Both the 29.2Hz and 92Hz structures seen in elog 38738 and 38803 have been eliminated from the environmental sensors (thanks to the VAC team). Firstly the 29.2Hz line has been associated with the west end scroll pump (on the floor near the cryotrap), it has been determined that the fan responsible for the 29.2Hz is not neccessary. Secondly the 92Hz source is a result of a small fan on the signal recycling tower (again can be kept off). It is worth noting that there is a similar fan on the power recycling, and a switch off of that fan will follow. Once we have an interferometer we can check these structures are gone from LSC_DARM as well.
It has been confirmed the 29.2Hz line is gone from Hrec (figure 1). The 92 Hz bump was previously confirmed to have disappeared (38738) we just turned on the fan yesterday and observed the change in enviromental sensors to verify the source then it was switched back off. So, there is not a recent lock with the fan on for comparison, but none the less the 92Hz region is flat. Yesterday the operator recieved a flag for the ENV_WE_CT_ACC_Z being out of it's thrshold. The top right of figure 2 shows the significant reduction in the overall noise when the scroll pump was switched off, which resulted in the flag.
