等离子体鞘层加速模拟质子辐照连续谱数值仿真研究

Numerical simulation of production of protons with continuous energy spectrum by plasma sheath acceleration

质子辐照是导致空间飞行器热控涂层性能衰退的重要原因。目前地面多采用单一能量的粒子替代空间能量连续分布的粒子来开展质子辐照模拟试验。文章提出了在一个脉冲宽度内获得连续能量质子谱的方法,即脉冲偏压等离子体鞘层加速方法。文章利用细胞粒子(particle-in-cell,PIC)模型对在3种脉冲偏压三角波作用下等离子体鞘层加速质子以获得连续能量质子谱的动力学过程进行了数值仿真研究,分析了3种脉冲三角波形对鞘层扩展、离子加速及能量分布的影响。结果表明,电势空间分布和离子运动状态紧密联系,鞘层内离子密度变化受到脉冲波形和离子热扩散运动的综合影响,通过调整脉冲偏压三角波形,能够获得不同的能量-剂量分布,从而为下一步工作打下基础。

The proton irradiation is one of the most important causes of the performance degradation of spacecraft thermal control coatings. The effects of proton irradiation are mainly investigated by using protons of single energy instead of those with continuous energy spectrum in ground testing. In this paper, a method of producing protons with continuous energy spectrum by plasma sheath acceleration in the period of waveform pulse is proposed, which involves the plasma sheath acceleration of bias voltage waveform pulse. The plasma sheath acceleration dynamics is simulated numerically to obtain the protons with continuous energy spectrum under three kinds of triangular bias voltage pulse waveforms by using a particle-in-cell model. The effects of three kinds of triangular bias voltage pulse waveforms on plasma sheath expansion, proton acceleration and energy-dose distribution are discussed. The results show that the space potential distribution has a close relationship with the ion movement, and the ion density is affected by both bias voltage pulse waveforms and ion thermal diffusion. The energy-dose distribution can be adjusted by changing the bias voltage pulse waveforms, which provides a platform for further studies.