Upgrade of the Cryogenic Systems of Wendelstein 7-X

The Wendelstein 7-X experimental device has completed the third plasma operation campaign in November 2018. The running, two-year shut down phase is being used to install new diagnostics, new in-vessel-components (steady-state divertor and cryopumps), and their auxiliary supply systems. In particular, the installation of the ten cryopumps requires a substantial upgradation of the cryosystems. The work package comprises the installation of a 55-m long new transfer line from the cryoplant to the new valve box and the installation of ten transfer lines with lengths up to 15 m from the valve box to the ten cryovacuum pumps (CVPs) in the plasma vessel. The tasks have been split into two main contracts in industry. Both contracts are presently running, the production of the transfer lines and the valve box per September 2019 is in an advanced status. The aim is to complete the production in early 2020 and the installation work by the end of 2020. A second task regarding the cryosystems is the upgrade with respect to the foreseen long pulse operation of W7-X. Therefore, new storage tanks for helium gas and for liquid nitrogen are necessary. The helium gas storage has been installed at the end of 2018 whereas the liquid nitrogen storage tank is presently under design. This article gives an overview about individual upgrade tasks of the W7-X cryosystems, highlights the special design requirements, and reports the status of the contracts.