Unternehmung WENDELSTEIN 7-X Max-Planck- Institut für Plasmaphysik Torsten Bräuer1CMSC, Charlotte,...

Unternehmung

WENDELSTEIN 7-X

Max-Planck-Institut für Plasmaphysik

Torsten Bräuer 1CMSC, Charlotte, July 2008

High geometric precision in the construction of the

WENDELSTEIN 7-X fusion experiment

T. Bräuer

Max-Planck-Institut für PlasmaphysikUnternehmung 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

Fusion Experiment WENDELSTEIN 7-X

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WENDELSTEIN 7-X



WENDELSTEIN 7-X is a fusion experiment !

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

p p D e

D p 3 He

3He 3

He 4He 2p

WENDELSTEIN 7-X: fusion basics

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WENDELSTEIN 7-X



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)

WENDELSTEIN 7-X: assembly strategy

• Fivefold symmetry of torus

• Flip symmetry of a module

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WENDELSTEIN 7-X



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


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Steps of half module assembly:

1. Adjustment of coilsAccuracy requirements: 0.5 … 1.5 mm

2. Adjustment of coil support structure Accuracy requirements: 1.0 … 1.5 mm


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WENDELSTEIN 7-X



Module and torus assembly:

3. Two half modules are jointed together

4. Module is lowered in half shell of outer vessel and adjusted to final position


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WENDELSTEIN 7-X



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 !


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WENDELSTEIN 7-X: second order datum points

Half module of support structure:

Size [m]: 1,5 x 2,5 x 2,5; weight 5 t

Creation of a second order datum point system for photogrammetry on the components

Non planar coil: size [m]: 2,5 x1,5 x 3,5; weight 5.5 t

• Usually 12…20 original datum points per component

• Installation of additional 200 second order points for photogrammetry

• Roughly 200…300 pictures necessary

• Roughly 1day

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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

Coil with original datum points

Feature targets for using in fitted holes, i. e. original datum points

Usually 12…15 original datum points per coil

200 new points per coil

Comparison of photogrammetry and Laser-Tracker at 15 datum points


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WENDELSTEIN 7-X



repeatability accuracy of new points

0 1

16

103

52

34

111 3 0 0

0

20

40

60

80

100

120

10 20 30 40 50 60 70 80 90 100 110

RMS per point [µm]

nu

mb

er

of

po

ints Number of points: 221

Number of surveys: 6Mean RMS: 42µm

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

32%68%

Accuracy analysis of second order datum points:

• 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

comparison of photogrammetry and LTD

0

2

3

6

4

0 00

1

2

3

4

5

6

7

0.05 0.10 0.15 0.20 0.25 0.30 0.35deviation per point [mm]

num

ber o

f poi

nts

Number of points: 15RMS: 0.17 mm

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WENDELSTEIN 7-X



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 …

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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

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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

Accessibility of datum points of amagnet half module

7

6

10 10

3

9

88

5

9

11

8

9

7

0

2

4

6

8

10

12

14

16

AAB13 AAB17 AAB22 AAB45 AAB51 AAC13 AAC51

coils

nu

mb

er o

f p

oin

ts

Phg

LTD

sec. order Phg *10

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comparision: actual - nominal coil position

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

first order datum points of coils

devi

atio

n [m

m]

AAB13 AAB22 AAB45 AAB51 AAC13 AAC51AAB17


Results of photogrammetry survey: comparison of actual and nominal coil position

• 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

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repeatability accuracy

11

364

539

202

56

16 6 4 0 00

100

200

300

400

500

600

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

RMS per point

nu

mb

er o

f p

oin

ts

Repeatability accuracy analysis:

32%68%

Number of points: 1198Mean RMS: 0.25 mm


• 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

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• 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

Cross check with Laser-Tracker:


comparison of photogrammetry and Laser-Tracker

3

2

5

3

2

5 5

3

1

0 0 00

1

2

3

4

5

6

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6

deviation [mm]

nu

mb

er o

f p

oin

ts

number of points: 29Mean deviation: 0.22 mmRMS: 0.25 mm

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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 intooperation in 2014 !

Unternehmung WENDELSTEIN 7-X Max-Planck- Institut für Plasmaphysik Torsten Bräuer1CMSC, Charlotte,...

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