I remeasured the TFs of IM stage after the recovery work of PRM today (detail will be posted later, hoefully).
Holizontal TFs seem better but IMV TF (fig1) is obviously strange.

We will again check the situation below BF tomorrow but it might be due to the upper stage.
In that case, it is hard to access from the lower flange, so it might be necessary to open the top chamber of PRM.

Anyway, we need to check the lower stage tomorrow morning to confirm there is no problem at IM and TM stages.

Abstract:

PRM BF GAS seems rubbing somewhere when PRM GAS key stone is going to lower.
Also, SF GAS might have a problem but not confirmed yet.

Detail:

After visual inspection in the morning (it will be posted later, hopefully), I checked the GAS filters motion.
Figure 1 shows the time-series data when moving BF GAS filter.
As you can see, BF GAS signals move only slightly if we applied DAC output betwen -30000 and +10000 cnts while GAS can move several hundreds of micrometers when applying DAC output over 10000 cnts.

Also, I checked SF GAS filter motion by applying DAC output to SF GAS actuator (fig2).
SF motion is much smoother but there are several jumps during the motions.
I have no idea this isrelated to strange response of BF GAS, so this phenomena also needs to be investigated.
 

Before the health check of 28551, I gently touched the PRM suspension to inspect if BF spring's movability would be soft or hard. According to 28547, the BF vertical spring now would be 6-7 Hz, which one should feel hard. First of all, I felt that the vertical softness of SF spring; most of the suspended parts move at once, so the SF might be kind of ok. But for the BF spring, I felt somehow hardness by touching IM mostly vertically. When touching too much, responded was SF sping, not BF spring. So the BF spring's hardness would correspond to this 6-7 Hz resonance.

After the recovery work reported in klog28595, I measured the all TFs of PRM for the health check.
Though I haven't checked all TFs, SF and BF GAS TFs (fig 1 and 2) seem strange.
Somehow peak appeared at 4 Hz, which cannot be seen previously.
Also, TF around the second peak (~0.7 Hz) couldn't be measured well.

Further repairement work is necessary.

I checked all TFs that were measured yesterday (fig1-33).
Though all TFs of SF, BF, and IM stages seem strange, IM H2 TF (fig22) shows almost no response.
So, it is very likely that IM hits somewhere around H2 OSEM.

I measured TFs of PRM again after recovery work yesterday (klog28694).
Suspension condition seems much helthier but IM V3 TF has smaller gain than before (fig1).
It seems due to OSEM position is close to the edge of linear range, so it is necessary to fix.

[Hirata, Ikeda, Washimi, Takahashi]

We checked the maximum outputs of the IM V OSEMs. The outputs were as follows when the OSEM bodies were pulled up maximum.

We adjusted the OSEM position to around half of the above values.

I checked all TFs of PRM.
All TF seem fine though resonant frequency of GAS filter is shifted slightly.

Following is an additional note, which is not problematic.
1. BF coil DoF measurement have a larger gain than before because of the calibration factor update (klog21311 and klog21315).