Fast Orbit and Bunch-by-Bunch Feedback
The concentration of almost 50 experimental stations in BESSY’s experimental hall increases environmental noise (acoustic, electronic), thereby adversely affecting the resolution and stability of measurement setups. To allow BESSY to maintain its top ranking within the SR-facilities this challenge must be met. A joint task force of the accelerator and experimental divisions are identifying the sources of electron and photon beam instabilities in order to improve resolution and stability.
An important goal is a significant improvement of the machine stability. Measures to be introduced on the storage ring side include Top-Up operation for improved thermal stability and a fast orbit feedback system to cope with stochastic disturbances of the electron beam created by ground motion and changing operating conditions of insertion devices. With the proposed installation of small-gap in-vacuum insertion devices the impedance of the ring increases. This lowers the beam instability thresholds and places higher demands on the existing bunch-by-bunch feedback systems operational at BESSY II. Within the renewal program the old digital longitudinal and the analogue transverse feedback system will be replaced to improve the performance of the ring under much more challenging conditions. For example the injection transients of the stored beam during Top-Up injection experiments can be further reduced with a new and strong digital transverse feedback system.
On the beamline side, the diagnostics will have to be improved to precisely locate sources of instability such as ground vibrations or cooling water turbulences. Active and passive shielding measures, e.g., soundproof hutches or active damping systems along the beamline are under construction or planned.
