Plasma drift and inhomogeneity suppression in the two drivers multi-cusp negative ion source for neutral beam injector

Plasma drift and the suppression of plasma inhomogeneity in a multi-cusp negative ion source with two drivers designed for a neutral beam injector were numerically investigated. A 2.5D MCC-PIC model via the KARAT code was employed alongside a fluid dynamic model of inductively coupled plasma. The modeling showed that the plasma drift in this two-driver system exhibited clockwise movement, whereas the plasma density was concentrated in the lower region of the expansion chamber. Under symmetric power feeding conditions (P = 40 kW), the calculated plasma asymmetry was A = 0.44, the coefficient of variation CV = 0.76, and the average value of the electron density ne = 2.0 × 1017 m−3. With an asymmetric feeding power of P1 = 40 kW and P2 = 20 kW, the plasma parameter results were A = 0.14, CV = 0.58, and ne = 1.3 × 1017 m−3. The feed power P1 = 40 kW, P2 = 10 kW results were A = −0.52, CV = 0.66, and ne = 0.8 × 1017 m−3. The estimated value of the power of the lower driver required for A = 0 is P2 ≈ 17 kW. Plasma drift and plasma inhomogeneity suppression were evaluated. The power feeding configuration that creates a symmetric plasma density distribution near the plasma grid was found.