Simon, Akutsu, Miyo

We released WAB from support flame, detaching the triangle shape plate for fixing WAB, and checked alignment using laser leveler as an attached image (pit_alignment.png). Because this checking is for pitch and roll rotation of WAB, not for yaw. We'll also check yaw rotation tomorrow. However as far as we seen with our eyes, alignment was good.

After checking the alignment, we centered the Oplev beam at the QPD again, and check spectrum. 
First, some difference between fixed WAB to the support flame and free WAB are shown in attached image (fixfree.png). Upper graph shows that there are no big difference without 20 Hz region. A peak in 20 Hz appeared after releaseing. Is this derived from some mechanical structure in WAB suspension? Basicaly we just remove a support flame, I hope that there are no mechanical change in Optical pylon.

Second, some difference between free WAB without wind cover and free WAB with cover are shown in attached image (cover.png). Thanks to wind cover, spectrum around 1-10Hz was getting better. On the other hand, spectrum around 40-70Hz was getting worse. Because wind cover is attaching to cryostat to protect wind the stage of Oplev gets some noise from cryostat.

There are some peak when inject a shake to the optical table under WAB along with vertical direction (shake.png). I think Akutsu-san have some information about mechanical peak.