Looked at the cameras for PR3, PR2, PRM and all 16 arm baffle PDs during a power up. Bottom line: The lost power is found on the ETM baffle PDs.
- Plot 1 and 2 show the ETMX and ETMY baffle PDs. Note the huge increase in baffle PD4 in both arms. At the same time, baffle PD 1, on the opposite side of PD4, also sees an increase, so we can't explain this with arm alignment.
- The ITM baffle PDs show much less signal - there is some on ITMY baffle PD 4, but nowwhere near as much as on the ETM. (:Plot 3 and 4)
- PRM, PR2 and PR3 roughly track the recycling gain, i.e. they increase less than linear with input power. (Plot 5)
I should also say that the Beckhof whitening and digital gain setting were the same for all 16 PD. I attached a representative snapshot for H1:AOS-ETMX_BAFFLEPD_4.
The y-axis on all these plots (labeled arbitrary) is in Microwatt/Watt input power for the Baffle PDs, and recycling gain for POP_LF.
Here is a plot of the recycling gain behaviours of carrier, 9MHz and 45MHz sideband.
Now that POP is not saturating, it looks like the 9MHz RG is still dropping faster than the carrier, but the 45MHz RG is actually dropping slower. This would not agree with a simple PRC loss - it would require some SRC loss to enhance the 45MHz sideband.
