LIGO Document G2301888-v2

September 2023 PEM Update

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1) O3-O4 vibration coupling reduction projects successful

2) Does vibration coupling tend to increase with main laser power?

3) PEM injections successfully completed before O4 run at LLO, and at LHO at 75W – redo’s after LHO power drop to 60W almost complete.

4) Low vibration coupling at LHO and LLO Filter Cavity End Stations.

5) New electronic grounding noise injection technique reveals grounding problems.

6) There is a non-zero TM bias that minimizes electronic ground noise coupling.

7) Arm Cavity Baffle identified as scattering source at LLO, hanging problems corrected.

8) HVAC shutdown, LHO, increases range by about 10Mpc, HVAC coupling likely due to: A) coupling at EX cryobaffle, B) PSL (jitter), and C) unknown source of vibration coupling in LVEA.

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