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					                                                   Columbia University & the Max-Planck-Institute




      Review & Status of Frictional Cooling
       A. Caldwell, R. Galea, D. Kollar

                   • Principle
                   • Simulations
                   • Review of Nevis Experiment
                   • Outline next experimental steps at MPI
                   • Summary


NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan
                                 Principle
        Same as freefall and reaching terminal velocity
                Gravity opposing friction
        Muons energy loss in gas is compensated by applied
        electric field resulting in equilibrium energy


      • Need low energy ms below
      ionization peak
      • Here energy loss is a to T,
      the faster ms lose energy
      faster than slow ms                            (Ionization Cooling)




NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan
        Cooling aim/obvious problems
     • In this regime dE/dx extremely        • Low average density
     large                                   (gas)
     • Slow ms don’t go far before          • Apply EB to get
     decaying                               below the dE/dx peak
     d = 10 cm sqrt(T) T in eV              • Make Gas cell long as
                                            you want but transverse
     • m+ forms Muonium                     dimension (extraction)
     • m- is captued by Atom                small.


       s(Mm) dominates over       s small above electron binding
       e-stripping in all gases   energy, but not known. Keep T as
       except He                  high as possible



NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan
                                                      dT 
                                            F  q ( E  v  B)     r
                                                                 dx




                        Oscillations around
                        equilibrium limits final
                        emittance

NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan
                  Phase rotation sections                    Results of
                                                             simulations to
                                                             this point
                                    Cooling cells




    •Full MARS target simulation,                    He gas is used for m+, H2 for m-.
    optimized for low energy                        There is a nearly uniform 5T Bz
    muon yield: 2 GeV protons on                    field everywhere, and Ex =5 MV/m
    Cu with proton beam                             in gas cell region
    transverse to solenoids                          Electronic energy loss treated as
    (capture low energy pion                        continuous, individual nuclear
    cloud).                                         scattering taken into account since
                                                    these yield large angles.

    Not to scale !!
NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan
                                      Baseline parameters for high energy muon colliders. From “Status of Muon Collider
      Results:                        Research and Development and Future Plans,” Muon Collider Collaboration, C. M.
                                      Ankenbrandt et al., Phys. Rev. ST Accel. Beams 2, 081001 (1999).



    • Simulation of previous                COM energy (TeV)
                                            p energy (GeV)
                                                                             0.4
                                                                             16
                                                                                                   3.0
                                                                                                   16
                                            p’s/bunch                    2.5  1013            2.5  1013
    scheme yielded final beam               Bunches/fill
                                            Rep. rate (Hz)
                                                                              4
                                                                             15
                                                                                                    4
                                                                                                   15
                                            p power (MW)                      4                     4
    emittances of                           m/ bunch
                                            m power (MW)
                                                                          2  1012
                                                                              4
                                                                                                2  1012
                                                                                                   28
    2-6x10-11 (m)3                         Wall power (MW)
                                            Collider circum. (m)
                                                                            120
                                                                            1000
                                                                                                  204
                                                                                                  6000
                                            Ave bending field (T)            4.7                   5.2
    At yields of 0.001-0.003                rms p/p (%)
                                            6D  (m)3
                                                                            0.14
                                                                         1.7  1010
                                                                                                  0.16
                                                                                               1.7  1010

    m+/GeV proton.                          rms n ( mm mrad)
                                            * (cm)
                                                                             50
                                                                             2.6
                                                                                                   50
                                                                                                   0.3
                                            sz (cm)                          2.6                   0.3
                                            sr spot (mm)                     2.6                   3.2

   • Yield could be better yet
                                            s IP (mrad)                     1.0                   1.1
                                            Tune shift                     0.044                 0.044
                                            nturns (effective)              700                   785
   emittance is better than                 Luminosity (cm2 s1)           1033                7  1034


   ”required”
   • Cooler beams                                      1.7x10-10 (m)3
        • smaller beam elements
        • less background
        • lower potential radiation
        hazard from neutrinos
NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan
                            THE GOOD: Simulations include:
                            • individual nuclear scatters
                            • Muonium formation
                            • m- capture in H2 & He
                            • tracking through thin windows
                            • initial reacceleration
                            Sufficiently cool muon beams

    THE BAD:                                  THE UGLY:
    • Yields are somewhat low                 • Large amount of free
                                              charge which would screen
                                              field
                                              • Not simulated




NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan
                                        Nevis Experiment already
                                        reported at NuFact03
                                        R.Galea, A.Caldwell, L.Newburgh, Nucl.Instrum.Meth.A524, 27-38 (2004)
                                        arXiv: physics/0311059




                                                  RAdiological
                                                  Research
                                                  Accelerator
    •Perform TOF measurements with                Facility
    protons
        •2 detectors START/STOP
        •Thin entrance/exit windows for a
                                                  Look for a bunching in time
        gas cell
        •Some density of He gas                      •Can we cool protons?
        •Electric field to establish
        equilibrium energy
        •NO B field so low acceptance
NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan
                                  4 MeV p




NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan
               Assumed initial conditions
               •20nm C windows
               •700KeV protons
               •0.04atm He




           TOF=T0-(Tsi-TMCP)           speed   Kinetic energy

NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan
   Results of RARAF experiment
                                                 • Various energies/gas
                                                 pressures/electric field
                                                 strengths indicated no cooled
                                                 protons
              Experiment showed that MC          • Lines are fits to MC & main
                                                 peaks correspond to protons
              could reproduce data under         above the ionization peak
              various conditions. Simulations
              of Frictional Cooling is
              promising.
              Exp. Confirmation still desired.

    Low acceptance but thicker windows was the
    culprit

NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan
  Frictional Cooling Demonstration at MPI Munich

      • Repeat demonstration
      experiment with protons
      with IMPROVEMENTS:
      • No windows
      • 5T Superconducting
      Solenoid for high
      acceptance
      • Silicon detector to
      measure energy directly




NuFact04 July26-August 1, 2004   Cryostat housing 5T solenoid.
Osaka University, Osaka, Japan
                                                      Si Drift detector

                                                
                                               E, B
                                                      He gas

                                 HV Cable

                                 Up to 100KV
                                                      Source




NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan
    Where do we get protons?
    • Use strong a source match range to thickness in plastic
    • Note E||B, but protons starting from rest

                                                                Mylar Window




NuFact04 July26-August 1, 2004                                      a Source
Osaka University, Osaka, Japan
       Heating (cooling) to equilibrium…
       What do we expect?
                                 He

                                      1MV/m
                                               • Vary gas
                                               pressure/density
                                      .9MV/m   • Vary Efield strength
                                               • Vary distance
                                               • Measure energy directly
                                      .8MV/m   • Can our MC predict
                                               equilibrium energies?
                                      .7MV/m

                                      .6MV/m




NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan
                                                  Assorted Insulating
             Efield coil                          Spacers & support
                                  Source holder
             Support structures                   structures




NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan
    Status of Experiment

      • Cryostat & Magnet
      commissioned
      • Grid constructed &
      tested. Maintained
      98KV in vacuum
      • Source & support                                     FWHM=250eV
      structures constructed
      • Electronics &
      detectors available



                                 • Silicon Drift Detector gives excellent resolution
                                 • Thus far Fe55 X-rays
NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan
                                   Summary
       • Frictional Cooling is being persued as a potential cooling
       method intended for Muon Colliders
       • Simulations of mostly ideal circumstances show that the 6D
       emittance benchmark of 1.7x10-10 (m)3 can be achieved &
       surpassed
       • Simulations have been supported by data from Nevis
       Experiment & will be tested further at the Frictional Cooling
       Demonstration to take place at MPI Munich
       • Future investigations are also on the program:
            • R&D into thin window or potential windowless systems
            • Studies of gasbreakdown in high E,B fields
            • Capture cross section measurements at m beams

                                 Frictional Cooling is an exciting potential
                                 alternative for the phase space reduction of
                                 muon beams
NuFact04 July26-August 1, 2004
Osaka University, Osaka, Japan

				
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