Design and Results of Arc Power Feedback of Ion Source Under EAST-NBI Long Pulse Operation

The fundamental requirements for experimental advanced superconducting tokamak neutral beam injection (EAST-NBI) are high power and long pulse. The electrostatic probe’s inherent properties, which affect the probability of electrode ignition, cause the extraction beam current to decrease with increasing extraction time in the probe feedback mode of arc power. A power feedback technique of arc power supply is suggested to stabilize the beam current and lengthen the extraction time. The output power of the arc power supply is adjusted via feedback to keep the plasma density in the arc chamber largely steady by multiplying the output voltage and current. The beam current decrease in the arc power feedback mode is substantially smaller than that of the probe feedback, which is helpful for extending the extraction time.