A MODIFIED QBA OPTICS FOR LOW-EMITTANCE STORAGE-RINGS

A modified quadruple bend achromat (QBA) optics as a lattice for a low emittance storage ring is presented. The novel feature of this lattic e is the use of horizontally defocusing bending magnets with different bending angles to keep the radiation integrals low. A realistic stora ge ring with six achromats, non-dispersive straight sections of 4.6 m each and a total circumference of 124.8 m is studied. At an energy of 2.5 GeV the emittance yields only 20 pi nm rad. The chromaticities and the sextupole strengths are moderate, the dynamic aperture is large a nd the momentum acceptance is more than +/-9% relative. A similar 3 Ge V storage ring with 12 achromats and a circumference of 300 m yields a n emittance of 3 pi nm rad. Possible applications and extensions of th e QBA structure for diffraction limited storage rings are discussed.