一种低喷气量微气室喷嘴在激光尾场加速中的应用  

Application of low flow rate micro gas cell nozzle in laser wakefield acceleration

作　　者：张晓辉 吴玉迟[1] 朱斌[1] 王少义[1] 闫永宏[1] 谭放[1] 于明海 杨月[1] 李纲[1] 张杰 温家星 周维民[1] 粟敬钦[1] 谷渝秋[1] Zhang Xiao-Hui;Wu Yu-Chi;Zhu Bin;Wang Shao-Yi;Yan Yong-Hong;Tan Fang;Yu Ming-Hai;Yang Yue;Li Gang;Zhang Jie;Wen Jia-Xing;Zhou Wei-Min;Su Jing-Qin;Gu Yu-Qiu(Science and Technology on Plasma Physics Laboratory,Research Center of Laser Fusion,China Academy of Engineering Physics,Mianyang 621900,China)

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,绵阳621900

出　　处：《物理学报》2023年第3期169-174,共6页Acta Physica Sinica

基　　金：等离子体物理重点实验室基金(批准号:6142A04210101,6142A04200103);国家自然科学基金(批准号:12004353,11975214,11991071,11905202,12175212)资助的课题。

摘　　要：激光尾场加速是一种利用超强飞秒激光与气体靶作用加速电子的新型加速技术,经过40多年的发展已经日益成熟,但是重复频率相比传统加速器还有很大的差距.高重复频率加速是未来激光尾场加速的一个重要发展方向,届时气体靶给真空系统带来的负载将不可忽视,这可能会成为限制重复频率的重要因素.本文设计了一种应用于中小规模激光器的微气室喷嘴,并通过三维流体模拟对比了这种喷嘴和常用的超音速喷嘴的喷气量差异,证明它不仅能够产生和超音速喷嘴类似的密度分布,还能够大幅降低喷气量,从而减小真空系统的负载,提高重频的上限.此外,把这种微气室喷嘴应用于激光尾场加速实验中,在多条件下产生了稳定性很好的电子束.这个工作将为高重频、高稳定性的尾场加速做出贡献.After forty-year tremendous advances,laser wakefield acceleration(LWFA),in which an ultra-intense femtosecond laser interacts with a gas target to produce energetic electrons,is becoming more and more mature.Acceleration with a high repetition rate will be an important topic in the near future.When operating at a high repetition rate,the influence of the gas load on the vacuum system cannot be neglected.Among the widely used gas targets,gas cells have a lower flow rate than supersonic gas nozzles.However,most of gas cells are several centimeters long,unsuitable for a moderate-size laser facility.In this work,we design a kind of micro gas cell with a sub-centimeter length.The flow rate of the micro gas cell and the supersonic nozzle are compared by hydromechanics simulations.Comparing with the supersonic nozzle,the flow rate of the micro gas cell is reduced by 97%.Moreover,the gas cell sustains a longer flattop region.The reduced flow rate is attributed to two reasons.The first reason is that the area of the nozzle exit decreases significantly.In the case of the supersonic nozzle,the laser intera.cts with the gas jet outside the nozzle exit.Therefore,the exit size is determined by the interaction length.In the case of the micro gas cell,the laser interacts with the gas inside the gas cell.The exit only needs to be larger than the laser focal,which is much smaller than the interaction length.The second reason is that the velocity of the gas jet decreases.When using a supersonic nozzle,the velocity at the nozzle exit must be high enough to generate a flattop density distribution,which is required by LWFA.As a comparison,in the micro gas cell,the gas is confined by the cell wall.As a consequence,the gas velocity has little influence on the density distribution inside the cell.By changing the inner radius of the cell,1-4 mm-long flattop regions can be generated while keeping a low flow rate.Experiments using the micro gas cell are conducted on a 45 TW femtosecond laser facility at the Laser Fusion Research Center.The

关 键 词：激光尾场加速 高重复频率 微气室喷嘴 

分 类 号：TN249[电子电信—物理电子学]