In order to investigate the contribution of the CO2 laser chiller to the frequency noise we switched them off at 11.48 am local time. In the attached plots there is a comparison of the RFC frequency noise spectrum (with IB angular control noise projections) with the chillers off and on. 

We confirmed that when the chillers are off the 1 Hz comb noise disappears. There is some smaller residual comb noise about 50 Hz to be better investigate.

Chillers will be swiched on again as soon as TCS people need it.