Conceptual design of cesium removal device for ITER NBI maintenance

Oka, Kiyoshi; Shibanuma, Kiyoshi

Cesium is required in order to generate a stable negative ion of hydrogen in an ion source of the neutral beam injector (NBI), which is one of the plasma-heating devices for International Thermonuclear Experimental Reactor (ITER). After long time operation of NBI, the cesium deposits to the insulators supporting the electrode. Due to the deterioration of the insulation resistance, the continuous operation of the NBI will be difficult. In addition, the NBI device is activated by neutron from D-T plasma, so that a periodic removal and cleaning of the cesium on the insulators by remote handling is required. A study of the cesium removal scenario and device is therefore required considering remote handling. In this report, a cesium removal procedure and conceptual design of the cesium removal device using laser ablation technique are studied, and the feasibility of laser ablation is shown.