Speaker
Description
A fast orbit feedback (FOFB) system is being developed for the upgraded Advanced Photon Source (APS) where beam sizes of 13 µm horizontally and 2.8 µm vertically with a target unity-gain bandwidth of 1 kHz. The system uses a distributed network of 20 feedback controllers to compute orbit corrections at 22 kHz, utilizing 560 Beam Position Monitors (BPMs), 160 fast correctors, and 160 slow correctors per plane. A Bunch Lengthening System (BLS) has been installed at APS to enhance beam lifetime, with the synchrotron tune ranging between 100 and 650 Hz, overlapping the FOFB closed-loop bandwidth.
Building on the FOFB framework, we developed a feedback algorithm that uses horizontal beam position measurements at dispersive BPMs as input and the low-level RF (LLRF) phase as an actuator. Experimental results and simulations demonstrate that this approach effectively corrects synchrotron frequency oscillations while operating concurrently with orbit feedback to damp betatron oscillations. To unify the operation of fast and slow correctors in a single algorithm, we implemented two methodologies: (1) modifying the response matrix to ensure orthogonality between slow and fast corrector subspaces, and (2) employing a multi-variable mid-ranging control strategy leveraging the cross-directional nature of the FOFB system. These unified algorithms were validated through experiments and/or simulations using a prototype FOFB system with 16 BPMs, 4 fast correctors, and 4 slow correctors. In addition, we demonstrated >1 kHz closed-loop bandwidth in beam studies with the prototype FOFB system. This presentation will summarize recent advancements, experimental and simulation findings, and ongoing efforts in orbit feedback control at APS.