Title: Ultra-Thin Large-Aperture Vacuum Windows for Millimeter Wavelengths Receivers Show Chinese title

Title: 超薄大孔径毫米波接收器真空窗

Abstract: Targeting faint polarization patterns arising from Primordial Gravitational Waves in the Cosmic Microwave Background requires excellent observational sensitivity. Optical elements in small aperture experiments such as Bicep3 and Keck Array are designed to optimize throughput and minimize losses from transmission, reflection and scattering at millimeter wavelengths. As aperture size increases, cryostat vacuum windows must withstand larger forces from atmospheric pressure and the solution has often led to a thicker window at the expense of larger transmission loss. We have identified a new candidate material for the fabrication of vacuum windows: with a tensile strength two orders of magnitude larger than previously used materials, woven high-modulus polyethylene could allow for dramatically thinner windows, and therefore significantly reduced losses and higher sensitivity. In these proceedings we investigate the suitability of high-modulus polyethylene windows for ground-based CMB experiments, such as current and future receivers in the Bicep/Keck Array program. This includes characterizing their optical transmission as well as their mechanical behavior under atmospheric pressure. We find that such ultra-thin materials are promising candidates to improve the performance of large-aperture instruments at millimeter wavelengths, and outline a plan for further tests ahead of a possible upcoming field deployment of such a science-grade window. Show Chinese abstract

Abstract: 针对宇宙微波背景中来自原初引力波的微弱偏振图案，需要出色的观测灵敏度。小型孔径实验中的光学元件，如Bicep3和Keck Array，设计用于优化通量，并在毫米波长下最小化传输、反射和散射造成的损失。随着孔径尺寸的增加，低温恒温器真空窗必须承受更大的大气压力作用力，解决方案通常是通过增加窗的厚度来实现，但这会导致更大的传输损失。我们发现了一种用于制造真空窗的新候选材料：其抗拉强度比之前使用的材料大两个数量级，编织高模量聚乙烯可以使窗变得显著更薄，从而大幅减少损失并提高灵敏度。在本文中，我们研究了高模量聚乙烯窗在地面CMB实验中的适用性，如Bicep/Keck Array项目中的当前和未来接收器。这包括表征它们的光学透过率以及在大气压力下的机械行为。我们发现这种超薄材料是改善毫米波长大孔径仪器性能的有希望的候选材料，并概述了一个计划，在可能的科学级窗即将部署到现场之前进行进一步测试。