Assembly Technology for the W7-X Stellarator

Abstract

Wendelstein 7-X is a super conducting Sellarator being constructed in Greifswald, Germany. The technology needed to assemble the basic-machine W7-X requires a complex integration of engineering disciplines from the accuracy of manufacture through to the metrology techniques and equipment to successfully assemble the machine. The spiral shape of the Stellarator vacuum vessel means the 70 coils must be threaded individually over the vacuum vessel. To avoid damage to the thermal insulation 5 axis lifting devices have been designed to thread coils into their final position.The distance between the coils is fixed by a series of radial and lateral support elements, central support elements and planar support elements, the assembly technology is being developed and tested by an extensive test programme.W7-X is equipped with 299 ports for diagnostics and supply of in vessel components; they connect the ICRH, ECRH and neutral injection systems to the plasma vessel. All ports must be positioned accurately at various angles around the vacuum vessel, ranging in weight from 100 kg up to 900 kg. For the ports this requires close integration of the manufacturing, metrology and assembly technologies. At present it is planned to use a powered ramp. It is planned that the ramp and its support structure will also be used to insert the thermal insulation of the port, the 'plug in' in vessel component supply bundles and possibly diagnostics. The bus bar system links all coils to the power supply system. Space constraints within the machine cryostat require compact super conducting joints which, have been designed and tested with a resistance in the range of lnOhm.The paper will give an overview of the various technologies being used to solve the assembly problems on the various components and the status of the assembly of the basic-machine.

Wendelstein 7-X, Overview and Status of Construction

“…The process itself is divided in 5 major steps [16] to be described below. For these very complex steps many technologies have been developed and qualified, assembly steps have been trained to train the personnel but also to commission and to optimize the newly developed tools [17]. Threading of the coils has been simulated with interactive CAD-models to check early for possible collisions.…”

Assembly Status of the W7-X Stellarator

“…Two proof of principle joints were tested in SULTAN test facility, Switzerland in 2003, a second joint test with a production design joint was tested in SINTEZ, Efremov Institute, St Petersburg, Russia in 2005. All joints had a resistance at 2T and 18 kA of less than InQ, the specification allows 5nQ [4,5]. The bus bar system, including all supports, clamps and the joint components is designed and manufactured in collaboration with Forschungzentrum Jiulich, Germany [6,7].…”