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Muon Colliders

m -. m +. Muon Colliders. Physics Landscape. Decision Tree. 0.5 TeV e + e -. 3 TeV e + e -. 3-4 TeV m + m -. Pierre Oddone. Muon Collider Motivation.

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Muon Colliders

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  1. m- m+ Muon Colliders Steve Geer SLAC/LBNL November, 2009 1

  2. Physics Landscape Steve Geer SLAC/LBNL November, 2009 2

  3. Decision Tree 0.5 TeV e+e- 3 TeV e+e- 3-4 TeV m+m- Pierre Oddone Steve Geer SLAC/LBNL November, 2009 3

  4. Muon Collider Motivation • If we can build a multi-TeVmuon collider it’s an attractive option because muons don’t radiate as readily as electrons (mm / me ~ 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)-DTbunch ~ 10 ms … (e.g. 4 TeV collider) Lots of time for readout Backgrounds don’t pile up -(mm/me)2= ~40000 Enhanced s-channel rates for Higgs-like particles COST PHYSICS Steve Geer SLAC/LBNL November, 2009 4

  5. Muon Colliders are Compact 3 TeV 0.5 TeV 4 TeV Steve Geer SLAC/LBNL November, 2009 5

  6. Narrow Energy Spread Shiltsev Beamstrahlung in anye+e- collider E/E  2 Steve Geer SLAC/LBNL November, 2009 6

  7. Challenges ● Muons are born within a large phase space (p→mn) - To obtain luminosities O(1034) cm-2s-1, need to reduce initial phase space by O(106) ● Muons Decay (t0 = 2ms) - 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, 2009 7

  8. Muon Collider Schematic √s = 3 TeV Circumference = 4.5kmL = 3×1034 cm-2s-1m/bunch = 2x1012 s(p)/p = 0.1% b* = 5mm Rep Rate = 12Hz Proton source: Upgraded PROJECT X (4 MW, 2±1 ns long bunches) 1021 muons per year that fit within the acceptance of an accelerator Steve Geer SLAC/LBNL November, 2009 8

  9. Target Facility Design • 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. V. Graves, ORNL T. Davonne, RAL 4MW Target Station Design Proton Hg Beam Dump Steve Geer SLAC/LBNL November, 2009 9

  10. MERcury Intense Target Experiment (MERIT) • Proof-of-principle demonstration of a liquid Hg jet target in high-field solenoid ran at CERN PS in Fall 2007. • 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 ! 1 cm Hg jet in a 15T solenoid Measured disruption length = 28 cm Steve Geer SLAC/LBNL November, 2009 10

  11. Front-End Specifications p±→mn m/p within reference acceptance = 0.085 at end of cooler → » 1.5 1021 μ/year Steve Geer SLAC/LBNL November, 2009 11

  12. Front-End Simulation Results Neuffer Steve Geer SLAC/LBNL November, 2009 12

  13. Ionization Cooling • 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 Zabsorber. Hydrogen is best, but LiH also OK for the early part of the cooling channel. Cooling Heating Steve Geer SLAC/LBNL November, 2009 13

  14. MuCool • Developing & bench testingcooling 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) New beamline MTA 42cm ÆBe RF window Liq. H2 absorber Steve Geer SLAC/LBNL November, 2009 14

  15. RF in Magnetic Field: 805 MHz Results • When vac. copper cavities operate in multi Tesla co-axial mag. field, the maximum operating gradient is reduced. • 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) >2X Reduction @ required field Peak Magnetic Field in T at the Window Steve Geer SLAC/LBNL November, 2009 15

  16. Instrumentation m Ionization Cooling Instrumentation MICE 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. • Beam Line Complete • First Beam 3/08 • Running now • PID Installed • CKOV • TOF • EM Cal • First Spectrometer • Spring 2010  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 Spectrometer Solenoid being assembled Steve Geer SLAC/LBNL November, 2009 16

  17. 6D Cooling Palmer • MC designs require the muon beam to be cooled by ~ O(106) 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. Alexhin & Fernow Steve Geer SLAC/LBNL November, 2009 17

  18. 6D Cooling Channel Scheme Palmer Steve Geer SLAC/LBNL November, 2009 18

  19. 6D Cooling Channel Development REQUIRES BEYOND STATE OF ART TECHNOLOGY → Ongoing R&D Detailed Simulations for candidate 6D cooling schemes Helical Cooling Channel- Muons Inc. FOFO Snake - Alexhin Magnet develop-ment for 6D cooling channels HCC magnet4 coil test Steve Geer SLAC/LBNL November, 2009 19

  20. Final Cooling • 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). Steve Geer SLAC/LBNL November, 2009 20

  21. The Promise of HTS Steve Geer SLAC/LBNL November, 2009 21

  22. HTS Solenoid R&D NHMFL test coil LBL Test Coil FNAL test cable. Test degradation of Jc in the cabling process Steve Geer SLAC/LBNL November, 2009 22

  23. Acceleration ● 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, ... 1.0 Accelerating muons from 3 GeV to 2 TeV Bogacz 0.8 0.6 MUON SURVIVAL FRACTION 0.4 Example: TESLA cavities: Real estate gradient ~31 MV/m → 97% survival 0.2 0.1 1 2 5 10 20 50 AVERAGE GRADIENT (MV/m) Steve Geer SLAC/LBNL November, 2009 23

  24. 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, 2009 24

  25. Neutrino Radiation • With L ~ E2 → • OK at √s = 1 TeV • OK at √s = 3 TeV if D = 200m • Above 3 TeV need to pay attention (wobble beam, lower b*, higher Bring , … ) Steve Geer SLAC/LBNL November, 2009 25

  26. Background from Muon Decay m-→ e-nenm 2  2 TeV Collider • 2 x 1012 muons/bunch • 2 x 105 decays/m • Electron decay angles O(10) mrad • Mean electron energy = 700 GeV Number of Decays 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. Mean energy= 700 GeV 0 500 1000 1500 2000 Electron Energy (GeV) Steve Geer SLAC/LBNL November, 2009 26

  27. Detector Backgrounds • Muon Collider detector backgrounds were studied actively ~10 years ago (1996-1997). The most detailed work was done for a 22 TeV Collider → s=4 TeV. • Since muons decay (t2TeV=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. Steve Geer SLAC/LBNL November, 2009 27

  28. Background Simulations • 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. Steve Geer SLAC/LBNL November, 2009 28

  29. Final Focus Setup  Fate of electrons born in the 130m long straight section: 62% interactupstream of shielding, 30% interact in early part of shielding, 2% interact in last part, 10% pass through IP without interacting. Steve Geer SLAC/LBNL November, 2009 29

  30. IP Region Steve Geer SLAC/LBNL November, 2009 30

  31. More Shielding Details r=4cm Designed so that, viewed from the IP, the inner shielding surfaces are not directly visible. Z=4m Steve Geer SLAC/LBNL November, 2009 31

  32. MARS GEANT N. Mokhov I. Stumer 4 TeV Collider Backgrounds Results from Summer 1996 Background calculations & shielding optimization was performed using(independently) MARS & GEANT codes … the two calculations were inbroad agreement with each other (although the designs were different in detail). Steve Geer SLAC/LBNL November, 2009 32

  33. Particles/cm2 from one bunch with 2  1012 muons (2 TeV) 4 TeV Collider Backgrounds GEANT (I. Stumer) Results from LBL Workshop, Spring 1997 Steve Geer SLAC/LBNL November, 2009 33

  34. Occupancies in 300x300 mm2 Pixels TOTAL CHARGED Steve Geer SLAC/LBNL November, 2009 34

  35. Vertex Detector Hit Density  Consider a layer of Silicon at a radius of 10 cm: GEANT Results (I. Stumer) for radial particle fuxes per crossing: 750 photons/cm2 2.3 hits/cm2 110 neutrons/cm2 0.1 hits/cm2 1.3 charged tracks/cm2 1.3 hits/cm2 TOTAL 3.7 hits/cm2 •  0.4% occupancy in 300x300 mm2 pixels MARS predictions for radiation dose at 10 cm for a 2x2 TeV Collider comparable to at LHC with L=1034 cm-2s-1 • At 5cm radius: 13.2 hits/cm2 1.3% occupancy • For comparison with CLIC (later) … at r = 3cm hit density about ×2 higher than at 5cm → ~20 hits/cm2→ 0.2 hits/mm2 Steve Geer SLAC/LBNL November, 2009 35

  36. Pixel Micro-Telescope Idea S. Geer, J. Chapman: FERMILAB-Conf-96-375 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 (tomaintain pointing) &take coincidence. Blind to soft photon hits& tracks that don’t come from IP Steve Geer SLAC/LBNL November, 2009 36

  37. Pixel Micro-Telescope Simulation - 1 Steve Geer SLAC/LBNL November, 2009 37

  38. Pixel Micro-Telescope Simulation - 2 Steve Geer SLAC/LBNL November, 2009 38

  39. TPC V. Tchernatine •  Exploit 10ms between crossings •  Large neutron flux – gas must not contain hydrogen: 90% Ne + 10% CF4 • Vdrift = 9.4 cm/ms with E = 1500 V/cm. Ion buildup DE/E = 0.7%  Cut on pulse height removes photon & neutron induced recoils Steve Geer SLAC/LBNL November, 2009 39

  40. Electromagnetic: Consider calorimeter at r=120 cm, 25 r.l. deep, 4m long,22 cm2 cells:  GEANT  400 photons/crossing with <Eg> ~1 MeV  <ETower>~400 MeV  sE ~ (2<ng>) <Eg> = 30 MeV  For a shower occupying 4 towers: <E> = 1.6 GeV and sE = 60 MeV Hadronic: Consider calorimeter at r=150 cm, 2.5m deep (~10l), covering30-150 degrees, 55 cm2 cells:  <ETower> ~ 400 MeV  sE ~ (2<ng>) <Eg> = O(100 MeV) Calorimeter Backgrounds These estimates were made summer 1996, before further improvements tofinal focus + shielding reduced backgrounds by an order of magnitude … so guess background fluctuations reduced by 3 compared with above. Steve Geer SLAC/LBNL November, 2009 40

  41. Bethe-Heitler Muons (gZ  Zm+m-) 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, 2009 41

  42. Comparison with CLIC • We are not yet in a position to make an apples-to-apples comparison with CLIC, but ….. FROM CLIC Machine-Detector interface studies: hits/mm2/bunch train 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 CLIC Note: CLIC shielding cone= 7o c.f. 20o for MC (but we hope to improve on this) 30mm O(1) hit/mm2/bunch train  Steve Geer SLAC/LBNL November, 2009 42

  43. 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, 2009 43

  44. 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, 2009 44

  45. R&D – Ongoing NFMCC/MCTF HISTORY & FUTUREPROPOSAL Steve Geer SLAC/LBNL November, 2009 45

  46. Anticipated Progress NOW5 YEARS Key component models Steve Geer SLAC/LBNL November, 2009 46

  47. Aspirational Bigger Picture Steve Geer SLAC/LBNL November, 2009 47

  48. Muon Collider R&D: A National Program Steve Geer SLAC/LBNL November, 2009 48

  49. 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, 2009 49

  50. Illustrative Staging Scenario 4MW multi-GeVProton Source 4 GeVNF a Accumulation &Rebunching 3 25 GeV NF b 4 Steve Geer CERN Neutrino Workshop October 1-3, 2009 50

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