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Design and heat transfer characteristics evaluation of liquid helium vessel for development of cryostat
Myung Su Kim, Yojong Choi, Seunghyun Song and Yeon Suk Choi

Operating superconducting magnets at low temperatures requires effective storage and management of cryogenic liquid. The development of cryostat with low boil-off rate, therefore, is essential and should be preceded for stable and efficient operation of superconducting magnets. The conductive heat transfer through the neck of the liquid helium vessel in the cryostat is the main source of the heat invasion because it is directly connected between room temperature flange and cryogenic liquid. Reducing conductive heat transfer can be achieved by the thermal property and shape dimension of the neck of the liquid helium vessel. Three types of the liquid helium vessel are designed and fabricated, considering material and dimension. The boil-off rates of the liquid helium are measured and the slopes of helium level as a function of elapsed time are acquired. The amount of liquid helium boil-off depending on the material of the neck is discussed quantitatively. In addition, the temperature distribution along the neck is discussed with respect to the amount of boil-off of liquid helium.

Keywords: neck of liquid helium vessel, cryostat, boil-off rate, conductive heat transfer