In the hummering test and acoustic injection before/after the O3GK, we found the bellows between IFI and IMC were most effective to DARM but chambers and their legs were not effective.
So I guess the most serious ghost beam was coming back from the down stream to these bellows directly, not hitted any object inside the IFI chamber.

In the picture took from IMM chamber side today, we can see the aluminium hoil directly in the marked space.

Other pictures I took are here.

Kokeyama, Sato, Nakano(remote), Kenta

Today, We looked into the ghost beams by reflected beam from PRM in IFI chamber. We found the 2 ghosts (rGB1, 16) and the some beams that we don't understand where they come from.

What we did

• We set the power of input beam 5 W, and aligned PRM, we investigated the ghost beam by reflected beam from PRM based on Tanioka-san's data as yesterday investigation. 
• As a result, we found two ghost beams (rGB 1, 16). We confirmed that they were indeed the ghost beams from the reflected beam, by blocking the beam reflected from the PRM only.
• We also found some ghost beams between the MCF and IFI chambers, but we could not determine where they were coming from .
• I attached a paint that summarizes the ghost beams we've found in our research so far.

Todo

• investigate where the unknown ghost beams come from again.
• In particular, we are somewhat concerned about the shape of the transmitted beam from the STM2, so we will re-examine the area around the STM2. In some cases, the STM2 may be replaced.
• Also, we found that the clamping of some optical instruments is not good, so we re-clamp them.

Some minor notes:

We connected the picomotor LAN cable back to the MCF pico driver. It is back online.

MC suspensions seemed to jump at ~7am today. (Did we have EQ?) They were recovered using both pico and coil outputs.