Quasi-linear ion distribution function during ion cyclotron heating in tokamaks
A new, very fast code, SSFPQL, has been written to solve the steady quasi-linear kinetic equation describing the ion distribution function during ion cyclotron heating in two velocity variables. By omitting toroidal trapping of energetic ions but otherwise including finite Larmor radius effects to all orders, SSFPQL offers a very efficient complement to wave codes and tokamak radial transport codes. In particular, the velocity space information supplied by SSFPQL can easily be used to take into account quasi-linear effects in the description of wave propagation and absorption with a reasonably modest numerical effort. A few applications of SSFPQL to first harmonic ion cyclotron heating of tritium in a typical ITER plasma are presented. At the power levels to be expected in ITER, the suprathermal ion population is strongly anisotropic; the parallel energy increase is typically only 20 % of the total. The total energy in the ion tail is never very high, and its effects on the heating rate are rather modest; in particular, self-boosting of first harmonic heating by finite Larmor radius effects can hardly compensate for the poor efficiency of this heating method at ohmic temperatures. On the other hand, near ignition the quasi-linear increase of the fusion reactivity by first harmonic heating of tritium is not negligible and could lower the ignition temperature by a few keV.
Bibliographic Reference: Article: Nuclear Fusion, Vol. 34 (1994) No. 8, pp. 1121-1143
Record Number: 199411440 / Last updated on: 1994-12-06
Original language: en
Available languages: en