Improving the Performance of an Orbit Feed-forward Based on Quadrupole Motion at the KEK ATF

The high luminosity requirement for a future linear collider sets a demanding limit on the beam quality at the Interation Point (IP). Even the natural motion of the ground could misalign the quadrupole magnets to such an extent that the resulting dipole kicks would require compensation. The novel technique described in this paper uses seismometers to measure the positions of the quadrupole magnets in real time and a kicker to counteract the effect of their misalignment. The prototype system deployed at the Accelerator Test Facility (ATF) at KEK in Japan has already demonstrated a reduction in the pulse-to-pulse vertical position jitter of the beam by about 10%. Based on the observed correlation of the beam position to the quadrupole positions the maximum possible jitter reduction from such a system is estimated to be about 25%. This paper details the latest improvements made to the system with the aim of achieving this limit.