[Hirata, Takahashi-san, Ikeda-san]

We checked PR3 mirror height. It was higher than nominal height, so we lower the mirror.

• The reference is on the pillar at +X,+Y side of the chamber.(pic.1)
• We used 2 laser levelers and ruler.
• We checked stands off and scratch lines which are on the HR side recoilmass frange.
• -Y side and +Y side stands off are both higher than laser leveler.(pic.2:-Y, pic.3:+Y)
• -Y and +Y side scratch lines are about 1.5mm higher than laser leveler.(pic.4:-Y, pic.5:+Y)
• We lower the SF keystone 2100um by fishing rod.
• -Y side is about 0.1mm lower than laser leveler. +Y side is 0.25mm higher than laser leveler.(pic.6:-Y, pic.7:+Y) It means mirror center is 0.125mm higher than nominal, but it's within measuring error.
• Pic.7 and 8 show the stands off.(pic.8:-Y, pic.9:+Y)
• We checked earthquake stops for recoilmass. They are not touching to the recoilmass.

Now PR3 mirror is at the nominal height.