超短超强激光驱动静电激波加速准单能离子束

Intense laser-accelerated ion beams have been widely studied because of their potential applications in many fields, such as ion therapy, proton radiography. Compared with the two most studied mechanisms, namely, target normal sheath acceleration (TNSA) and radiation pressure acceleration (RPA), collisionless shock-wave acceleration exhibits some advantages for generating high quality ion beams of high energy and narrow energy spread. Our project aim to present experimental and theoretical investigations on high-quality ion beams acceleration by electrostatic shock from ultrathin CH-foil target irradiated by 800 nm femtosecond intense laser pulses. The topics are shown as follows: theoretical simulation and optimization of experimental parameters using MULTI hydrodynamic code and PIC simulation, meanwhile studying how the peak energy and energy spread of the monoenergetic ion beams accelerated by electrostatic shock wave change with the laser intensity, contrast and polarization; investigating the effects of the laser prepulse on shock acceleration through the comparison experiments of different laser contrast conditions using high contrast PW laser pulses; investigating the effects of the laser polarization on shock acceleration through the comparison experiments of different laser polarization conditions (linear and circular polarization) using high contrast PW laser pulses. Our project also intends to study the relation between proton spectrum and carbon spectrum to demonstrate shock-wave acceleration mechanism driven by 800 nm laser pulses from the other side.

强激光加速离子束被广泛研究因其在医用离子治疗肿瘤、质子成像等领域具有潜在的应用价值。相比于两种研究最多的激光加速离子机制（靶后法线鞘层加速和光压加速），无碰撞静电激波加速在获得能量较高、单能性较好的高性能离子束方面有很大的优点。本项目拟开展800 nm飞秒强激光脉冲与超薄碳氢靶相互作用驱动静电激波加速高品质离子束的实验和理论研究。主要的研究内容是：利用MULTI流体程序和PIC程序理论模拟和优化实验参数，同时研究静电激波加速产生的准单能离子束能量、能散随激光光强、对比度和偏振的变化关系；利用高对比度PW激光进行不同激光对比度条件下的对比实验，研究激光预脉冲对激波加速的影响；利用高对比度PW激光进行不同激光偏振(线偏振和圆偏振)条件下的对比实验，研究激光偏振对激波加速的影响。本项目还计划研究质子束能谱与碳离子束能谱之间的变化关系，从另一个方面证实800 nm激光驱动的静电激波加速机制。

强激光加速离子束被广泛研究因其在医用离子治疗肿瘤、质子成像等领域具有潜在的应用价值。相比于两种研究最多的激光加速离子机制（靶后法线鞘层加速和光压加速），无碰撞静电激波加速在获得能量较高、单能性较好的高性能离子束方面有很大的优点。.本项目开展800 nm飞秒强激光脉冲与超薄碳氢靶相互作用驱动静电激波加速高品质离子束的实验和理论研究。利用240 TW的圆偏振飞秒激光脉冲与40 nm厚的CH靶相互作用，实验上获得了高流强、准单能的高品质质子束。质子能谱峰能量达到9 MeV，能散30%，峰值流强高达3×1012 protons/MeV/sr，激光到质子（能量区间6至12 MeV）的转换效率约1%。二维PIC模拟表明，在膨胀等离子体中，圆偏振激光有效激发了无碰撞激波，加速产生了准单能质子束。同时，该机制还预言了在现有的激光条件下，可以产生150 MeV准单能质子束，这代表着向质子刀等应用迈出了重要的一步。