Orbit feedback system for maintaining an optimum beam collision

Abstract

An orbit feedback system around the interaction point (IP) has been developed and successfully employed at KEKB for more than 6 years. The purpose of the system is to maintain an optimum geometrical relationship of orbits of two beams at the IP and to prevent a luminosity degradation due to orbit drifts. The feedback system is based on orbit measurements around the IP rather than a direct measurement of the luminosity. Owing to the system, the luminosity degradation due to the orbit drifts is suppressed to around or less than 1%.

Electron beam optics and trajectory control in the Fermi free electron laser delivery system

“…A trajectory control to a 5 m level is achieved with the implementation of theoretical response matrices. The adoption of theoretical matrices for the entire machine, versus standard methods that are based on the measurement or postprocessing of empirical response matrices [17][18][19][20], speeds up the process when sizable changes are made to the lattice, avoids particle losses that may occur during the computation of experimental matrices, and confirms the agreement of the experimental magnetic focusing with the model.…”

Interaction-point phase-space characterization using single-beam and luminous-region measurements at PEP-II

“…In the vertical, the much smaller beam size leads to considerably tighter crossing-angle tolerances, not only to ensure the geometrical overlap of the ribbon-like beams, but mainly because the deleterious impact of the beam-beam interaction rapidly grows when the vertical crossing angle exceeds ∼ 10 µrad: a similar sensitivity has been observed in KEKB [19]. Figure 48 displays the measured mean vertical boost angle y B and the vertical luminous tilt y L , whose difference is consistent with zero considering the measurement uncertainties.…”

The Largest Accelerators and Colliders of Their Time

“…• In the case of the crossing angle at KEKB, the horizontal offset at the IP was controlled by looking at the vertical beam size measured by the interferometer [158]. • Tuning of the local coupling and dispersion at the IP by making offsets of orbits at sextupoles near the IP [149].…”