LAMOST子镜真空镀铝系统中的多点蒸发源建模分析

Multi-source ring geometry modeling for aluminizing of LAMOST sub-mirror

选取多个钨丝均匀的分布在一个圆周上,形成一个环状蒸发源。把每个钨丝看成一个标准的点蒸发源,与LAMOST子镜建立模型形成一个蒸发沉积系统。把镜面离散成一个致密的具有特定坐标点的阵列,把每个点蒸发源对镜面上特定点的膜层厚度的贡献相加,从而得出膜层厚度的采样值。文章分析了点源的个数、圆环的半径、源基距、以及蒸发源的发射特性对膜层均匀性的影响,最终确定选取了12个钨丝,把源基距定为0.8m,把圆环半径定为0.55m。设计了相应的挡板实现了膜层不均匀性低于5%的要求。

The muhi-source ring consists of several tungsten filaments which are uniformly distributed around a circle to form a ring evaporation source for aluminizing. Each and every filament is regarded as a standard point evaporation source, and they form an evaporation/deposition system together with the LAMOST sub-mirror which is discretized to form an array of those points which the coordinates are given. The sampling value of A1 coating thickness on the mirror is the sum of coating thicknesses contributed by all of the point evaporation sources.The effects of the number of point sources, ring radius, source- substrate distance and the emission properties of the evaporation source on the coating uniformity are computed and analyzed. As a resuh, 12 tungsten filaments are picked up with the ring radius and source-substrate distance determined to be 0.55m and 0.8m, respectively. Six baffles to compensate for the thickness of the verge area of the mirror are introduced into the system, thus satisfying the requirement that the non-uniformity of coating is lower than 5%.