CYCLOTRON-RESONANCE FOR FAST MAGNETOSONIC WAVES IN INHOMOGENEOUS MAGNETIC-FIELDS OF TOROIDAL CONFINEMENT DEVICES

A theoretical investigation of ion cyclotron absorption of fast magnetosonic waves (FMSWs) in tokamaks and stellarators is presented. An expression is obtained for the left hand polarized component of the resonant current density, allowing for the inhomogeneity of the magnetic field and plasma density, and for the influence of Coulomb collisions on the phase of particle motion along the magnetic field lines. This expression is obtained by assuming a small Larmor radius and neglecting the contribution of trapped particles. Its main feature is the non-local behaviour of the left hand polarized component of the electric field. An exact solution to the integral equation defining this field is obtained. The expressions obtained may be used in numerical calculations of FMSW excitation, propagation and absorption in toroidal confinement devices. Particular attention is given to the fundamental and multiple harmonic resonances for majority ions, and the fundamental resonances for minority ions. For these cases, expressions are derived for the power absorbed by the plasma. Also, the conditions are determined under which collisions detune the influence of a particle's repeated transit through the resonance zone.