Dilution refrigerators (DR) are required to get to temperatures below ~ 0.5K.
We have a large mass of material that needs to be cooled, resulting in unusually high cooling power demands (two refrigerators, with 80 mW cooling capacity each).
In addition, one of the DR’s is near the center of the apparatus, resulting in stringent non-magnetic requirements.
High-powered Dilution Refrigerator at the University of Illinois.