1. Laser repointing scheme for octahedral spherical hohlraums on the SGIII laser facility
- Author
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Hui Cao, Xufei Xie, Yaohua Chen, Yunsong Dong, Liquan Wang, Zhurong Cao, Xu Chen, Qiangqiang Wang, Wei Zhou, Wei Zhang, Zhichao Li, Sanwei Li, Bo Deng, Liang Hao, Shu Li, Junfeng Wu, Guoli Ren, Xudeng Hang, Wenyi Huo, Xiaoxia Huang, Xiaoshi Peng, Dong Yang, Tao Xu, Lifei Hou, Xingsen Che, Liang Guo, Huabing Du, Xiaoan He, Chaoguang Li, Pin Yang, Qianqian Gu, Yuancheng Wang, Kuixing Zheng, Yunbao Huang, Bin Feng, Guanghui Yuan, Baibin Jiang, Haijun Zhang, Feng Wang, Jiamin Yang, Shenye Liu, Jun Xie, Zhibing He, Kai Du, Jie Liu, Shiyang Zou, Yongkun Ding, Qihua Zhu, and Ke Lan
- Subjects
Condensed Matter Physics - Abstract
The novel octahedral spherical hohlraum can provide an ideal and practical approach for the next generation of laser systems to support both direct and indirect drive to achieve predictable and reproducible fusion gain via multiple schemes. To demonstrate its advantage in a naturally high symmetry at a cylindrically configured laser facility, it requires to repoint the laser beams to approach as close as possible the ideal octahedral beam configuration with an injection angle (the angle between a beam and the normal direction of its laser entrance hole (LEH)) ranging from 50° to 60°. We report our investigation and experiment on the optimum repointing scheme at the SGIII facility, which uses 32 beams, with 8 beams entering each polar LEH at 49.5° and 55°, and 4 beams entering each equatorial LEH at 61.5° and 62.1°. It contains residual imbalance between the polar and equatorial beams, leading to an asymmetry dominated by the spherical harmonic Y20 mode, which can be remarkably reduced by the stronger backscatters of equatorial beams. Our experiment demonstrated the feasibility of the 32-beam optimum repointing scheme and generation of 175 eV under 86 kJ inside a 2.4-mm-radius octahedral hohlraum with 0.7-mm-radius LEHs, which provided a strong support for the later experiment on proof-of-concept of octahedral spherical hohlraum [Lan et al., Phys. Rev. Lett. 127, 245001 (2021)]. 2D simulations on LEH closure agree well with the observations. This work opens a novel way of realization of a quasi-spherical irradiation at a cylindrically configured laser facility without supplementary symmetry control.
- Published
- 2023