Optimization of Dynamic Aperture of PEP-X Baseline Design

SLAC is developing a long-range plan to transfer the evolving scientific programs at SSRL from the SPEAR3 light source to a much higher performing photon source that would be housed in the 2.2-km PEP-II tunnel*,**. The proposed PEP-X storage ring is one of the possibilities. The goal of the PEP-X design is to develop an optimal light source design with horizontal emittance less than 100 pm at 4.5 GeV and vertical emittance of 8 pm corresponding to the diffraction limit of 1-Å X-ray. The low emittance design requires a lattice with strong focusing leading to high natural chromaticity and therefore to strong sextupoles. The latter cause reduction of dynamic aperture. The horizontal dynamic aperture required at PEP-X injection point is about 10 mm. In order to achieve the desired dynamic aperture, transverse non-linearities of PEP-X are studied. The program LEGO*** is used for particle tracking simulations. The technique of frequency map is used to analyze the nonlinear behavior. The effects of the non-linearities are tried to minimize. The details and results of dynamic aperture optimization are discussed in this paper.