防离子反馈膜粒子阻透率随环境温度变化的模拟研究

Simulations on the particle blocking and transmitting performance of ion barrier film versus environmental temperature

覆有防离子反馈膜的微通道板是第三代微光像增强器的核心部件之一。真空高温烘烤除气过程对防离子反馈膜粒子阻透特性会产生破坏性的影响。文中利用分子动力学方法模拟计算并得到Al2O3薄膜的膜层密度随环境温度的变化规律。利用蒙特卡洛方法模拟计算了Al2O3薄膜的电子透过率和离子阻挡率随入射粒子能量的变化曲线。得到Al2O3薄膜的死电压在235 V左右,同时得出防离子反馈膜离子阻挡率在入射离子能量降低后有所增加。在入射离子能量降低为250 eV时,C、N、O离子被Al2O3薄膜阻挡的比率高达96%-99%。综合以上因素分析得出,随着外部温度的升高,电子透过率线性增加,而离子阻挡率非线性的下降。合理优化并调整高温烘烤时间和量值将有助于防离子反馈膜工作性能的改善。

Microchannel Plate (MCP) with ion barrier films (IBFs) is one of the key components in Low Light Level (LLL) Image Intensifier (I2) tubes in Generation III. Vacuum high-temperature baking process plays a destructive role in the particle blocking and transmitting performance of ion barrier film. Al2O3 thin film density as a function of the temperature of the environment was studied using molecular dynamics simulation. Electron transmittance and ion barrier blocking ratio of Al2O3 thin film versus the energy of incident particles were simulated and calculated using the Monte Carlo method. The dead voltage of Al2O3 thin films was about 235 V, and with the decrease of the incident ion energy, ion blocking ratio increased. When the incident energy was 250 eV, the preventing ability of Al2O3 films on C, N, O ions was 96%-99%. Based on the above factors analysis, with the increase of the external temperature, electron transmittance increased linearly, while the blocking ratio of ion barrier decreased nonlinearly. Optimization and adjustment of high temperature baking time and quantity will contribute to the ion barrier film performance improvement.