Beam steering and stabilizing systems: Present status and considerations for the future

Instability of the stored beam orbit, with its deleterious effects on synchrotron radiation beam stability, has compelled the development of photon beam position monitors and closed-loop orbit correcting systems at SSRL and other facilities. The vertically steering servo system used presently at SSRL can stabilize the beam to the 10 μm level within the single photon position monitor used for each beam line, but extending this level of stability to all critical points along the beam line will necessitate a two-monitor, two-loop servo system. Such a system is being developed for beam lines at PEP. Closed-loop steering for SPEAR undulator beam lines has not been regularly successful because the position monitor signal is degraded by bending magnet radiation. The need for new types of position monitors, horizontal as well as vertical, and the eventual need for closed-loop horizontal steering on undulator beam lines, is evident. Requirements needed to achieve the 10 μm or better stability, demanded for the new generation of low emittance and small aperture sources, include improved stored beam and photon beam position monitoring, a higher degree of mechanical and electrical stability of storage ring and beam line components, and optimized ring lattice designs. (orig.)