Spectral transmittance and con-trast in breast diaphanography

A vessel for storing and transporting cryogenic fluids such as liquid helium. The vessel comprises a plurality of elongated containers supported one within another in coaxial circumjacent relation in a manner minimizing heat transmission therebetween, and it further comprises a cooling system forming a temperature barrier that restricts inward migration of heat from the outer to the inner container. Respecting the support system, the inner fluid-receiving container is supported by an encapsulating intermediate heat shield container which in turn is supported by an outer jacket surrounding and enclosing the intermediate heat shield. The support means effecting such interrelationship includes both transverse support structure constraining the containers relative to each other against transverse or radial displacements and longitudinal support structure interconnecting the containers one with another and constraining the same against relative longitudinal displacements at least at one end of the vessel. The transverse support structure constitutes a plurality of structurally independent supports as respects the interconnection of the inner container with the intermediate heat shield and interconnection of the heat shield with the outer jacket; and all of the support structures define restricted thermal flow paths through which heat migration from the outer container to the inner container is sharply limited. Respecting the cooling system, two flow-separated cooling coils surround the heat shield container, one of which carries a coolant such as liquid nitrogen and the other of which connects both with the inner fluid-receiving container and with a delivery system through which fluid is withdrawn from the inner container.