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 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 IO-5-532-HP according to 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