Yutaro, Koseki, Yuya, Yoshinori,

As mentioned in klog#6183, we adjusted PRM in pitch and yaw. Yaw adjustment was done successfully without any problem though Pitch adjustment was not.

= What we did (for pitch) =
 - Once we tilted IM in pitch by the picomotor using main beam as the reference, and then we revisited a setting before this tilt adjustment since we found a few issues to be checked deeply.

= Issues =
1. When we tilted the IM in pitch by the picomotor along with the main beam we found one of the IM-V OSEMs went outside the linear range as we expected; even if we injected noise, we could not found any oscillation at the OSEM (IM-V2). Except for this IM-V2, it seemed that IM-V3 was edge of its linear range. IM-V1 also might be like IM-V3, although the sensor could sense its motion successfully when a noise was injected.

2. We measured some transfer functions for the health check before/after the IM was tilted in pitch. We then found that in the both cases we missed one resonance peak in the vertical transfer function like SF-GAS to SF-GAS. FYI, BF-GAS and IM-V did not oscillate much when we were measuring transfer functions such as SF-GAS to BF-GAS, SF-GAS to IM-V.
From this issue, we tried inputting a step (like 3000 counts from COILOUTF w/o ramp time) to SF-GAS, BF-GAS in order to check if they were properly suspended freely. Then we found SF-GAS oscillated as we expected when the step was input though, BF-GAS did not; When we input the step, BF-GAS height was slightly changed without oscillation.

Consequently, we started to suspect THE BF-GAS KEYSTONE WERE TOUCHING TO THE RING.

Even though it seemed the BF-GAS keystone were touching gently, since when we touch the IM (accidentally), BF-GAS oscillated indeed (I did not measure the amplitude though). However, we have to check the condition of BF.

= Next step =
- For issue-1, we will refine the positions of vertical OSEMs, especially IM-V2 and IM-V3 after doing the tilt adjustment again. We might change the position of IM-V1 as well if we find problem after tilting. this time, we will use the optical lever as the reference.

[NOTE] WE WILL DO THIS ADJUSTMENT IF WE ARE ABLE TO STAND ON THE OPTICAL TABLE. IF NOT, WE WILL WANT TO AVOID THIS ADJUSTMENT AT ALL SINCE THE ACCESS TO THE OSEMs ARE PRETTY BAD, AND THE PROCEDURE WILL BE DANGEROUS.

- For issue-2, we will want to check the followings:
  -- BF-body is not touching to the EQ-stops?
  -- BF-body is not touching to the secondary coils of BF-LVDTs?
  -- BF-keystone will be able to oscillate when we adjust the position by the fishing rod on BF?
Then if we cannot suspend the BF-GAS and we want to have enough vibration isolation performance, we will have to open the top-chamber for the inspection since we cannot observe anything around the BF from the side-door.

- For all the PR suspensions, we have to check if they are suspended properly, i.e., we have to check the transfer functions (and spectra etc).

= Note =
- During the transfer function measurement, we found it seemed the coil polarity of IM-V2 and IM-V3 was not correct. The current setting is:
IM-V1: +1 / IM-V2: -1 / IM-V3: -1 / IM-H1: +1 / IM-H2: +1 / IM-H3: +1