在ELISE试验设备中通过发射光谱进行光束表征
Beam characterization by means of emission spectroscopy in the ELISE test facility
摘要：
位于IPP Garching的ELISE测试设施拥有一个RF H-/D-离子源和一个加速系统。它的目标是展示ITER NBI系统在提取电流密度（H/D），共提取电子的分数和脉冲持续时间方面的预期性能。ELISE提取区域的大小是ITER NBI预期的一半。本文详细研究了ELISE激光束的发散角和均匀性。特别是，可以将光束描述为两个发散角非常不同的分量之和：大约2° vs. 5° ~ 7°。作为测试用例，光束特性已被测量为两个源参数的函数。第一个是电流流过面向等离子体的网格，等离子体网格，以产生磁过滤场。第二个是在等离子体栅极和源极壁之间流动的偏置电流。过滤场和偏置电流都影响共提取电子的分数，而且还影响提取系统前面的等离子体的性质和束的性质。光束的发散度和均匀性已被测量的光束发射光谱（BES）的诊断;由BES收集的原始光谱的详细分析导致描述的光束具有两个不同的发散度的组件。这一概念得到了诊断量热计热成像信息的支持。在加速系统和束线组件中流动的电流的行为中发现了对所提出的束模型的进一步支持;这些电流由束的最发散（带电）粒子给出。
英文摘要：
The ELISE test facility at IPP Garching hosts a RF H-/D- ion source and an acceleration system. Its target is to demonstrate the performance foreseen for the ITER NBI system in terms of extracted current density (H/D), fraction of co-extracted electrons and pulse duration. The size of the ELISE extraction area is half that foreseen for the ITER NBI. This paper presents a detailed study of the ELISE beam divergence and uniformity. In particular, it was possible to describe the beam as the sum of two components at very different divergence: about 2° vs. 5°÷7°. As test cases, the beam properties have been measured as function of two source parameters. The first one is the current flowing through the grid facing the plasma, the Plasma Grid, in order to generate the magnetic filter field. The second one is the bias current flowing between the Plasma Grid and the source walls. Both the filter field and the bias current influence the fraction of co-extracted electrons, but also the properties of the plasma just in front of the extraction system and the beam properties. The divergence and the uniformity of the beam have been measured by a Beam Emission Spectroscopy (BES) diagnostic; the detailed analysis of the raw spectra collected by BES led to describing the beam with two components of different divergence. This concept has been supported by the information given by thermal imaging of the diagnostic calorimeter. Further support to the proposed beam model has been found in the behavior of the currents flowing in the acceleration system and beamline components; these currents are given by the most divergent (charged) particles of the beam.
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