Key operations for production of laboratory cryostats for photodetectors

BACKGROUND: A microcryogenic system for cryostatting the photosensitive matrix is a main component of the photodetector cryomodule. This paper discusses a passive cryostatting system for laboratory photodetectors used in research to expand the capabilities of cooled infrared systems. The passive microcryogenic system is a nitrogen filling high-vacuum Dewar cryostat. Its most common issue is the loss of thermal insulation properties due to atmospheric air leakage.

AIM: This study aimed to minimize atmospheric air leakage into the evacuated volume of a laboratory cryostat to extend its service life.

METHODS: The study is an experimental correlation study based on monitoring the cryostat service life to find a solution increasing it by reducing the amount of leakage and follow-up leak monitoring. The study object is a high-vacuum cryostat based on a brazed Dewar container. The study was conducted over a period of two weeks. We selected a soldering technique, conducted an experiment with follow-up leak monitoring and assessment of the cryostat operating life.

RESULTS: The findings are shown in photographs of different soldering techniques. The welding seam produced with PSr8KTsN solder shows no erosion of the base metal with the minimum chemical compound layer and no cracks.

CONCLUSION: Gaseous helium leakage rate into the vacuum cavity of the laboratory cryostat was 3.2 · 10^-13 Pa · m³/s, which corresponds to a continuous operation time of the product of at least 5 years under laboratory operating conditions.