神光Ⅱ升级装置激光加速质子照相初步实验研究  

Proton radiography of indirect-driven implosion by high-intensity laser generated protons on SGⅡ-U laser facility

作　　者：滕建[1] 洪伟[1] 贺书凯[1] 邓志刚[1] 朱斌[1] 张天奎[1] 于明海 钱凤[1] 张博[1] 齐伟[1] 张智猛[1] 毕碧[1] 单连强[1] 张发强[1] 杨雷[1] 卢峰[1] 张锋[1] 李晋[1] 陈韬[1] 吴玉迟[1] 崔波[1] 周维民[1] 曹磊峰[1] 谷渝秋[1] 

机构地区：[1]中国工程物理研究院激光聚变研究中心等离子体物理重点实验室,四川绵阳621900

出　　处：《强激光与粒子束》2017年第9期54-59,共6页High Power Laser and Particle Beams

基　　金：中国工程物理研究院科学技术发展基金项目(2013A0103003);科技部重大科学仪器设备开发专项(2012YQ03014206)

摘　　要：在神光Ⅱ升级装置上开展了首轮激光加速质子对间接驱动快点火靶内爆过程的照相实验研究。通过激光与靶参数的优化,获得了能量高于18MeV的质子束。通过静态客体的照相,获得了优于20μm的高空间分辨网格图像,为开展时间分辨的啁啾质子照相奠定了基础。开展了质子动态照相实验,获得了内爆压缩晚期的质子照相图像。实验发现内爆区域质子照相图像存在大量排空现象。内爆压缩区域不足以阻挡如此大范围质子束,证明了其中存在电磁场使得质子向外排开。动态照相的质子能量较低,分析是ns激光打靶过程产生的X射线及等离子体对质子加速存在影响。后续实验中需要进一步优化靶的屏蔽设计。A preliminary experimental study of the indirect-driven implosion by means of proton radiography has been car- ried out on the SG Ⅱ-U laser facility. In the experiment, the probing protons were generated by a picosecond laser irradiating on a thin Au target via the target normal sheath acceleration scheme. Maximum proton energy up to 18 MeV was achieved as a result of optimizing the laser and target parameters. In the static imaging of objects, the spatial resolution of proton radiography was demonstrated to be better than 20 tim. In the time-resolved imaging of the implosion, the proton radiographs of the capsule at va- rious stages of compression were obtained. It is found that the probing protons were expelled from the center region, which, cov- ered an area much larger than the size of the compressed capsule. The detailed analysis reveals that the protons are expelled by the surrounding electric-magnetic fields as well as by the compressed capsule itself. It is also found that the energy of probing protons decreased when the nanosecond laser was present in the experiment. This is because the X-ray, generated from the nanosecond la- ser irradiation on targets, would partially destroy the rear side of proton target, thus leading to the less efficient proton accelera- tion. To improve the proton energy, the shielding design of proton target should be further considered in the next experiments.

关 键 词：激光加速 质子照相 间接驱动 内爆 电磁场 

分 类 号：O539[理学—等离子体物理]