Effects of non-Maxwellian species on ion cyclotron waves propagation and absorption in magnetically confined plasmas

Magnetically confined plasmas can contain significant concentrations of nonthermal particles, arising from neutral beam injection, fusion reactions, shock heating, or wave-driven acceleration of resonant plasma species. The associated distribution functions can depart significantly from Maxwellians, which may impact the propagation and absorption of radio frequency waves. The potential effect of these particles has been investigated using a full-wave code that has been extended to handle gyrotropic, but otherwise arbitrary distribution functions. This code has been used to numerically simulate ion cyclotron resonance heating (ICRH) in magnetic fusion plasmas in which coresonant neutral beam injection (NBI) heating may also be applied. The presence of nonthermal ion populations generated by the NBI can alter the ICRH characteristics. Two situations involving ion cyclotron range of frequency waves are presented: fast wave to ion Bernstein wave mode conversion and high harmonic fast wave electron heating. In both cases, the adequacy of an equivalent Maxwellian-based description is discussed. Results indicate that the absorption profiles are more strongly affected than the wave fields by the presence of nonthermal species.

[1]  P. M. Ryan,et al.  Fast ion absorption of the high harmonic fast wave in the National Spherical Torus Experiment , 2004 .

[2]  M. Hellberg,et al.  Generalized plasma dispersion function for a plasma with a kappa-Maxwellian velocity distribution , 2002 .

[3]  C. Russell,et al.  Long‐wavelength mirror modes in multispecies plasmas with arbitrary distributions , 2002 .

[4]  Eduardo F. D'Azevedo,et al.  All-orders spectral calculation of radio-frequency heating in two-dimensional toroidal plasmas , 2001 .

[5]  D. Campbell,et al.  28th European Physical Society Conference on controlled fusion and plasma physics, Madeira, 18-22 June 2001 , 2001 .

[6]  C. Russell,et al.  Mirror modes: Non-Maxwellian distributions , 2000, physics/0009040.

[7]  E. D. Fredrickson,et al.  ICRF heating and profile control techniques in TFTR , 2000 .

[8]  M. Ono,et al.  Physics design of the national spherical torus experiment , 1999 .

[9]  Self-consistent modelling of ion cyclotron resonance heating , 1994 .

[10]  O. Sauter,et al.  Nonlocal Effects of Alpha-Particles on Icrf Heating , 1992 .

[11]  T. H. Stix.  Waves in plasmas , 1992 .

[12]  R. Koch.  Dielectric tensor expression for non-Maxwellian distribution functions and applications to α-particle damping in ICRH , 1991 .

[13]  D. Batchelor,et al.  Ion cyclotron emission from energetic fusion products in tokamak plasmas—A full‐wave calculation , 1989 .

[14]  Local full-wave energy and quasilinear analysis in nonuniform plasmas , 1989 .

[15]  Kashuba,et al.  Effect of parallel magnetic field gradients on absorption and mode conversion in the ion-cyclotron range of frequencies. , 1988, Physical review letters.

[16]  D. Start,et al.  A 2-D Fokker-Planck treatment of the ICRF enhancement of beam-driven currents , 1984 .

[17]  Charles F. F. Karney,et al.  Numerical studies of current generation by radio‐frequency traveling waves , 1979 .

[18]  I. Bernstein,et al.  Geometric optics in space− and time−varying plasmas , 1975 .

[19]  T. H. Stix.  Fast-wave heating of a two-component plasma , 1975 .