Ions in ATF ISG-X June 20th, 2003

Introduction Fast Beam-ion instability is still a potential limitation in future e- damping rings Numerous recent observations are consistent with FBII but detailed numerical comparisons have still not been done With low beam emittance and excellent diagnostics, the ATF provides an opportunity for detailed measurements Growth rates are calculated to be quite short

Growth Rates in Rings

Simulations Start from MAD deck At every lattice element: Track ½ way through Generate ions Calculate beam and ion fields on 2-D grid Calculate kicks on beam and ion macro-particles Track 2nd ½ of element Tends to be very slow but …

ATF Simulations Use lattice: drlbw44_twiss.tape nx = 15.14 ny = 8.76 1300 elements in ring gex is too small but gey is too large  1 mA per bunch with a total of 80 mA Growth rates scale as N * P  2 x higher pressure = 40 mA

ATF Simulations (1)

ATF Simulations (2)