Design of electronics system for Langmuir probes on ITER

Abstract

An electronics system for Langmuir probes to be used on ITER has been developing. The electronics system should meet the physics measurement requirements, which means that the electronics system should include power supply for driving probes, single and double probes operation mode switching circuit, measurement signal conditioning circuit, control and long cable transmission. It would make sense to use a single power supply to control a probe pair, which could be configured for one of the two operating modes foreseen and reduce costs while minimizing risk. The R&D of power supply is most critical activity. The power supply is characterized by 2.5 A, 175 V rating. At the same time, the power supply has been designed to ensure output waveforms ripple, high frequency, four quadrant and compatibility with the electromagnetic noise close to the components and with the plasma etc., which behaves as a nonlinear rapidly varying load. For reducing risk of R&D and exploring different technical prototype, one of the technical prototypes based on a full-bridge converter concept, using a pulse width modulation (PWM) technique is relatively simple and adopted first. Relays array circuit and adequate voltage and current signal conditioning circuit are also effective guarantee for data acquisitioning and drawing the probe current-voltage characteristic. The main design activities of electronics system are presented as detailed as possible in this paper. Besides, the detailed design activities should be continuously optimized and changed based on the results of the future relevant tests and changed requirements.