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MARS Simulations of Muon Collider Ring Energy Deposition

Explore energy deposition, radiation issues, MARS15 modeling, and magnet parameters in the Muon Collider at the 2011 workshop in Telluride. Learn about power density, heat loads, and recent improvements in this detailed study.

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MARS Simulations of Muon Collider Ring Energy Deposition

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  1. Fermilab Accelerator Physics Center MARS Simulations of Muon ColliderRing Energy Deposition Muon Collider 2011 Workshop Telluride June 27 – July 1, 2011 Nikolai Mokhov Fermilab

  2. OUTLINE • Sources and Radiation Issues • MARS15 Modeling • Recent Improvements • Tagging Source • Power Density and Heat Load Distributions • Summary Energy Deposition in MC Ring - N.V. Mokhov

  3. Muon Collider Ring Parameters Energy Deposition in MC Ring - N.V. Mokhov

  4. Source of Radiation Loads: Muon Beam Decays • Electromagnetic showers, induced by energetic electrons (1/3 of muon’s E) and synchrotron photons in the collider components, result in high radiation levels in the storage ring. • For 0.75-TeV muon beam of 2x1012: 4.28x105 dec/m per bunch crossing, or 1.28x1010 dec/m/s for 2 beams. • This corresponds to 0.5 kW/m in electrons and almost all of this power is deposited in lattice components. • Compare this to ~2 W/m in hadron collider SC rings, and ~10 W/m in their final focus regions. Energy Deposition in MC Ring - N.V. Mokhov

  5. Radiation Issues in MC SC Magnets • Quench stability: peak power density and heat transfer • Dynamic heat loads: cryo plant capacity and operational cost • Radiation damage: Component lifetime • Residual dose rates: Hands-on maintenance Energy Deposition in MC Ring - N.V. Mokhov

  6. MARS15 Modeling • Detailed magnet geometry, materials, magnetic fields maps, tunnel, soil outside and a simplified experimental hall plugged with a concrete wall. • Detector model with Bz = 3.5 T and tungsten nozzle in a BCH2 shell, starting at ±6 cm from IP with R = 1 cm at this z. • 750-GeV bunches of 2×1012m- and m+ approaching IP are forced to decay at |S| < Smax, where Smax up to 250 m at 4.28×105 / m rate, 1000 turns. Plus regular arcs. • All physics processes included. • Cutoff energies optimized for materials & particle types; in arcs: 0.001 eV (n) and 0.2 MeV (others). Energy Deposition in MC Ring - N.V. Mokhov

  7. Energy Deposition in IR Dipoles Dynamic heat load:200 W/m in W-rods, and 245 W/m in cold mass The open midplane design for the dipoles provides for their safe operation. The peak power density in the IR dipoles is about 2.5mW/g, below the quench limit for the Nb3Sn superconductor based coils at the 1.9-K operation. Energy Deposition in MC Ring - N.V. Mokhov

  8. Ring Dipole Magnets Nb3Sn dipole coils are arranged in a shell-type configuration. The coil aperture is 80 mm, the coil to coil gap is 30 mm with two 3-mm wide AlBemet spacers. Magnetic length is 6 m, straight (RBEND). The nominal field is 10 T. Energy Deposition in MC Ring - N.V. Mokhov

  9. Recent Improvements and Studies • Optimized tungsten masks between each magnet element • 7.5-mm tungsten liner in quad aperture • Two 3×30 mm AlBemet spacers in open midplane dipoles • Tagging energy deposition in dipoles • Thorough study of dynamic heat loads in lattice components Energy Deposition in MC Ring - N.V. Mokhov

  10. Fragment of Ring Model Quad Dipole Magnet local coordinate system W masks D21 D22 Energy Deposition in MC Ring - N.V. Mokhov

  11. Ring Dipole and Tungsten Mask 2×4cm L=20cm, R=15cm Albedo trap in water-cooled W-rods; two 3×30mm AlBemet spacers Energy Deposition in MC Ring - N.V. Mokhov

  12. Ring Quadrupole 7.5-mm W liner Energy Deposition in MC Ring - N.V. Mokhov

  13. m+ Beam Decays (1) Horizontal Magnet local coordinate system Ring outside Energy Deposition in MC Ring - N.V. Mokhov

  14. Source Asymmetry & Energy Deposition Decay electrons are swept toward the ring center, heating mainly inward magnet components, but outward parts are also irradiated at a few % level. Open geometry and magnetic field of open mid-plane dipole further enhance later spread of electromagnetic showers towards more symmetric transverse profile of energy deposition in magnet. Peak energy deposition in the inward W-rod is 100 times higher than in the outward one. Energy Deposition in MC Ring - N.V. Mokhov

  15. m+ Beam Decays (2) Magnet local coordinate system Vertical Ring outside Energy Deposition in MC Ring - N.V. Mokhov

  16. Tagging for m+ Beam Main contribution to energy deposition in arc dipole SC coils: 22% from 100-400 GeV e+ and 39% from >400 GeV e+. Remainder is distributed rather uniformly between other energies and other particles. Energy Deposition in MC Ring - N.V. Mokhov

  17. Power Density Isocontours in Ring: m+ Beam Horizontal Magnet local coordinate system Ring outside Energy Deposition in MC Ring - N.V. Mokhov

  18. Power Density Isocontours in Ring: m- Beam Horizontal Magnet local coordinate system Ring outside Energy Deposition in MC Ring - N.V. Mokhov

  19. Power Density Isocontours in Ring: Two Beams Magnet local coordinate system Horizontal Ring outside Energy Deposition in MC Ring - N.V. Mokhov

  20. Power Density Isocontours in Ring: Two Beams Magnet local coordinate system Vertical Energy Deposition in MC Ring - N.V. Mokhov

  21. Power Density Isocontours in Ring Dipole Ring outside Peak in SC: 1.2 mW/g safely below quench limit Energy Deposition in MC Ring - N.V. Mokhov

  22. Power Density Isocontours in Ring Quad Ring outside Peak in SC: 1.2 mW/g, safely below quench limit It was ~30 mW/g in old configuration Energy Deposition in MC Ring - N.V. Mokhov

  23. Dynamic Heat Loads to Arc Components With a high accuracy, mean in the arc = 0.5 kW/m Averaged over corresponding component types (W/m): • Comments • Dipole: “cold” = 15 (coils+collar+spacers) + 10 (yoke) • Dipole: “room temp” is 40-mm OD W-rods • Quad: “room temp” is 7.5-mm W-liners • Mask: “D/Q” - between dipole and quad • Mask: “D/D” – between two dipoles Energy Deposition in MC Ring - N.V. Mokhov

  24. Residual Dose Isocontours in Dipole & Quad Peak on outside = 0.5mSv/hr: at least 100 times less of that at LHC Energy Deposition in MC Ring - N.V. Mokhov

  25. Summary • Source term for energy deposition in arc magnets is well understood. • Peak power density in ring magnets can be reduced safely below the quench limit with a proposed mask/liner protection system. • With that system, dynamic heat loads to ring dipole cold mass can be reduced to a 5% level, from 500 to 25 W/m; the later is not that far from the LHC IR levels at nominal and, certainly, at upgrade luminosities. • Radio-activation of arc magnets is substantially lower than at LHC. Energy Deposition in MC Ring - N.V. Mokhov

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