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Suppression of damages on cathodes in the negative hydrogen ion source for the stable NBI system

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Published under licence by IOP Publishing Ltd
, , Citation Y Shimabukuro et al 2022 J. Phys.: Conf. Ser. 2244 012106 DOI 10.1088/1742-6596/2244/1/012106

1742-6596/2244/1/012106

Abstract

A protection system of ion source components from local abnormal discharge has been developed with ITER-class filament-driven negative ion source for high power and stable long-term operation. Protection from unpredictable discharge is a common issue for filament and RF-driven ion sources. To understand how fast should be cut off the discharge, threshold energy not to cause critical damage on the filament was investigated. The experimental exploration concluded that the energy less than 1.87 J or fast cut-off faster than 343 μs is the threshold for the robust protection of the filaments. A developed system successfully detected and cut off the discharge at 100 μs under noisy environments with the high current power supply. Moreover, the detection system is remotely adjustable. Such versatile protection system can contribute to any abnormal discharges in high current system including various ion sources, gyrotron, and high voltage components.

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10.1088/1742-6596/2244/1/012106