ULTRALOW TEMPERATURES IN A TRANSPORT VESSEL - A DILUTION REFRIGERATORTO ACHIEVE 30 MK BY CONTINUOUS ADSORPTION PUMPING

A novel design of dilution refrigerator (DR) is described for continuo us operation inside a transport dewar with a neck diameter more than 5 1 mm. The time required for cooling the mixing chamber from room tempe rature to 30 mK is 3.5-4.5 h. Warming up to 300 K requires 0.5-1.0 h. The cooling power achieved is 40 at 100 mK. The DR is fitted with 6-mm line-of-sight access down to the mixing chamber. A distinguishing fea ture of this refrigerator is the absence of a conventional gas-handlin g system, which makes it easy to transport in a small car and quickly commission in a new laboratory within a few hours. (C) 1997 American I nstitute of Physics.