Ion cyclotron waves and fast waves in a toroidal cavity

The propagation of ion cyclotron waves and fast waves in a toroidal cavity with a spatially varying static magnetic field as in a tokamak or stellarator is examined. Using a cold plasma model in a square cross section conducting toroidal cavity and neglecting effects of electron inertia, the wave equation is reduced to an ordinary differential equation which is numerically integrated subject to boundary conditions to find eigenmodes which represent cavity resonances. For the fast wave, only very small perturbations from the corresponding uniform plasma guide problem are found, and it is concluded that effects of toroidicity on the fast wave are not significant. For the ion cyclotron wave it is found that the region of propagation is generally confined to the high magnetic field side of the cyclotron resonance and for low order modes vertically and azimuthally, the region of propagation does not extend to the resonance location. A new type of wave behavior appears due to toroidicity which is similar to the ion cyclotron wave but depends differently on wavelength and may be important for fusion plasma heating because of its possibly greater accessibility. On the basis of the wave profiles, optimum antenna designs will be profoundly affected by toroidicity.