Suppressing Plasma Inhomogeneity in the Multi-cusp Single Driver Negative Ion Source for Neutral Beam Injector

Methods for suppressing plasma inhomogeneity in the multi-cusp single-driver negative ion source for neutral beam injector were investigated via a 2.5D MCC-PIC model in KARAT code, accompanied by a 2D hydrodynamic model of inductively coupled plasma. In the basic ion source configuration plasma density parameters near PG are: asymmetry A = 0.24, coefficient of variation CV = 0.74, average value of electron density ne = 2.3·1017 m−3. Magnetic field alignment results are A ≈ 0, CV = 0.64, ne = 1.8·1017 m−3. Change of ∇p drift flow direction results are A = 0.20, CV = 0.64, ne = 2.1·1017 m−3. Blocking plasma drift via thin barrier plates results are A = 0.16, CV = 0.74, ne = 2.3·1017 m−3. Methods for plasma inhomogeneity suppression are successfully evaluated and useful negative ion source configurations have been found.