超短脉冲激光与固体靶作用产生光核中子的数值模拟研究

Numerical Simulation of Photoneutron Generation in Ultra-Intense Short Laser-Solid Interactions

采用超短脉冲激光与固体靶作用产生光核中子的模型,使用蒙特卡罗程序Fluka研究了激光诱导光核中子源的特性。对不同材料和电子温度条件下中子产生的模拟表明,钨是最佳的靶材料,且对于不同的超热电子温度,存在不同的产额饱和厚度。对源尺寸的模拟表明,中子源的尺寸决定于入射电子束发散角和靶厚,可以通过增加靶半径的方式提升前向与侧向中子通量的比值至5。当电子温度大于4 MeV时,可以获得能谱结构稳定的光核中子源。对时间分布的模拟表明,中子源的脉宽小于30 ps,且飞行后的脉宽展宽系数为100 ps/mm。

The generation of photoneutrons in ultra-intense short laser-solid interactions is modeled, and the properties of the laser-induced photoneutron sources are studied using the Monte Carlo simulation code Fluka. Further, neutron generation is simulated for different materials and electron temperatures. The results denote that tungsten exhibits the optimal performance and that the neutron yield exhibits different saturation thickness values at different temperatures. The neutron source size can be determined using the electrons' spread angle and the target thickness. Ratios that are as high as 5 can be achieved between the fluxes in the forward and sideways directions by increasing the target radius. Further, stable energy spectra can be obtained for the photoneutron source when the electron temperature is greater than 4 MeV. The time distribution results denote that the neutron pulse duration is less than 30 ps and that its stretching factor after flight is 100 ps/mm.