I remeasured error signals of WFS on Yarm ASC.

The setpoints of IY and EY were set to the same values as before.
The results for both days were plotted in the same figure.
 

I remeasured the error signal for the third time.

This time I adjusted IY and EY set points to match TMSY QPD position on 12th before the measurement
and also measured TRANS power.
My brief consideration is as follows.

• According to result of TRANS power, TRANS power is max on about 0 point of error singal.
  (If the maximum amount of transmitted light occurs at a position outside of the reference 0, it is possible that the process of aligning in the first ADS is not aligning enough globally.)
• In the case of linear match of the three times results, the offset changes.
• If it is not a linear error signal, it varies from day to day; It's hard to get reproducibility.
  （The sensitivity of the WFS may be poor??）

This consideration needs more thought.
I took pictures of the beam spot position with T-cam and will summarize them later.

I measured error signals two times.

Since the PIT error signal was not reproducible, I adjusted the IY and EY operetive set points to match the TMSY beam position and checked it.
The first was aligned with the beam position on the 14th and the second with the beam position on the 11th.
I post the first and second results overlaid and the results of all of them overlaid.

I confirmed the transmission power and reflection power for these results.

I compared the results of error signals measured five times in PIT direction and three times in YAW direction.
PIT→the 11th, 12th, 14th, first of 17th,  second of 17th (klog23600 )
YAW→the 11th, 12th, 14th (klog23569 )

About REFL power

• REFL power on 14th and 17th was about 0.045-0.046. I checked the angle of HWP and it was not changed. (Figures)
  There was a possibility of clipping in the process. (klog23788)
• [ITMY and ETMY in PIT] The results in PIT direction on the 14th and 17th are almost the same, but it is unclear whether ASC error signal has been detected because of possible clipping.
• [ITMY in YAW] The 14th results of WFS1 in YAW direction of ITMY could be seen to go out of range.

About TRANS power

• [ETMY in PIT and YAW] TRANS power was unstable when measured ETMY on the 11th, possibly caused because it took some time since ADS was turned off (since TRANS power was Max).

About of Offset

• [ITMY in PIT] Offsets appeared in the results on the 11th and 12th, but it is not known from the time series whether they are the same on each offset of the two days. -> 
• [ETMY in PIT] Offsets also appeared in the results of ETMY_PIT on the 11th and 12th, but trans power of the 11th was unstable.　
• [ITMY in YAW] Offsets in the results on the 11th and 12th were linear functions and NO offset when trans power is Max. The results for the 14th were partly out of range, but the results for all days were consistent within the range, the movement is typical of an error signal.
• [ETMY in YAW] The results of WFS1 were also linear functions and NO offset when trans power is Max. And the results of the all-day WFS1 were consistent, but trans power of 11th was unstable and refl power of 14th was too small.  So it is difficult to determine exactly what happened. 

Summary and future plan

• Results on the 14th and 17th could have been clipped from refl power.
• Error signals in YAW direction are likely not to appear with offsets.
• Error signals in PIT direction appear with a non-constant offset from the results of the 11th and 12th. 
  ->Before turning on the Yarm ASC, it might be better to introduce a process such as turning on ADS and measuring and inserting WFS offsets when ADS is stable.

Notes    I could turn on ASC without offset in this work(klog23758). Offset could change on different days, so is not known. One way to check is to try turning ASC on again with and without OFFSET. (We will consider whether we do this.)
(Sorry for the late analysis.)

Hirose-san,

>Results on the 14th and 17th could have been clipped from refl power.

I don't believe this is due to clipping. If the power reduction of REFL is due to clipping, It means over 70% of beam was clipped at that time.
In that case, it is probably difficult to stably lock YARM but it doesn't seem the case because you could do some measurements.
Since we have HWP trouble several times (for example, please see klog23785), it might happen that REFL HWP setting was changed even though epics value of HWP angle was the same.
So, it is better to check the trend of HWP angle and REFL power and confirm that it is really the same condition.