Deposition and Fuel inventory in the castellated structure of beryllium limiters after campaigns in JET with the ITER-Like Wall

摘要

Introduction Castellated structure of plasma-facing components (PFC) is deemed as the best solution to ensure thermo-mechanical durability and integrity under high power loads. Narrow grooves of castellation and gaps between tiles are areas in which deposition may take place. Therefore, the assessment of fuel inventory is one of main concerns for ITER where all PFC will be castellated. Joint European Torus (JET) is the only tokamak in which large scale tests of castellated structures were carried out already in the carbon-wall machine in nineties of the 20~(th) century: [1-4]. A large scale test in the metal surrounding has been carried out since year 2011 at the JET with the ITER-Like Wall (JET-ILW): castellated beryllium limiters and lamellae-type bulk tungsten divertor tiles. This contribution is focused on the morphology of beryllium limiters after two campaigns in JET-ILW: 2011-2012 and 2013-2014, both about 19.5 h of plasma discharges including approx. 13 h of limiter and 6.5 h of X-point operation. The emphasis is on: (i) material mixing on plasma-facing surfaces; (ii) fuel inventory and deposition inside 0.4 mm wide grooves of the castellation, i.e. on surfaces located in the gaps.