Vacuum Cooling Workshop Magnet Design Challenges Holger Witte

Vacuum Cooling Workshop Magnet Design Challenges Holger Witte Brookhaven National Laboratory Advanced Accelerator Group

Overview Activities • Mechanical Analysis (FEA) – Support structure for magnets • Magnetic Analysis – Re-design of coil geometry / currents to allow principle mechanical feasibility – Coil alignment: effect on temperature margin • Magnet Design for Dipole Field – Tilting of solenoids undesirable – Options: • Saddle coil/ helical coil 25 February 2021 2

Magnet Configuration From: Bob Palmer, 3/15/2014, ‘dikt 3 ck’ Nb 3 Sn 25 February 2021 Nb. Ti 3

Peak Field From: F. Borgnolutti, MAP Cooling Solenoid, VCC Meeting 4/15/14 25 February 2021 4

Layer 1 1. 5 MN t=28 mm 5. 5 MN Nb 3 Sn: εmax 0. 25% 316 LN support structure 5. 5 MN 1. 5 MN 25 February 2021 t=25 mm 5

Proposed Changes J: 220 → 202. 4 A/mm 2 J: 135 → 182. 25 A/mm 2 Original configuration: From: Bob Palmer, 3/15/2014, ‘dikt 3 ck’ 25 February 2021 6

Effect on Field Small change, but…. impacts performance 25 February 2021 7

Operating Margin • In % of short sample Ic – Layer 1: 50% (strain limited) – Layer 2: 66% – Layer 3: 30% • Von-Mises stress support structure – Layer 1: 500 MPa – Layer 2: 750 MPa – Layer 3: 430 MPa Operating margin coils layer 1 25 February 2021 8

Options for Dipole Field • Tilting solenoids – Mechanically challenging – No adjustment possible • Separate Dipole – Required dipole component: 0. 2 T for 0. 3 m • Position – Outside: very challenging aspect ratio – Solenoids see field increase (>0. 5 T) – Best options: inside other coils or between layer 1 and 2 25 February 2021 9

Option 1: Saddle Coil Conductor: Nb 3 Sn Bpeak: 16 T (15 T Background) J: 220 A/mm 2 Rinner: 41 mm Router: 43 mm Length: 330 mm Temperature margin: 1. 8 K Field quality: 1% (to be confirmed) 25 February 2021 Decreases usable bore (10%) 10

Option 2: Helical Dipole Conductor: Nb 3 Sn Bpeak: 8. 5 T (8 T Background) J: 853 A/mm 2 Rinner: 140 mm Router: 142 mm Length: 390 mm Temperature margin: 3. 5 K Field quality: 1 x 10 -4 (to be confirmed) 25 February 2021 Space for support structure reduced 11

Comparison Dipole Field Saddle Coil Helical Coil Impact on performance? 25 February 2021 12

Assembly Independent formers RF RF Support structure? Cryogenics? Power leads? Coil quench – forces? Single former – stresses worse? MICE AFC 25 February 2021 13

Magnetic Shielding? MICE Partial Return Yoke 25 February 2021 14

Things to work on… • Engineering – Assembly? – Cooling? – Power leads – Alignment: displacements of mm change temperature margin by 5 -10% • Dipole field – Reduction of usable bore? • Quenches – Forces? 25 February 2021 15

Material Properties • Nb 3 Sn – Wire: OST (int. tin) – 55% non Cu – Jc: A. Godeke, Ph. D. Thesis 2005. – Mechanical properties: D. R. Chichili et al. , DOI 10. 1109/77. 828478. D. R. Chichili et al. , Investigation of Cable Insulation and Thermo- Mechanical Properties of Nb 3 Sn Composite. • Nb. Ti – OST, Cu/Sc ratio 1. 35 : 1 – Jc: L. Bottura, DOI 10. 1109/77. 828413 – Mechanical properties: I. Dixon et al. DOI 10. 1109/20. 511486 25 February 2021 I. Dixon et al. Mechanical properties of epoxy impregnated superconducting solenoids 16

Load Line Saddle Dipole 25 February 2021 17

Load Line Helical Dipole 25 February 2021 18