百太瓦飞秒强激光驱动产生单个大电量高能电子束及其应用

High-charge energetic electron bunch has potential applications on positron generation, femtosecond-scale gamma source etc. We have proposed a new scheme to increase the electron bunch charge to several tens nano-Coulomb: a large complex bubble forms when the focus size of a laser pulse is much larger than the plasma wavelength and the laser power is hundreds of times larger than the critical power required for the relativistic self-focusing. Electrons continuously self-injected into such a complex bubble serve as an efficient source of the high-charge energetic electron bunch. Our project experimentally aims to increase the electron bunch charge to several tens nano-Coulomb based on large complex bubble regime, driven by a multi-100 TW laser pulse with a large focus size. When the laser focus size matches to plasma density, the large complex bubble forms and can support huge number of electrons to be injected and accelerated. The gold target will be inserted into the experimental setup for positron generation when the electron bunch charge is high enough.

相对论高能大电量电子束在正电子产生、飞秒尺度的超快伽马光源等方面有着重要的潜在应用。申请人提出利用大尺寸焦斑的百太瓦强激光脉冲与等离子体相互作用产生大尺寸的等离子体空泡结构——可以承载更多数目的电子。电子通过自注入方式不断注入到大尺寸空泡中获得加速而形成单个数十纳库、连续能谱的高能电子束源。本项目在前期理论基础上开展实验，研究百太瓦飞秒激光脉冲与气体靶相互作用产生大电量高能电子束的方法。研究激光和等离子体各参数对大尺寸空泡结构形成的影响，重点优化激光脉冲的焦斑尺寸、等离子体密度等参数利于大尺寸空泡结构形成。利用电子自注入机制，使得尽可能多的电子注入到大尺寸空泡中获得加速，在实验上获得数十纳库的大电量高能电子束。在大电量电子束产生的基础上，加入金靶，进行正电子产生的探索性实验。

利用飞秒拍瓦激光装置，实验研究了相对论强度的飞秒激光脉冲与气体靶相互作用产生大电量电子束的物理过程，获得了电量为15nC的单个高能电子束。利用大电量电子束与高Z固体靶相互作用，获得了超快正电子束和高通量的MeV量级伽马光源。激光驱动产生的超快正电子束在材料无损探测方面有着重要的应用价值，高通量伽马光源在则在光核物理、医用同位素、超快中子源、高密度物体内部结构探测等方面有着广泛的应用前景。同时我们也开展了基于飞秒强激光脉冲产生反质子束和TW量级的单个半周期阿秒脉冲的理论研究工作。