ACTIVE OPTICS STABILISATION MEASURES AT THE DIAMOND STORAGE RING

The Diamond storage ring is currently operated with 26 insertion devices (IDs), including 14 in-vacuum IDs, 7 APPLE-II type helical undulators and 2 superconducting wigglers. Differences in the design, construction and operation of these devices, combined with different Twiss parameters at the source point, mean each has a different impact on tune stability and beta-beat. In turn, these parameters affect the on and off-momentum dynamic aperture and ultimately impact on the injection efficiency and lifetime. Another source of optics variation arises from the coherent tune shift with current, which when injecting from zero current causes the tune to span the available good-tune region. In this paper we discuss the difficulties of operating the Diamond storage ring in top-up mode with these effects, and present the various measures taken to stabilise the storage ring optics.