Quasi-isochronous storage ring for enhanced FEL performance

A compact storage ring is designed to be used as driver for a free electron laser (FEL). This ring can be operated very close to zero momentum compaction factor (α) to increase the electron density and thus the gain of the FEL. In order to control α with zero dispersion in the straight sections we use an inverted dipole located between the bending magnets and 4 families of quadrupoles. By using 3 families of sextupoles we can control the 2 transverse chromaticities and 2nd order momentum compaction. We find that the ring has sufficient dynamic aperture for good performance.