Fig. 1. Schematic diagram of power ramp control method

Fig. 2. Schematic diagram of open-loop/closed-loop control switching according to breakdown signal

Fig. 3. Hardware structure of the beam feedback control system

Fig. 4. Workflow of beam feedback control system

Fig. 5. Test results of power ramp function

Fig. 6. Test results of beam feedback control function

Fig. 7. Comparison of the negative ion current with and without the beam feedback control system (I_H-) and the adjustment action of the RF power (P_RF)