A high quality liquid helium dewar is necessary to minimize the heat flow into the liquid helium and maintain a stable operating environment for the magnet. Dewars manufactured of both stainless steel and aluminum are available. Stainless steel dewars are considered optimum in performance and durability, while aluminum dewars represent a cost effective alternative to stainless steel and an economical way to maintain the liquid helium environment.

Many liquid helium dewars utilize liquid nitrogen shielding to reduce the liquid helium consumption. Liquid nitrogen shielding is recommended if the application requires repetitive warming and cooling of the dewar or if helium consumption must be minimized. The vacuum jackets of the nitrogen and helium reservoirs are typically connected by a common vacuum pumping port so that a quick vacuum pump down can be achieved.

Vapor shielded dewars use multilayer superinsulation to reduce the radiation heat load of the helium reservoir. The multilayer superinsulation is cooled by the venting helium gas. Vapor shielded dewars operate best when experimental run times are prolonged. Enlarged helium reservoirs are a common feature on vapor shielded dewars so that larger quantities of helium can be transferred to the dewar.

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