A cryogenic cooling system is provided comprising a cryogenic refrigerator assembly and two or more connected modules. The cryogenic refrigerator assembly comprises one or more cryogenic refrigerators. Each said connected module comprises: a housing defining an internal volume for the module, the housing having a plurality of side faces, and a plurality of stages arranged within the internal volume for the module, wherein one or more of the plurality of stages is thermally coupled to the cryogenic refrigerator assembly. The two or more said modules are mutually connected at respective side faces, and a first said stage of a first said module is thermally coupled to a first said stage of a second said module.