Abstract:

Touching of the suspension might start from May 6, which is earlier than the last day when we could lock PRFFPMI (May 7).
Since the drift of the photosensor signals due to cooling is large, it is hard to say suspensions drift to which direction.

Detail:

To investigate where is the suspisious touching point, I checked ITMX photosensor signals.
Figure 1 and 2 show the time series data of MN and IM photosensor signals (euler coordinate), respectively.

In both cases, slope of the drift changed at the left T cursor (around 19:00 of May 6).
It means suspension might be touched each other even May 7 (the last day wee could lock PRFPMI).
Also, we can see large jump of MNT photosensor signals around 2025/5/9 0:30 JST (right cursor in fig1) while the other DoF doesn't change.

Since there is a large drift due to the efficiency change of photosensors (LED light emmission efficiency increases when temperture becomes low), it is difficult to say where is a suspicious position for touching.

Images attached to this report

33772_1747183798_Screenshot from 2025-05-14 09-46-50.png

33772_1747184869_Screenshot from 2025-05-14 10-07-06.png

Comments to this report:

shinji.miyoki - 19:31 Friday 16 May 2025 (33805)

I found a correlation between the change in VIS-ITMX_MN_DAMP_L_INMON that was pointed out by Ushiba-kun and the sudden temperature reduction of IX_4K_REF4_HEAD and IX_4K_COOLING_BAR_REF2.

So, some heat shock caused this change.

In addition, the cryocooler, which was turned off today, seemed to be connected with the REF4 cooling bar, not REF2. So, should we change the cryocooler that should be turned off?

Images attached to this comment

33805_1747385069_Screenshot from 2025-05-16 17-43-52.png

33805_1747386122_Screenshot from 2025-05-16 18-01-26.png

takahiro.yamamoto - 20:41 Friday 16 May 2025 (33807)

Note that following is EY situation not IX.

Current (wrong) channel assignment:
- EY-No.1 #Ch3 = K1:CRY-TEMPERATURE_EY_4K_COOLING_BAR_REF4
- EY-No.1 #Ch6 = K1:CRY-TEMPERATURE_EY_4K_COOLING_BAR_REF2

Correct channel assignment:
- EY-No.1 #Ch3 = K1:CRY-TEMPERATURE_EY_4K_COOLING_BAR_REF2
- EY-No.1 #Ch6 = K1:CRY-TEMPERATURE_EY_4K_COOLING_BAR_REF4

Is it possible that a same thing is happening in IX (IY and EX)?

shinji.miyoki - 21:23 Friday 16 May 2025 (33808)

> Is it possible that a same thing is happening in IX (IY and EX)?

I guess YES in IX, however, No in IY and EX, I confirmed.

Although I expected that the IX_4K_COOLING_BAR_REF2 temperature would increase because of the IM heatup, no changes at all. So we need to turn off the REF4 cryocooler.