Research on Thermal Expansion Characteristics Measurement of Launch Lock Mechanism for SIS Mixer’s Space Application

The High Sensitivity Terahertz Detection Module (HSTDM) is one of the scientific payloads of the Chinese Space Survey Telescope. The core of the HSTDM is the NbN superconducting SIS (Superconductor Insulator Superconductor) mixer, operating around 10 K. The installation structure of the SIS mixer needs to be specially designed to cope with the mechanical vibration during the launch phase and the thermal insulation requirements during the operation phase. Material thermal expansion characteristics investigation based on low-temperature LVDT (Linear Variable Differential Transformer) measurement and scratch marking measurement were carried out to confirm the validity of the thermal expansion lock mechanism design. The two methods are cross verified. The LVDT experimental measurement results show that the shrinkage rate of Teflon changes with temperature and meets the theoretical model. At the same time, we verified the LVDT results with scratch marking method. Consistently, the shrinkage rate of the material is 1.86$\%$ at 80 K, so the Teflon front-end lock mechanism of the SIS mixer can achieve effective separation after cooling down.