DIAGNOSTICS AND OPTIMIZATION PROCEDURES FOR BEAMLINE CONTROL AT BESSY

Experimental requirements at a 3rd generation light source translate to very high demands on storage ring stability, insertion device control and monochromator performance. Especially the “scanning mode” of combined undulator and monchromator movement is very demanding. Experimental Physics and Industrial Control System (EPICS) based software provides the interface to control the elements of the new BESSY-Beamline at the UE112-low energy Plane Grating Monochromator (PGM). The performance of the monochromator control system has been improved by evaluating waveform records for diagnostics and optimization of position feedback, servo data of the monochromator as well as the complex motions of helical undulators. Algorithms have been implemented for the determination and minimization of quadrature errors of the encoder system (RON905, Heidenhain) that runs on a Linux based EPICS Soft-IOC. A new servo algorithm has been designed to run on a motion controller (PMAC2-VME, Delta-Tau) for robust performance and proper compensation of non-linearity characteristics of in-vacuum piezo motors (Nanomotion).