浮上式鉄道用超伝導磁石の４Ｋ／８０Ｋ両用ＧＭ冷凍システムの開発 窒素自然循環方式熱シールド板の冷却特性

Abstract

An onboard refrigeration system is one of the most important components in the superconducting magnetically levitated system (Maglev system). In the superconducting magnet, liquid helium and nitrogen are used to cool the superconducting coils and the radiation shields. At the Yamanashi Maglev Test Line, the operation of the superconducting magnet without a supplement of liquid helium has been achieved by the onboard 4K Gifford-McMahon/Joule-Thomson (GM/JT) refrigerators. As for the liquid nitrogen, it is supplied to the radiation shields periodically. Our final target for an onboard refrigeration system for commercial use is to operate magnets with no supplementation of cryogen. That is, the operations of magnets should not depend on a helium liquefaction plant or a liquid nitrogen supplying system in the train depot, except for occasions of the magnet's precooling or when the vehicle is being overhauled. To meet these requirements, we have been developing a new type of onboard GM refrigeration (GM refrigerator application) system that features a combination of a 4K/80K multiple-operating type of GM refrigerator and a self-circulated cooling-type radiation shield. The nitrogen self-circulated cooling-type radiation shield plate was demonstrated by using the radiation shield plate mock-up.