Development of a charge-discharge circuitry based on supercapacitor and its application to the limiter probe diagnostics in EAST

Abstract

The EAST limiter probe is installed on the front surface of guard limiter, which consists of two columns and can operate in floating potential mode, ion saturation current mode, and swept single-probe mode simultaneously. It is required to provide a stable biasing voltage for the Langmuir probe when it operates in ion saturation current mode. To address this requirement, a large capacitor is used to provide biasing voltage for the probe. Compared to the 9V dry batteries that are commonly used in magnetic confinement fusion devices, employing a large capacitor offers advantages such as flexible voltage adjustment, easy maintenance, and environmental friendliness. Additionally, we have designed, and tested a complete set of supercapacitor charge-discharge control circuitry. In this study, a control software is developed for the supercapacitor charge-discharge control circuitry based on the python language to enable remote and automatic control of the circuitry operation. As demonstrated in experiments, the capacitor chargedischarge control circuitry can supply stable biasing voltage output for the probe under long-pulse discharge, and it is able to work in complex electromagnetic environment of magnetic confinement fusion device. By implementing the supercapacitor charge-discharge control circuitry in EAST limiter probe diagnostics, the three-dimensional plasma parameters are measured, such as ion saturation current, floating potential, electron temperature, and plasma density. In a lower hybrid wave (LHW) heating experiment, the 2.45 GHz LHW is found to generate large electron density than the 4.6 GHz LHW, and the largest electron density appears when both the 2.45GHz and 4.6GHz LHWs are turned on simultaneously. These experimental results confirm that super capacitor charge-discharge control circuitry can be operated reliably and stably.