The Lattice Design of the LEP Electron Positron Accumulator (EPA)

In large accelerators, the lattice cell is generally made as simple as possible. Special requirements are then fulfilled by appropriate insertions (dispersion suppressors, low ß schemes, wigglers, etc.). In small machines, where space is limited, the lattice cell itself has to deal with all the machine constraints and requirements. The lattice design method developed consists of splitting the superperiod into specialized sections. Each section is built up to fulfil some of the basic requirements, then matched to the neighbouring sections. The best parameter values are deduced from systematic variation in the analytical expression of the corresponding beam transfer matrix. Applied to the LEP E¿lectron P¿ositron A¿ccumulator (EPA), this method was very efficient in optimizing a large number of constraints.