2D full-wave simulations of different scenarios of ECR plasma heating at the L-2M stellarator

Abstract

Different scenarios of electron cyclotron resonance (ECR) plasma heating under the conditions typical of L-2M experiments (ηe(0) = 1.75 × 1013 cm−3, Te(0) = 1 keV, λ0 = 0.4 cm) are simulated using a 2D full-wave model with allowance for the nonlocal (differential) thermal correction to the plasma dielectric tensor. It is shown that, under central ECR heating, due to the specific shape of the resonance surface ω0 = 2ωce, a significant fraction of the input microwave power is deflected downward and escapes onto the chamber wall. During off-axis heating at the midradius of the plasma column, about one-half of the microwave power is reflected upward from the resonance surface. Optimal conditions for the deposition of the microwave power in plasma are achieved under ECR heating at the vacuum magnetic axis, when the microwave beam is incident normally onto the resonance surface. In this case, the microwave power is almost completely (≈99.5%) absorbed by the plasma, while the coefficient of microwave reflection into the aperture of the incident microwave beam amounts to ∼0.1%, which agrees with results of 1D full-wave simulations.