Abstract SPIDER experiment is operating at the PRIMA site in Padova (I) since June 2018, with the aim of testing and optimizing the negative ion source prototype for ITER Heating Neutral Beam Injectors. In the first operational phase it was discovered that, as the in-vessel hydrogen pressure exceeds the design requirements, discharges occur on the back of the radio frequency source. A specific operational campaign allowed defining a threshold below which the discharge probability is strongly reduced. In order to extend the operational range of the source pressure above the nominal value, while a significant upgrade of the vacuum pumping system is designed and realized, it was decided to proceed with the SPIDER operations by applying a temporary solution. A mask was installed on the beam source plasma grid, closing most of its apertures, in order to reduce the gas conductance between the inside of the radio frequency source and the surrounding volume. At first only 80 over 1280 apertures are left open, with a specific layout properly arranged so as to guarantee the possibility to diagnose the beam characteristics and to evaluate its uniformity. In the paper the plasma grid masking system is described. Finally, an overview of the behavior of plasma grid mask during SPIDER operations is given.

中文翻译：

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用于降低真空容器中的气体电导率和压力的 SPIDER 等离子格栅掩模

摘要 SPIDER 实验自 2018 年 6 月起在帕多瓦 (I) 的 PRIMA 站点进行，旨在测试和优化 ITER 加热中性射束喷射器的负离子源原型。在第一个运行阶段发现，当容器内氢气压力超过设计要求时，射频源背面会发生放电。特定的作战活动允许定义一个阈值，低于该阈值，排放概率将大大降低。为了将源压力的操作范围扩展到标称值以上，在设计和实现真空泵系统的重大升级的同时，决定通过应用临时解决方案来进行 SPIDER 操作。一个掩膜安装在束源等离子体网格上，关闭了它的大部分孔径，以减少射频源内部与周围体积之间的气体电导。起初只有 1280 个以上的 80 个孔洞是开放的，并适当安排了特定的布局，以保证诊断光束特性并评估其均匀性的可能性。在论文中描述了等离子网格掩蔽系统。最后，概述了 SPIDER 操作期间等离子网格掩模的行为。