Low periodicity lattice for third generation light sources: avoidance of dynamic aperture reduction by sextupole compensation

We propose a lattice consisting of many arcs containing combined function (or usual) magnets and focusing (and defocusing) quadrupoles separated by identical optical channels consisting of either one, two or more dispersionless straight sections. A significant advantage of such a design is the ability to separate the functions of the arcs and the straight sections. The periodic part of the arcs is a pseudo-second order achromat joined with the straight sections through a dispersion suppressor and it differs from the second order achromat by non-zero chromaticity. The lattice has one focusing and one defocusing family of sextupoles located on the periodic part of the arc. Varying the chromaticity of arcs by sextupoles and the chromaticity of straight sections by quadrupoles and keeping the total chromaticity equal to zero, we can modify the tune shift at any working point