Koji spent some time earlier this evening exploring where the excess RIN that we see in the PRC is coming from.
He did this by locking the PRMI (MICH on AS55Q, PRCL on REFL33I, Pnorm for MICH = sqrt(POP110) with 0.1, Pnorm for PRCL = sqrt(POP110) with 10, MICH gain = -30, PRCL gain = 8), and then exciting each relevant optic, one at a time, in yaw. The excitation was always using the ASCYAW excitation point on each of the optics (BS, PRM, ITMX, ITMY), with a frequency of 4.56 Hz, and an amplitude of 30 counts.
He also took reference traces with no optics excited.
Here, I plot (for each excited optic separately) the reference traces and traces during excitation for POP110_I_ERR, POPDC, and the OPLEV_YERROR for the optic that is being excited.
What we are looking for (only in yaw, since we see on the cameras that the dominant motion is in yaw) is an increase in POPDC and POP110 at the same frequency as an optic's excitation.
We see that neither ITM is contributing a noticeable amount to either POPDC or POP110. BS is contributing a little bit, but PRM is clearly contributing. No this entry should be read. (KA)
A week or two ago, I calculated in elog 8489 that the angular motion that we see does not explain the RIN that we're seeing, unless our cavity is much more unstable than Jamie calculated in elog 8316.
I think that I need to install one of the T240's on the new granite slab, and see what kind of coherence we have between seismic and PRM yaw motion, and if FF can get rid of it.