A continuous 3He cryostat with pulse-tube pre-cooling and optical access

We have designed and constructed a continuously operating 3He cryostat with windows for laser ablation and spectroscopy. A two-stage pulse-tube refrigerator cools two platforms to base temperatures of approximately 40 K and 4 K respectively. The platforms are equipped with heat exchangers that cool separate streams of 4He and 3He. The 4He stream is used to run a thermally isolated evaporative refrigerator with a base temperature of approximately 1.5 K and a cooling power of 20 mW. The 4He refrigerator is used to condense 3He, which is used to run a 3He evaporative refrigerator on the experimental cell. The cryostat runs continuously at temperatures from 10 K to 0.4 K with a cooling power of 1.5 mW at 0.5 K.

► We constructed a closed cycle 3He cryostat using a pulse-tube refrigerator.
► Heat exchangers on the pulse-tube refrigerator are used to liquefy the He.
► Cryostat runs at temperatures down to 0.4 K with a cooling power at 0.5 K of 1.5 mW.
► The cryostat has large windows for optical access.