Kashiwagi M, Kisaki M, Saquilayan G Q, Kojima A, Hiratsuka J, Ichikawa M, Shimabukuro Y, Murayama M, Tobari H
Fusion Energy Directorate, National Institutes for Quantum Science and Technology, Naka, Ibaraki 311-0193, Japan.
Rev Sci Instrum. 2022 May 1;93(5):053301. doi: 10.1063/5.0080804.
A beam optics study using the ITER-relevant high intense negative ion beams, such as 1 MeV, 200 A/m, has been performed experimentally and analytically using a multi-aperture and five-stage accelerator. Initially, multi-beamlets generated from this accelerator were deflected in various directions due to the magnetic field and space charge repulsion between beams and showed various divergences. These had limited the pulse length and the beam energy. Compensation methods of the beamlet deflections have worked effectively and contributed to achieving the ITER requirement, the divergence angle of <7 mrad, and the deflection angle of <1 mrad for 1 MeV beam. The beam pulse has been gradually extended from 1 to 100 s and is now going to a longer pulse based on these results. One of the remaining issues is to understand and suppress peripheral components of the beam, namely, the halo, and to reduce the local heat loads observed around the aperture edge. This halo component has been successfully distinguished from the beam core by using a newly developed beam emittance measurement system for high intense beams. By combining this measured beam emittance and the beam simulation, it was clarified for the first time that the halo components are generated in an area of 1 mm width from the aperture edge.
利用与国际热核聚变实验堆（ITER）相关的高强度负离子束，如1兆电子伏特、200安培/米的束流，使用多孔径五级加速器进行了束流光学研究。通过实验和分析手段开展研究。最初，由该加速器产生的多束小子束由于磁场以及束与束之间的空间电荷排斥作用而向不同方向偏转，并呈现出不同程度的发散。这些情况限制了脉冲长度和束流能量。小子束偏转的补偿方法已有效发挥作用，有助于满足ITER的要求，即对于1兆电子伏特的束流，发散角小于7毫弧度，偏转角小于1毫弧度。基于这些结果，束流脉冲已逐渐从1秒延长至100秒，并且现在正朝着更长的脉冲发展。剩下的问题之一是理解并抑制束流的周边成分，即晕圈，并降低在孔径边缘周围观察到的局部热负荷。通过使用新开发的用于高强度束流的束流发射度测量系统，已成功将这种晕圈成分与束流核心区分开来。通过结合测量的束流发射度和束流模拟，首次明确了晕圈成分是在距孔径边缘1毫米宽的区域内产生的。
