Yesterday I switched on the optical lever of the end mirror. The signals in time were showing a clear excess of noise with respect to the last time I have looked at them (july 2016).

Since the end chamber was put under vacuum few weeks ago, we suspeced the pumps. We first switched of the turbo pump (after closing the valve) and wait for the frequency to go to zero without notice any remarkable improvement in the noise. After that, we switched off the rotary pump and we could observe that many lines have disapeared in the spectrum. Indeed the signal in time was much better than before.

We also monitored the change in the vacuum level after closing the valve. Its trend in the first 45 minutes is plotted in the attached figure. 

The value today (after about 18 h)  is  2.1e-4 torr.