SC Magnet Summary Michael Lamm SC Magnets in High Radiation Environment RESMM’12 February 15, 2011

2 Talks Feb. 15, 2012 RESMM'12 Solenoid Summary Conceptual Design of COMET and radiation hardness -Makoto Yoshida Mu2e experiment and issues-R. Coleman Superconducting magnets of the Mu2e experiment -Michael Lamm Mu2e production solenoid design -Vadim Kashikhin Superconducting Magnets for the FRIB Fragment Separator –Al Zeller HTS-based quadrupoles (FRIB)- Ramesh Gupta Radiation damage issues for Muon Collider target system magnets-K. McDonald

3 COMET Topic Covered COMET Physics Overview Muon Sources with Solenoid Capture Magnet –MuSiC, SuperOmega, COMET COMET Solenoid Design Overview –Emphasis on Capture Solenoid Radiation Design Issues –Rad hard materials –Radiation studies presented later in workshop –With Tungsten aborber expect RT anneal 1-2/year Feb. 15, 2012 RESMM'12 Solenoid Summary

4 Feb. 15, 2012 RESMM'12 Solenoid Summary

5 Talks Feb. 15, 2012 RESMM'12 Solenoid Summary Conceptual Design of COMET and radiation hardness -Makoto Yoshida Mu2e experiment and issues-R. Coleman Radiation damage issues for Muon Collider target system magnets-K. McDonald Superconducting Magnets for the FRIB Fragment Separator –Al Zeller HTS-based quadrupoles- Ramesh Gupta Superconducting magnets of the Mu2e experiment -Michael Lamm Mu2e production solenoid design -Vadim Kashikhin

6 COMET Topic Covered COMET Physics Overview Muon Sources with Solenoid Capture Magnet –MuSiC, SuperOmega, COMET COMET Solenoid Design Overview –Emphasis on Capture Solenoid Radiation Design Issues –Rad hard materials –Radiation studies presented later in workshop –With Tungsten aborber expect RT anneal 1-2/year Feb. 15, 2012 RESMM'12 Solenoid Summary

7 JPARC Muon Program Feb. 15, 2012 RESMM'12 Solenoid Summary Mu

8 Talks Feb. 15, 2012 RESMM'12 Solenoid Summary Conceptual Design of COMET and radiation hardness -Makoto Yoshida Mu2e experiment and issues-R. Coleman Radiation damage issues for Muon Collider target system magnets-K. McDonald Superconducting Magnets for the FRIB Fragment Separator –Al Zeller HTS-based quadrupoles- Ramesh Gupta Superconducting magnets of the Mu2e experiment -Michael Lamm Mu2e production solenoid design -Vadim Kashikhin

9 Mu2e Topics Covered Mu2e Physics and Experiment Overview Mu2e Solenoid Review Production Solenoid Design Issues –Magnetic, Mechanical, Quench, Thermal Design Compare Aluminum and Copper WRT stability Feb. 15, 2012 RESMM'12 Solenoid Summary Rick Coleman Mike Lamm Vadim Kashikhin

Mu2e Apparatus Mu2e experiment consists of 3 solenoid systems Production Solenoid Transport Solenoid Detector Solenoid Production Target Collimators Stopping Target TrackerCalorimeter (not shown: Cosmic Ray Veto, Proton Dump, Muon Dump, Proton/Neutron absorbers, Extinction Monitor, Stopping Monitor) protons 2.5T ~5T 2.0T 1.0T ee     10 RESMM'12 Solenoid Summary Feb. 15, 2012

RESMM'12 Solenoid Summary Muon Campus for Mu2e and g-2 with Cryo Plant Compressed He from existing TeV compressors Three TeV refrigerators installed in MC-1 Cold He lines to experiments g-2 building (MC-1) has evolved to support needs of g-2 and Mu2e Low bay is Muon Campus Cryo Building Medium Bay will house beamline power supplies and equipment. New transfer line for compressed He built from recycled parts 11Feb. 15, 2012

L2 Solenoid Feb. 15, 2012 Power Supply/Quench Protection Cryoplant (actually off project) Field Mapping Ancillary Equipment Insulating vacuum Installation and commissioning Production Solenoid (PS) Transport Solenoid (TS) Detector Solenoid (DS) Cryogenic Distribution 12 RESMM'12 Solenoid Summary

Production Solenoid- Some Engineering Aspects – Heat Shield 13 RESMM'12 Solenoid Summary Feb. 15, kW version Requires Tungsten  $$$ Heat Transfer issues 8.3 kW current version

MARS radiation analysis Feb. 15, 2012 RESMM'12 Solenoid Summary 14 3D MARS model included all the details of the PS magnet and the radiation shield; The coil properties were approximated as a mixture of the relevant materials. See presentation of Vitaly Pronskikh

15 RESMM'12 Solenoid Summary Feb. 15, 2012 Studies performed to optimize length and peak field

Study of Muon Yield vs Maximum Field in Production Solenoid 16 R. Coleman 2/13/12

Gradient made by 3 axial coils same turn density but increase # of layers (3,2,2 layers) –Wound on individual bobbins –I operation ~9kA –Trim power supply to adjust matching to TS –Indirect Cooling (Thermal Siphon) PS Baseline Design 4-5T  2.5 T Axial Gradient Vadim Kashikhin, task leader See Next Presentation 17 Aluminum stabilized NbTi –reduce weight and nuclear heating –Special high strength/high conductivity aluminum needed (like ATLAS Central Solenoid) Feb. 15, 2012 RESMM'12 Solenoid Summary

Magnetic field 18 RESMM'12 Solenoid Summary Feb. 15, 2012

Coil-flange interface Coil envelope is surrounded with the ground insulation: –2x250  m of composite insulation (2x25  m of Kapton, fiberglass balance); Thermal bridges at the inner and outer surfaces; Metal to metal connection between thermal bridges and plates; Thermal plates are stress-relieved at the corners of the support shells; Layers of mica between the thermal plates, flanges and shells. 19 RESMM'12 Solenoid Summary Feb. 15, 2012

Thermal model 20 RESMM'12 Solenoid Summary Feb. 15, 2012 Peak power density is 17.9 mW/kg; Total power deposition in the cold mass 21.0 W.

Thermal parameter space Feb. 15, 2012 RESMM'12 Solenoid Summary 21 The thermal models are identical: same geometry, boundary conditions and heat sources; The only difference is the material of cable stabilizer and thermal bridges/plates (Al or Cu, RRR=100); The difference in thermal performance is due to the change of densities and thermal conductivities.

22 Conclusion (mu2e) Present design meets mu2e experiment requirements Radiation studies (presented in related talks) show that magnet temperature will not exceed 5K. Warm up to repair radiation damage: >1 between thermal cycles –Time for warm up/cool down 1-2 weeks –Consistent with reasonable expectations for accelerator operations At 300 kGy/year, –Damage to epoxy and superconductor  > 20 year life time Feb. 15, 2012 RESMM'12 Solenoid Summary

23 FRIB Topics Covered FRIB Project Overview Radiation Issues Remote Handling for Target, Beam Dump and Magnet Magnets in High Radiation Environment Development of HTS Magnets Rad Hardness of HTS Magnets –Suitability to FRIB Feb. 15, 2012 RESMM'12 Solenoid Summary Al Zeller Ramesh Gupta

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RIA HTS Mirror Model Test Results (operation over a large temperature range) A summary of the temperature dependence of the current in two, four, six and twelve coils in the magnetic mirror model. In each case voltage first appears on the coil that is closest to the pole tip. Magnetic field is approximately three times as great for six coils as it is for two coils. More coils create more field and hence would have lower current carrying capacity Feb. 15, 2012 RESMM'12 Solenoid Summary 27

Relative Change in Ic due to Irradiation of SuperPower and ASC Samples SuperPower and ASC samples show very similar radiation damage at 77 K, self field Feb. 15, 2012 RESMM'12 Solenoid Summary 28

Radiation Damage from 142 MeV protons in SP & ASC Samples (measurements in 1 T Applied Field) SuperPower ASC SuperPower ASC Minimum and maximum values of I c are obtained from the graphs on the right While the SuperPower and ASC samples showed a similar radiation damage pattern in the absence of field, there is a significant difference in the presence of field (particularly with respect to the field angle). HTS from both vendors, however, show enhancement to limited damage during the first 10 years of FRIB operation (good news)!!! Feb. 15, 2012 RESMM'12 Solenoid Summary 29

Test of ~100 mm HTS Solenoid As per Superpower and search of literature, this is the first test of large aperture high field 2G magnet and also one that uses over 1 km (1.2 km) wire Solenoid could have reached above 10 T, but we decided to hold back to protect our electronics 250 A ==> 9.2 T on coil Feb. 15, 2012 RESMM'12 Solenoid Summary 30

Summary (GUPTA) HTS offers a unique magnet solution for challenging fragment separator environment of FRIB. R&D for FRIB has demonstrated that HTS magnets can be successfully built using a large amount of HTS (~5 km in 1 st generation and ~9 km equivalent in 2 nd generation It has been demonstrated that HTS can be reliably operated at elevated temperatures in presence of large heat loads. Experiments show that HTS is robust against radiation damage. Record high field magnet test show that HTS can be used and magnets can be protected in demanding conditions. FRIB could be the 1 st major accelerator with HTS magnets. Feb. 15, 2012 RESMM'12 Solenoid Summary 31

Radiation Damage Considerations for the High-Power Target System of a Muon Collider or Neutrino Factory K. McDonald Princeton U. (Feb 6, 2012) Workshop on Radiation Effects in Superconducting Magnet Materials Fermilab Feb. 15, 2012 RESMM'12 Solenoid Summary 32

The Target is Pivotal between a Proton Driver and or  Beams A Muon Collider is an energy-frontier particle-physics facility (that also produces lots of high-energy ’s). Higher mass of muon  Better defined initial state than e + e - at high energy. A muon lives  1000 turns. Need lots of muons to have enough luminosity for physics. Need a production target that can survive multmegawatt proton beams. Feb. 15, 2012 RESMM'12 Solenoid Summary 33

R.B. Palmer (BNL, 1994) proposed a 20-T solenoidal capture system. Low-energy  's collected from side of long, thin cylindrical target. Solenoid coils can be some distance from proton beam.  10-year life against radiation damage at 4 MW. Liquid mercury jet target replaced every pulse. Proton beam readily tilted with respect to magnetic axis.  Beam dump (mercury pool) out of the way of secondary  's and  's. Target and Capture Topology: Solenoid Desire   /s from  p/s (  4 MW proton beam) Present Target Concept Shielding of the superconducting magnets from radiation is a major issue. Magnet stored energy ~ 3 GJ! Superconducting magnets Resistive magnets Proton beam and Mercury jet Be window Tungsten beads, He gas cooled Mercury collection pool With splash mitigator 5-T copper magnet insert; 15-T Nb 3 Sn coil + 5-T NbTi outsert. Desirable to replace the copper magnet by a 20-T HTC insert. Feb. 15, 2012 RESMM'12 Solenoid Summary 34

The conductor is stabilized by copper, as the temperatures during conductor fabrication comes close to the melting point of aluminum. The conductor jacket is stainless steel, due to the high magnetic stresses. Cable in Conduit Conductor Used for ITER NB3Sn in this case but could also be NbTi Advantage: direct cooling of SC Feb. 15, 2012 RESMM'12 Solenoid Summary 35

Overview of Radiation Issues for the Solenoid Magnets The magnets at a Muon Collider and Neutrino Factory will be subject to high levels of radiation damage, and high thermal loads due to secondary particles, unless appropriately shielding. To design appropriate shielding it is helpful to have quantitative criteria as to maximum sustainable fluxes of secondary particles in magnet conductors, and as to the associated thermal load. We survey such criteria first for superconducting magnets, and then for room-temperature copper magnets. A recent review is by H. Weber, Int. J. Mod. Phys. 20 (2011), Most radiation damage data is from exposures to “reactor” neutrons. Models of radiation damage to materials associate this with “displacement” of the electronic (not nuclear) structure of atoms, with a defect being induced by  25 eV of deposited energy. Classic reference: G.H. Kinchin and R.S. Pease, Rep. Prog. Phys. 18, 1 (1955), Hence, it appears to me most straightforward to relate damage limits to (peak) energy deposition in materials. [Use of DPA = displacements per atom seems ambiguous due to lack of a clear definition of this unit.] Feb. 15, 2012 RESMM'12 Solenoid Summary 36

Radiation Damage to the Stabilizer Superconductors for use in high thermal load environments are fabricated as cable in conduit, with a significant amount of copper or aluminum stabilizer (to carry the current temporarily after a quench). The resistivity of Al is 1/3 that of Cu at 4K (if no radiation damage),  Could be favorable to use Al. [Al not compatible with Nb3Sn conductor fabrication  Must use Cu stabilize in high-field Nb magnets.] Radiation damage equivalent to n/m 2 doubles the resistivity of Al and increases that of Cu by 10%. Annealing by cycling to room temperature gives essentially complete recovery of the low-temperature resistivity of Al, but only about 80% recovery for copper. Cycling copper-stabilized magnets to room temperature once a year would result in about 20% increase in the resistivity of copper stabilizer in the “hot spot” over 10 years; Al-stabilized magnets would have to be cycled to room temperature several times a year). Hence, Cu stabilizer is preferred if want to operate near the ITER limit (and in high fields). Feb. 15, 2012 RESMM'12 Solenoid Summary 37

38 Summary and discussion points Overview of SC, insulator and stabilizer –Problematic neutron fluence levels –Nb3Sn ~2-3 10^22 –Insulators: CE resins for high rad. Environ Sheer strength is key –Stabilizer damage and recovery Regimes for Copper vs. Aluminum Stabilizer –Copper has milder RRR degradation with dose –Aluminum 100 percent repair with RT anneal –There are other considerations in magnet design besides radiation Feb. 15, 2012 RESMM'12 Solenoid Summary

39 Summary and discussion points Direct cooling (CICC) vs. Indirect cooling –Both methods could be employed to built PS/CS –Limitation to energy dissipation from indirect cooling For mu2e PS ~100 Watts –Judge CICC to be more expensive, require R&D Is DPA the best unit of quantifying radiation damage? Feb. 15, 2012 RESMM'12 Solenoid Summary