Self‐pressurizing liquid‐nitrogen filler

A self‐pressurizing, two‐level automatic liquid‐nitrogen filler is described which utilizes the vapor from the natural evaporation of cryogen in both the research and supply Dewars to continuously pressurize the liquid‐nitrogen reservoir. The system has greatly improved response time compared to other self‐pressurizing systems while avoiding the disadvantages of using heating elements or external gas sources for pressurization.