Experimental Study of the Dilution Refrigerator without 1K Pot

This chapter helps in constructing a simple dilution refrigerator without 1K pot, and it investigates its basic characteristics extensively. Several features peculiar to this type of the dilution machine have become clear for the first time and they are discussed in detail. The 3He-4He dilution refrigerator without 1K pot liquefies the circulating 3He by Joule-Thomson expansion and by making use of refrigeration capacity of the still and the 3He gas evaporated from it. The highest 3He inlet pressure is less than 1.4 atm, which enables one to circulate 3He without a compressor. The lowest temperature of the mixing chamber is 19.8 mK and highest temperature is 570 mK. The 3He circulation rate is limited in the range of 40 ∼ 70 μ mol/sec. Over this rate, the mixing chamber temperature becomes unstable.