A Band Rejection Filter of High Current Radio Frequency Ion Source for Neutral Beam Injector

As a promising ion source, the radio frequency (RF)-driven ion source is widely equipped in the neutral beam injector of magnetic-confinement fusion devices. In order to study the characteristics of the RF-driven ion source and plasma generation, a prototype RF negative ion source-based test facility has been developed at the Institute of Plasma Physics, Chinese Academy of Sciences. Many diagnostic tools have been developed for this test facility. The electrostatic sensors are a critical part of the diagnostic methods. Considering the electrostatic sensors to be used in the harsh RF environment, an improved RF compensation circuit [band rejection filter (BRF)] has been developed that effectively reduces RF interference and improves signal acquisition accuracy. The BRF has been successfully verified for frequency response characteristics in a magnitude plot.