= In-vac PD/QPD layout meeting 2025/10/22 =
Time: October 22, 2025 14:00-14:30

Participants: Huali Chen, Ryan Yang, Ray-Kuang Lee, Yuta Michimura

Zoom meeting

== Minutes ==
 * POP design (Ryan)
  * POP in-vac, POP in-air, POP forward in-air path populated. Not yet for green and POP in-air polarization monitor optics.
  * POP in-vac RF QPD path has quite large astigmatism (sagittal has 45 deg Gouy phase separation but tangential has ~30 deg).
  * For green optics, basically copying the current layout is fine.

 * In-vac periscope (Ryan)
  * New design following [[https://dcc.ligo.org/LIGO-D1002350|LIGO-D1002350]] is ongoing.
  * The top mirror height will be 200 mm, and the lower mirror height will be 4 inch - 15 mm for the periscope.
   * RF QPD plates with 15 mm thick will be put on the OMC vibration isolation table.
  * Beam dump will be put behind the mirror, and not the baffle in front of the mirror.
  * Because of the size of the periscope, RF QPD path layout and RF QPD baseplate need to be re-adjusted slightly.

 * In-vac periscope fabrication
  * Two periscopes for OMC chamber needed. Not for REFL and POP.
  * As a first step, Ray-Kuang will see if company in Taiwan can fabricate.


 * '''A/I'''
  * Consult with VAC people to start designing REFL/POP PD tank [Yuta]
  * Design a new periscope with 2 inch mirrors fixed on plates (not mirror mounts) on a rectangular structure. [Ryan]
   * Check the resonant frequencies with FEM [Ryan]
   * Re-adjust the OMC chamber layout based on the new periscope design [Ryan]
  * Send Ryan with the details of GFI and DC PD for POP [Yuta]
   * GFI is probably [[https://www.thorlabs.com/thorproduct.cfm?partnumber=IO-5-532-HP|IO-5-532-HP]] according to [[https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=9919|Yokogawa thesis]].
   * DC PD is probably either PDA100A or PDA100A2. Both have aperture of 9.8 mm dia.
  * Create cable list (RF QPDs, picomotors, PZTs, beam shutter, beam diverter) for OMC chamber to see their weight for designing OMC vibration isolation table [Yuta; by the end of September?] -> Done on September 25 with Akutsu-san and Sato-san.

 * Next meeting: TBD