Low emittance lattices for the Duke FEL Storage Ring
In this paper we present two options for a new lattice of the 1 GeV Duke FEL Storage Ring reducing horizontal beam emittance from existing 18 nm*rad to 1.4 nm*rad and 0.9 nm*rad respectively. One of proposed lattices reuses existing magnetic elements, another is based on completely new design. The use of combined function magnets with dipole, quadrupole and sextupole components allows us to keep the ring compact and fit it into existing footprint. 2D and 3D field simulations for such a magnet showed good quality of magnetic field. Preliminary results for dynamic aperture simulations are also presented. We also discuss the choice of lattice cell and tune advances and the concept of local compensation of nonlinear aberrations.