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Muon Colliders - LBNL

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									                    Muon Colliders
MCTF




                    m +                        m -




       Steve Geer         SLAC/LBNL   November, 2009   1
MCTF
                    Physics Landscape




       Steve Geer    SLAC/LBNL   November, 2009   2
MCTF
                        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
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 (mm / me ~ 207):
   - COMPACT
       Fits on laboratory site
   - MULTI-PASS ACCELERATION




                                                                COST
       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)




                                                                PHYSICS
    - 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
       Steve Geer        SLAC/LBNL       November, 2009           4
MCTF
                     Muon Colliders are Compact



                                             3 TeV
                                   0.5 TeV

             4 TeV




       Steve Geer          SLAC/LBNL         November, 2009   5
MCTF
                    Narrow Energy Spread
                                                       Shiltsev




                      Beamstrahlung in
                      any e+e- collider
                           E/E  2




       Steve Geer        SLAC/LBNL        November, 2009          6
MCTF
                          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
MCTF
                    Muon Collider Schematic




                                              √s = 3 TeV
       Proton source:   1021 muons per        Circumference = 4.5km
       Upgraded         year that fit         L = 3×1034 cm-2s-1
       PROJECT X (4     within the            m/bunch = 2x1012
       MW, 2±1 ns       acceptance of         s(p)/p = 0.1%
       long bunches)    an accelerator        b* = 5mm
                                              Rep Rate = 12Hz


       Steve Geer       SLAC/LBNL        November, 2009        8
MCTF
                    Target Facility Design

  • A 4MW target station design                          V. Graves, ORNL
    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
                                        4MW Target Station Design
    one of the main Neutrino
    Factory challenges requiring     T. Davonne, RAL

    proof-of-principle
    demonstration.
  • Beam dump = liquid Hg pool.
    Some design studies started.
                                           Proton Hg Beam Dump

       Steve Geer      SLAC/LBNL        November, 2009               9
MCTF
              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
MCTF
                     Front-End Specifications


           p± → mn


  Parameter         Drift          Buncher        Rotator         Cooler
  Length (m)        56.4           31.5           36              75
  Focusing (T)      2              2              2               2.5 (ASOL)
  RF f (MHz)                       360  240      240  202       201.25
  RF G (MV/m)                      0  15         15              16
  Total RF (V)                     126            360             800

           m/p within reference acceptance = 0.085 at end of cooler
                             →  1.5 1021 μ/year

       Steve Geer            SLAC/LBNL          November, 2009             11
MCTF
                    Front-End Simulation Results
                                                       Neuffer




       Steve Geer         SLAC/LBNL   November, 2009         12
MCTF
                         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 Z
 absorber. Hydrogen is best, but LiH also
 OK for the early part of the cooling channel.

 d N  - 1 dE m  N + b  (0.014 GeV )
                                         2

  ds     b 2 ds E m     2 b 3 E m mm X 0

             Cooling       Heating




       Steve Geer           SLAC/LBNL        November, 2009   13
MCTF
                                          MuCool

  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
                                                                    New beamline

    -5T solenoid (805 MHz fits
    in bore)
    -Beam from linac (soon)




                                                MTA
       42cm  Be RF window   Liq. H2 absorber

       Steve Geer                 SLAC/LBNL        November, 2009           14
MCTF
               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)
                         >2X Reduction @
                                                   - Magnetic insulation
                         required field
                                              Effect is not seen in
                                              cavities filled with high
                                              pressure hydrogen gas
                                              (Johnson & Derbenev) –
                                              possible solution (but needs
   Peak Magnetic Field in T at the Window     to be tested in a beam –
                                              coming soon)
       Steve Geer        SLAC/LBNL          November, 2009            15
MCTF
                                   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.


            m
                                                              Beam Line Complete
   Multi-stage expt.
                                                                 First Beam 3/08
   First stage being                                            Running now
  installed at purpose-built                                  PID Installed
  muon beam at RAL (first                                        CKOV
  beam to hall March 2008).                                      TOF
                                                                 EM Cal
   10% cooling measured to     Spectrometer Solenoid
                                                              First Spectrometer
  ±1%. Anticipate completed       being assembled                Spring 2010
  ~2011/12
       Steve Geer          SLAC/LBNL               November, 2009             16
MCTF
                              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




                                                                    H2
                                                                    liquid
                                             solenoid
       phase space (6D) must mix                        Alexhin & Fernow




                                                            RF
       degrees of freedom as the
       cooling proceeds
        This can be accomplished
       with solenoid coils
       arranged in a helix, or with
       solenoid coils tilted.

       Steve Geer          SLAC/LBNL   November, 2009                        17
MCTF
                    6D Cooling Channel Scheme

                                                      Palmer




       Steve Geer        SLAC/LBNL   November, 2009            18
MCTF
                6D Cooling Channel Development

          REQUIRES BEYOND STATE OF ART TECHNOLOGY
          → Ongoing R&D

                                                      Detailed
                                                      Simulations for
                                                      candidate 6D
                                Helical Cooling       cooling schemes
         FOFO Snake - Alexhin
                                Channel- Muons Inc.



                                                   Magnet develop-
           HCC magnet                              ment for 6D
           4 coil test                             cooling channels




       Steve Geer          SLAC/LBNL        November, 2009         19
MCTF
                      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
MCTF
                                                   The Promise of HTS

               10000
                              YBCO B Tape
                              Plane
                                                                                   YBCO B|| Tape
                                                                                   Plane
                                                                                                                                              SuperPower tape
                                                                RRP Nb3Sn                                                                     used in record
                                     N b- Ti                                                                                                  breaking NHMFL
                                                                                        Compli ed from
                                                                                                                                              insert coil 2007
                                                                                        ASC'02 and
               1000                                                                     ICMC'03 papers
                                                                                        (J. Parrell OI-ST)                    427 filament strand with
                                                                                                             2212             Ag alloy outer sheath
                                                                                                                              tested at NHMFL
  JE (A/mm²)




                                                                                                                     YBCO Insert Tape (B|| Tape Plane)
                                                   Maximal JE for
                                                   entire LHC                                                        YBCO Insert Tape (B Tape Plane)
                100                                Nb-Ti strand
                                                   production          Bronze                                        MgB2 19Fil 24% Fill (HyperTech)
                             MgB2                  (CERN-
                                                                       Nb3Sn
                                                   T. Boutboul '07)                                                  2212 OI-ST 28% Ceramic Filaments
                                                                                                                     NbTi LHC Production 38%SC (4.2 K)
                                                                           4543 filament High Sn                     Nb3Sn RRP Internal Sn (OI-ST)
                       18+1 MgB2/Nb/Cu/Monel                                  Bronze-16wt.%Sn-
                       Courtesy M. Tomsi c, 2007                            0.3wt%Ti (Mi yazaki -                    Nb3Sn High Sn Bronze Cu:Non-Cu 0.3
                                                                                 MT18-IEEE’04)
                  10
                       0            5               10                15             20              25             30         35             40            45
                                                                              Applied Field (T)


               Steve Geer                                    SLAC/LBNL                                       November, 2009                                      21
MCTF
                            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
MCTF
                                                     Acceleration

                                                                             Acceleration
                                                                          ● Early
                               Accelerating muons from 3 GeV to 2 TeV (to 25 GeV ?) could
                                                                      be the same as NF.
                            1.0
   MUON SURVIVAL FRACTION




                                                                      Needs study.
                                    Bogacz
                            0.8                                           ● Main Acceleration –
                                                                          Attractive Candidates
                            0.6                                             - RLAs (extension of
                                                       Example:              NF accel. scheme ?)
                                                       TESLA                 - Rapid cycling
                            0.4
                                                       cavities: Real        synchrotron – needs
                                                       estate gradient       magnet R&D
                            0.2                        ~31 MV/m →            - Fast ramping RLA
                                                       97% survival
                                                                          ● Options need
                              0.1            1   2    5 10 20     50      study → particle
                                  AVERAGE GRADIENT (MV/m)                 tracking, collective
                                                                          effects, cavity
                                                                          loading, ...
              Steve Geer                         SLAC/LBNL          November, 2009         23
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
                                                                                       WE
       DESIGN PROCESS




                         Comparison of different schemes, choice of the baseline      ARE
                         Detailed lattice design with tuning and correction “knobs”   HERE
                         Dynamic aperture studies with magnet nonlinearities,
                        misalignments and their correction
                         Transient beam-beam effect compensation
                         Coherent instabilities analysis

        Steve Geer                          SLAC/LBNL          November, 2009           24
MCTF
                    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
MCTF
                                  Background from Muon Decay


                                                           m- → e- ne nm
                                        2  2 TeV
                                         Collider
  Number of Decays




                                                         2 x 1012 muons/bunch
                                                         2 x 105 decays/m
                                                         Electron decay angles O(10) mrad
                                                         Mean electron energy = 700 GeV
                          Mean energy                    As the decay electrons respond to
                          = 700 GeV                      the fields of the final focus
                                                         system they lose 20% of their
                                                         energy by radiating on average 500
                     0      500    1000 1500 2000        synchrotron photons with a mean
                          Electron Energy (GeV)          energy of ~500 MeV … & are then
                                                         swept out of the beampipe.


                     Steve Geer             SLAC/LBNL           November, 2009          26
MCTF
                    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
MCTF
                    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
MCTF
                       Final Focus Setup




    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.

       Steve Geer        SLAC/LBNL          November, 2009          29
MCTF
                        IP Region




       Steve Geer   SLAC/LBNL   November, 2009   30
MCTF
                    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
MCTF
                    4 TeV Collider Backgrounds
                         Results from Summer 1996

                           I. Stumer                        N. Mokhov
                          GEANT                                MARS




   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).

       Steve Geer        SLAC/LBNL         November, 2009        32
MCTF
              4 TeV Collider Backgrounds
  Particles/cm2 from one bunch with 2  1012 muons (2 TeV)

            GEANT (I. Stumer) Results from LBL Workshop, Spring 1997

  r (cm)                    n            p    p                e       m
     5   2700              120          0.05  0.9              2.3     1.7
    10    750              110          0.20  0.4                      0.7
    15    350              100          0.13  0.4                      0.4
    20    210              100          0.13  0.3                      0.1
    50     70              120          0.08 0.05                     0.02
   100     31               50          0.04 0.003                   0.008
   calo                                                              0.003
  muon                                                               0.0003

       Steve Geer           SLAC/LBNL         November, 2009           33
MCTF
             Occupancies in 300x300 mm2 Pixels

                    TOTAL                          CHARGED




       Steve Geer           SLAC/LBNL   November, 2009       34
MCTF
                    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
MCTF
                    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 (to
                                                maintain pointing) &
                                                take coincidence.


                                                Blind to soft photon hits
                                                & tracks that don’t come
                                                from IP

       Steve Geer          SLAC/LBNL        November, 2009            36
MCTF
            Pixel Micro-Telescope Simulation - 1




       Steve Geer     SLAC/LBNL   November, 2009   37
MCTF
            Pixel Micro-Telescope Simulation - 2




       Steve Geer     SLAC/LBNL   November, 2009   38
MCTF
                                     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
MCTF
                    Calorimeter Backgrounds

   Electromagnetic: Consider calorimeter at r=120 cm, 25 r.l. deep, 4m long,
   22 cm2 cells:

    GEANT  400 photons/crossing with <E> ~1 MeV  <ETower>~400 MeV

    sE ~ (2<n>) <E> = 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), covering
   30-150 degrees, 55 cm2 cells:
    <ETower> ~ 400 MeV

    sE ~ (2<n>) <E> = 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.
       Steve Geer         SLAC/LBNL          November, 2009           40
MCTF
              Bethe-Heitler Muons (Z  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
MCTF
                      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                                   CLIC
   … 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
   = 7o c.f. 20o for MC (but
   we hope to improve on         30mm O(1) hit/mm2/bunch train 
   this)

       Steve Geer           SLAC/LBNL       November, 2009          42
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, 2009   43
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, 2009    44
MCTF
                          R&D – Ongoing



                    NFMCC/MCTF HISTORY
                        & FUTURE
                        PROPOSAL




       Steve Geer        SLAC/LBNL   November, 2009   45
MCTF
                    Anticipated Progress




                                                   NOW
                                                   5 YEARS




       Steve Geer     SLAC/LBNL   November, 2009         46
MCTF
                    Aspirational Bigger Picture




       Steve Geer        SLAC/LBNL   November, 2009   47
MCTF
         Muon Collider R&D: A National Program




       Steve Geer   SLAC/LBNL   November, 2009   48
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, 2009       49
MCTF
                 Illustrative Staging Scenario


          4MW multi-GeV
           Proton Source



                                                                        4 GeV
                  Accumulation &
                   Rebunching         3             a                     NF




                                                                        25 GeV
                                                                          NF
                                                    b
                                     4

   Steve Geer              CERN Neutrino Workshop   October 1-3, 2009      50
MCTF
                    Muon Collider Parameters




       Steve Geer       SLAC/LBNL   November, 2009   51

								
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