Geant Simulation of Muon Cooling Rings Amit Klier University of California Riverside

A. Klier - Geant simulation Outline A short reminder from Nufact03 The RFOFO ring Geometry Software improvements Simulation results The small dipole ring Some Results June 21 2005 A. Klier - Geant simulation

A. Klier - Geant simulation Muc_Geant Modified, data-driven Geant3 application for simulating muon cooling Electric fields added Runge-Kutta changed to include changing electric fields (eg RF cavities) Realistic magnetic fields can be read from external field maps June 21 2005 A. Klier - Geant simulation

From Nuact03 Tetra ring simulated Rajendran Raja – Nufact 03 June 21 2005 A. Klier - Geant simulation

A. Klier - Geant simulation The RFOFO ring A few code changes w.r.t. Tetra Realistic magnetic field maps read-in (R. Godang, S. Bracker – MC-Note 271) June 21 2005 A. Klier - Geant simulation

A. Klier - Geant simulation The RFOFO ring Full Geant simulation: A. Klier – MC-Note 298 June 21 2005 A. Klier - Geant simulation

A. Klier - Geant simulation The ring geometry 33 m circumference 12 cells (2.75m): A wedge absorber opening angle 110°, pointing ’upwards’ 6 RF cavities 28.75 cm long, iris radius 25 cm flat E field in z direction 2 tilted solenoids inner/outer r = 77/88 cm tilt angle ±3° Only for display here June 21 2005 A. Klier - Geant simulation

Closed orbits in a single cell Solid line – the reference orbit 200 MeV 270 MeV 227 MeV 250 MeV 227 MeV 250 MeV E = 200 MeV E = 270 MeV June 21 2005 A. Klier - Geant simulation

Software improvements ICOOL input/output format used, ecalc9 can be used to calculate emittance Use initial time of particle at entry Use virtual detectors June 21 2005 A. Klier - Geant simulation

A. Klier - Geant simulation Cooling of a muon beam June 21 2005 A. Klier - Geant simulation

A. Klier - Geant simulation Comparison with ICOOL Transmission 6-D emittance June 21 2005 A. Klier - Geant simulation

A. Klier - Geant simulation More comparisons Results after 10 turns: Merit factor Trans. W/O decay With decay Merit Factor Balbekov (MC-264) 70% 56% 55 ICOOL (Fernow) -- 58% 66 Geant 72% 57% 70 June 21 2005 A. Klier - Geant simulation

Change beam entry angle June 21 2005 A. Klier - Geant simulation

A. Klier - Geant simulation The small dipole ring “Weak” (edge) focusing (ideally) scaling Filled with ~10 Atm. hydrogen gas @ 77K Dipole field ~ 2 T For P~200 MeV/c, the radius should be ~60 cm June 21 2005 A. Klier - Geant simulation

A. Klier - Geant simulation Field map (from S. Kahn) By in a single quadrant By at R=60 cm Return yoke June 21 2005 A. Klier - Geant simulation

A. Klier - Geant simulation Reference orbit Scale B down to 90% closed orbit: P=171.25 MeV/c Rmin=56.32 cm (x=0 in virtual detectors) Rmin Virtual detector plane RF cavity (active region) June 21 2005 A. Klier - Geant simulation

A. Klier - Geant simulation Ellipses Stable up to y~13 cm Y plane symmetry imposed June 21 2005 A. Klier - Geant simulation

A. Klier - Geant simulation Acceptance of the ring “A blob” Py=~19 MeV/c y=~8.5 cm Px=~34 MeV/c More “natural” decrease with no x-z plane symmetry x=~6.5 cm June 21 2005 A. Klier - Geant simulation

“Cooling” with no scattering Xinitial=6 cm Yinitial=8 cm tinitial= –1.5 ns Xcentral=0.04 cm Ycentral=0 cm tcentral=0 ns PXinitial=30 MeV/c PYinitial=17.5 MeV/c Einitial=213 MeV PXcentral=0.12 MeV/c PYcentral=0 MeV/c Ecentral=201.8 MeV June 21 2005 A. Klier - Geant simulation

Software improvements More flexibility – less “hard-coding”, more external parameters Field map reading code used to be RFOFO-specific, now more general More RF parameters Cavities in small dipole ring are off-center So far, only perfect pillbox (or flat field..) cavity are simulated Flexibility: different frequencies, gradients, types can be used in the same channel June 21 2005 A. Klier - Geant simulation

A. Klier - Geant simulation To do Simulate the small dipole ring with a beam Introduce more realistic features: Injection Detectors June 21 2005 A. Klier - Geant simulation

A. Klier - Geant simulation June 21 2005 A. Klier - Geant simulation

A. Klier - Geant simulation Additional Slides June 21 2005 A. Klier - Geant simulation

A. Klier - Geant simulation Comparison with ICOOL Transverse emittance Longitudinal emittance June 21 2005 A. Klier - Geant simulation