Vacuum vessel having a cooled member.

摘要

A vacuum vessel has a member (24) to be cooled to a low operating temperature inside the vessel (2) and a main cooling circuit (15-20) for fluid for cooling the member (24) to operating temperature. The main cooling circuit has first fluid refrigerating means (14) located at the vessel (2). To achieve rapid cooling, there is a pre-cooling circuit (22, 23) for fluid for pre-cooling the member (24) towards operating temperature. The pre-cooling circuit has second fluid refrigerating means (23) operable independently of the first fluid refrigerating means (14). The pre-cooling circuit effects cooling of the main cooling circuit, prior to operation of the main cooling circuit, by passage of fluid from the pre-cooling circuit into the main cooling circuit. A heat shield cooling circuit for cooling a heat shield (32) cools the second fluid refrigerating means (23) of the pre-cooling circuit. <IMAGE>