Abstract

A cryopump works on the principle of cooling down a metal surface or a surface coated with a porous material, namely, cryopanels, to cryogenic temperature. The gases stick to cryopanels thus lowering pressure and thereby creating a vacuum in an enclosed space. Materials used in the development of cryopumps include metals like copper and steel as structural materials, composite material like G10 for supports, thermal insulation, adhesive to fix sorbent to the metal surface, Vespel as an insulator, and various kinds of coatings on metal surfaces. Thermal properties govern heat load management and thereby the temperature of the cryopanels and hence pumping phenomena. This paper focuses on the experimental investigation of properties like specific heat, thermal diffusivity, thermal conductivity of materials, and their variation with lowering of temperature to cryogenic levels. A study was carried out to quantify the thermal properties of adhesive to fix the sorbent, the metal sheet of the cryopanel coated with activated charcoal granules using the adhesive, materials like G10 and Vespel, and high-emissivity black coating. The thermal conductivity (studied up to −150°C) for different kinds of adhesives was found to be in the range of 0.48 to 0.9 W/m‧K; for Vespel SP21 and G10, it is 0.58 and 0.8 W/m‧K, respectively. The emissivity at room temperature of the sorbent-coated cryopanels was 0.94, and for the high-emissivity black coating, it was in the range of 0.93 to 0.94.

摘要

低温泵的工作原理是将金属表面或涂有多孔材料的表面，即低温板，冷却到低温。气体会粘在低温板上，从而降低压力，从而在封闭空间中形成真空。低温泵开发所用的材料包括作为结构材料的铜和钢等金属，作为支撑、隔热材料的G10等复合材料，将吸附剂固定在金属表面的粘合剂，作为绝缘体的Vespel，以及金属表面的各种涂层。热特性控制热负荷管理，从而控制低温板的温度，从而控制泵送现象。本文重点对材料的比热、热扩散率、热导率等性质进行实验研究，以及它们随着温度降低到低温水平而发生的变化。进行了一项研究以量化用于固定吸附剂的粘合剂、使用该粘合剂涂有活性炭颗粒的低温板金属片、G10 和 Vespel 等材料以及高发射率黑色涂层的热性能。发现不同类型粘合剂的热导率（研究至 -150°C）在 0.48 至 0.9 W/m‧K 范围内；Vespel SP21 和 G10 分别为 0.58 和 0.8 W/m‧K。涂有吸附剂的低温板在室温下的发射率为0.94，对于高发射率黑色涂层，其在0.93至0.94的范围内。低温板的金属片上涂有使用粘合剂的活性炭颗粒，G10和Vespel等材料，以及高发射率的黑色涂层。发现不同类型粘合剂的热导率（研究至 -150°C）在 0.48 至 0.9 W/m‧K 范围内；Vespel SP21 和 G10 分别为 0.58 和 0.8 W/m‧K。涂有吸附剂的低温板在室温下的发射率为0.94，对于高发射率黑色涂层，其在0.93至0.94的范围内。低温板的金属片上涂有使用粘合剂的活性炭颗粒，G10和Vespel等材料，以及高发射率的黑色涂层。发现不同类型粘合剂的热导率（研究至 -150°C）在 0.48 至 0.9 W/m‧K 范围内；Vespel SP21 和 G10 分别为 0.58 和 0.8 W/m‧K。涂有吸附剂的低温板在室温下的发射率为0.94，对于高发射率黑色涂层，其在0.93至0.94的范围内。