  The beam test for the Shintake monitor succeeded in measuring signal
modulation with the laser interference fringe pattern in November 2009. We have
studied the error sources, and evaluated the systematic error to be less than
30% for 1 minute measurements. This paper centers on the evaluation of the
Shintake monitor performance through analyzing beam tests deta. Most systematic
error sources are well understood, enabling accurate measurement of the beam
size when it reaches 37 nm.
