Lattice Upgrade Options for the ESRF Storage Ring

Several scenarios of lattice upgrade for the ESRF storage ring are under study. In order to minimise the cost, their design is based on the length constraints of the exist ing tunnel with the ID beam-lines kept in place. The goal is to shrink the emittance in order to increase the undulator brilliance. The two main options are a double bend achromat structure with non-uniform field dipoles and a triple bend achromat lattice. The two designs are detailed and compared with respect to their linear optics solutions, correction of chromatic effects and non-linear dynamics. It is also attempted to reveal the horizontal effective emittance dependence on important design parameters, such as optics functions maxima, chromaticity and dynamic aperture. Technological challenges concerning magnet design with small physical aperture in a reduced space are finally addressed.