{TAIL ~ Superconducting operating temperatures} can be provided by a cryogenic container refrigerated by a closed cycle cryogenic refrigerator, a stored cryogen, or in space, {HEAD ~ a heat sink} 
{ TAIL ~ Superconducting operating temperatures } can be provided by a cryogenic container refrigerated by a closed cycle cryogenic refrigerator , a stored cryogen , or in space , { HEAD ~ a heat sink }
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