A continuously-cooled 3He/4He phase separation refrigerator

Abstract: We present a novel cooling method that uses the phase separation and evaporative cooling of 3He to reach and continuously maintain sub-kelvin temperatures. While less complex than a dilution refrigerator, the system performs similarly to a continuous 3He cryostat but with a simpler design, a more efficient cooldown process, and a significantly smaller 3He requirement. Our prototype demonstrated a base temperature of 585 mK and 3 mW cooling power at 700 mK using just two gaseous liters of 3He. Lower temperatures could be expected in systems with improved heat exchangers and pumping efficiency.