Design aspects of the joints for the bus bar system of the Wendelstein 7-X stellarator

Abstract

The superconducting magnet system of the Wendelstein 7-X experiment consists of 50 non-planar and 20 planar coils. The coils are connected by 121 bus bars arranged in a series of seven groups each of 10 coils. The electrical and hydraulical interconnections of the bus bars will be provided by means of 184 joints each with the required resistance of less than 5 nΩ. The joint structure should withstand the internal pressure arising from the quench event. In order to permit joint replacement and repair after installation the joints have to be designed as demountable structures. Based on a conceptual design for an internal pressure of 30 bar and a current of 18 kA, the disconnectable joints have been redesigned for a pressure of 200 bar and a current of 20 kA. The report describes design, tests and stress analysis.