Numerical simulation of helicon waves current drive in the HL-2M tokamak for the steady-state scenario

The helicon wave heating and current drive in the HL-2M tokamak for the steady-state scenario is studied numerically. Based on the theory of fast wave current drive proposed by Chiu, we analyze the characteristics of helicon waves damping for the HL-2M tokamak. For wave frequencies larger than 420 MHz, strong wave damping occurs, and electron Landau damping is dominant. Moreover, a strong wave absorption region associated with the dimensionless parameters β _e and ξ _e that depend on the wave frequency is obtained. The helicon wave propagation and current drive are simulated using the GENRAY/CQL3D code. The results show that an off-axis current drive with profiles peak at ρ∼ 0.4 can be generally received at a wave frequency f∼ 500 MHz and the launched parallel refractive index n_//=3.8 and that the current drive efficiency reaches up to ∼ 140 kA/MW. A scan of n_// showed that both the current drive profile peak and the generated current could be adjusted by changing the launched n_// . Finally, a feasible scheme for the helicon wave off-axis current drive in the HL-2M tokamak is proposed.