1. Ionization Cooling for Muon Accelerators Prepared by Robert Ryne Presented by Jean-Pierre Delahaye MICE Optics Review 14-15 Jan, 2016 RAL

2. Accelerator-Based HEP at a Crossroads Following EU strategy and US P5 processes, Near/Mid-term HEP is well defined: –Energy Frontier: HL-LHC –Intensity Frontier: superbeams, precision expts Long-term HEP depends on ability to develop novel technologies and overcome roadblocks –conventional accelerators too expensive and power consuming major cost reduction and power efficiency improvements required to extend high intensity, high energy frontiers –advanced accelerator concepts face numerous physics limitations and technology challenges novel technologies to be developed and demonstrated to be feasible technical issues addressed by specific R&D MICE Optics Review (RAL, January 14-15, 2016)2

3. What might the far-term HEP look like? LHC run II sees no new physics or at energies beyond the present energy frontier reachable by available e + /e - accelerator technologies ILC construction not funded –Higgs physics covered by HL-LHC by 2030 CLIC development ramping down after next EU strategy in 2018 –if new physics above ~ 2 to 2.5 TeV CLIC energy reach FCC considered too expensive MICE Optics Review (RAL, January 14-15, 2016)3 Consider what might happen in next several years:

4. Where does that leave Energy Frontier HEP? Future will depend on advanced concepts that make Energy Frontier accelerators cost and power consumption affordable –Laser-Wakefield accelerator –Plasma-Wakefield accelerator –Dielectric-Wakefield accelerator –Muon accelerators MICE Optics Review (RAL, January 14-15, 2016)4 Novel technologies to be developed to: address their feasibility identify their potential and limitations

5. Outstanding potential of Muon Colliders MICE Optics Review (RAL, January 14-15, 2016)5 Luminosity/MW is critical when considering the feasibility of future multi-TeV colliders Muon accelerators provide the most performing option for a lepton collider in the multi-TeV range (E ≥ 2.5 TeV) in regard to –Absolute Luminosity –Luminosity/MW Negligible synchrotron radiation compared with e+/e- –Not limited in energy by synchrotron radiation as circular collider are –Not limited in luminosity by beam- strahlung as linear colliders are Power efficiency: –Multipass acceleration –Multipass collisions in multi detectors Precise Higgs width measurement in a muon-based Higgs Factory –Large cross section at S resonance

6. So far this discussion emphasized Energy Frontier; Muons also hold the key to Intensity Frontier What might Intensity Frontier future look like? –Or Long Baseline Neutrino Facilities like LBNF/DUNE or HyperK produce ambiguous results due to the difficulty of controlling systematics Muon facility like nuSTORM would provide cross-sections needed to control systematics If short-baseline neutrino program validates an extension to the SvM, then a facility like nuSTORM will be essential to fully study the neutrino sector and is needed to improve LBNF/DUNE physics results. –Or Long Baseline Neutrino Facilities demonstrates the needs for higher precision measurements Muon facility like IDS-Neutrino Factory (NuMAX) would be needed MICE Optics Review (RAL, January 14-15, 2016)6 In both scenarios, muon accelerators are essential to the future of Intensity Frontier facilities

7. Muons: a long history of development C.Rubbia proposal 2015 7 MASS, IBS, R&D Demonstration nuSTORM design MICE Optics Review (RAL, January 14-15, 2016)

8. Muon Accelerator Concepts Key issues and R&D to address feasibility  ~10 13 -10 14  / se  Tertiary prby MW p+  od.: p     cosund  (1kHz0 8 Key Challenges ~10 13 -10 14  / sec Tertiary particle p     Fast cooling (  =2  s) by 10 6 (6D) Fast acceleration mitigating  decay Background by  decay Key R&D MW proton driver MW class target NCRF in magnetic field Ionization cooling High field solenoids (30T) High Temp Superconductor Cost eff. low RF SC Fast pulsed magnet (1kHz) Detector/ machine interface MICE Optics Review (RAL, January 14-15, 2016)

9. Neutrino Factory Parameters 9MICE Optics Review (RAL, January 14-15, 2016)

10. Muon Collider Parameters MICE Optics Review (RAL, January 14-15, 2016)10 Success of advanced cooling concepts  several 10 32 [Rubbia proposal: 5.10 32 ] Exquisite Energy Resolution Allows Direct Measurement of Higgs Width

11. Impressive progress in the development of Muons technology Key technology issues that were once a big concern have been solved or significantly mitigated under MAP –high-power target issues –high-gradient rf in high magnetic fields –collider magnet design & protection –detector background issues –muon cooling Muon cooling, in particular, is a critical issue. –Cooling by a factor ~10^6 needed for a collider –Under MAP credible designs to reach >10^5 emittance reduction have been developed before MAP design & simulation effort was terminated MICE Optics Review (RAL, January 14-15, 2016)11

12. Y Cooling: The Emittance Path 12 Transverse Emittance (microns) Longitudinal Emittance (mm) Bunch Merge For acceleration to Higgs Factory For acceleration to multi-TeV collider Final Cooling post-merge 6D Cooling For acceleration to NuMAX (325MHz injector acceptance 3mm,24mm) Initial Cooling MICE Optics Review (RAL, January 14-15, 2016) Target Phase Rotator Front End  pre-merge 6D Cooling (original design) Exit Front End (15mm,45mm) Initial (X) Initial (Y) VCC & Hybrid HCC Final Specification Achieved (simulations)

13. MICE Optics Review (RAL, January 14-15, 2016)13 Ionization cooling is the only known approach that cools muons fast enough

14. MICE is a proof-of-principle experiment for 4D ionization cooling MICE is both a beam physics expt and a technology demo Initial and final state of every particle will be measured –not just the usual beam centroid, rms size, etc. MICE Optics Review (RAL, January 14-15, 2016)14 Output muon beam Input muon beam 201MHz cavities Solenoids

15. Key Points Muon accelerators provide an attractive novel technology option in the post HL-LHC era Muon accelerators have the best potential for a lepton collider in the multi-TeV energy range if required by physics –In particular the ability to provide high luminosity with affordable power consumption –best luminosity/MW of all approaches considered Muon accelerators also benefit the Intensity Frontier Major progress under MAP strengthens the feasibility argument for muon accelerators MICE Optics Review (RAL, January 14-15, 2016)15

16. Summary After more than 3 decades of R&D, technology solutions have been developed for credible designs of Neutrino Factories and Muon Colliders Experimental validation of ionization cooling is now needed MICE experiment is on the verge of –measuring ionization energy loss in a regime relevant to muon accelerators –demonstrating ionization cooling in a system with ionization and re-acceleration MICE Optics Review (RAL, January 14-15, 2016)16