Abstract
Various DD and DT plasmas are analysed for effects of fast ion transport with a time dependent, 1 1/2 -D transport simulation code (TRANSP). The sensitivity of the simulations to fast ion diffusion modelling is tested against numerous parameters. Strong correlations are found with beam power and plasma stored energy. The neutron emission sensitivity is mostly affected by the fraction of beam-beam neutrons. Wall recycling is essential in interpreting the results for DT plasmas heated with pure deuterium or pure tritium beams. The decay of the 14 MeV neutron emission following a short DT beam pulse implies a small fast ion diffusion coefficient (Df<0.05 m2/s). The agreement of the measured neutron emission and diamagnetic flux with the simulations in DT plasmas heated with various numbers of tritium and deuterium beams, and power, implies that Df<or=0.2 m2/s
Highlights
The behaviour of fast ions is a central physics issue for reactor plasmas
Confinement times 2 1 s are required for alpha particles in International Thermonuclear Experimental Reactor (ITER), which sets a limit on the fast ion diffusion coefficient (Df < 0.5 m2/s) [2]
The transport simulation code (TRANSP) predicted neutron emission and diamagnetic flux are compared with the baseline (Of = 0) simulations, as well as with measurement
Summary
The behaviour of fast ions is a central physics issue for reactor plasmas. The d(t, n)4He reactions are selfsustaining only if the alpha particles are confined long enough to transfer their 3.5 MeV energy to the thermal background plasma. Confinement times 2 1 s are required for alpha particles in ITER, which sets a limit on the fast ion diffusion coefficient (Df < 0.5 m2/s) [2]. At JET, the measured stored energy of tail ions produced by hydrogen minority ICRF heating was compared with the prediction from the Stix model [8]. Their excellent agreement set a limit Df < 0.2 m2/s. (b) To parametrize the sensitivity of fast ion diffusion modelling with regard to (global) quantities that are measurable, such as the total neutron emission and the diamagnetic flux. < port the major result of this study (i.e. Df 0.2 m2/s for high power D T plasmas), a systematic error analysis of TRANSP simulations for one DT shot is given in the Appendix
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