ISSN:
1089-7674
Source:
AIP Digital Archive
Topics:
Physics
Notes:
The time-dependent flux-surface-averaged Fokker–Planck equation for the distribution function of minority ions during ion cyclotron resonant heating introduced by Stix in a classic paper [T. H. Stix, Nucl. Fusion 15, 737 (1975)] is solved keeping two dimensions (2-D) in velocity space (speed and pitch-angle). An analysis of the applicability of the method of expansion of the distribution function f in Legendre polynomials of the pitch-angle, a method suggested by Stix and subsequently used by others, is given. A full numerical 2-D solution is also calculated. It is shown that the convergence of the Legendre polynomial expansion is very slow and non-uniform with respect to both particle energy and pitch-angle, making the method impractical when f is required at energies much higher than the background plasma thermal energy. However, the iterative sequences for the moments of f are found to converge very fast. In particular, a good approximation to the pitch-angle average of the distribution function is obtained already with two terms kept in the expansion, for a wide range of heating parameters. The validity of Stix's analytical one-dimensional approximations is analysed in detail. © 1997 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.872371
