Memo:
- Unfortunately, RELF beam spot seems not TEM00, rather TEM01. This is strange, as our design should be to take signals as a beat of RF sideband vs AF sideband, and the PRC+arm should be over-couple for the relevant RF sideband; if this theory would be true, the nominal behavior should be that REFL should be dominated by TEM00 of RF sideband. For carrier, the compound cavity of PRC+arm seems like almost critical coupling, so the cariier power at REFL might be low, or some junk component might dominate for carrier. Anyway, checking the power budget/RF signals for REFL would be high priority to resolve some issues we are now facing (REFL WFS S/N, CARM S/N, and maybe noise bump??).
- Intersetingly, according to the gige cameras for REFL and AS, the beam spot flashing on each camera seems not correlated! This might reinforce the theory that REFL and AS dominated by differenent component; maybe RF for REFL, and carrier for AS. In fact, the arm transmission power's drop is coincident/correlated with AS power up (or contrast drop at AS); see 24519. This fact would support this theory.