K. Tanaka, Akutsu

Abstract

Installed black shields for the MCi and MCo suspensions (see also this, this, and this) as shown in Figs 1, 2, and 3. Never touch the fragile black surfaces!!!, in particular the inner knife edges of the apertures!! A so tough work that this is sure to be one of the top six tasks I never want to do again for KAGRA.

Details

As the parts for the black shileds were packed in several transporting canisters (also specially designed for these shields) accordinng to their sizes (Figs. 4 and 5), we started by sorting those parts for each of the MCi, MCo, and MCe suspensions. Then we installed them on the base plates that were installed the other days (see for example 16497.) To increase the workability, we closed the laser shutter in the PSL room after we confirmed the IMC flashing was ok.

When we were working for MCi, we only monitored the MCi oplev, but just after we attached one of the shileds for MCo, we found that the MCo oplev yaw had been rapidly drifted about -160 urad! Then we stopped the installation, and opened the shutter in the PSL, and found that the IMC flashing was not nice (seemed in very higher order modes). So we pico-ed the MCo yaw, and the other DoFs that were drifted, then the IMC flashing recovered. So we again closed the shutter.

Immediately after we restarted the installation work for MCo, however, we noticed that the MCo oplev yaw changed rapidly +160 urad or more this time! Hmmm... this time we did not stop for pico-ing, and continued the installation work until the last shield for MCo. Then, opened the shutter, and found the IMC flashing became bad again, and so pico-ed the MCo yaw and the other drifted DoFs for MCi and MCo, and the IMC flashing recovered again. Oplev is nice.