提出了一种新型的双锥靶结构用于准单能质子束加速。利用二维PIC粒子模拟程序研究了强激光与双锥靶作用加速产生质子束的物理过程以及质子束品质。双锥靶产生的质子束在峰值能量和发散角度等方面都明显优于相同激光条件下单锥靶和平面靶的结果。尤其与平面靶相比,双锥靶质子束的峰值能量提高了5倍以上,而且很好地保持准单能性。一方面双锥靶的内锥部分是临界密度材料,提高了激光的吸收效率;另一方面双锥靶内形成了更强的准静态磁场,可以约束引导更多的超热电子传输过锥尖,进而增强加速质子束的鞘层电场。

A new double cone target for accelerating quasimonoenergetic proton beam is proposed in this paper. Using two-dimensional PIC(particle-in-cell)simulation, the physical process of accelerating protons and the quality of proton beam from interaction of intense laser with the double cone target are investigated. In the case of same laser parameters, the peak energy and divergence angle of proton beams accelerated by the double cone target are superior to those by the single cone or planar target. Especially, compared to the planar target, the peak proton energy in the double cone target is increased by more than five times and quasimonoenergy can be well maintained. The critical density of the inner cone of the double cone target can increase the laser absorption efficiency. Moreover, the larger quasistatic magnetic field inside the double cone target can confine and guide more fast electrons to transport through the cone tip, which may enhance the sheath field for proton acceleration.