Ex / p 1-28 plasma and diagnostics preparation for alpha-particle studies in jet dt

A deuterium-tritium (D-T) experimental campaign DTE2 on JET scheduled for 2020, will take place in the Be/W vessel and will address essential operational, technical, diagnostic and scientific issues in support of ITER. In preparation for the campaign, experiments have been performed on JET aiming at studies of alpha-particles. For studying AEs driven entirely by alpha-particles, a scenario similar to the TFTR beam “afterglow” has been developed for JET. In DT plasmas, after NBI is switched off, alpha-particles will be the only energetic ions during time interval τ between slowing-down times for NBI-produced ions and alpha-particles,   NBI tSD < <    SD t . Detection of alpha-driven AEs in this time window may help in diagnosing the temporal evolution of the alpha-particle pressure profile and slowing-down time. JET advanced tokamak scenarios with q ≈ 1.5-2.5 were chosen and discharges have been successfully developed. The transport modelling extrapolated to DT predicts that alpha-particle beta of ≈ 0.1% could be achieved, comparable to that in successful TFTR experiments. In “hybrid” scenario plasmas with q0~ 1, fast ion losses in the MeV energy range were observed during n=1 fishbones driven by a resonant interaction with D beam ions in the energy range ≤ 120 keV. The losses are identified as an expulsion of D-D fusion products, 1 MeV tritons and 3 MeV protons. A mode analysis with the MISHKA code combined with the study of nonlinear wave-particle interaction with the codes HAGIS and HALO show that the loss of toroidal symmetry strongly affects the confinement of high energy tritons and protons by perturbing their orbits and expelling them in good agreement with experiment. The extrapolation to the case of alpha-particles in DTE2 hybrid scenarios with similar fishbones has shown an additional alpha-particle loss of ~ 1%. Further development of alpha-particle and Alfvén wave diagnostics suitable for JET DT operation is also reported.