  The wire scanners are used for a measurement of the very small beam size and
the emittance in Accelerator Test Facility (ATF). They are installed in the
extraction beam line of ATF damping ring. The extracted beam emittance are
ex=1.3x10-9 m.rad, ey=1.7x10-11 m.rad with 2x109 electrons/bunch intensity and
1.3GeV energy. The wire scanners scan the beam by a tungsten wire with beam
repetition 0.78Hz. The scanning speed is, however, very slow(~500um/sec). Since
the extracted beam is quite stable by using the double kicker system, precision
of the size measurement is less than 2um for 50 - 150um horizontal beam size
and 0.3um for 8 - 16um vertical beam size. The detail of the system and the
performance are described.
