Quadruple-bend achromatic low emittance lattice studies

A quadruple-bend-achromatic (QBA) cell, defined as a super cell made of two double-bend (DB) cells with different outer and inner dipole bend angles, is fo und to provide a factor of two in lowering the beam emittance of electron synchrotron light sources, the ratio of bending angles of the inner dipoles to that of the outer dipoles is numerically found to be about 1.5 to 1.6 for an optimal low beam emittance in the isomagnetic condition. The QBA lattice provides an advantage over the double-bend achromat or the double-bend non-achromat in performance by providing some zero dispersion straight-sections and a small natural beam emittance. A lattice with 12 QBA cells with a preliminary dynamic aperture study serves as an example.