Dewar with improved efficiency

In a Dewar for the containment of a volatile cryogenic liquid, the improvement, within the vacuum enclosure of the Dewar, comprising:

• neck, belly and tail sections in which the tail and neck comprise adjacent sections of the same extending element;
• the tail being an extended volume for containing a quantity of the liquid located centrally within the sections;
• the belly comprising an annular volume capable of containing a quantity of the liquid, said belly surrounding the tail and being thermally anchored to the tail by an isothermal means at an upper section of the belly in communication with an upper section of the tail, the belly further having at the upper section thereof means between the belly and tail for permitting gas flow from the belly to the tail to the neck,
• the tail further including a cooling source at a location in the tail which is beneath the level of liquid to be contained in the tail, said cooling source comprising means for absorbing the residual heat, Q.sub.t, conducted or radiated from the ambient environment of the Dewar to the tail;
• the neck section of the extending element including a terminal section open to the ambient environment of the location of the Dewar.