Cryogenic system of China Dark matter Experiment (CDEX-10)

• The CDEX-10 system needs a very quiet liquid argon environment. In order to realize the quiet environment of the inner tank, a special thermal shield was designed.
• In order to meet the requirements of the experiment, the inner tank uses a wide mouth design. The inside diameter of the inner tank is 1112 mm and the height is 1745 mm. Some methods are used to reduce the heat leakage.
• Two pulse tube refrigerators realize the closed thermosyphon loop of inner tank and thermal shield.

Dark matter is a type of matter hypothesized in astronomy and cosmology to account for a large part of the mass that appears to be missing from the universe. China Dark matter EXperiment (CDEX) is a direct detection system of dark matter. A cryogenic system for CDEX-10 has been designed and constructed. This note describes the cryogenic system of the CDEX-10, theoretical predictions of the heat loads to the cryostat, and measured heat loads at operation. The cryostat is an argon cooled bath type cryostat. Two pulse tube refrigerators are used for argon liquefying. The dark matter detecting needs a very quiet condition, so a special thermal shield is designed to reduce the radiation heat leakage.