CLOSE TO ABSOLUTE ZERO
Realization of the kelvin with MK2, a
‘dilution refrigerator with copper de-
magnetization stage’ at a PTB lab in
Berlin. For calibration, the cryostat
cools thermometers – inside the
compartment at center – down to
0.000065 K close to absolute zero,
thus setting a cornerstone of our
temperature scale. During operation,
the stage rests inside a supercon-
ducting coil and a thermally insula-
ting vessel and is helium pre-cooled.