Abstract: A device for supplying coolant to a cryostat has a container containing liquified gas. An insulated first tube supplies coolant gas from the container to the cryostat. An end part of this tube is located inside the container and is bent into a U-shape so that the bend is immersed in the liquified gas, but the mouth of the tube at the free end thereof inside the container, opens above the level of the liquified gas so that the coolant gas can enter the first tube. After leaving the cryostat, the coolant is conveyed to a suction inlet of a pump which propels the coolant along a second tube which opens into the container below the liquid level. A heat exchanger to give a cooling effect is disposed adjacent this U-bend.