  A double kicker system which extracts the ultra-low emittance multi-bunch
beam stably from ATF damping ring was developed. The performance of the system
was studied comparing an orbit jitter with single kicker extraction in single
bunch mode. The position jitter reduction was estimated from the analysis of
the extraction orbits. The reduction was confirmed for the double kicker system
within a resolution of BPMs. More precise tuning of the system with a wire
scanner has been tried by changing a beta function at the second kicker to get
more reduction of kick angle jitter. The results of these studies are described
in detail.
