HFM ESAC Review : Insert interfacing HTS insert/ Fresca II

1. HFM ESAC Review:Insert interfacingHTS insert/ Fresca II M. Devaux Dipole design review- II-10 Insert intefacing- M. Devaux

2. Outline Global aim and introduction Layout of the insert Mechanical structure Mechanical interface Thermal interface Quench protection Magnetic interface Tests of insert inside Fresca II Dipole design review- II-10 Insert intefacing- M. Devaux

3. Global aim and introduction • EUCARD WP7: “On the very long term (> 20 years), an LHC upgrade to 2-3 times the energy is an option to be considered. For such an energy level, dipole magnets with a field of around 20 T would be needed […] Recent progress has shown outstanding performance on the intrinsic current transport properties of HTS Bi-2212 round wires, well adapted to magnets (je=450 MA/m2 and jc=1800 MA/m2 at 4 K under 25 T). This should open the road to higher magnetic fields. This work package is a very first step to prospect for this possibility” • Reach 19 T at 4.2 K with • 13 T from FRESCA 2 • 6T from the HTS insert • EUCARD program is limited to the design and the realization of the dipolar insert. • Insert tests (alone or with the dipole) are not included Dipole design review- II-10 Insert intefacing- M. Devaux

4. Layout of the insert 796 mm 3 D model of the insert Field map of Fresca 2 with the insert • Insert : 3 double pancakes • Inner coil diameter of the insert = 20 mm: It allows to use a Hall detector to measure the expected field Dipole design review- II-10 Insert intefacing- M. Devaux

5. Mechanical structure • Two independent structures: • - The insertion and the dismounting of the insert will be possible without disassembling Fresca II • The insert will be maintained by the exterior. • Schematic cross section of the insert: • External tube • External diameter = 99 mm • Thickness = 3 mm Steel Coils (je = 250 A/mm2) Iron pole Contribution of 10% on the main field Dipole design review- II-10 Insert intefacing- M. Devaux

6. Mechanical interface (1/2) • The insert is self-supporting under 19 T: • Fxper quadrant = 3.4 MN/m • Fyper quadrant = -0.25 MN/m • Influence on the forces of Fresca II: • Significant augmentation on Fy, however: • It is the less critical direction • Calculations are on going to confirm that Fresca II structure is well dimensionedfor this case Dipole design review- II-10 Insert intefacing- M. Devaux

7. Mechanical interface (2/2) Dipole design review- II-10 Insert intefacing- M. Devaux • Force resultants on the conductorsif the insert is not centered: Forces resultants on the whole system {dipole + insert} is not null because the forces on the other magnetic circuits (yoke, poles and pads) have been not calculated • Force resultants created by the misalignment of the insert are negligent comparing to global forces

8. Thermal interface • The two magnets are operated at the same temperature. • They will cool down at the same time (using the inertia of FRESCA 2 for the insert) with the same way • The temperature of the insert cannot be under Tλ(otherwise the quench detection on the HTS is almost impossible) Dipole design review- II-10 Insert intefacing- M. Devaux

9. Quench protection • FRESCA 2 should not be damaged in case of quench of the insert     • Different scenario risks (quench of the dipole, of the insert) will be considered and modeled • Calculations will be done to evaluate: • The energy transfer in different cases between the two magnets • The forces in the two magnets in case of quench on one of them Dipole design review- II-10 Insert intefacing- M. Devaux

10. Magnetic interface • In Fresca II, the magnetic flux due to the insert is opposite to the one due to Fresca II: This contributes to reduce the peak field of Fresca II • Magnetic calculations in 2D and 3D have been done with the two magnets. • Field vector maps with current or not in Fresca II : Dipole design review- II-10 Insert intefacing- M. Devaux

11. Tests of the insert insideFRESCA II • The sequence of power setting of FRESCA II with the insert will be studied: → The load line of the dipole in function of the field B will be calculated with or without the insert → The value of the residual pre-stress on the Nb3Sn dipole will be plotted in function of the load line • Preliminary tests of the insert will be done outside Fresca II and are limited at je< 250 A/mm2 • First tests of the insert inside FRESCA II will be done with a low field to study the resistive component of the insert. Dipole design review- II-10 Insert intefacing- M. Devaux

12. Conclusion The insert will be designed in order to minimize the interaction with the dipole Additional mechanical calculations are on going Careful evaluation of the critical quench situation is underway Dipole design review- II-10 Insert intefacing- M. Devaux