1. SC Magnets at Fermilab New Collaring and Coil Pre-stress Limit for a Nb3Sn Magnet Alexander Zlobin Technical Division Fermilab

2. SC Magnets at Fermilab Introduction Fermilab is developing a new generation of accelerator magnets based on Nb 3 Sn superconductor o LHC luminosity upgrade o Muon Collider New recent results within the Fermilab’s base High Field Magnet (HFM) program o Assembly and test of Nb3Sn Quadrupole model (TQC) with dipole style collar and coil alignment o Study of the effect of coil pre-stress on magnet performance All Experimenters’ Meeting, May 10, 2010 2

3. SC Magnets at Fermilab  Collaring using short vertical 4-jaw press with partial coil compression along the length  Requires additional horizontal to vertical handling of the coils  Time consuming process for Nb3Sn magnets with many (~6-8) passes and some risk of damage to coils Quadrupole collar All Experimenters’ Meeting, May 10, 2010 3

4. SC Magnets at Fermilab Dipole-style collar Dipole-style collar:  Similar for Dipole and Quadrupole magnets  Collaring using full-length horizontal press  Collaring with a single pass reducing coil degradation risks and construction time (<1 week) All Experimenters’ Meeting, May 10, 2010 4

5. SC Magnets at Fermilab  Multiple handling and test cycles => robust technology  Consistent coil quench performance in shell and collar structures  No significant field quality distortions related to the dipole style Effect on QP and FQ All Experimenters’ Meeting, May 10, 2010 5

6. SC Magnets at Fermilab Nb3Sn TQC is modification of NbTi LHC IRQ (MQXB) HGQ (MQXB):  70-mm NbTi IRQ  Cable 15 mm wide  Gop=200 T/m @ 11.1 kA  Top=1.9K  Margin ~20% dTc~2K TQC:  90-mm Nb3Sn IRQ  Cable 10 mm wide  Gop=200 T/m @12.0 kA  Top=4.5K, 5% Ic margin, dTc~2K  Top=1.9K, 15% Ic margin, dTc~6K Nb3Sn TQC vs. NbTi HGQ All Experimenters’ Meeting, May 10, 2010 6 Nb3Sn TQC: Gmax~211 T/m at 4.5 K Instabilities at T<3K Gmax~217 T/m at 3.2K Gmax~230 T/m at 1.9 K with stable conductor

7. SC Magnets at Fermilab Coil pre-stresses in Quadrupole mirror  Quadrupole mirror based on TQC quadrupole structure  Quadrupole coil made of improved (more stable) RRP 108/127 Nb3Sn strand  Different warm and cold coil pre-stress (see Table) All Experimenters’ Meeting, May 10, 2010 7 MIRRORMeasured warm stress Predicted cold stress TQM0110090 TQMO2100110 TQM03a100 TQMO3b105145 TQM03c135185

8. SC Magnets at Fermilab  Small (<5%) Ic degradation in conductor at coil pre-stress up to ~190 MPa.  Noticeable degradation of conductor stability at T more stable conductor for operation at 1.9 K and ~200 MPa. Effect of coil pre-stress All Experimenters’ Meeting, May 10, 2010 8

9. SC Magnets at Fermilab Conclusions and Plans  Dipole style collar design and collaring process were successfully tested at Fermilab using 90-mm Nb3Sn TQ coils o Quench performance and field quality are consistent with the test results for models based on shell (TQS02a/c) and quadrupole collar (TQC02Ea) structures o Gmax=217 T/m (Bmax~12 T) => higher with better conductor o Dipole style collar structure can be easily adopted for long Nb3Sn quadrupole (and dipole) magnets => important for LARP and LHC upgrade needs  Coil pre-stress limit for Nb3Sn magnets is larger than 150 MPa (up to ~190 MPa) => o Possibility of higher field/field gradient o More room for pre-stress variation in long magnets  Next step: o Assemble and test in FY2011 a 4-m long quadrupole based on dipole style collars (recycle LARP LQ coils) o Continue work on Nb3Sn strand and cable improvement All Experimenters’ Meeting, May 10, 2010 9