激光加速质子束对电磁孤立子的照相模拟研究

Simulation of electromagnetic soliton radiography under laser-produced proton beam

激光在次稠密等离子中传输,由于频率下移而被俘获,从而产生电磁孤立子.根据先前理论及PIC模拟给出的孤立子的演化过程,对不同阶段孤立子的电磁场分布进行了建模.使用Geant4蒙特卡罗程序,模拟研究了激光加速产生的能量为几个MeV的质子束对后孤立子的照相.分析了质子能量,质子源尺寸等因素对照相结果的影响,并利用了TNSA加速产生质子束的分幅特性,开展了时间分辨的孤立子照相模拟研究.模拟给出的质子照相结果验证了文献中给出的孤立子静电场模型,为以后在实验上探测孤立子提供了理论依据.

During propagating through an underdense plasma, a laser will experience significant energy loss and will be trapped in the plasma as the frequency undergoing a redshift. Thus the electromagnetic （EM） soliton is formed. EM field distribution at different stage is constructed for the soliton in terms of primary theory and particle in cell （PIC） simulation. Radiography of solitons produced by laser accelerated MeV protons is investigated using Monte Carlo methods. The influencing fact or such as proton energy and source size is analyzed. Time-resolved radiography of the soliton is also carded out as the protons accelerated by the target normal sheath acceleration （TNSA） mechanism have a wide energy spectrum. Results validate the static electric field model of the soliton, and provide the basis for the future experiments.