I was thinking tonight about more possible reasons that our PRC sucks, and I wonder if dust on the BS could create the problem.
Historically, Kiwamu and I found a few dust particle scattering centers every time we inspected the test masses before drag wiping. Sometimes, there would be one frustratingly close to the center of the optic. I'm not sure if we ever made note of how many we saw and where they were, except out loud to the assembled crowd.
Anyhow, the BS is the only IFO optic that was not replaced, so I'm not sure how long it has been since it was cleaned. If the PR-flat cavity looks okay and we take out the BS to do a PRM-ITMY cavity, we should inspect the beam splitter.
Also, the PRM could need cleaning, but at least it has been drag wiped within recent memory.
My question is, could a few scattering centers cause the behavior that we are seeing?
EDIT: List o' elogs....
Elog 5301 - Some details on dust seen on ITMs and ETMs, Aug 2011.
Elog 4084 - Kiwamu's in-situ drag wiping how-to, with details on some of the dust we saw. Dec 2010.
Elog 3736 - PRM drag wiped before suspension (Oct 2010)
Elog 3111 - June 2010, BS drag wiped.