In-vac PD/QPD layout meeting 2025/07/29

Time: July 29, 2025 14:00-15:00

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

Zoom meeting

Minutes

• In-vac periscope (Ryan)

  • First design based on modification of https://dcc.ligo.org/LIGO-D1201410 presented.

    • Modified the direction of the beam
    • Modified to use Opto-Sigma VMHG-50.8 instead of Siskiyou LIGO mirror mounts.
    • Modified to have slotted holes to make it height adjustable
    • Default height is 4 inch - 15 mm (baseplate thickness) for lower mirror, 210 mm for upper mirror
  • Baffle hole size need to be checked to see if it is not too small or not too large compared with the beam size
  • Resonant frequency need to be checked with FEM
    • If too low, re-design needed (e.g. make the slotted holes short).
• POP design (Ryan)
  • Used the distance of 1399 mm for in-vac POP steering mirror and HBS1 on POP table [Check]
  • Found that the beam size on HBS1 (2 inch mirror) is quite large (~10 mm radius)
  • POP forward beam need to be added to the layout
  • In-air POP beam and green beam layout need to be updated to see if they fit in POP table
  • Beam is quite elliptic although currently assuming a circular beam from PR2

    • Try to use qx and qy in ModeMatch wiki page for designing the telescope

• OMC chamber update (Yuta)

  • Periscopes and fast beam shutter (https://dcc.ligo.org/D2200426) need to be added to the CAD layout to see if they fit.

  • If the fast beam shutter does not fit, OFI need to be moved towards Y-arm, and the position of ORM1 need to be re-adjusted. Note that the OFI bases are not moved.
  • Base plate for RF QPD paths need to be designed.
    • May be split into two so that it won't be too big for installing through the door of the OMC chamber.
    • Start with 15 mm thick, and try FEM to see if this thickness is enough.

• A/I

  • Consult with VAC people to start designing REFL PD tank [Yuta]
  • Check the resonant frequency of the in-vac periscope with FEM [Ryan]
  • Double check the beam size on HBS1 [Yuta]

  • Try to use qx and qy in ModeMatch wiki page for designing the telescope for POP [Ryan]

  • Add POP forward beam to the POP layout [Ryan]
  • Add in-air POP layout and green layout [Ryan]
  • Check if the in-vac periscope fits in OMC chamber layout [Ryan]
  • Check if the fast beam shutter fits in OMC chamber layout, and move OFI towards Y-arm if needed [Ryan]
  • Start designing the base plate for the RF QPD paths in the OMC chamber [Ryan]

  • Add beam diverter (https://dcc.ligo.org/LIGO-D1100642), base plate, and beam dumps to the OMC chamber layout [next step...]

    • https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=16705

  • 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 this year]
• Next meeting: TBD