C.Limborg-Deprey Beam Dynamics for RF gun November 3 rd 2004 Beam Dynamics Justification of RF Gun Modifications C.Limborg-Deprey Dual Feed – Racetrack Dual Feed Racetrack shape Beam Dynamics (from PARMELA) for 4 cases 2D => no ports Reference case compared with superfish 3D => coupling port but original cylindrical cell shape Exhibits head-tail quadrupole mode 3D => with racetrack shape in full cell Corrects for quadrupole mode effect 3D => with laser ports in ½ cell and racetrack shape Laser ports do not deteriorate emittance

C.Limborg-Deprey Beam Dynamics for RF gun November 3 rd 2004 Dual Feed Racetrack shape Laser ports

C.Limborg-Deprey Beam Dynamics for RF gun November 3 rd 2004 Beam Dynamics, Nominal tuning 1nC, 10ps

C.Limborg-Deprey Beam Dynamics for RF gun November 3 rd 2004 Dual Power Feed  twiss = 7 m  on = m.rad  = 12 Assumption : head-tail kick from phase term Can be corrected partially by using the transverse wakefield in L01 But, not convenient since : Charge, bunch length dependent Offset in GunToLinac introduces other transverse wakefields Symmetrization of field see D.Palmer, R.Miller et al. SLAC PUB  Corrects for amplitude term but not for phase term Will be confirmed with Computations (upgrades of Omega3P)

C.Limborg-Deprey Beam Dynamics for RF gun November 3 rd 2004 With coupling ports No coupling ports Suppression of quadrupole head-tail with the racetrack shape of the full cell Slice emittance along the bunch (100 slices) at the end of L02

C.Limborg-Deprey Beam Dynamics for RF gun November 3 rd 2004 Retuning the beamline for the “full” map (= map including racetrack plus laser ports) E gun field close to optimum Solenoid field reduced by 1%  RF decreased by 2degrees Efield Coefficient on Solenoid

C.Limborg-Deprey Beam Dynamics for RF gun November 3 rd 2004 Full Map Including, laser ports in ½ cell racetrack in full shape  x,80% = mm.mrad  y,80% = mm.mrad

C.Limborg-Deprey Beam Dynamics for RF gun November 3 rd 2004 Conclusion Dual Power Feed perfect symmetry still to be justified with numerics Racetrack shape importance demonstrated Laser ports Do not affect dynamics