= In-vac PD/QPD layout meeting 2025/01/23 =
Time: Nov 20, 2024 10:00-10:30

Participants: Ray-Kuang Lee, Huali Chen, Yoichi Aso, Yuta Michimura

Zoom meeting

== Minutes ==
 * Huali showed the layout idea for AS RF and OMC REFL, with squeezing injection optics.
  * Add periscope to reduce the height approx. 210 mm -> 4 inch) and use smaller pedestals (footprint for 210-mm-high mirror is dia. 78 mm; see [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=3916|JGW-D1503916]]).
  * Add existing AS RF in-air and OMC REFL in-air paths in the layout and see if all of them can co-exist.
  * Try to simplify the layout by removing some of the steering mirrors to avoid scattered light from steering mirrors as much as possible.
  * We can also add some extension plate to extend the table
  * Do we really need two steering mirrors (one for piezo and one for picomotor) before each QPD?
   * We can also mount disc+piezo+mirror on a picomotor mirror mount to realize both actuation with one steering mirror
 * '''A/I'''
  * Check if OMC REFL RF QPD in-air is necessary [Michimura]
   * May be not. Beacon WFS is used only after locking OMC (before handing over to DC readout). LIGO is also not using OMC REFL in-air (they only have in-vac OMC REFL DC QPDs; [[https://dcc.ligo.org/LIGO-T1000264/public|LIGO-T1000264]])
  * Check what LIGO is doing for RF QPD centering (only picomotors?) [Michimura]
   * REFL WFS: Two tip-tilts before WFS sled, two picomotor mirrors on WFS sled [[https://dcc.ligo.org/LIGO-D1000313|LIGO-D1000313]]
   * AS WFS: Two tip-tilts (OM1, OM2) before WFS sled, two picomotor mirrors on WFS sled [[https://dcc.ligo.org/LIGO-D1000342|LIGO-D1000342]] [[https://dcc.ligo.org/LIGO-T1200410|LIGO-T1200410]]
  * Upload the slides to JGWdoc, and present the current status at the ISC meeting on Jan 27 from 15:00 JST [Huali]
 * Next meeting: TBD