon detectors to enhance jet neutral particle Analysers for DT operations

JET neutral particle analysers (NPA) need to operate under demanding conditions. The main difficulty is the overlap between true ion signals and neutron-induced background. We have improved the background rejection dramatically by developing thin, custom silicon detectors optimised for ion detection on JET NPAs. The detectors have a silicon-on-insulator structure with the active layer ground to only a few microns but supported by a thick substrate to create a robust detector with an active thickness of 5 μm or 25 μm initially[1] and recently down to 3 μm. Although designed for JET, these detectors could find use in other fusion machines as well. With the first batch of detectors, the JET high energy NPA has been upgraded and its performance demonstrated in high-power DD campaigns. With 5 μm detectors, there is essentially no overlap between ion signals and background, and with 25 μm detectors the signal and background are better separated due to improved pulse-height response. With the second batch, the aim is to upgrade also the low-energy NPA. We will also discuss MCNP results on the anticipated performance in DT conditions.