ALFVEN EIGENMODE AND ENERGETIC PARTICLE RESEARCH IN JT-60U

Recent results on investigations of Alfven eigenmodes, fast ion confin ement and fast ion diagnostics in JT-60U are presented. It was found t hat toroidicity induced Alfven eigenmodes (TAEs) were stable in negati ve shear discharges with a large density gradient at the internal tran sport barrier (ITB). If the density gradient was small at the ITB, mul tiple TAEs appeared around the q = 2 surface (pitch minimum) and showe d a large frequency chirping (Delta f approximate to 80 kHz). In low-q positive shear discharges, the location of the TAEs changed from outs ide to inside the q = 1 surface, owing to a temporal change of the q p rofile. A significant depression of the megaelectronvolt ion populatio n was observed only with high-n (n up to 14) multiple TAEs inside the q = 1 surface. Non-circular triangularity induced Alfven eigenmodes we re observed for the first time. Considerable depression of the triton burnup was observed in negative shear discharges. Orbit following Mont e Carlo simulations indicated that ripple loss was responsible for the enhanced triton losses. The fast ion stored energies in ICRF heated n egative shear discharges were comparable to those of positive shear pl asmas. Tail ion temperatures in high (second to fourth) harmonic ICRF heating experiments were first analysed with an MeV neutral particle a nalyser. The behaviour of MeV ions produced by ICRF heating was studie d with gamma ray diagnostics. A scintillating fibre detector system fo r detecting the 14 MeV neutron emission was developed for the triton b urnup studies. Ion cyclotron emission measurements discriminating betw een parallel and perpendicular components of the electric field were c arried out for the first time.