Overview of Some Feedback & Control Systems at Synchrotron Soleil
Résumé
This paper gives an overview of some feedback & control systems in Synchrotron SOLEIL that are in use or in development today. Electron Beam stability is something that is being addressed in several SOLEIL applications; Fast Orbit Feedback is a multi-input multi-output control system made to stabilize beam position perturbations with slow and fast corrections. In addition, active RF cavities are used to maintain stable beam energy & spread as well as keeping electron density even throughout the storage ring. Beam stability also comes from feedforward non-linear control in particle trajectory compensation on both sides of electromagnetic undulators. On beamlines, multi-actuator piezos or pneumatics are used to regulate photon flux to keep within detector operating range; a method to maximize the photon flux while keeping detector below damage thresholds. Currently in development at the sample stage level, the Nanoprobe Project (collaboration MAXIV & Soleil) focuses on sample stabilization during step- & fly- scans which is realized through multi-axis nano-positioning with high- & low- frequency closed-loop control implementing interferometer feedback &/or compensation tables.