A Muon Collider Based on a Proton Source Muon Collider – Preparatory Meeting, April 10-11, 2019 Mark Palmer Acknowledgements

• MAP Collaboration • IDS-NF Collaboration • MICE Collaboration

Muon Collider Preparatory Meeting, CERN, April 10-11, 2019 2 Neutrino Factory (NuMAX) Proton Driver Front End Cool- Acceleration µ Storage Ring n Factory Goal: Broad Applications: 1021 µ+ & µ− per year ing µ+ • Neutrino Factories ν within the accelerator • Colliders from ~100 GeV to 5 GeV acceptance

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s I 3 MAP Approach

• Conceptual design of individual accelerator sub-systems • Identify performance parameter targets and limitations • Identify R&D requirements • Provide realistic sub-system conceptual designs • Muon Accelerator Staging Study • Explored potential staging options and estimated overall performance • R&D Program • Identify potential showstoppers • Provide targeted effort to identify viable paths forward • Next step planned • Full conceptual design • Sub-system prototypes Support from the European Strategy • Detector & physics analysis process would allow these steps to be pursued Muon Collider Preparatory Meeting, CERN, April 10-11, 2019 4 Muon Accelerator Complex as envisioned by MASS for 1 GeV Proton Fermilab: Linac LBNE Superbeam nSTORM  NuMAX 1-3 GeV Proton  Higgs Factory To Linac SURF Fermilab no longer a 1 GeV Muon Linac (325MHz) realistic site option 3-7 GeV Proton & To Near Detector(s) for 1-5 GeV Muon Short Baseline Linac(s) Studies

Muon Beam R&D Facility

A 6 TeV Muon Collider would ft ft have a similar circumference as the Tevatron Ring 5 5 A Multi-TeV Collider Collider Footprint with FNAL site outline

Fermilab no longer a realistic site option

3-7 GeV Proton & 1 GeV Proton 1-5 GeV Muon Linac A TeV-Scale Linac(s) Accelerator 1-3 GeV Proton To Linac System SURF NuMAX: ns to SURF R SC Linac L 1 GeV Muon A t Linac (325MHz) o

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6 6 MAP Neutrino Factory Parameters

7 MAP Collider Parameters

Muon Collider Preparatory Meeting, CERN, April 10-11, 2019

8 MAP References

• The future prospects of muon colliders and neutrino factories, Boscolo, Delahaye, Palmer, to appear in RAST volume 10, arXiv:1808.01858v2 [physics.acc-ph]. • Muon Accelerators for Particle Physics (MUON), special volume in the Journal of Instrumentation • https://iopscience.iop.org/journal/1748-0221/page/extraproc46 • 20 articles presently posted, with a few more to come…

Muon Collider Preparatory Meeting, CERN, April 10-11, 2019 9 Slides to follow:

• Will provide an overview of the status of the MAP concepts • Sub-system by sub-system

Muon Collider Preparatory Meeting, CERN, April 10-11, 2019 10 Challenges for a m+m- Collider

• MW-class proton beam on target a pions a muons • Efficient capture of the produced pions • Capture of both forward and backward produced pions loses polarization • Phase space of the created pions is very large! • Transverse: 20p mm-rad • Longitudinal: 2p m-rad • Emittances must be cooled by factors of ~106-107 to be suitable for multi-TeV collider operation ~1000x in the transverse dimensions ~40x in the longitudinal dimension • The muon lifetime is 2.2 ms lifetime at rest

Muon Collider Preparatory Meeting, CERN, April 10-11, 2019 11 Characteristics of the Proton Driver Muon Source

• Overarching goals

• NF: Provide O(1021) m/yr within the acceptance of a m ring 34 -2 -1 2 • MC: Provide luminosities >10 cm s at TeV-scale (~nb ) Enable precision probe of particles like the Higgs

• How do we do this? • Tertiary muon production through protons on target (followed by capture and cooling) 13 12 • Rate > 10 /sec nb = 2×10

Muon Collider Preparatory Meeting, CERN, April 10-11, 2019 12 MAP Feasibility Issues

• Proton Driver High Power Target Station • Target Capture Solenoid • Front End Energy Deposition RF in Magnetic Fields • Cooling Magnet Needs (Nb3Sn vs HTS) Performance • Acceleration Acceptance (NF) Rapid cycling magnets or FFA lattices for high E • Collider Ring IR Magnet Strengths/Apertures • Collider MDI SC Magnet Heat Loads (m decay) • Collider Detector Backgrounds (m decay)

Muon Collider Preparatory Meeting, CERN, April 10-11, 2019 13 Proton Driver H- beam

Recommendations: • No showstoppers Accumulator Ring identified Layout & Injection Orbits • Adapt concept for (Alexahin, Kapin) likely proton source

3.87 kicker for MHz vertical RF extraction V=11 kV

Optics:  Based on 6-8 GeV Linac Buncher Ring ½ staight + Source Layout & Optics 1 arc cell  Accumulator & Buncher (Alexahin) Ring Designs in hand  H- stripping requirements same as those established for Fermilab’s Project X

Muon Collider Preparatory Meeting, CERN, April 10-11, 2019 14 High Power Target Recommendations: • No showstoppers identified • Challenging engineering required • Optimized capture solenoid • Target module • Remote handling design 1 cm • Leverage neutrino program target MERIT development efforts @CERN  MERIT Expt: Compact • LHg Jet in 15T Taper Design • Capability: 8MW @70Hz  MAP Staging aims at 1-2 MW a C Target  Improved Compact C Target Option Taper Design with 20T • Performance & Cost Solenoid

Muon Collider Preparatory Meeting, CERN, April 10-11, 2019 15 Capture Solenoid • A Neutrino Factory and/or Muon Collider Facility requires challenging magnet design in several areas: • Target Capture Solenoid (15-20T with large aperture)

Estored ~ 3 GJ

O(10MW) resistive coil in high radiation environment

Possible application for High Temperature Superconducting magnet technology

Muon Collider Preparatory Meeting, CERN, April 10-11, 2019 16 Front End Control of FE Energy Deposition

FE Energy Deposition

Neuffer

17 CERN SPC Working Group on Future Colliders

Buncher and Phase  Energy Deposition Rotator Matched to a Validation of FE  Full 325 MHz RF Design 325 MHz Initial Cooling performance  Validation of gas-filled Channel with gas-filled RF cavity performance cavities Recommendations: • Ready for updates leading to full conceptual design

Muon Collider Preparatory Meeting, CERN, April 10-11, 2019

17 17 Cooling Options

• Electron/Positron cooling: use synchrotron radiation a For muons DE~1/m3 (too small!) • Proton Cooling: use • A co-moving cold e- beam a For muons this is too slow • Stochastic cooling a For muons this is also too slow • Muon Cooling: use • Use Ionization Cooling a Likely the only viable option • Optical stochastic cooling a Maybe, but far from clear

Muon Collider Preparatory Meeting, CERN, April 10-11, 2019 18 Cooling Methods • The unique challenge of muon cooling is its short lifetime • Cooling must take place very quickly • More quickly than any of the cooling methods presently in use a Utilize energy loss in materials with RF re-acceleration

Muon Ionization Cooling

Muon Collider Preparatory Meeting, CERN, April 10-11, 2019 19 Kaplan Muon Ionization Cooling

Advanced techniques a Improved HF Luminosity Simplified Final Cooling requirements

MAP Higgs Factory Target PIC assumed in Carlo Rubbia’s Proposal

Muon Collider Preparatory Meeting, CERN, April 10-11, 2019 20 Muon Ionization Cooling (Design)

Recommendations: • Designs assumed 3 3 Initial 6D Cooling: e6D 60 cm a ~50 mm ; Trans = 67% 20 MV/m RF in magnetic field • Demonstration of 50 MV/m in magnetic field means that a new optimization study is required!!

6D Rectilinear Vacuum Cooling Channel (replaces Guggenheim concept):

eT = 0.28mm, eL = 1.57mm @488m Transmission = 55%(40%) without(with) bunch recombination

Muon Collider Preparatory Meeting, CERN, April 10-11, 2019 21 Muon Ionization Cooling (Design)

Matching

• Helical Cooling Channel (Gas-filled RF Cavities): eT = 0.6mm, eL = 0.3mm Late Stage w/ Induction Linac

• Final Cooling with 25-30T solenoids (emittance exchange): eT = 55mm, eL = 75mm Muon Collider Preparatory Meeting, CERN, April 10-11, 2019 22 Longitudinal Merge

Muon Ionization Cooling (Design) 40 20 a) Bunch Merge 0 -20

0 1000 2000 3000 4000 5000 -4040 ct [m] 20 b) 0 -20

] 13000 14000 15000 16000 17000 • MAP Baseline Designs offer -4040 ct [m]

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34000 35000 36000 37000 38000 39000 (gas-filled structures) Merge -4040 ct [m] 20 e) – Parametric Ionization Cooling 0 -20

60000 61000 62000 63000 64000 65000 – Alternative Final Cooling -4040 ct [m] 20 f) One example: 0 -20 a Early stages of existing scheme -40 0 1 2 3 4 5 a Round-to-flat Beam Transform ct [m] Transverse Bunch Slicing Î [ m m ] , B [ T ] , T r a n s m i s s i o n [ 1 0 0 % ] , r m s [ n s ] a TransverseT 0.5 Merge 1.5 0 2 1 a Longitudinal Coalescing 0

(at ~10s of GeV) 10 eT a Considerable promise to exceed our 20 original target parameters Trans 30

a Every improvement in emittance st 40

makes the collider designs more 50 bunch length [ns] Transmission [100%] Î Bx [T] Bz [T] T readily achievable [mm] 60 70 80 Muon Collider Preparatory Meeting, CERN, April 10-11, 2019 z [m] 23 Cooling: The Emittance Path

Target Specification Achieved (simulations)   For acceleration to For acceleration to NuMAX  multi-TeV collider Phase (325MHz injector acceptance End Front Rotator 3mm,24mm) Exit Front End Final (15mm,45mm) Initial Y Initial Initial Cooling (X) Final (Y) Cooling post-merge 6D Cooling pre-merge 6D Cooling For acceleration (original design) Longitudinal (mm) Emittance Longitudinal to Higgs Factory HCC VCC & Bunch Hybrid Merge

Transverse Emittance (microns)

24 Muon Collider Preparatory Meeting, CERN, April 10-11, 2019 Cooling Technology R&D

Successful Operation of

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Single strand 0 -200 0 2 4 6 8 10 12 14 16 MICE 201 MHz RF Module – B (T) MTA Acceptance Test in B-field Complete Breakthrough in HTS 11MV/m in Fringe of 5T Lab-G Solenoid Cable Performance with <4×10-7 Spark Rate (0 observed) Cables Matching Strand Performance World Record LTS- FNAL-Tech Div HTS Hybrid Magnet T. Shen-Early Career Award 32T on-axis field

1.0 1% Dry Air (0.2% O2) in GH2 NHFML Pure GH 0.8 2 1% Dry Air

0 0.6 (0.2 % O ) E 2 Demonstration of High E in GH at 0.4 2 B = 3T Pressure RF Cavity in 3T Magnetic Field with Beam 0.2 ~50X reduction in RF power dissipation Extrapolates to required 0.0 0 10 20 30 40 m-Collider Parameters E0 = 25 MV/m Time Μs Muon Collider Preparatory Meeting, CERN, April 10-11, 2019 MuCool Test Area 25 Muon Collider PreparatoryMuon Meeting, Ionization CERN, April 10-11, Cooling 2019 Experiment

See Paul Soler’s Presentation

26 Ionization Cooling Summary

 6D Ionization Cooling Designs • Designs in hand that meet performance targets in simulations with stochastic effects • Ready to move to engineering design and prototyping Recommendations: • Able to reach target performance with Nb3Sn conductors (NO HTS) • Designs and  RF operation in magnetic field (MTA program) performance should • Gas-filled cavity solution successful and performance extrapolates be updatd for to the requirements of the NF and MC 50 MV/m RF • Vacuum cavity performance now consistent with models • Followed by • MICE Test Cavity significantly exceeds specified operating engineering design requirements in magnetic field of 6D Cooling Cell  MICE Experiment data now in hand Prototypec  Final Cooling Designs • Baseline design meets Higgs Factory specification and performs within factor of 2.2× of required transverse emittance for high energy MC (while keeping magnets within parameters to be demonstrated within the next year at NHMFL). • Alternative options under study

Muon Collider Preparatory Meeting, CERN, April 10-11, 2019

27 Acceleration Requirements Technologies include: • Key Issues: • Superconducting Linacs (NuMAX choice) • Muon lifetime a ultrafast acceleration chain • Recirculating Linear Accelerators (RLAs) • NF with modest cooling a accelerator acceptance • Fixed-Field Alternating-Gradient (FFAG) Rings • Total charge a cavity beam-loading (stored energy) • (Hybrid) Rapid Cycling Synchrotrons (RCS) • TeV-scale acceleration focuses on hybrid Rapid for TeV energies Cycling Synchrotron a requires rapid cycling magnets Hybrid RCS Bpeak ~ 2T f > 400Hz

RCS requires  Design concepts in hand 2 T p-p magnets  Magnet R&D indicates at f > 400 Hz parameters achievable (U Miss & FNAL) Recommendations: • Recent FFA results should be incorporated into designs • Detailed look at requirements for multi-TeV Muon Collider Preparatory Meeting, CERN, April 10-11, 2019 acceleration needed 28

Collider Rings • Detailed optics studies for Higgs, 1.5 TeV, 3 TeV and now 6 TeV CoM • With supporting magnet designs Higgs Ring (single IR) and background studies Recommendations: • 3 TeV collider design is the most  Higgs, 1.5 TeV CoM and Higgs refined of the MAP 3 TeV CoM Designs designs • With magnet • Evaluate MDI and concepts backgrounds with • Achieve target 3 TeV design next parameters  Preliminary 6 TeV CoM 1.5 TeV design • Key issue is IR design and impact on luminosity • Utilizes lower 3 TeV power on target

Muon Collider Preparatory Meeting, CERN, April 10-11, 2019 29 Summary

• MDI and detector discussed extensively in yesterday’s session • Have skipped over those topics here • Critical issue is that the MC design is fully coupled from source to detailed collider and background performance • Priorities (my thoughts at this meeting): • Re-optimization of the cooling channel based on current technology limits • Detector, MDI and physics studies • A thorough review of acceleration designs and options • Make the first full conceptual design

Muon Collider Preparatory Meeting, CERN, April 10-11, 2019 30