Yoichi, Takahiro, Kiwamu, Ayaka (on the phone)

Today we found that the PR3 mirror having pitched down a lot after an accidental power-cycle of the IO chasis for the PR3 suspension controlloer.

We successfully pico-motored the IM stage and brought the TM back to the oplev range.

However, on the other hand, we found that the relative pitch angle between the IM and TM stages have shifted by roughly several mrad.

While Yamamoto kun will report on the digital part of this story, we here report on the recovery process and mechanical part of the issue.

[Some details]

• All the LVDT signals were found to be almost zero counts at the ADCs.
  • Later, we found that this was due to the modulation source which had been set to something incorrect presumably due to an accidental power-cycling.
  • With help from Shoda san, we set the modulation source back to how it is supposed to be.
  • This fixed the issue -- the LVDTs started showing some reasonable digital counts.
• Also we found that the Oplev return light was missing the QPD.
  • Visually inspecting the QPD, we determined that the return beam was too high by approximately 1 cm on the QPD, corresponding to an angle shift on the order of 10 mrad.
• Both IM OSEMs and Oplev light consistently showed large pitching to the same direction.
• Consulting with Shoda san, we moved the IM pico motor mainly in pitch to recover the TM angle so that the oplev return beam comes back on the QPD.
  • Strangely, we noticed that the IM needed to overshoot the leveling point in order to recover the TM angle.
  • When the IM was almost back to the leveling angle, the oplev light was still too high by roughly several mm on the QPD.
  • This made us conclude that the relative pitch angle between the IM and TM stages have shifted by roughly several mrad.
• We kept going with the picomotor and got the oplev beam back on the QPD.
  • Although, as expected, this pushed one of the vertical IM OSEMs to a point where it reads only a few 100 counts.
  • This means that the OSEM flag is too deep inside the shadow sensor.
  • This must be fixed by re-adjusting the OSEM position.
• We asked Shoda san to remotely have a look at the PR3 transfer function for the night.
  • We will leave the PR3 suspension as it is.
• The plan is that Shoda san et al., will perform visual inspection and re-position the IM OSEMs next week when she is on site.