激光粒子加速及其应用

Laser-driven wakefield acceleration (LWFA) of electrons and target normal sheath acceleration (TNSA) of ions have made remarkable progress in the last decade. Electrons and protons with energy about 2 GeV and near 100MeV have been obtained respectively. However, there are still several serious problems about this novel accelerating approach: the total charge of a typical energetic electron beam from LWFA is only at the pC level; proton energy in TNSA is still quite low; the accelerating efficiency is relatively low, less than 10%. These parameters are still quite far from applicable and severely limit the realization of laser acceleration technique. This project then aims to break through the above restrictions and motivate multi-applications of laser-electron/ion acceleration. The experiments will be performed on the Peta-watt system in Shanghai Institute of Optics and Fine Mechanics (SIOM). For LWFA, intense laser pulses will be employed to produce 30 nC energetic electron beams. Furthermore, the high-charge electron beam will impinge on gold target to generate positron source. For TNSA, based on the former results, where 7MeV protons have been obtained, the project will use improved target structures and multi-stage acceleration to improve the proton/ion energy and accelerating efficiency. The possibility of energetic protons/ions from TNSA driving fast-ignition fusion will also be discussed. On the other hand, the project will perform theoretical researches to explore new novel accelerating schemes and applications, such as using lasers with high electro-optic efficiency, e.g. CO2 lasers, accelerating electrons and protons to drive fast-ignition fusion, multi-stage laser pressure acceleration of ions, proton beam driven wakefield acceleration of protons and using laser-accelerated electrons to produce X/γ ray sources.

激光尾波电子加速和靶后鞘层离子加速已经取得了瞩目的进展，电子能量超过GeV，质子能量也达到近100MeV。但激光粒子加速目前面临多个难点：高能电子束总电量仅为pC量级；高能质子能量还不高；加速效率还停留在10%内，这离应用需求有很大距离，其应用实现受到了严重阻碍。本项目旨在突破上述制约，推动发展激光粒子加速的多种应用。实验上依托上海光机所的拍瓦级激光器，拟通过激光驱动尾波加速产生30nC量级的高能电子束，并将其轰击金靶，获得正电子源；针对靶后鞘层离子加速，在已有基础上（已获得截至能量为7MeV的质子），利用改进靶形、级联加速等方案，提高能量与加速效率，并对其应用于快点火核聚变进行探讨。理论上，开展高电光效率激光（如二氧化碳激光）加速电子、离子，高效驱动快点火核聚变的机理研究；探讨级联的光压整体加速；研究质子束驱动尾波加速质子、激光加速电子产生X、伽马射线等新型机制与应用方案。

项目利用超强超短激光进行物理研究。主要研究内容包括，1）超强激光产生大电量达高能电子束，并利用电子束轰击金靶，实验上观测到正电子。 2)超强激光作用于固体靶，进行靶后鞘层离子加速，提高离子能量和激光能量转换效率，质子能量达到20 MeV以上，初步实现靶后鞘层级联加速。拍摄到质子束对等离子体的清晰成像。 3)对超强激光脉冲的新物理进行，包括级联加速新方法，加速新机制，产生高亮度X射线、伽马射线的新方案等。主要研究结果包括激光驱动产生大电子电荷量，并成功观测到了正电子，正电子实验结果入选2016年“两院院士评选中国十大科技进展新闻”。质子最高能量已超过50MeV, 并成功进行了质子成像实验，质子加速的新机制研究也取得进展。截至目前共发表学术论文53篇，其中包括PRL论文8篇，Nature communications 1篇，Scientific Reports论文4篇。