Title: Absolute reflectance of a concave mirror used for astro-particle physics experiments Show Chinese title

Title: 凹面镜的绝对反射率用于天体粒子物理实验

Abstract: The absolute reflectance of a reflector and its point spread function are the key parameters of a telescope for measuring light flux. Typically, one is using low-cost technologies for producing mirrors for the needs of astro-particle physics experiments. As a rule, these are operating telescopes in open air conditions at desert or mountainous locations, for cost reasons without protecting domes. The mirrors on such telescopes are exposed to sand in strong winds, precipitation and large temperature variations. Due to weathering, their reflectance is declining within few years. In this report we describe in a great detail the application of an in-situ method to the MAGIC imaging air Cherenkov telescopes for regularly monitoring their absolute reflectance and the point spread function. Compared to similar work that was previously performed, in this report we focus on important details of light losses due to scattering. These allowed us to further refine the method and significantly improve its precision. Also, we report on an in-situ comparison of two mirror types produced with different technologies. Show Chinese abstract

Abstract: 反射器的绝对反射率及其点扩散函数是测量光通量的望远镜的关键参数。 通常，人们使用低成本技术来生产天体粒子物理实验所需的镜子。 一般来说，这些望远镜在沙漠或山区等露天条件下运行，出于成本原因，没有保护性圆顶。 这种望远镜上的镜子会暴露在强风带来的沙尘、降水和大温度变化中。 由于风化作用，它们的反射率在几年内会下降。 在本报告中，我们详细描述了在MAGIC成像切连科夫望远镜上应用原位方法，以定期监测其绝对反射率和点扩散函数。 与之前进行的类似工作相比，本报告重点介绍了由于散射导致的光损失的重要细节。 这些使得我们能够进一步完善该方法，并显著提高其精度。 此外，我们还报告了两种采用不同技术生产的镜面类型的原位比较。