International Linear Collider damping ring lattice design based on modified FODO arc cells

Abstract

In this paper, we present a new lattice design for the International Linear Collider (ILC) positron damping ring. The same lattice could be used also for the electron damping ring. This lattice is based on modified FODO arc cells, and has a freely tunable momentum compaction factor from $2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ to $6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$. In comparison with the baseline design which uses the theoretical minimum emittance arc cells, the advantages of this design are: freely tunable momentum compaction factor; smaller number of quadrupole and sextupole magnets; larger dynamic aperture; simplified layout and lower cost. The design principles and analysis techniques used in this paper to change the momentum compaction factor by a large amount while keeping a very low emittance and large dynamic aperture are very important for the ILC damping ring; at the same time it could be very useful for any high bunch density storage ring.