Suprathermal deuterium ions produced by nuclear elastic scattering of ICRH driven He-3 ions in JET plasmas

摘要

Measurements of the suprathermal tail of the energy distribution function of deuterium ions, in plasmas containing MeV energy ICRH driven minority He-3 ions and majority deuterium ions, revealed that the suprathermal tail ion density exceeded by nearly an order of magnitude that expected due to nuclear elastic scattering (NES) of He-3 projectile ions on deuterium target ions. The experiments were performed on the Joint European Torus (JET), measurements of the line-of-sight integrated energy distribution functions of He-3 and suprathermal deuterium ions were made using a high energy neutral particle analyzer. The NES or 'knock-on' deuterium ion energy distribution function was simulated using the FPP-3D Fokker-Plank code (Zaitsev et al 2002 Nucl. Fusion 42 1340) which solves the 3D trajectory averaged kinetic equations in JET tokamak geometry while taking into account NES of He-3 ions on the deuterium ions. The required input energy distribution function of ICRH driven He-3 ions was simulated using the SELFO code (Hedin et al 2002 Nucl. Fusion 42 527). The comparison between measurement and simulation in the He-3 ICRH experiments is contrasted with an analogous previous comparison between measurements and simulation of JET plasmas in which 3.5MeV DT fusion alpha-particles were the projectile ions, where measurement and simulation roughly agreed. Possible explanations for the observed excess knock-on deuterium tail in the experiments with He-3 minority