Feasibility study and physics performance of a fast-ion loss diagnostics for the JT-60SA tokamak

A good fast-ion confinement is essential for a self-maintained burning plasma. However, several transport mechanisms, such as Magnetohydrodynamic (MHD) instabilities [1] and externally applied magnetic perturbations [2,3] can lead to a significant and premature fastion loss and redistribution. Fast-ion losses are undesirable, not only because they imply plasma energy and momentum reduction, but also because they can damage the plasma facing components within the machine [4]. Furthermore, in the case of JT-60SA, where the plasma current will be driven by fast-ions injected by the 500 keV Negative Neutral Beam Injector (N-NBI), their losses will imply a deficit in the current drive. Scintillator based Fast-Ion Loss Detectors (FILD) are used to study fast-ion losses in almost all major fusion devices [1,5,6]. In particular, JT-60SA will operate in scenarios with a large fraction of fast-ion pressure and a FILD detector will be used to assess the direct wave-particle interaction of fast-ions with MHD instabilities such as Alfven eigenmodes, fishbones, neoclassical tearing modes (NTMs), resistive wall modes (RWM), etc. Also, edge 3D field effects on fast-ions, like edge localized modes (ELMs), error field correction coils (EFCC) and resistive wall modes correction coils (RWMCC), will be analyzed using this diagnostic. In this work, the conceptual design of the JT-60SA FILD is described. Also, a feasibility study dealing with important aspects, such as the expected signal and the thermo-mechanical behavior of the detector during the tokamak operation, is presented.