CONCEPTUAL DESIGN OF D2 MECHANICAL STRUCTURE (DOUBLE COLLARING OPTION) S. Farinon, P. Fabbricatore (INFN-Sezione di Genova) Sept. 24 th 2015

Sept. 24 th 2015 S. Farinon 2 Introduction  Sept. last year, we presented a single collar mechanical structure for the D2 magnet  as already noticed, it has several drawbacks…

Sept. 24 th 2015 S. Farinon 3 Considerations on the single collaring  it is a difficult operation (the coil is not symmetric)  it needs a huge press (particularly negative for the prototype)  it is not possible to couple in the same magnet coils with compatible field quality  we decided to explore the double collaring option

Sept. 24 th 2015 S. Farinon 4 Preliminary considerations on the double collaring  to reduce the risks of the collaring operation, a fully symmetric collar is the best option the collar dimensions are determined by the distance D between the coils  the Lorentz forces being repulsive, we need to design a mechanical structure able to withstand them  to preserve the field quality, we should avoid coils misalignments respect to one another and respect to the iron yoke  the shell being elliptical, it is preferable to give it no mechanical function  we look for a solution where the collars only have a mechanical role, the iron yoke being a mere magnetic component D

Sept. 24 th 2015 S. Farinon 5 The concept Collaring of a single coil  to follow the iron yoke window, collars are squared  the overall dimensions are 188.7×188.7 mm 2 (188.7 mm is the warm beam distance)  the inner radius is 69 mm, so the thickness on the midplane is ~25 mm  in order to need 1 single blancking die, the nose is modular mm 69 mm

Sept. 24 th 2015 S. Farinon 6 The concept Collared coils and iron yoke coupling  once the collared coils are inside the iron yoke, there is a gap (9 mm thick on the midplane, and 10 mm thick axially)  instead of simply filling this gap with inert materials, we decided to give it multipole mechanical functions

Sept. 24 th 2015 S. Farinon 7 The concept Aluminum alloy ring thick between collared coil and Al alloy ring (closed at cold)  this gap can be almost doubled by heating the rings  to compensate the thermal contractions, the selected material is Al alloy (  Al alloy =4.3‰,  SS =2.4‰,  iron =1.8‰)  we are still evaluating the length of the Al alloy rings (50 mm max)  to make the insertion possible, there is a warm gap 0.4 mm

Sept. 24 th 2015 S. Farinon 8 The concept Aluminum alloy ring functions  two small holes are used to align horizontally the coils at warm (no mechanical function)  at cold the gap between Al alloy rings and collared coils closes. No movement of a coil with respect to the other is still possible  a pin between iron an Al alloy ring keeps the vertical alignment

Sept. 24 th 2015 S. Farinon 9 The concept Iron yoke  the iron yoke has no mechanical function  a 1.2 mm gap is closed at warm under pressure to allow the insertion of the C-clamps  this mechanism ensures the horizontal alignment  a continuous bar is then welded on the top of the C-clamps to give longitudinal strength to the assembly

FE analysis

Sept. 24 th 2015 S. Farinon 11 Steps of the mechanical analysis  The magnetic design is performed using the conductor warm 70 MPa  The windings undergo an azimuthal thermal expansion that brings them from 70 MPa to 0 MPa  The collars are closed under pressure and the Al rings inserted  The iron yoke is closed under pressure and the C-clamp inserted  The magnet is cooled down and energized, using the Lorentz forces coming from the magnetic analysis

Sept. 24 th 2015 S. Farinon 12 Material properties Material Young modulus (GPa) Thermal expansion coefficient (10 -3 ) conductor (including insulation) kapton2.59 copper (wedges) steel (pins and rods)2203  The following materials are elastic, no temperature dependence is taken into account

Sept. 24 th 2015 S. Farinon 13 Material properties IronSSAl alloy E (GPa) E T (GPa)0.1 Y 300 K (MPa) Y 4 K (MPa)  ·  Iron, collar stainless steel and Al alloy have temperature dependent plastic properties

Collaring of a single coil

Sept. 24 th 2015 S. Farinon 15 Collaring mechanism  a pressure is applied to align the holes, the keys are inserted, the pressure is released F=386 ton/m P=123 MPa  y=+0.06 mm  x=+0.07 mm xxxx xxxx yyyy yyyy

Sept. 24 th 2015 S. Farinon 16 The modular nose  due to the asymmetry of the winding, up and down collars are different  the modular nose (at list for the prototype) allows using one single blanking die  for small variations, it is possible to modify the nose avoiding the use of shims 0.1 mm gap 0.2 mm gap no gap - dimensional tolerances set so as to ensure the insertion

Sept. 24 th 2015 S. Farinon 17 Stresses due to collaring UNDER PRESSUREPRESSURE RELEASED average stress in the winding: 85 MPa average stress in the winding: 76 MPa

Al alloy ring insertion

Sept. 24 th 2015 S. Farinon 19 Al alloy ring insertion  no stress results from this operation because of the continuous gap between collars and rings

Iron yoke assembly

Sept. 24 th 2015 S. Farinon 21 Iron yoke assembly  0.6 mm per side are cut from the iron yoke lamination to get 1.2 mm gap  the gap is dimensioned not to close at cold

Sept. 24 th 2015 S. Farinon 22 Iron yoke assembly  0.6 mm per side are cut from the iron yoke lamination to get 1.2 mm gap  the gap is dimensioned not to close at cold  the assembly is done under pressure with no effect on the collared coil F=352 ton/m

Sept. 24 th 2015 S. Farinon 23 Stress due to iron yoke assembly  the stress is absorbed by the Al alloy ring, with no effect on the collared coil  the average stress of Al alloy ring is =105 MPa (in compression)  except the pressing locations, the stress in the yoke is quite low ( =36 MPa)

Sept. 24 th 2015 S. Farinon 24 Warm magnet  the peak stress in the iron moves to the clamping locations  in average, the stress is slightly discharged, in Al alloy rings =85 MPa

Cool down

Sept. 24 th 2015 S. Farinon 26 Gaps at 4 K  the gap between Al alloy rings and collared coils is closed and there is a residual stress in the rings  the gap between the two halves of the iron yoke doesn’t close completely; the residual gap is 0.1 mm =15 MPa =15 MPa =13 MPa =13 MPa

Sept. 24 th 2015 S. Farinon 27 Stress in winding and collars after cool-down =52 MPa =52 MPa

Energization up to 4.5 T

Sept. 24 th 2015 S. Farinon 29 Lorentz forces at 4.5 T  F x =31 MN/m and corresponds to the unbalance between the left and right part of each coil (F xA =+228 MN/m and F xB =-197 MN/m)  Fy=135 MN/m (F xA =69 MN/m and F xB =66 MN/m) AB

Sept. 24 th 2015 S. Farinon 30 Stress in winding and collars after energization at 4.5 T =55 MPa =55 MPa

Sept. 24 th 2015 S. Farinon 31 Stress in Al alloy rings after energization at 4.5 T =15 MPa =15 MPa =20 MPa =20 MPa =15 MPa =15 MPa

Sept. 24 th 2015 S. Farinon 32 Conclusions  We completed the conceptual design of the D2 mechanical structure for the double collaring option  No major problem emerged from the finite element analysis  We think this is the most feasible option for the D2 prototype

THANKS FOR YOUR ATTENTION S. Farinon, P. Fabbricatore (INFN-Sezione di Genova) Sept. 24 th 2015