Fig. 1. Structure diagram of plasma light monitoring system for negative ion source with multi RF driver

Fig. 2. On-site physical photos (a) Quarter of CRAFT NNBI test platform, (b) Expansion chamber

Fig. 3. #71900 RF discharge with single RF driver (top acquisition) (color online)

Fig. 4. Diagram of CRAFT 1/4 size negative ion source diagram and multi-channel measurement position

Fig. 5. (a) #72045 RF climbing discharge, (b) #72051 RF discharge with filtered magnetic field of 900 A, (c) #72053 RF discharge with filtered magnetic field of 700~1 850 A (color online)