Long pulse negative ion beams of 500 keV and 154 A/m2 for 118 s have been achieved for the first time, which exceeds the requirement of the JT-60SA negative ion source. In order to solve the issues of such long pulse beams, the fast cutoff system of the power supply aims to reduce the surge current and to extend the lifetime of filaments and the suppression method of excess cesium (Cs) accumulation on the plasma grid (PG) to achieve stable negative ion production. By developing the fast cutoff system using a field programmable gate array unit for the arc power supply, the cutoff time has been reduced to 1/10 that of the original system and the lifetime of the filament was extended by three times. In order to achieve stable negative ion production, incoming Cs on the PG surface has been reduced by keeping the chamber wall temperature below 40 °C. As a result, a stable beam current drift of <6% has been achieved for the 118 s duration.

中文翻译：

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在JT-60SA的Cs种子负离子源样机中实现长脉冲束操作的Cs种子稳定产生负离子

首次实现了118s 500keV、154A/m2长脉冲负离子束，超过了JT-60SA负离子源的要求。为了解决这种长脉冲束的问题，电源的快速截止系统旨在减少浪涌电流和延长灯丝的寿命以及抑制等离子体网格（PG）上过量铯（Cs）积累的方法) 实现稳定的负离子产生。通过为电弧电源开发使用现场可编程门阵列单元的快速切断系统，切断时间减少到原来系统的1/10，灯丝的寿命延长了三倍。为了实现稳定的负离子产生，通过将室壁温度保持在 40 °C 以下，减少了 PG 表面上的 Cs。