Barbisan M, Pasqualotto R, Agnello R, Pilieci M, Serianni G, Taliercio C, Cervaro V, Rossetto F, Tiso A
Consorzio RFX, Corso Stati Uniti 4, 35127 Padova, Italy.
Ecole Polytechnique Fédérale de Lausanne (EPFL), Swiss Plasma Center (SPC), CH-1015 Lausanne, Switzerland.
Rev Sci Instrum. 2021 May 1;92(5):053507. doi: 10.1063/5.0043226.
The neutral beam injectors of the ITER experiment will rely on negative ion sources to produce 16.7 MW beams of H/D particles accelerated at 1 MeV. The prototype of these sources was built and is currently operated in the SPIDER (Source for the Production of Ions of Deuterium Extracted from a Radio frequency plasma) experiment, part of the Neutral Beam Test Facility of Consorzio RFX, Padua. In the SPIDER, the H/D ion source is coupled to a three grid, 100 kV acceleration system. One of the main goals of the experimentation in SPIDER is to uniformly maximize the extracted current density; to achieve this, it is important to study the density of negative ions available in the proximity of the ion acceleration system. In SPIDER, line-integrated measurements of negative ion density are performed by a cavity ring down spectroscopy diagnostic. Its principle of operation is based on the absorption of the photons of a laser beam pulse by H/D photo-detachment; the absorption detection is enhanced by trapping the laser pulse in an optical cavity, containing the absorbing medium (i.e., negative ions). This paper presents and discusses the CRDS diagnostic setup in the SPIDER, including the first measurements of negative ion density, correlated with the main source parameters.
国际热核聚变实验堆（ITER）项目的中性束注入器将依靠负离子源来产生能量为1兆电子伏特、功率达16.7兆瓦的氢/氘粒子束。这些离子源的原型已制造完成，目前正在帕多瓦的RFX协会中性束测试设施的SPIDER（从射频等离子体中提取氘离子的源）实验中运行。在SPIDER实验中，氢/氘离子源与一个三栅极、100千伏的加速系统相连。SPIDER实验的主要目标之一是使提取的电流密度均匀最大化；要实现这一目标，研究离子加速系统附近的负离子密度非常重要。在SPIDER实验中，负离子密度的线积分测量是通过腔衰荡光谱诊断法进行的。其工作原理基于氢/氘光剥离对激光束脉冲的吸收；通过将激光脉冲捕获在包含吸收介质（即负离子）的光学腔中，增强了吸收检测。本文介绍并讨论了SPIDER实验中的腔衰荡光谱诊断装置，包括首次测量的与主要源参数相关的负离子密度。
