Aso, Ushiba, Hirose

This is continued to klog24705.

We locked PR2 of BPC and tried to do centering of PR3. But these loops are taken many times like hours order.

details

• We tried a BPC for PR2 from POP back to PR2 with PR2 oscillating.
  The error signal did not go to zero in this PR2 control. Also, the transmission power dropped during the process.
  When turning off the control, a sign-reversed average of the PR2 error signal was inserted into the offset.
  Fig1: the timescale when PIT ON, Fig2: the timescale when YAW ON (after PIT was null on),
  Fig3, Fig4: PRCL power spectrum when PIT or YAW
  /users/Commissioning/data/PRCL/2023/0410/SPE_PR2BPC_{PIT,YAW}_20230410.xml 
• We oscillated PR3 and fed it back to IMMT1 from the PD signal of the POP. 
  It is necessary to center PR3 after centering PR2. Also, due to the large beam spot on PR3, we tried to center it.
  Fig5: Filter MEDM screen where its filter is set,
  Fig6, Fig7: The demodulation phase was measured from the transfer function of the oscillator signal and the PRCL length signal.
  /users/Commissioning/data/ASC/2023/PRFPMI/BPC/PR3_demophase_{pit,yaw}.xml
  When only the PIT was turned on, the POP signal was lowered. The transmission power of both arms went up. The max transmission power of Y-arm is 150, and the max transmission power of X-arm is 130, which is unbalanced between X and Y arms. The sign set in the PIT seems to be correct.Transmission power was frustrated after turning on the ASC, but the average did not move slightly.
  Fig8: the timescale when BPC ON
• We will try to control PR3's BPC (return to PR2) without PR2's BPC control.