The Arm locks again, with the spectra attached (first attachement). The positive message is that the ISI performance has greatly improved. The drop at 0.5 Hz is the Quad pendulum  mode. At higher frequencies (above ~0.6 Hz) we are most likely dominated by frequency noise.

We optimised the SHG temperature, so there is more power in the green (an extra 10mW). This is meant to remidy the power fluctuations we were seeing when we drifted further away from our nominal VCO frequency. We will see if that is the case. I reduced the CMB-B input gain by 3dB (down to -17dB!)  to make up for the increase of light on the diode, but I forgot to measure the UGF of the PDH loop (nominal 11 kHz).

Local damping to M0 and L1 on both Quads are engaged, and the length feedback is of loaded to the ETM M0. The power drops over the longer time scale (>1 hr), is most likeli becasue I haven't inserted the decoupling. I tried to decouple it in pitch without much succes.

In the spectrum, the features at 2.75 Hz and 4 Hz are seen in the Reference Cavity transmitted power, and are imposed on the laser in the end station.

The problem we currently having is that the VCO seems to jump every ~8 min, when it reaches 40.2 MHz (about 600 kHz from the nominal 39.6 MHz), seen in the second attachment. The cavity seems to stay lock and all keeps running 'smoothly'. Due to this jump I was not able to do more than 4 averages in the spectrum.

The cavity has been locked for over an hour, which is an improvement. I unlocked the cavity before I left.

On request ... the traces are taken at 1) 27/7/2012-02:47:57, 2) 19/7/2012-7:17:00, 3) 19/7/2012-6:40:00 and 4) 19/7/2012-7:40.