Method of cooling a current feed for very low temperature electrical equipment and device for implementing it

Device for cooling an electrical current feed between a terminal at ambient temperature and an electrical equipment immersed in a cryogenic fluid, the equipment being adapted to operate at variable electrical current, the cooling being obtained by circulating an auxiliary cooling fluid at ambient temperature within an electrical current feed and exchanging heat therewith, by introducing the auxiliary cooling fluid at an intermediate level within the current feed when the electrical current exceeds a particular threshold, and introducing at least some of the auxiliary cooling fluid at other levels nearer the electrical equipment at higher electrical current, said device comprising:

• a first enclosure for surrounding an electrical current feed and delimiting a first passage for circulation of said auxiliary cooling fluid in thermal contact with said current feed;
• means for admitting at lest some of said cooling fluid into said first passage at a level selected according to the level of electrical current carried by said current feed;
• a second enclosure around said first enclosure defining a space therebetween for circulating said auxiliary cooling fluid;
• and means for separating said space into a second passage and a third passage, each of which has access to said first passage at a different level.