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M m ON Cooling : Frictional Cooling

M m ON Cooling : Frictional Cooling. Project Review 11/12/03. OUTLINE:. Muon Collider Frictional Cooling Demonstration experiment with protons at Nevis Labs FCD experiment at MPI Conclusions & Outlook. A. Caldwell R. Galea C. Buettner.

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M m ON Cooling : Frictional Cooling

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  1. MmON Cooling : Frictional Cooling Project Review 11/12/03 OUTLINE: • Muon Collider • Frictional Cooling • Demonstration experiment with protons at Nevis Labs • FCD experiment at MPI • Conclusions & Outlook A. Caldwell R. Galea C. Buettner Columbia University & the Max-Planck-Institute

  2. Physics at a Muon Collider Less synchrotron radiation (~m-4)…small ring size Less brems, ISR… better energy determination From target, stored  • Stopped m physics • n physics • Higgs Factory • Higher Energy Frontier = 40000 ee • Muon Collider Complex: • Proton Driver 2-16GeV; 1-4MW leading to 1022p/year • p production target & Strong Field Capture • COOLING resultant m beam • m acceleration • Storage & collisions Benchmark for m collider: e6D=1.7x10-10 (pm)3 which corresponds to a reduction in initial emittance of 106

  3. Problems…to name at least one: • Muons decay, so are not readily available – need multi MW source. Large starting cost. • Muons decay, so time available for cooling, bunching, acceleration is very limited. Need to develop new techniques, technologies. • Large experimental backgrounds from muon decays (for a collider). Not the usual clean electron collider environment. • High energy colliders with high muon flux will face critical limitation from neutrino induced radiation. • Cooler beams would allow fewer muons for a given luminosity, thereby • Reducing the experimental background • Reducing the radiation from muon decays • Allowing for smaller apertures in machine elements, and so driving the cost down

  4. Cooling Ideas: • Standard techniques… Stochastic,Electron … too slow • Nominal approach… Ionization cooling • muons are maintained at ca. O(100 MeV) while passed successively through an energy loss medium followed by an acceleration stage • Cooling factors~100 simulated • without scheme for injection or • extraction.

  5. Frictional Cooling Nuclear scattering, excitation, charge exchange, ionization Ionization stops, muon too slow • Bring muons to a kinetic energy (T) where dT/dx increases with T • Constant E-field applied to muons resulting in equilibrium energy • Big issue – how to maintain efficiency • Similar idea first studied by Kottmann et al., PSI 1/2 from ionization

  6. Problems/comments: E dominates • large dE/dx @ low kinetic energy  low average density (gas) • Apply EB to get below the dT/dx peak • m-has the problem of Atomic capture s small above electron binding energy, but not known. Keep T as high as possible • Slow muons don’t go far before decaying d = 10 cm sqrt(T) T in eV so extract sideways (EB) • m+has the problem of Muonium formation s(Mm) dominates over e-strippingin all gases except He vxB dominates

  7. Results of simulations to this point Phase rotation sections Cooling cells • Full MARS target simulation, optimized for low energy muon yield: 2 GeV protons on Cu with proton beam transverse to solenoids (capture low energy pion cloud). • He gas is used for m+,H2 for m-. There is a nearly uniform 5T Bz field everywhere, and Ex =5 MV/m in gas cell region • Electronic energy loss treated as continuous, individual nuclear scattering taken into account since these yield large angles. Not to scale !!

  8. Dangerous because of - capture possibility Lorentz angle drift, with nuclear scattering Oscillations about equilibrium define emittance.

  9. Initial reacceleration region After gas cell, E(z,t) E E B Lorentz angle sT = 4 ns at Z=444m P = 200 MeV/c Eff = 40% E gas

  10. Yields & Emittance Look at muons coming out of 11m cooling cell region after initial reacceleration. Yield: approx 0.002  per 2GeV proton after cooling cell. Need to improve yield by factor 5 or more to match # m/proton/GeV in specifications. Emittance: rms x = 0.015 m y = 0.036 m z = 30 m (actually ct) Px = 0.18 MeV Py = 0.18 MeV Pz = 4.0 MeV 6D,N = 5.7 10-11 (m)3

  11. RAdiological Research Accelerator Facility • Perform TOF measurements with protons • 2 detectors START/STOP • Thin entrance/exit windows for a gas cell • Some density of He gas • Electric field to establish equilibrium energy • NO B field so low acceptance • Look for a bunching in time • Can we cool protons?

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

  13. The proton energy spectrum from the Si calculated using SRIM (J. F. Ziegler, J. P. Biersack and U. Littmark, Pergamon Press, 1985). The transport through the gas performed with our detailed simulation. Need first to fix the window thickness and gas pressure.

  14. Calibration Data: 3 distances, no cell, no grid Time resolution of system=17ns Protons have 100-200 KeV after Si window. Good agreement with SRIM.

  15. Add cell, no gas, no E field. Extract effective window thickness by comparison with simulation. Much thicker than expected ! Add gas, still no field. Gas pressure extracted from comp. With sim. Compatible with expectations.

  16. After background subtraction, see no hint of cooled protons. Also predicted by simulation. Problem – windows too thick, acceptance, particularly for slow protons, too small. Need to repeat the experiment with solenoid, no windows. arXiv:physics/0311059

  17. MPI FCD Experiment • Repeat demonstration experiment with protons • No windows,Magnetic field • 5T Superconducting Solenoid in MPI lab

  18. Designs by K. Ackermann Si Drift detector He gas HV Cable Up to 100KV Source

  19. Where do we get protons? • Use strong asource match range to thickness in plastic • Note E||B, but protons starting from rest Mylar Window a Source

  20. Heating (cooling) to equilibrium… He 1MV/m • Vary gas pressure/density • Vary Efield strength • Vary distance • Measure energy directly • Can our MC predict equilibrium energies? .9MV/m .8MV/m .7MV/m .6MV/m

  21. Assorted Insulating Spacers & support structures Efield coil Support structures Source holder

  22. Conclusions • Muon Collider complex would be invaluable to HEP • We need to solve the muon cooling problem • Different schemes should be investigated • We are doing some simulation and experimental studies of frictional cooling. • Monte Carlo simulation can provide a consistent picture under various experimental conditions • Nevis proton frictional cooling demonstration • Can use Monte Carlo to evaluate performance of Muon Collider based on frictional cooling…but still demonstrate • MPI studies • New FCD experiment in house • Gas breakdown • develop experience for m capture cross section measurement • Thin window issues

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