DEWARS
Since FPAs require cryogenic cooling, special packages called dewars are required. The two primary types of dewar packages are pour-fill liquid nitrogen (often referred to as just pour-fill) and hard vacuum (or closed cycle). The hard-vacuum packages are typically cooled by sterling coolers, but can be ordered to accommodate gas cryostats. A popular option for systems with pour-fill dewars is the cold filter wheel assembly which enables a number of cold filters to be installed at one time and switched externally by the user.
