NuFact04 July26-August 1, 2004 Osaka University, Osaka, Japan 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 (Ionization Cooling) Need low energy  s below ionization peak Here energy loss is  to T, the faster  s lose energy faster than slow  s

NuFact04 July26-August 1, 2004 Osaka University, Osaka, Japan Cooling aim/obvious problems In this regime dE/dx extremely large Slow  s don’t go far before decaying d = 10 cm sqrt(T) T in eV  + forms Muonium  - is captued by Atom Low average density (gas) Apply E  B to get below the dE/dx peak Make Gas cell long as you want but transverse dimension (extraction) small.  dominates over e-stripping  in all gases except He  small above electron binding energy, but not known. Keep T as high as possible

NuFact04 July26-August 1, 2004 Osaka University, Osaka, Japan Oscillations around equilibrium limits final emittance

NuFact04 July26-August 1, 2004 Osaka University, Osaka, Japan Cooling cells Phase rotation sections Not to scale !!  He gas is used for  +, H 2 for  -. There is a nearly uniform 5T B z field everywhere, and E x =5 MV/m in gas cell region  Electronic energy loss treated as continuous, individual nuclear scattering taken into account since these yield large angles. 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). Results of simulations to this point

NuFact04 July26-August 1, 2004 Osaka University, Osaka, Japan Results: 1.7x (  m) 3 Simulation of previous scheme yielded final beam emittances of 2-6x (  m) 3 At yields of  + /GeV proton. Yield could be better yet emittance is better than ”required” Cooler beams 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  - capture in H 2 & He tracking through thin windows initial reacceleration Sufficiently cool muon beams THE BAD: Yields are somewhat low THE UGLY: Large amount of free charge which would screen field Not simulated

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

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-(T si -T MCP ) speedKinetic 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 Lines are fits to MC & main peaks correspond to protons above the ionization peak Low acceptance but thicker windows was the culprit Experiment showed that MC could reproduce data under various conditions. Simulations of Frictional Cooling is promising. Exp. Confirmation still desired.

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 Cryostat housing 5T solenoid.

NuFact04 July26-August 1, 2004 Osaka University, Osaka, Japan HV Cable Si Drift detector He gas Source Up to 100KV

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

NuFact04 July26-August 1, 2004 Osaka University, Osaka, Japan Heating (cooling) to equilibrium… What do we expect? He 1MV/m.9MV/m.8MV/m.7MV/m.6MV/m Vary gas pressure/density Vary Efield strength Vary distance Measure energy directly Can our MC predict equilibrium energies?

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

NuFact04 July26-August 1, 2004 Osaka University, Osaka, Japan Status of Experiment FWHM=250eV Silicon Drift Detector gives excellent resolution Thus far Fe55 X-rays Cryostat & Magnet commissioned Grid constructed & tested. Maintained 98KV in vacuum Source & support structures constructed Electronics & detectors available

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 1.7x (  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  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 Something about simulations Individual nuclear scatters are simulated – crucial in determining final phase space, survival probability. Incorporate scattering cross sections into the cooling program Include  - capture cross section using calculations of Cohen (Phys. Rev. A. Vol ) Electronic energy loss treated as continuous Difference in  + &  - energy loss rates at dE/dx peak (parameterized data from Agnello et. al. (Phys. Rev. Lett. 74 (1995) 371)) Partly due to charge exchange for  +

NuFact04 July26-August 1, 2004 Osaka University, Osaka, Japan Other problems/solutions: B E Thin windows important issue – Nevis Experiment Breakdown in Gas Paschen Curves Large amount of free charge which would screen field In ExB field particle undergoes cycloid motion limiting max kinetic energy a 2mE/B. Choose E & B appropriately to keep energy below ionization energy to prevent multiplication