MCTF Steve Geer SLAC/LBNL November, Muon Colliders  

MCTF Physics Landscape Steve Geer SLAC/LBNL November,

MCTF Decision Tree Steve Geer SLAC/LBNL November, Pierre Oddone 0.5 TeV e + e - 3 TeV e + e TeV  +  -

MCTF Muon Collider Motivation  If we can build a multi-TeV muon collider it’s an attractive option because muons don’t radiate as readily as electrons (m  / m e ~ 207): - COMPACT Fits on laboratory site - MULTI-PASS ACCELERATION Cost Effective (e.g. 10 passes → factor 10 less linac) - MULTIPASS COLLISIONS IN A RING (~1000 turns) Relaxed emittance requirements & hence tolerances - NARROW ENERGY SPREAD Precision scans - TWO DETECTORS (2 IPs)  -  T bunch ~ 10  s … (e.g. 4 TeV collider) Lots of time for readout Backgrounds don’t pile up - (m  /m e ) 2 = ~40000 Enhanced s-channel rates for Higgs-like particles Steve Geer SLAC/LBNL November, COST PHYSICS

MCTF Muon Colliders are Compact Steve Geer SLAC/LBNL November, TeV 0.5 TeV 3 TeV

MCTF Narrow Energy Spread Beamstrahlung in any e+e- collider  E/E   2 Steve Geer SLAC/LBNL November, Shiltsev

MCTF Challenges ● Muons are born within a large phase space (  →  ) - To obtain luminosities O(10 34 ) cm -2 s -1, need to reduce initial phase space by O(10 6 ) ● Muons Decay (  0 = 2  s) - Everything must be done fast → need ionization cooling - Must deal with decay electrons - Above ~3 TeV, must be careful about decay neutrinos ! Steve Geer SLAC/LBNL November,

MCTF Muon Collider Schematic Steve Geer SLAC/LBNL November, Proton source: Upgraded PROJECT X (4 MW, 2±1 ns long bunches) muons per year that fit within the acceptance of an accelerator √s = 3 TeV Circumference = 4.5km L = 3×10 34 cm -2 s -1  /bunch = 2x10 12  (p)/p = 0.1%  * = 5mm Rep Rate = 12Hz

MCTF Target Facility Design Steve Geer SLAC/LBNL November, A 4MW target station design study was part of “Neutrino Factory Study 1” in 2000  ORNL/TM2001/124 Facility studied was 49m long = target hall & decay channel, shielding, solenoids, remote handling & target systems. Target: liquid Hg jet inside 20T solenoid, identified as one of the main Neutrino Factory challenges requiring proof-of-principle demonstration. Beam dump = liquid Hg pool. Some design studies started. 4MW Target Station Design V. Graves, ORNL T. Davonne, RAL Proton Hg Beam Dump

MCTF MERcury Intense Target Experiment (MERIT) Steve Geer SLAC/LBNL November, Proof-of-principle demonstration of a liquid Hg jet target in high-field solenoid ran at CERN PS in Fall Successfully demonstrated a 20m/s liquid Hg jet injected into a 15T solenoid, & hit with a suitably intense beam (115 KJ / pulse !). Results suggest this technology OK for beam powers up to 8MW with rep. rate of 70Hz ! Hg jet in a 15T solenoid Measured disruption length = 28 cm 1 cm

MCTF Front-End Specifications Steve Geer SLAC/LBNL November, ParameterDriftBuncherRotatorCooler Length (m) Focusing (T) (ASOL) RF f (MHz)360   RF G (MV/m)0  Total RF (V) ± → ± →   /p within reference acceptance = at end of cooler →  μ/year

MCTF Front-End Simulation Results Steve Geer SLAC/LBNL November, Neuffer

MCTF Ionization Cooling Steve Geer SLAC/LBNL November,  Must cool fast (before muons decay)  Muons lose energy by in material (dE/dx). Re-accelerate in longitudinal direction  reduce transverse phase space (emittance). Coulomb scattering heats beam  low Z absorber. Hydrogen is best, but LiH also OK for the early part of the cooling channel. CoolingHeating

MCTF MuCool Steve Geer SLAC/LBNL November,  Developing & bench testing cooling channel components  MuCool Test Area at end of FNAL linac is a unique facility: -Liquid H2 handling -RF power at 805 MHz -RF power at 201 MHz -5T solenoid (805 MHz fits in bore) -Beam from linac (soon) Liq. H2 absorber MTA 42cm  Be RF window New beamline

MCTF RF in Magnetic Field: 805 MHz Results Steve Geer SLAC/LBNL November, Peak Magnetic Field in T at the Window >2X required field  Data reproducible & seem to follow universal curve.  Possible solutions: - special surfaces (e.g. beryllium) -Surface treatment (e.g. ALD) - Magnetic insulation  Effect is not seen in cavities filled with high pressure hydrogen gas (Johnson & Derbenev) – possible solution (but needs to be tested in a beam – coming soon)  When vac. copper cavities operate in multi Tesla co-axial mag. field, the maximum operating gradient is reduced.

MCTF MICE Steve Geer SLAC/LBNL November,  Ionization Cooling Instrumentation GOALS: Build a section of cooling channel capable of giving the desired performance for a Neutrino Factory & test in a muon beam. Measure performance in various modes of operation.  Multi-stage expt.  First stage being installed at purpose-built muon beam at RAL (first beam to hall March 2008).  10% cooling measured to ±1%. Anticipate completed ~2011/12  Beam Line Complete  First Beam 3/08  Running now  PID Installed  CKOV  TOF  EM Cal  First Spectrometer  Spring 2010 Spectrometer Solenoid being assembled

MCTF 6D Cooling Steve Geer SLAC/LBNL November,  MC designs require the muon beam to be cooled by ~ O (10 6 ) in 6D  Ionization cooling reduces transverse (4D) phase space.  To also cool longitudinal phase space (6D) must mix degrees of freedom as the cooling proceeds  This can be accomplished with solenoid coils arranged in a helix, or with solenoid coils tilted. Palmer Alexhin & Fernow

MCTF 6D Cooling Channel Scheme Steve Geer SLAC/LBNL November, Palmer

MCTF 6D Cooling Channel Development Steve Geer SLAC/LBNL November, Detailed Simulations for candidate 6D cooling schemes Magnet develop- ment for 6D cooling channels HCC magnet 4 coil test REQUIRES BEYOND STATE OF ART TECHNOLOGY → Ongoing R&D FOFO Snake - Alexhin Helical Cooling Channel- Muons Inc.

MCTF Final Cooling Steve Geer SLAC/LBNL November,  When the emittance is very small, to continue cooling we need very high field solenoids (to continue winning against scattering)  For fields up to ~50T, the final luminosity is ~ prop-ortional to the solenoid field at the end of the channel.  For higher fields we no longer expect to continue to win (limited by beam- beam tune shift).

MCTF The Promise of HTS Steve Geer SLAC/LBNL November,

MCTF HTS Solenoid R&D Steve Geer SLAC/LBNL November, NHMFL test coil LBL Test Coil FNAL test cable. Test degradation of J c in the cabling process

MCTF Acceleration Steve Geer SLAC/LBNL November, AVERAGE GRADIENT (MV/m) MUON SURVIVAL FRACTION Bogacz Accelerating muons from 3 GeV to 2 TeV Example: TESLA cavities: Real estate gradient ~31 MV/m → 97% survival ● Early Acceleration (to 25 GeV ?) could be the same as NF. Needs study. ● Main Acceleration – Attractive Candidates - RLAs (extension of NF accel. scheme ?) - Rapid cycling synchrotron – needs magnet R&D - Fast ramping RLA ● Options need study → particle tracking, collective effects, cavity loading,...

MCTF Collider Ring Muons circulate for ~1000 turns in the ring Need high field dipoles operating in decay back- grounds → R&D First lattice designs exist  New ideas → conceptual designs for various options  Comparison of different schemes, choice of the baseline  Detailed lattice design with tuning and correction “knobs”  Dynamic aperture studies with magnet nonlinearities, misalignments and their correction  Transient beam-beam effect compensation  Coherent instabilities analysis WE ARE HERE DESIGN PROCESS Steve Geer SLAC/LBNL November,

MCTF Neutrino Radiation Steve Geer SLAC/LBNL November,  With L ~ E 2 →  OK at √s = 1 TeV  OK at √s = 3 TeV if D = 200m  Above 3 TeV need to pay attention (wobble beam, lower  *, higher B ring, … )

MCTF Background from Muon Decay Steve Geer SLAC/LBNL November, As the decay electrons respond to the fields of the final focus system they lose 20% of their energy by radiating on average 500 synchrotron photons with a mean energy of ~500 MeV … & are then swept out of the beampipe.  2 x muons/bunch  2 x 10 5 decays/m  Electron decay angles O(10)  rad  Mean electron energy = 700 GeV Mean energy = 700 GeV 2  2 TeV Collider Electron Energy (GeV) Number of Decays  - → e - e 

MCTF Detector Backgrounds Steve Geer SLAC/LBNL November,  Muon Collider detector backgrounds were studied actively ~10 years ago ( ). The most detailed work was done for a 2  2 TeV Collider →  s=4 TeV.  Since muons decay (  2TeV =42ms), there is a large background from the decay electrons which must be shielded.  The electron decay angles are O(10) microradians – they typically stay inside the beampipe for about 6m. Hence decay electrons born within a few meters of the IP are benign.  Shielding strategy: sweep the electrons born further than ~6m from the IP into ~6m of shielding.

MCTF Background Simulations Steve Geer SLAC/LBNL November, Shielding design group & final focus design group worked closely together & iterated Used two simulation codes (MARS & GEANT), which gave consistent results Shielding design & simulation work done by two experts (Mokhov & Stumer) in great detail, & involved several person-years of effort.

MCTF Final Focus Setup Steve Geer SLAC/LBNL November,  Fate of electrons born in the 130m long straight section: 62% interact upstream of shielding, 30% interact in early part of shielding, 2% interact in last part, 10% pass through IP without interacting.

MCTF IP Region Steve Geer SLAC/LBNL November,

MCTF More Shielding Details Steve Geer SLAC/LBNL November, r=4cm Z=4m Designed so that, viewed from the IP, the inner shielding surfaces are not directly visible.

MCTF 4 TeV Collider Backgrounds Steve Geer SLAC/LBNL November, Background calculations & shielding optimization was performed using (independently) MARS & GEANT codes … the two calculations were in broad agreement with each other (although the designs were different in detail). Results from Summer 1996 GEANT MARS I. Stumer N. Mokhov

MCTF 4 TeV Collider Backgrounds Steve Geer SLAC/LBNL November, r (cm)  np  e  calo0.003 muon GEANT (I. Stumer) Results from LBL Workshop, Spring 1997 Particles/cm 2 from one bunch with 2  muons (2 TeV)

MCTF Occupancies in 300x300  m 2 Pixels Steve Geer SLAC/LBNL November, TOTALCHARGED

MCTF Vertex Detector Hit Density Steve Geer SLAC/LBNL November,  Consider a layer of Silicon at a radius of 10 cm: GEANT Results (I. Stumer) for radial particle fuxes per crossing: 750 photons/cm 2  2.3 hits/cm neutrons/cm 2  0.1 hits/cm charged tracks/cm 2  1.3 hits/cm 2 TOTAL 3.7 hits/cm 2  0.4% occupancy in 300x300  m 2 pixels  MARS predictions for radiation dose at 10 cm for a 2x2 TeV Collider comparable to at LHC with L=10 34 cm -2 s -1  At 5cm radius: 13.2 hits/cm 2  1.3% occupancy  For comparison with CLIC (later) … at r = 3cm hit density about ×2 higher than at 5cm → ~20 hits/cm 2 → 0.2 hits/mm 2

MCTF Pixel Micro-Telescope Idea Steve Geer SLAC/LBNL November, S. Geer, J. Chapman: FERMILAB-Conf Photon & neutron fluxes in inner tracker large but mean energies O(MeV) & radial fluxes ~ longitudinal fluxes (  isotropic) Clock 2 layers out at variable clock speed (to maintain pointing) & take coincidence. Blind to soft photon hits & tracks that don’t come from IP

MCTF Pixel Micro-Telescope Simulation - 1 Steve Geer SLAC/LBNL November,

MCTF Pixel Micro-Telescope Simulation - 2 Steve Geer SLAC/LBNL November,

MCTF TPC Steve Geer SLAC/LBNL November,  Exploit 10  s between crossings  Large neutron flux – gas must not contain hydrogen: 90% Ne + 10% CF 4  V drift = 9.4 cm/  s with E = 1500 V/cm. Ion buildup   E/E = 0.7%  Cut on pulse height removes photon & neutron induced recoils V. Tchernatine

MCTF Calorimeter Backgrounds Steve Geer SLAC/LBNL November, Electromagnetic: Consider calorimeter at r=120 cm, 25 r.l. deep, 4m long, 2  2 cm 2 cells:  GEANT  400 photons/crossing with ~1 MeV  ~400 MeV   E ~  (2 ) = 30 MeV  For a shower occupying 4 towers: = 1.6 GeV and  E = 60 MeV Hadronic: Consider calorimeter at r=150 cm, 2.5m deep (~10 ), covering degrees, 5  5 cm 2 cells:  ~ 400 MeV   E ~  (2 ) = O(100 MeV) These estimates were made summer 1996, before further improvements to final focus + shielding reduced backgrounds by an order of magnitude … so guess background fluctuations reduced by  3 compared with above.

MCTF Bethe-Heitler Muons (  Z  Z  +  - ) Special concern: hard interactions (catastrophic brem.) of energetic muons travelling ~parallel to the beam, produced by BH pair production. Believe that this back- ground can be mitigated using arrival-times, pushing calorimeter to larger radius, & spike removal by pattern recognition … but this needs to be simulated Steve Geer SLAC/LBNL November,

MCTF Comparison with CLIC Steve Geer SLAC/LBNL November, We are not yet in a position to make an apples-to-apples comparison with CLIC, but ….. hits/mm 2 /bunch train 30mm  O(1) hit/mm 2 /bunch train  FROM CLIC Machine- Detector interface studies: CLIC NOT AN APPLES-to- APPLES COMPARISON … BUT … Background hit densities appear to be similar to MC … so there may be many detector design issues in common between the 2 machines Note: CLIC shielding cone = 7 o c.f. 20 o for MC (but we hope to improve on this)

MCTF MC R&D – The Next Step In the last few years MC-specific R&D has been pursued in the U.S. by Neutrino Factory & Muon Collider Collaboration (NFMCC) & Muon Collider Task Force (MCTF) Last December the NFMCC+MCTF community submitted to DOE a proposal for the next 5 years of R&D, requesting a greatly enhanced activity, aimed at proving MC feasibility on a timescale relevant for future decisions about multi-TeV lepton colliders. Steve Geer SLAC/LBNL November,

MCTF NFMCC/MCTF Joint 5-Year Plan ● Deliverables in ~5 years: -Muon Collider Design Feasibility Report - Hardware R&D results → technology choice - Cost estimate - Also contributions to the IDS-NF RDR ● Will address key R&D issues, including - Maximum RF gradients in magnetic field - Magnet designs for cooling, acceltn, collider - 6D cooling section prototype & bench test - Full start-to-end simulations based on technologies in hand, or achievable with a specified R&D program ● Funding increase needed to ~20M$/yr (about 3x present level); total cost 90M$ Steve Geer SLAC/LBNL November,

MCTF R&D – Ongoing NFMCC/MCTF HISTORY & FUTURE PROPOSAL Steve Geer SLAC/LBNL November,

MCTF Anticipated Progress Key component models NOW 5 YEARS Steve Geer SLAC/LBNL November,

MCTF Aspirational Bigger Picture Steve Geer SLAC/LBNL November,

MCTF Muon Collider R&D: A National Program Steve Geer SLAC/LBNL November,

MCTF Final Remarks Steady progress on the Front-End develop- ment for Muon Colliders - Cooling channel design concepts - NF R&D (IDS-NF, MERIT, MICE, … ) The time has come to ramp up the Muon Collider specific R&D → a National Program There are many challenges to be overcome - RF in magnetic fields & 6D Cooling Channel - Cost effective acceleration scheme - Collider Ring - Detector/Backgrounds optimization The incentive to meet these challenges is great → “5 Year Plan” → Design Feasibility Study Steve Geer SLAC/LBNL November,

MCTF   GeV NF 25 GeV NF Illustrative Staging Scenario 4MW multi-GeV Proton Source Accumulation & Rebunching Steve Geer CERN Neutrino Workshop October 1-3,

MCTF Muon Collider Parameters Steve Geer SLAC/LBNL November,