Simulation Studies on the Vertical Emittance Growth in the ATF Extraction Beamline

Significant dependence of the vertical emittance growth on the beam intensity was experimentally observed at the ATF/KEK extraction beamline. This technical note describes the simulations of possible vertical emittance growth sources, particularly in the extraction channel, where the magnets are shared by both the ATF extraction beamline and its damping ring. The vertical emittance growth is observed in the simulations by changing the beam orbit in the extraction channel even with all optics corrections. The possible reasons for the experimentally observed dependence of the vertical emittance growth on the beam intensity are discussed. An experiment to measure the emittance vs beam orbit at the existing ATF extraction beamline is proposed