Ushiba-kun also reported on the sum signal oscillation of Oplevs after this event.

I checked the VIS-EYMX_TM_OPLEV_{LEN,TILT}_SUM_OUT_DQ for the last 1 day (Fig.1) and 10 days (Fig.2) and 30 days (Fig.3). Actually, they have power oscillations.

About 10 days ago, the oscillation itself seemed to start and became remarkable from the last evening. It could be because of H2O freezing layer effect on AR windows on 2-layer radiation shields and/or the AR surface of ETMX.

Fig.4 shows with ETMX IM temp. This seems to show the oscillation is triggered by the IM temp timing to reach around 20K.

If the source of this oscillation is H20 layer on the AR surface of ETMX, why it can be regarded to start when the IM temp reached ~20K? It should start much before.

So, this is due to Not H20 but N2 or other?? However, H20 is the super main component of the residual gas in the EXC area.

We need deeper understandings.

[miyoki, k.tanaka]

>>The air cooler at EXC was set from weak to strongest mode. I turned off the Sunrise heater (1.2kW) at EXC and the Delonghi heater (900W) at EXV.  

The second air cooler at EXC1F was on at strong mode. Also, we opened the door of the EXV area to introduce cooler air inside around 15:30.

The Sunrise heater was operated again at 600W at EXC.

Fig.1 shows that TMPs pumping is now overcoming the outgassing from the radiation shield duct.

Fig.2 shows that oplev outputs mean also decreased (2 days data). Is the reduction related to the vacuum level or is some loss increasing due to molecular(N2 or H2O) adsorption? Of course, increasing the vacuum level again can answer it, but we don't want to do such thing now. The pressure moved the structure of the suspension and actually, ETMX moved?

Attached figure shows 2-day trend of temperatures of several places.
Around 17:00 JST on 12 of Aug., sudden increase (~30 K) of cold head temperature happened (top right graph in fig1).
Then, cooling bar and duct shield were gradually warmed up.

Currently, cold head temperature was gradually decreased and consequently cooling bar and duct shield seem starting to be cooled again.

3 days data (Fig.1) and 35 days data (Fig.2) from now for the vacuum level around EXC and OPLEV_SUM_OUTs. 

Although the oscillation amplitude became smaller, the absolute mean value was drastically smaller than the accident. Is it better to check the reflected beam scattering status? How about the GR/IR transmitting beam power? If these transmitting beam powers are OK, should we suspect the frosting on the windows on radiation shields?

Ah, seems the oplev windows would be frosting, only judging from the time trend of the oplev sum you showed, though. Maybe scattered light due to the frosting would be visible onsite. Hope that the oplev sum reduction would stop within an allowable range.

4 days data (Fig.1) from now for the vacuum level around EXC and OPLEV_SUM_OUTs. 

The drastic Oplev SUM reduction seems to be stopping. However, a slight oscillation is visible?