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

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

Sept. 17 th 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

Sept. 17 th Steps of the mechanical analysis  The magnetic design is performed using the conductor warm 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 50 MPa. This stress level will be partly reduced by cooling down

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

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

Sept. 17 th 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

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

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

Sept. 17 th Nominal collaring (2/5): stress in the windings (MPa) pole interface (MPa) 1 - collaring after collaring (pressure released) cool-down energization 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

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

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

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

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

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

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

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

Sept. 17 th Collaring with 0.3 mm thick shimming (1/2): stress in winding (MPa) pole interface (MPa) leftright 1 - collaring after collaring (pressure released) cool-down energization F col =2*348 tons/m P col =F col /(4*15.35 mm)=111 MPa

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

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

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

Sept. 17 th Collaring a 0.3 mm bigger winding: stress in the windings (2/3) (MPa) pole interface (MPa) leftright 1 - collaring after collaring (pressure released) cool-down energization F col =2*353 tons/m P col =F col /(4*15.35 mm)=113 MPa

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

Sept. 17 th 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

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