Study Of The Absorption Of Alpha Particles To Lower Hybrid Waves

In order to control the plasma current profile in tokamak, it might be a good way to apply lower hybrid waves in tokamak. However, the efficiency of the lower hybrid current drive may be affected by the high energy fusion-born alpha particles during the LH wave propagation, since the fusion-born alpha particles whose energy is very high can interact with LH waves through the perpendicular landau damping mechanism. In this particle, the absorption coefficient γα of Lower Hybrid waves due to α particles changing with some typical parameters is calculated. Results show that, the γα increases with the parallel refraction index n‖while decreases with the frequency of LH waves ω over a wide range. Higher background plasma temperature and toroidal magnetic field will increase the absorption. γα increases with electron density (ne) when ne≤8×1019m-3while decreases with ne when ne become larger, and there is a peak value of γα when ne≈8×1019m-3for ITER-like scenario. The influence of spectral broadening in parametric decay instabilities (PDIs) on the absorption coefficient is also evaluated. The γα with n‖being2.5is almost two times larger than that with n‖being2.0, and the case of2.9is even lager, which will obviously increase the absorption of LH power by alpha particles.