Successful physical experiment campaigns have been performed on the most advanced modular stellarator Wendelstein 7-X (W7-X) during the second operation phase (OP1.2). The completion phase (CP2) lasting until 2021 is devoted to the installation of cryo-vacuum pumps (CVPs), new diagnostics, and actively cooled in-vessel components instead of the inertially cooled ones used in OP1.2. This update allows us to move forward to achieve the steady state operation during the next operation phase (OP2). Several first wall components which are exposed to heat flux in the range from 250 to 500 kW/m 2 are covered by graphite tiles facing the plasma. Due to construction constraints, the backside area of the graphite tiles is not fully covered by the actively cooled CuCrZr heat sinks. This results in the presence of high-temperature graphite rims, which become an additional heat radiation source for the components behind the first wall. This article presents stepwise development of backside protections (BSPs) to mitigate the problem mentioned above. The process is supported by: 1) the study of BSP shielding performances through thermal analysis taking into account plasma radiation and electron-cyclotron resonance heating (ECRH) loads; 2) BSP sizing restricted by electromagnetic forces during main coil/plasma current decay; and 3) mechanical analysis to confirm the structural fixation of BSP. In addition, several analysis iterations for CVP have been repeated to minimize BSP cost by identification of first wall components with minor heat radiation to the CVP and marginal influence on its cooling system capacity.
A. Bortolon 1 , E. Gilson 1 , R. Lunsford 1 , R. Maingi 1 , A. Nagy 1 , C. Chrobak 2 , A. Hyatt 2 , T. Wilks 3 , M. Fenstermacher 4 , T. Rognlien 4 , C. Samuell 4 , M. Umansky 4 , J. Boedo 5 , I. Bykov 5 , D. Rudakov 5 , R. Smirnov 5 , M. Shafer 6 , D. Curreli 7 , J. Drobny 7 , D. Donovan 8 , J. Duran 8 , J. Ren 8 , A. Drenik 9 , R. Dux 9 , A. Herrmann 9 , A. Kallenbach 9 , R. McDermott 9 , R. Neu 9 , V. Rohde 9 , E. Wolfrum 9 and the DIII-D and ASDEX-Upgrade teams
The final design process of the ITER EC upper launcher (UL) was carried out between 2011 and 2018 under a Grant agreement between the European Domestic Agency F4E and a consortium of European associations, namely KIT (D), SPC (CH), DIFFER (NL), IPP (D), CNR (I), and IPF (D). The final design is scheduled for 2019. The final design review (FDR) will be split into several review processes for dedicated sub-components. One of these sub-components is the structural system of the EC launcher. This article presents a brief overview on the final design status of the ITER EC UL structure of spring 2018, including the history of development since 2004. It highlights the most challenging design issues and debates demanding project management steps. The lesson learned in the technical development of the design will be discussed, in view of the design work for future fusion devices.
The superconducting stellarator Wendelstein 7-X has completed the first three experimental phases, the first one with a limiter only and two phases with an inertially cooled carbon divertor configuration. The main mission of the latter two phases (the last one with two scraper elements) was to pave the way for the planned steady-state operation with high-power plasmas and a steady-state divertor. Presently, the device is being completed by installing a high-heat-flux (HHF) divertor and the corresponding water-cooling and ten cryo pumps in the divertor chambers. After this completion phase of W7-X, the device is ready for long-pulse divertor operation with heating power beyond 10 MW.
