Selecting Liquid Cryogenic or Cryogen-Free Cooling
Cryostats are available as pour-filled liquid cryogen dewars or cryogen-free refrigerators. In general terms, dewars are passive cooling devices that contain vacuum-insulated reservoirs of LN2, LHe, or LN2 plus LHe that provide all cooling power needed in these open cycle systems. Refrigerators use mechanically refrigerated cold heads embedded in a vacuum case in a closed cycle system. Both dewar and refrigerator systems are readily adapted to many different applications.