Research and development toward a future Muon Collider Katsuya Yonehara Accelerator Physics Center, Fermilab On behalf of Muon Accelerator Program Draft v2 5/3/121APC seminar: Practice talk for IPAC

Why muon collider? Low synchrotron radiation Low beamstraulung Large sqrt[s] (Hopefully) spin polarized beam 5/3/122APC seminar: Practice talk for IPAC

Physics rich machine Multi TeV Muon Collider Higgs factory Z’ physics SUSY WW scattering Critical events to test modern theory 5/3/123APC seminar: Practice talk for IPAC tt scattering New physics

Design beam collision parameter Peak luminosity: (or more) cm -2 s -1 Integrated luminosity: 10 (or more) fb -1 Number of interaction points: 2 Center of mass: 1.5 TeV (baseline) β * : 0.5 – 2 cm (baseline) Circumference of ring: 2.73 km Dp/p: ± (baseline) 5/3/124APC seminar: Practice talk for IPAC

Challenge in muon acceleration Muon is unstable particle Extraordinary large phase space volume 5/3/12APC seminar: Practice talk for IPAC5 Make a monochromatic muon beam  Muon source  Beam can be accelerated by SCRF Muon Accelerator Program (MAP)

Muon collider complex Proton driver π production Target Frontend – Capture&Decay&Buncher Cooling Extra cooling Bunch merging Acceleration Collider ring 5/3/126APC seminar: Practice talk for IPAC

Initial stage Proton driver – Project-X + accumulator ring to generate 4 MW 8 GeV proton beam – R&D of SCRF is a key element π production target – Successful Hg jet target experiment (MERIT) – Study production efficiency Frontend (Decay/Capture) – 11 % mu/proton conversion in latest design – Need to eliminate huge amount of secondary particles 5/3/127APC seminar: Practice talk for IPAC

Ionization cooling Muon loses its kinetic energy via ionization process Energy loss is compensated in one direction by acceleration Similar as the electron cooling – Denser electron condition than electron cooling (fast cooling) – Heated phase space by nuclei (large equilibrium emittance) 5/3/128APC seminar: Practice talk for IPAC

6D cooling Takes ionization cooling process with a dispersion magnet High (Low) momentum particle passes a cooling material with longer (shorter) trajectory 5/3/129APC seminar: Practice talk for IPAC

Technical challenge in muon cooling channel 5/3/1210APC seminar: Practice talk for IPAC Perpendicular momentum before cooling absorber Perpendicular momentum after cooling absorber becomes smaller due to ionization energy loss process μ beam Absorber RF cavity Magnet After π → μ decay & μ collection Longitudinal momentum is regained by RF cavity RF cavity is embedded in strong B field (> 2 T) Beam envelop

Maximum RF gradient in B field 5/3/12APC seminar: Practice talk for IPAC11 Gradient in MV/m Peak Magnetic Field in T at the Window >2X required field X Required E in cooling channel Data were taken in an 805 MHz vacuum pillbox cavity

Recent R&D of cavity Demonstrated Be coated RF cavity Demonstrated gas filled RF cavity 5/3/1212APC seminar: Practice talk for IPAC Green: Pure Hydrogen gas Red, Blue, Orange, Yellow : Dry Air doped H2 Beam on RF recovery RF envelop with 400 MeV Proton beam

5/3/12APC seminar: Practice talk for IPAC13

High field magnet technology Extra cooling channel (40 Tesla solenoid) Target (25 Tesla solenoid) Final focusing Quad in collider ring 5/3/12APC seminar: Practice talk for IPAC14

Plot maintained by Peter Lee at: HTS can now enable a new generation of magnets - > 30 Tesla J E floor for practicality

‘Dogbone’ RLA with Two-pass Arcs GeV (  ± ) 0.6 GeV/pass 3.6 GeV Muon Acceleration

Design collider ring 5/3/12APC seminar: Practice talk for IPAC17

Collider detector BG can be significantly reduced by using timing & tracking gates 5/3/12APC seminar: Practice talk for IPAC18

Summary Each element has its own technological challenge Breakthrough the issue step by step We see more realistic design 5/3/12APC seminar: Practice talk for IPAC19