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Superconducting Detector Magnets Evolution and Outlook

Explore the chronological evolution, major technology steps, indirect cooling, conductor and coil manufacturing, stability, materials, future directions of superconducting detector magnets.

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Superconducting Detector Magnets Evolution and Outlook

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  1. Superconducting Detector MagnetsEvolution and Outlook Roger Ruber and Akira Yamamoto Uppsala University and KEK

  2. Scope of this Presentation • Chronological Evolution • Identify Major Technology Steps • Indirect cooling • Conductor and Coil manufacturing • Review Specific Issues • Stability • Materials and strength • Protection • Future Directions INSTR08: Roger Ruber - Superconducting Detector Magnets, Evolution and Outlook

  3. Technology Drivers • Momentum resolution • depends on sagitta term • Transparency • reduction of material in the magnet structure • use low radiation length materials • Detector configuration • determines magnet configuration • Cost & reliability INSTR08: Roger Ruber - Superconducting Detector Magnets, Evolution and Outlook

  4. Solenoid Magnet • Resolution • inside solenoid: dp/p ~ {B·R2solenoid}-1 • outside solenoid: dp/p ~ {B·Rsolenoid}-1 • Transparency • wall thickness: t ~ (R/σh) • B2/2µ0 • Field & Symmetry • axial and uniform • but field lines parallel to particlepath at small angles • Installation • self supporting structure • iron yoke to contain stray field (improves bending power at small angles) INSTR08: Roger Ruber - Superconducting Detector Magnets, Evolution and Outlook

  5. q Toroid Magnet • Resolution • inside toroid: dp/p ~ sinθ {Bφ·Rin·ln(Rin/Rout)}-1 • Field & Symmetry • tangential field (1/r) • field lines perpendicular to particle path • closed field: centred on and circulating around beam (no influence on beam) • Installation • support required to keep self balance • no stray field: no iron yoke required INSTR08: Roger Ruber - Superconducting Detector Magnets, Evolution and Outlook

  6. 8 degrees η = -ln tan(θ/2) ATLAS Toroids (2007) Largest Field Volume • good resolution at small forward angles • self contained 4 T field, volume 7000m3, no yoke • open structure barrel, cryostats occupy ~2% volume 8 coils barrel toroid 2x 8 coils end cap toroid INSTR08: Roger Ruber - Superconducting Detector Magnets, Evolution and Outlook

  7. Sag28mm Toroid Assembly with Barrel Calorimeter and Solenoid Solenoid End Cap Toroid INSTR08: Roger Ruber - Superconducting Detector Magnets, Evolution and Outlook

  8. Indirect Cooling Support Banding Series Cooling Circuit Aluminium Stabilised Conductor Mandrel CELLO (CEA, 1978) First Generation • monolithic NbTi/Cu conductor soldered to aluminium stabilizer • indirect cooling • BR2 ~ 1 Tm2 H. Desportes, Adv.Cryo.Eng. 25 (1980) 175 INSTR08: Roger Ruber - Superconducting Detector Magnets, Evolution and Outlook

  9. Design Requirements • Mechanical Safetycoil thickness µ RB2/ (E/M) µ RB2 γ/σh (γ=density) • E/M (stored energy/cold mass) to be increasedscaling parameter that indicates peak temperature at homogeneous energy dump (E = 0.5µ0∫B∙dV ; E/M=H= ∫CpdT) • σh (hoop stress) to be decreasedsuperconductor to be stronger • Thermal Safetyuniform energy absorption andlow peak temperature at quench to decrease thermal stress • fast quench propagationhigh RRR in stabilizer, or active/passive propagation techniques • energy extraction by external dump INSTR08: Roger Ruber - Superconducting Detector Magnets, Evolution and Outlook

  10. Indirect Cooling Circuit Welded to Al5083 Cylinder 20mm CDF (Tsukuba Univ/FNAL, 1984) Second Generation • co-extruded monolithic conductor • aluminium alloy support cylinder, shrink-fit • BR2 ~ 3 Tm2 H. Minemura et al., NIM A238 (1985) 18 • First full scale use of co-extruded conductor • High quality bonding between superconductor and pure aluminium • Mechanical: 30MPa > yield strength pure Al • Electrical: allowed conductor joints formed by welding between aluminium sections Shrink fit of coil into force support cylinder INSTR08: Roger Ruber - Superconducting Detector Magnets, Evolution and Outlook

  11. TOPAZ, VENUS (KEK, 1984) • direct internal winding, without mandrel • kapton based insulation VENUS: M. Wake et al., IEEE MAG-21 (1985) 494 TOPAZ: A. Yamamoto et al., JAPL 25 (1986) 1440 TOPAZ features:Insulation and bondingby B-stage epoxy on conductor + GFRP-Kapton on support cylinder • VENUS features: • CFRP vacuum vessel • Force support cylinder formed from extrusion sections – welded in situ INSTR08: Roger Ruber - Superconducting Detector Magnets, Evolution and Outlook

  12. 35mm ALEPH (CEA, 1987) Third Generation • parallel cooling circuits, thermo-siphon cooling • BR2 ~ 10 Tm2 J.M. Baze et al., IEEE MAG 24 (1988) 126. INSTR08: Roger Ruber - Superconducting Detector Magnets, Evolution and Outlook

  13. CMS (CEA/CERN/INFN, 2006): Fourth Generation • EM Calorimeter inside solenoid → thin wall not a goal! • 4 layers reinforced conductor • hybrid conductor: pure-Al/A6082 • BR2 ~ 40 Tm2 • Conductor • Pure Al + high strength alloy • YS > 250MPa @ 4K • RRR 1400 400 m3 D. Campi et al., IEEE TASC17-2 (2007) 1185 INSTR08: Roger Ruber - Superconducting Detector Magnets, Evolution and Outlook

  14. 67 < 2/3 < ６７ ４５ ATLAS Central Solenoid (KEK, 2006) • thin solenoid, fully integrated with LAr calorimeter cryostat • high strength pure aluminium stabilizer • Al-strip quench propagator A. Yamamoto at al., NIM A584 (2008) 53 INSTR08: Roger Ruber - Superconducting Detector Magnets, Evolution and Outlook

  15. Al Al ATLAS-CS Al3Ni 1µm High Strength Conductor Development • 0.1-2% Ni micro-alloying + 15-20% cold-work hardening Al3Ni precipitated contributes as structural component Pure-Al region keeps low resistivity Peak temperature after a full energy dump is less sensitive to RRR for RRR > 100. INSTR08: Roger Ruber - Superconducting Detector Magnets, Evolution and Outlook

  16. NbTi/Cu SC 3.4mm Al-Ni alloy BESS Polar (KEK, 2005) • thinnest solenoid, no support cylinder! • wall thickness 1gm/cm2 ~ 0.05X0 A. Yamamoto et al., IEEE TASC12-1 (2002) 438 INSTR08: Roger Ruber - Superconducting Detector Magnets, Evolution and Outlook

  17. BESS Polar: How Thin is Thin? thickness/diameter ~ 0.2% coil thickness/diameter ~ 0.34% INSTR08: Roger Ruber - Superconducting Detector Magnets, Evolution and Outlook

  18. SiD Conceptual Design: Future ILC/CLIC Detectors all proposals require • large scale field & volume:BR2 > 35 Tm2 • huge energy: 1.5 ~ 2 GJ SiD proposal requires: • 4~6 layer coil • high strength conductor • integrated dipole magnet 4th ILC Proposal: • double solenoid with end disk! R. Smith et al., IEEE TASC 16-2 (2006) 489 INSTR08: Roger Ruber - Superconducting Detector Magnets, Evolution and Outlook

  19. Future Technologies Strong conductors • for large field and thin-walled magnets Magnet protection • to prevent high peak temperatures during full energy dump good for physics difficult winding processMOI=moment of inertia magnet safety INSTR08: Roger Ruber - Superconducting Detector Magnets, Evolution and Outlook

  20. H = E/M = ∫ Cp dt 5,10,20 Thermal Expansion 65, 80, 100 80 120 Temperature [K] E/M: A Scaling Factor for Coil Design Stored energy increased ~300x from CELLO to CMS • Large field volume + transparent coils • leads to increased E/M ratio = enthalpy: CMS 12kJ/kg = 85K mean temperature after homogeneous energy dump • Design aim • peak temperature <120K → differential stress < 30MPa INSTR08: Roger Ruber - Superconducting Detector Magnets, Evolution and Outlook

  21. Status Aluminium Stabilized Conductor INSTR08: Roger Ruber - Superconducting Detector Magnets, Evolution and Outlook

  22. Future Development of Stabilized Superconductor Combine ATLAS and CMS technology for high strength stabilizer: ATLAS high strength stabilizer Ni-0.5 ~ 1 % CMS hybrid support A6058 → A7020 Yield strength (0.2%) = 400 MPa RRR ~ 400 S. Sgobba et al., IEEE TASC 16-2 (2006) 521 INSTR08: Roger Ruber - Superconducting Detector Magnets, Evolution and Outlook

  23. Summary and Outlook Indirect cooling + aluminium based conductor step made for CELLO has seen huge developments in all aspects of the technology: • Scale • Field volume ~700x for ATLAS • Stored energy ~ 300x for CMS • Conductors • advances in scale and strength • Coil winding and assembly • technology: materials(impregnation – bonding) • engineering: scale + accuracy Present state of the art can give 5 T.R&D efforts ongoing for Al-stabilized Nb3Sn/Nb3Al cables and solenoid beyond 10 T INSTR08: Roger Ruber - Superconducting Detector Magnets, Evolution and Outlook

  24. Acknowledgements Many thanks for contribution of material and advice Elwyn Baynham (RAL) Yasuhiro Makida (KEK) INSTR08: Roger Ruber - Superconducting Detector Magnets, Evolution and Outlook

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