超强激光与固体气体复合靶作用产生高能氦离子  

Helium ions acceleration by ultraintense laser interactions with foil-gas target

作　　者：矫金龙 贺书凯[1] 邓志刚[1] 卢峰[1] 张镱[1] 杨雷[1] 张发强[1] 董克攻[1] 王少义[1] 张博[1] 滕建[1] 洪伟[1] 谷渝秋[1,2,3] 

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 [2]上海交通大学聚变科学与应用协同创新中心,上海200240 [3]北京大学应用物理与技术中心,北京100871

出　　处：《物理学报》2017年第8期222-228,共7页Acta Physica Sinica

基　　金：中国工程物理研究院发展基金(批准号:2013A0103003);科学挑战计划资助的课题~~

摘　　要：激光氦离子源产生的MeV能量的氦离子因有望用于聚变反应堆材料辐照损伤的模拟研究而得到关注.目前激光驱动氦离子源的主要方案是采用相对论激光与氦气射流作用加速高能氦离子,但这种方案在实验上难以产生具有前向性和准单能性、数MeV能量、高产额的氦离子束,而这些氦离子束特性是材料辐照损伤研究中十分关注的.不同于上述激光氦离子产生方法,我们提出了一种利用超强激光与固体-气体复合靶作用产生氦离子的新方法.利用这种方法,在实验上,采用功率密度5×10^(18)W/cm^2的皮秒脉宽的激光脉冲与铜-氦气复合靶作用,产生了前向发射的2.7 MeV的准单能氦离子束,能量超过0.5 MeV的氦离子产额约为10^(13)/sr.二维粒子模拟显示,氦离子在靶背鞘场加速和类无碰撞冲击波加速两种加速机理共同作用下得到加速.同时粒子模拟还显示氦离子截止能量与超热电子温度成正比.Laser-driven helium ion source with multi-MeV energy has an important application in the field of fusion reactor material irradiation damage.At present,the generating of high energy helium ions by relativistic ultraintense laser interacting with helium gas jet is the main scheme of laser-driven helium ion source.However,so far,this scheme has been hard to generate the helium ion beam with the characteristics,i.e.,it is forward and quasi-monoenergetic and has multi-MeV in energy and high yield.These characteristics of helium ion beam are important for studying the material irradiation damage.In this paper,we propose a new scheme in which an ultraintense laser interacting with foil-gas complex target is used to generate helium ions.With this method,we perform an experiment on XingGuang III laser facility which has three laser beams with different laser durations（nanosecond,picosecond and femtosecond）.In our experiment,we use a ＂picosecond＂ laser beam.The wavelength of this laser beam is 1054 nm and its duration is 0.8 ps.We use an off-axis parabola mirror to focus the 100 J energy of this laser beam onto a focal spot of 25 μm far away.The laser intensity reaches 5 ×10^18W/cm^2.The foil-gas target is composed of a copper foil with 7 μm in thickness and a helium gas nozzle which is behind the copper foil.The helium gas nozzle can generate a helium gas jet with a full ionization electron density of 5 × 10^19/cm^3.We use the Thomson Parabola Spectrometer to record the helium ion signals and the Electron Magnetic Spectrometer to diagnose the hot electron temperature.In the experiment,the laser pulse interacts with the front surface of the copper foil and generates lots of hot electrons.These hot electrons result in the expansion of the rear surface of the copper foil.The expanding plasma accelerates the helium ions behind the copper foil.The experimental results show that the obtained helium ions are forward and quasi-monoenergetic（the peak energy is 2.7 MeV）,and the total energy of the helium ions whose

关 键 词：激光氦离子源 激光等离子体作用 离子加速 

分 类 号：TL503.3[核科学技术—核技术及应用]