Study of directly launched ion Bernstein waves in a tokamak

Excitation, propagation, and absorption of directly launched ion Bernstein waves were studied with ${\mathrm{CO}}_2$ laser scattering in the Alcator C tokamak. Optimum excitation is obtained when an ion-cyclotron harmonic layer is located just behind the antenna. Wave absorption at the ω=3${\Omega }_{\mathrm{D}=1.5\mathrm{}{\Omega }_{\mathrm{H}}}$ layer was observed. 3 It may be necessary to control the edge density fluctuation level in order to minimize scattering of the ion Bernstein waves and optimize heating.