Optimization of harmonic sextupoles in Indus-2 electron storage ring

Dynamic aperture is one of the deciding parameters of the low emittance electron storage ring performance. Sufficient dynamic aperture is required to reach higher injection efficiency as well as good beam lifetime. In low emittance storage rings, dynamic aperture is limited mainly by the chromaticity correcting sextupoles, which is enhanced by introducing more sextupole magnets in the dispersion free straight section of the ring lattice, known as “harmonic sextupoles”. In Indus-2 storage ring lattice also, there is a plan to accommodate harmonic sextupoles. In this paper we present, how the strength of harmonic sextupoles is optimized for suppressing resonance driving terms up to third order, those are responsible for reducing the dynamic aperture. In such optimization, one of the main difficulties is to choose the optimal weight factor for the different resonance driving terms. We evolved an approach for assigning the relative weight to the various resonances driving terms which is found to be working very well for Indus-2 storage ring. Following this approach, the strength of the harmonic sextupoles is optimized and there is a reasonable enhancement of dynamic aperture with harmonic sextupoles for two different working points of Indus-2.