Serianni G, Sartori E, Agnello R, Agostinetti P, Agostini M, Barbisan M, Brombin M, Candeloro V, Dalla Palma M, Delogu R, De Muri M, Fadone M, Mario I, Patton T, Pimazzoni A, Poggi C, Pouradier-Duteil B, Segalini B, Shepherd A, Spolaore M, Taliercio C, Ugoletti M, Veltri P, Zaniol B, Pasqualotto R
Consorzio RFX (CNR, ENEA, INFN, UNIPD, Acciaierie Venete SpA), Corso Stati Uniti 4, 35127 Padova, Italy.
Ecole Polytechnique Fédérale de Lausanne (EPFL), Swiss Plasma Center (SPC), 1015 Lausanne, Switzerland.
Rev Sci Instrum. 2022 Aug 1;93(8):081101. doi: 10.1063/5.0084797.
Giant negative ion sources for neutral beam injectors deliver huge negative ion currents, thanks to their multi-beamlet configuration. As the single-beamlet optics defines the transmission losses along the beamline, the extraction of a similar current for all beamlets is extremely desirable, in order to facilitate the beam source operation (i.e., around perveance match). This Review investigates the correlation between the vertical profile of beam intensity and the vertical profiles of plasma properties at the extraction region of the source, focusing on the influence of increasing cesium injection. Only by the combined use of all available source diagnostics, described in this Review, can beam features on the scale of the non-uniformities be investigated with a sufficient space resolution. At RF power of 50 kW/driver, with intermediate bias currents and a filter field of 2.4 mT, it is found that the central part of the four vertical beam segments exhibits comparable plasma density and beamlet currents; at the edges of the central segments, both the beam and electron density appear to decrease (probably maintaining fixed electron-to-ion ratio); at the bottom of the source, an increase of cesium injection can compensate for the vertical drifts that cause a much higher presence of electrons and a lower amount of negative ions.
中性束注入器的巨型负离子源由于其多束团配置可产生巨大的负离子电流。由于单束团光学器件决定了沿束线的传输损失，因此非常希望所有束团都能提取出相似的电流，以便于束源运行（即接近导流系数匹配）。本综述研究了束源提取区域束流强度的垂直分布与等离子体特性垂直分布之间的相关性，重点关注增加铯注入的影响。只有通过本综述中描述的所有可用的源诊断方法的联合使用，才能以足够的空间分辨率研究不均匀性尺度上的束流特征。在射频功率为50kW/驱动器、中等偏置电流和2.4mT的滤波场条件下，发现四个垂直束段的中心部分呈现出相当的等离子体密度和束团电流；在中心段的边缘，束流和电子密度似乎都在降低（可能保持固定的电子离子比）；在源的底部，增加铯注入可以补偿垂直漂移，这种漂移会导致电子的大量存在和负离子数量的减少。
