Alumina shunt for precooling a cryogen-free 4He or 3He refrigerator |
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| Affiliation: | 1. NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA;2. Bastion Technologies, 7515 Mission Drive, Suite 300, Lanham, MD 20706, USA;3. SGT Inc., 7701 Greenbelt Road, Suite 400, Greenbelt, MD 20770, USA;1. Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Fukuoka 819-0395, Japan;2. National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan;3. Taiyo Nippon Sanso Corp.,10 Okubo, Tsukuba, Ibaraki 300-2611, Japan;4. Hitachi High-Tech Science Corp., 36-1 Takenoshita, Oyama, Sunto, Shizuoka 410-1393, Japan;5. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229-8510, Japan;1. Department of Mechanical Engineering, University of Wisconsin – Madison, 1500 Engineering Drive, ERB – Room 1335, Madison, WI 53706, USA;2. Department of Mechanical Engineering, University of Wisconsin – Madison, 1500 Engineering Drive, ERB – Room 1341, Madison, WI 53706, USA |
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| Abstract: | In this technical report a cryogen-free 1 K cryostat is described where the pot of the 4He refrigeration unit is precooled by the 2nd stage of a pulse tube cryocooler (PTC) from room temperature to T ～ 3 K via a shunt made from sintered alumina (SA); the total mass of the 1 K stage is 3.5 kg. SA has high thermal conductivity at high temperatures; but below ～50 K the thermal conductivity drops rapidly, almost following a T3-law. This makes SA an interesting candidate for the construction of a thermal shunt, especially as the heat capacity of metals drops by several orders of magnitude in the temperature range from 300 K to 3 K. At the base temperature of the PTC, the heat conduction of the shunt is so small that the heat leak into the 1 K stage is negligible. |
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| Keywords: | Pulse-tube cryocooler |
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