Development of the EuCARD Nb 3 Sn Dipole Magnet FRESCA2 P. Ferracin, M. Devaux, M. Durante, P. Fazilleau, P. Fessia, P. Manil, A. Milanese, J. E. Munoz

Development of the EuCARD Nb3Sn Dipole Magnet FRESCA2

P. Ferracin, M. Devaux, M. Durante, P. Fazilleau, P. Fessia, P. Manil, A. Milanese, J. E. Munoz Garcia, J. C. Perez, L. Oberli, J. M. Rifflet, G. de Rijk, F.

Rondeaux, E. Todesco,

and the whole team of the Magnet Design and Technology (MDT) Section

EUCARD-WP7-HFM 9th collaboration meetingLASA, Milan

18 September, 2012

Introduction

• European Coordination for Accelerator R&D (EUCARD) Project – R&D on new technologies for future upgrades of the European

accelerators

• Work Package 7 dedicated to superconducting high field magnets for higher luminosities and energies

• Key objective: fabrication and test of FRESCA2– Upgrading the CERN cable test facility FRESCA

• 88 mm 100 mm aperture• 10 13 T bore field• NbTi Nb3Sn superconducting technology

– Provide the background field for an HTS coil insert• R&D towards 20 T magnet

18/09/2012Paolo Ferracin 2

IntroductionOverview of magnet design

• Target: 13 T in 100 mm clear bore

• OD: 1.030 m; length: 2.255 m• Al shell, 65 mm thick, 1.6 m long• Iron yoke

– Holes for axial rods• Horizontal stainless steel pad

– 3 bladders, 75 mm wide – 2 load keys

• Vertical iron pad– 2 bladders, 60 mm wide – 2 load keys

• Auxiliary bladders between yokes• Four double-layer coils• Iron and Ti alloy central posts


Conductor and cable parameters• Both PIT an RRP procured• Strand diameter: 1 mm• Cu/Sc: 1.3 56% Cu• Strand #: 40• Bare width after cabling: 20.900 mm• Bare thickness after cabling: 1.860 mm• Insulation: 0.200 mm• Assumed growth during HT

– 4% in thickness and 2% in width• Bare width after HT: 21.400 mm• Bare thickness after HT: 1.934 mm


PIT strand

Superconductor properties

• Jc of virgin strand (4.2 K) without self field (s.f.) correction (PIT)– 2400 A/mm2 at 12 T– 1400 A/mm2 at 15 T

• Self field corr. of 0.41 T/kA• ~5% cabling degradation

• Resulting Jc for comp.– 2450 A/mm2 at 12 T– 1400 A/mm2 at 15 T


Dilatation test• Goal: measure cable longitudinal

length variation during reaction– Feed-back on coil and tooling design

• 1.5 m of cable wound around 700 mm long winding pole– Stainless steel, iron, Ti alloy– Gaps vs. no-gaps

• First (out of 3) heat treatment completed, analysis in progress


Coil design

• Two double-layers with 36 and 42 turn

• Coil aperture 116 mm, bore 100 mm

• Iron and Ti (or SS) poles• Inter-coil gap and mid-plane

“tailored” shim• 730 mm of straight section• Hard-way bend of 700 mm• 17 inclined ends• Overall coil length of 1.6 m


vertical pad

iron yoke

iron post

100 mm aperture

Magnet parameters• Operational conditions (13 T)

– Iop: 10.9 kA– Bpeak_op: 13.4 T– 79% of Iss at 4.2 K

• Bbore: 16.0 T– 72% of Iss at 1.9 K

• Bbore: 17.2 T;• 15 T bore field: 86% of 1.9 K Iss

• Peak field in layer 1

• 1% homogeneity in 2/3 of aperture and 540 mm length

• 10% of margin in the ends


E.m. forces and support structure• E.m. forces in straight section directed

outwardly– Max . “accumulated” stress of 100 MPa

• Horizontal bladders pressurized to 30 MPa– Insertion of a shim in hor. load keys of 0.6 mm

• Shell from 65 (293 K) to 185 (4.2 K) MPa

• Axial force: 2.8 MN– LHC (8.3 T, 1 aperture): 0.25 MN– HQ (170 T/m): 0.8 MN

• Axial piston used to pre-load the rods – 60 mm diameter• Rod from 150 (293 K) to 260 (4.2 K) MPa


Coil stress

• 2D and 3D mechanical model

• Goal: contact pressure (or tension <20 MPa) between pole turn and pole pieces– From straight section to hard-

way and easy-way bent

• Coil peak (equiv.) stress– 140-150 MPa– Maximum stress moves to

low field region at full field


-137 MPa

134 MPa 154 MPa

-139 MPa

Coil fabrication status• Winding on 3 bolted blocks• Stainless steel fixture (top plates and side

rails) for reaction– Mica sheets for sliding

• Same parts in aluminium for impregnation

• Design completed, procurement in progress

• One set of coil part successfully fabricated– Plasma spray for insulation


Support structure fabricationYoke and shell


• 10 strain gauge stations • Azimuthal, axial with T comp.• Straight section and ends• Total: 20 gauges

Support structure fabricationYoke and shell


Support structure fabricationCoil-pack with dummy coils


• 14 strain gauge stations • Azimuthal, axial with T comp.• Straight section and ends• Total: 28 gauges

Support structure fabricationCoil-pack with dummy coils


Support structure fabricationAxial support system


• 2 strain gauge per rod• Axial direction.• Total: 8 gauges

Quench protection• At nominal field, total stored energy of 4.6 MJ

– 3.7 m long LARP LQ features: 1.4 MJ – But, comparable the stored energy density

• Protection system: 95 mΩ dump resistor and quench heaters on all layers– 50 W/cm2 and 50% coverage

• 150 or 200 K of peak T with tdetection of 40 or 100 ms


• Traces with 4 heaters– Wiggling shape for

better coverage• 9 voltage taps per layer

– Monitor pole turn and external turns

Conclusions and future plans

• Design of Nb3Sn dipole magnet FRESCA2 completed – Goal: 13 T in 100 mm bore

• According measured strand properties, the magnet operates with more than 20% of current margin

• Fabrication of coil fabrication tooling in progress• Structure components and parts for the first coil delivered

• Next steps– First coil wound with a copper cable early next year – In parallel, support structure assembled, pre-loaded and cooled-

down to 77 K around aluminium dummy coils. • Results to be used to validate models and define procedures and pre-

load levels


Documents

Development of the EuCARD Nb 3 Sn Dipole Magnet FRESCA2 P. Ferracin, M. Devaux, M. Durante, P. Fazilleau, P. Fessia, P. Manil, A. Milanese, J. E. Munoz