4137 / Temperature (Kelvin): Mischkryostat at the PTB in Berlin: EUROPA, DEUTSCHLAND, BERLIN (BERLIN, GERMANY), 3.5.2007: Dilution refrigerator MK2 with copper demagnetization stage at Physikalisch-Technische Bundesanstalt PTB in Berlin, Germany. Realization of SI base unit for temperature, the kelvin: the cryostat cools thermometers - inside the compartment at center - down to 0.000065 K for calibration, thus establishing a reference point close to absolute zero. When in operation, it rests inside a pressure vessel and a superconducting coil and is helium cooled. In back: physicist Dr. Dieter Heyer. - Marc Steinmetz / VISUM - Keywords: Germany, Physikalisch, Technische, Bundesanstalt, PTB, science, technology, physics, metrology, base, unit, international, system, of, units, SI, metrical, measure, measurement, standard, lab, temperature, kelvin, thermodynamic, calibrate, calibration, thermometer, thermometry, dilution, refrigerator, cryostat, absolute, zero