Fusion Experiment WENDELSTEIN 7-X High geometric precision in the construction of the WENDELSTEIN 7-X fusion experiment T. Bräuer Max-Planck-Institut für Plasmaphysik Unternehmung WENDELSTEIN 7-X D-17491 Greifswald, Wendelsteinstraße 1 Content: Fusion basics and assembly strategy Second order datum point system on components Survey of first magnet half module Conclusion, outlook

WENDELSTEIN 7-X is a fusion experiment ! WENDELSTEIN 7-X: fusion basics WENDELSTEIN 7-X is a fusion experiment ! p + ® D e n 3 He g 4 2 Physical Aim: Prove of the stellarator principle as a realistic concept for a future power plants but no break even, no Tritium Control of a plasma at very high temperatures of 100 Mio Kelvin Quasi stationary operation Technical aim: Construction of the device under industrial like conditions Very tight collaboration with manufacturers Creation of a very strong, very precise magnet field with a relative accuracy of 1...2·10-4

Fivefold symmetry of torus Flip symmetry of a module WENDELSTEIN 7-X: assembly strategy Design scheme of W7-X Main dimensions of W7-X Main radius: 5.5m High: 5.5m Mass: 725t 50 non planar coils (NPC) (Ø  3.0 m, m = 5 t) 20 planar coils (PLC) (Ø  3.5 m, m = 2 t) Coil support structure (CSS) Plasma vessel (PV) Outer vessel (OV) Fivefold symmetry of torus Flip symmetry of a module

Fivefold and flip symmetry: WENDELSTEIN 7-X: assembly strategy Fivefold and flip symmetry: Fivefold symmetry: 5 identical modules with 10 NPC and 4 PLC, CSS, PV Flip symmetry: 2 flip symmetric half modules per module 5 NPC und 2 PLC per half module Flip symmetric half modules of CSS Flip symmetric half modules of PV

Steps of half module assembly: WENDELSTEIN 7-X: assembly strategy Steps of half module assembly: Adjustment of coils Accuracy requirements: 0.5 … 1.5 mm Adjustment of coil support structure Accuracy requirements: 1.0 … 1.5 mm

Module and torus assembly: WENDELSTEIN 7-X: assembly strategy Module and torus assembly: Two half modules are jointed together Module is lowered in half shell of outer vessel and adjusted to final position

Adjustment of components: mainly done by Laser-Tracker (LTD) WENDELSTEIN 7-X: assembly strategy Adjustment of components: mainly done by Laser-Tracker (LTD) 6 … 12 datum points per component Adjustment residual: 0.5 … 1.5 mm Survey accuracy: 0.2 … 0.3 mm Final surveys and documentation: Mainly done by photogrammetry Short survey time Flexible lines of sight and camera positions possible Survey accuracy: 0.2 … 0.4 mm Access to datum points becomes more and more difficult with progress of assembly due to using fitted holes for assembly purposes and blocking of lines of sight by components and staff folders Creation of a second order datum point system with a high number of points is necessary !

WENDELSTEIN 7-X: second order datum points Creation of a second order datum point system for photogrammetry on the components Usually 12…20 original datum points per component Installation of additional 200 second order points for photogrammetry Half module of support structure: Size [m]: 1,5 x 2,5 x 2,5; weight  5 t Roughly 200…300 pictures necessary Roughly 1day Non planar coil: size [m]: 2,5 x1,5 x 3,5; weight  5.5 t

WENDELSTEIN 7-X: second order datum points Creation of a second order datum point system for photogrammetry on a coil sticky targets on the coil Support P1 Stand foot 2 Stand foot 1 Support M1 a. 2 Aux. point 3 Coil support 1 a. 2 Ref. points  3.5m Usually 12…15 original datum points per coil  200 new points per coil Comparison of photogrammetry and Laser-Tracker at 15 datum points Feature targets for using in fitted holes, i. e. original datum points Coil with original datum points

Accuracy analysis of second order datum points: WENDELSTEIN 7-X: second order datum points Accuracy analysis of second order datum points: Number of points: 15 RMS: 0.17 mm Number of points: 221 Number of surveys: 6 Mean RMS: 42µm 68% 32% Conditions: No air condition Different operators For each survey a new set up of scale bars and coded targets Removing and replacing targets of datum holes LTD repeatability accuracy (σ): 0.0625 mm Result: Under real conditions the second order datum points show additional but acceptable uncertainties and can be used in later surveys

Situation for survey of magnet half module: WENDELSTEIN 7-X: Survey of first magnet half module Situation for survey of magnet half module: Two assembly stands next to each other Workflow in work shop is ongoing (crane, transport, …) No air condition Volume of half module 4 x 5 x 4 m³ Max. high over ground: 6m Lots of fixing structures, platforms …

Situation for survey of magnet half module: WENDELSTEIN 7-X: Survey of first magnet half module Situation for survey of magnet half module: Access to the coils is blocked by: Machine table at bottom Support structure at inner side Fixing structures at back, left and right

Results of photogrammetry survey: accessibility of datum points WENDELSTEIN 7-X: Survey of first magnet half module Results of photogrammetry survey: accessibility of datum points 5 independent surveys Up to 750 pictures per survey First order datum points: Total number at all coils: 152 Accessible by photogrammetry: 53 Accessible by Laser-Tracker: 57 (only by using of T-Probe) Second order points: Total number at all coils: 1544 Accessible 780

Actual coil positions meet the tolerance requirements WENDELSTEIN 7-X: Survey of first magnet half module Results of photogrammetry survey: comparison of actual and nominal coil position AAB13 AAB22 AAB45 AAB51 AAC13 AAC51 AAB17 Required adjustment tolerance: 1.5 mm Maximum deviation: 1.3 mm Est. repeatability accuracy of survey (68%): 0.25 mm Cross check with Laser- Tracker survey shows similar results (see below) Actual coil positions meet the tolerance requirements

Repeatability accuracy analysis: WENDELSTEIN 7-X: Survey of first magnet half module Repeatability accuracy analysis: Number of surveys: 5 Duration of all 5 surveys: 1d 2 operators 1 camera In all surveys the same set up of scale bares and coded targets No air condition Ongoing workflow in workshop Number of points: 1198 Mean RMS: 0.25 mm 68% 32%

Cross check with Laser-Tracker: WENDELSTEIN 7-X: Survey of first magnet half module Cross check with Laser-Tracker: One Laser-Tracker survey (Laser-Tracker used with T-Probe) Duration: 1d Maximum deviation of a coil measured by Laser-Tracker: 1.41 mm Meets the tolerance requirement Average of 5 photogrammetry surveys Transformation of photogrammetry to Laser-Tracker survey number of points: 29 Mean deviation: 0.22 mm RMS: 0.25 mm

The experiment WENDELSTEIN 7-X will go into WENDELSTEIN 7-X: Conclusion, outlook Conclusion, outlook : Coils of fist magnet half module have been assembled inside required tolerance! Assembly methods have been proofed and can be used for future modules Assembly is feasible under industrial like conditions, especially under fast rate of construction Photogrammetry has been proofed as a reliable and fast survey technique for final surveys Accessibility can be improved by a second order datum point system for photogrammetry, especially for the next assembly steps: module assembly assembly of torus Second order datum points show an acceptable increase of uncertainty New generation of cameras will be tested to reduce survey time and improve accuracy The experiment WENDELSTEIN 7-X will go into operation in 2014 !