大尺寸天文光栅铝膜均匀性研究

Research on Uniformity of Large Size Astronomical Grating Aluminium Film

天文观测所使用的光栅为大尺寸中阶梯光栅,其制作方法是利用金刚石刻刀对铝膜进行加工,形成光栅槽形,所以铝膜的质量能够直接影响光栅的性能。铝膜的厚度均匀性是判断铝膜质量的重要指标,以现有的内径1.8米镀膜设备为例,对铝膜的厚度均匀性做理论分析和实验研究,得出了电子束制备铝膜的蒸气发射特性n为4.5,并确定了最佳的真空室布局:蒸发源位置l=500mm,工件架高度h=900mm。在直径680mm的镀膜面积范围内,铝膜的厚度均匀性可以达到±1%,满足大尺寸天文光栅研制对铝膜厚度均匀性的要求。

Large size echelle gratings used in astronomical observation are made by carving aluminum films with a diamond cutter to form grooves;so the performance of gratings is directly affected by the thickness of aluminum films.The thickness uniformity of aluminum film is an important index to judge its quality. Taking a coating equipment of inner diameter of 1.8 meters as the example,the steam emission characteristics(n =4.5) of aluminum films prepared by electron beam are summarized;and the optimum layout of the vacuum chamber(evaporation source location l =500 mm,workpiece frame height h =900 mm) is determined through theoretical analysis and experimental research on the uniformity of aluminum film thickness. In the coating area of 680 mm diameter,the uniformity of the aluminum film thickness can reach ±1% and the requirement of the thickness uniformity of the large size astronomical grating can be met.