COMPASS-D magnetic equilibria with lh and NBI current drive

Abstract

Plasma equilibria are investigated numerically, using the ACCOME and ASTRA codes, on the COMPASS-D tokamak (R ₀ = 0:56 m, a = 0:17 m, B _T = 1:2 T, I _p = 200 kA, k = 1:7, δ_x = 0:4) for the planned Neutral Beam Injection (NBI) and Low Hybrid Current Drive (LHCD) systems. The LH system provides P _LH = 0:4 MW at n _∥ = 2:1 and f _LH = 1:3 GHz. The NBI system has two 40 keV deuterium beams in co-or counter-directions with a total power of 0.6 MW. The COMPASS-D tokamak can typically operate in two configurations-single null divertor (SND) and single null divertor with a higher triangularity (SNT). Higher triangularity provides access to higher confinement and improved stability, and leads to larger n _∥ up-shifts for better slow LH wave absorption.We investigate the range of densities n = 2 ÷ 6 × 10¹⁹ m⁻³. Both the LH and NB driven currents decrease with density. The magnetic shear reverses with off-axis beam incidence. In the given plasma parameter range, typically up to 60 kA of bootstrap current is driven and with NB co-injection up to 80 kA of NB current is driven. LHCD is weak at f = 1:3 GHz and BT = 1:2 T, but at n = 3 × 10¹⁹ m⁻³ the LH driven current is about 40 kA, so that the required plasma current of 200 kA is supported almost non-inductively.