Lance, Genevieve and I used some of the time on Friday, when LLO was down for logging, to continue our search for scattering noise sources.

Projects and progress:

1) Identify frequency of the post-damping ITMX cryobaffle to compare to scattering frequencies in DARM. We were not successful in exciting the cryobaffle to produce noise in DARM. That probably means that it is not one of the scatter noise sources.

2) Search for source of 52 Hz and possibly related 48 and 38 Hz peaks. We did not convince ourselves that we were actually exciting the source of the 52 Hz peak. Search to continue.

3) Search for scattering at viewports using a guillotine retroreflector. In past runs we have used a guillotine with black glass to check viewports for scattering, watching DARM to see if noise is reduced when the black glass is inserted. This run we are using a retroreflector guillotine with the idea that if we increase noise dramatically by increasing the light returned to the scattering site, it will be easier to find than looking for slight improvements in DARM when we insert black glass. The retroreflector guillotine is made of retroreflector discs and tape (see figure) that I tested to make sure worked in near IR.

Genevieve and Lance noticed that they could make noise in DARM when the retroreflector guillotine was inserted in viewports on the -X side of HAM6. Full analysis of all of the data will begin this week.