100keV质子与低高能质子在绝缘微孔中输运特性的对比分析

Simulation analyses of 100-keV as well as low and high energy protons through insulating nanocapillary

为研究中能区带电粒子在绝缘微孔中传输的物理图像,利用MATLAB程序和蒙特卡罗方法建立理论模型,得到入射能量为10 keV,100 keV和1 MeV的质子,以-1?倾斜角入射到微孔后,出射粒子角分布、沉积电荷斑分布,以及粒子在微孔内的运动轨迹等传输特性.研究结果表明,在10 keV的低能区,微孔内壁沉积电荷的导向效应是主要的传输机制.在1 MeV的高能区,进入表面以下多次随机非弹性碰撞是主要的输运机制.在100 keV的中能区,无电荷斑时,主要是以进入表面以下的随机二体碰撞为传输机制;在电荷斑累积过程中,增强的库仑排斥力逐渐抑制入射质子在微孔内壁表面发生电子俘获;当达到充放电平衡后,主要传输机制为电荷斑辅助的近表面镜面散射行为.这一特性加深了对中能区质子在微孔中输运行为的认识,有助于对百keV质子微束的控制和应用.

In order to clearly understand the physical images of incident ions passing through the insulating nanocapillary, in this work we establish a theoretical model, in which the matlab program is combined with the Monte Carlo method,to estimate the time evolution of transmission features, such as the angular and deposited charge distribution, threedimensional（3 D） trajectories of H-＋particles with proton incident energies of 10 ke V, 100 keV and 1 MeV at-1？title angle. The simulation results show that the transmission mechanism of 100 keV protons is different from those of10 keV and 1 MeV protons. After a sufficiently charging and discharging stage, 10 keV H-＋particles are guided along the direction of capillary axis, indicating that the guiding force from the surface charge patches is significant, and the small-angle scattering of 1 MeV protons under the capillary inner wall is a physical process that determines the transport of H-＋particles through the nanocapillary. However, for 100 keV H-＋particles, the centroid angle gradually shifts from the guiding direction to the direction close to the incident beam, which is attributed to the fact that the stochastic inelastic binary collision below the surface is the main transmission mechanism at the beginning. After the charging and discharging reach an equilibrium state, the H-＋particles are likely to pass through the nanocapillary, and the main transmission mechanism is the charge-patch-assisted specular scattering. This mechanism deepens the understanding of the transport behavior of protons through the nanocapillary, which will contribute to the control and application of the100 keV proton beam.