1. CONCEPTUAL DESIGN OF D2 MECHANICAL STRUCTURE S. Farinon, P. Fabbricatore (INFN-Sezione di Genova) Sept. 17 th 2014

2. Sept. 17 th 2014 2 Introduction  the basic idea is to fill with collars the grey area between windings and iron

3. Sept. 17 th 2014 3 The concept  Packs of collars are kept together by pins  In each pack, the two different kind of collars are alternating  The packs of collars are assembled under pressure by inserting rods  Collars, pins and rods are made of stainless steel

4. Sept. 17 th 2014 4 Steps of the mechanical analysis  The magnetic design is performed using the conductor warm dimensions @ 50 MPa  The windings undergo an azimuthal thermal expansion that brings them from 50 MPa to 0 MPa  The collars are closed and the rod inserted  The collared coils are cooled down and energized, using the Lorentz forces coming from the magnetic analysis  TO BE NOTICED: the mechanical design is done to get the warm collared coils @ 50 MPa. This stress level will be partly reduced by cooling down

5. Sept. 17 th 2014 5 Material properties Material Young modulus (GPa) Thermal expansion coefficient (10 -3 ) conductor (including insulation) 95.63 kapton2.59 copper (wedges)1353.25 steel (collar, pins and rods)2203  All materials are elastic, no temperature dependence is taken into account

6. Sept. 17 th 2014 6 Windings at 0 MPa (1/2)

7. Sept. 17 th 2014 7 Windings at 0 MPa (2/2)  To check the validity of this approach, I made the following «ad hoc» model: E=10 E steel F col F col =2*156.5 tons/m P col =F col /(4*15.35 mm)=50 MPa =43 MPa

8. The collars fit exactly the magnetic design of the coils, i.e. their warm dimensions @ 50 MPa Nominal collaring

9. Sept. 17 th 2014 9 Nominal collaring (1/5)  Both collar assemblies are present in the mechanical model and are connected via the pins

10. Sept. 17 th 2014 10 Nominal collaring (2/5): stress in the windings (MPa) pole interface (MPa) 1 - collaring53-52-40 2 - after collaring (pressure released) 36-37-36 3 - cool-down18-16-18 4- energization23+5+7 leftright  Collars have to be overpressed by 0.1 mm:  F col =2*203 tons/m  P col =F col /(4*15.35 mm)=65 MPa 12 34

11. Sept. 17 th 2014 11 Nominal collaring (3/5): stress in the collars

12. Sept. 17 th 2014 12 Nominal collaring (3/5): stress in the collars

13. Sept. 17 th 2014 13 Nominal collaring (3/5): stress in the collars

14. Sept. 17 th 2014 14 Nominal collaring (3/5): stress in the collars

15. Sept. 17 th 2014 15 Nominal collaring (4/5): effect on b2/b3 harmonics

16. Sept. 17 th 2014 16 Nominal collaring (5/5): effect on higher harmonics

17. Is it possible to increase the stress in the coils so to guarantee continous contact between collar and winding? The easiest way is to insert a shimming Collaring with 0.3 mm thick shimming

18. Sept. 17 th 2014 18 Collaring with 0.3 mm thick shimming (1/2): stress in winding (MPa) pole interface (MPa) leftright 1 - collaring93-94-75 2 - after collaring (pressure released) 76-81-82 3 - cool-down55-54-55 4- energization57-32-26 F col =2*348 tons/m P col =F col /(4*15.35 mm)=111 MPa

19. Sept. 17 th 2014 19 Collaring with 0.3 mm thick shimming (2/2): effect on b2/b3

20. Is it really necessary to insert an additional shimming? Our experience with DISCORAP dipoles tells us that windings are usually bigger than expected (0.3 mm at minimum). Could it be enough? Winding 0.3 mm bigger

21. Sept. 17 th 2014 21 Collaring a 0.3 mm bigger winding (1/3) P col 0.3 mm

22. Sept. 17 th 2014 22 Collaring a 0.3 mm bigger winding: stress in the windings (2/3) (MPa) pole interface (MPa) leftright 1 - collaring94-92-70 2 - after collaring (pressure released) 72-72-74 3 - cool-down51-48-51 4- energization54-27-26 F col =2*353 tons/m P col =F col /(4*15.35 mm)=113 MPa

23. Sept. 17 th 2014 23 Collaring a 0.3 mm bigger winding: effect on b2/b3 (3/3)

24. Sept. 17 th 2014 24 Conclusions  We made a conceptual design of the mechanical structure of D2 dipoles  We investigated its mechanical behavior in various conditions as well as its effects on field quality  Further work will be dedicated to the collar geometry refinement and to include the effects of material properties nonlinearities  As final steps, iron yoke and outer shell will be also included in the mechanical model

25. THANKS FOR YOUR ATTENTION S. Farinon, P. Fabbricatore (INFN-Sezione di Genova) Sept. 17 th 2014