BNL solenoid capture workshop: magnet challenges are not trivial Summarized by Tengming Shen

The Muon Collider (MC) and Neutrino Factory (NF) aim to produce, capture, and accelerate O(10 21 ) muons/yr MCs and NFs require similar muon sources that use a 4 MW proton beam and a liquid Hg-jet target to maximum pion production. Pions would decay to muons and neutrinos latter. 4-TeV Muon collider 25-GeV Neutrino Factory S. Gere, Annu. Rev. Nucl. Part. Sci., 2009

The pion production and capture system need demanding solenoids A 20 T hybrid Nb 3 Sn/Cu solenoid is proposed. – 14 T generated by a superconducting magnet (ID~1.6 m) – 6 T generated by a resistive insert (ID~0.8 m) Magnets have to survive in a harsh radiation environment Neutrino Factory Study 2 Target Concept (H. Kirk, BNL) 1 m 10 m

Challenges are multi-aspects for large aperture, high field (20 T) magnet – Technical challenges: – Large heat load on superconducting cold mass. – Tremendous stress and high stored energy – Radiation damage to materials. – Magnet becomes ITER-like, very expensive. – Resistive magnet requires to be changed every two years, due to radiation damage.

More than 4.1 kw heat deposited on superconducting cold mass. Heat deposition study: Where does the 4 MW beam power go? RegionPower [kW] % of 4 MW beam power Peak power density [mW/g] WC shield2, Resistive coils Superconducting coils Beam pipe Hg target Hg pool Be window Design a cooling system capable of removing ~2.2 MW from the shielding is a challenge in its own right. 4.1 kw heat deposited onto cold mass, boiling off 5,700 liter helium per hour and $28,700 per hour. Data from N. Souchlas, BNL, presentation at the workshop

Large forces and store energy in large magnet systems Loveridge, BNL workshop

Cable-in-conduit has become a standard for large superconducting magnets. For YBCO coated conductor, No such cable technology exists. Heat generation associated with magnetization effects. Building YBCO small bore magnet is already challenging. For Bi-2212 round wire, CICC-like cable, in principle, can be made, but No one has ever built large magnets from 2212, due to complex high temperature reaction and its associated effects. Can HTS help? Can a 20 T all superconducting magnet with a bore of ~1 m built? No, unless there are breakthroughs in HTS conductor and cable technology.

All resistive magnets will reduce the use of shielding But 20 T resistive magnets will cost more than $10 million and has a life time of use for only 2 years.

The MC/NF capture solenoid is similar to ITER-CS-model MC/NF capture solenoid: 20 T solenoid, ~1 m bore, 10 m long, with heat load on superconducting coils more than 4 kW. Yoshida, BNL worshop

Other infomation Workshop address: