Sheila, Chris, Alexa, Stefan

This morning we looked for coherences with many signals with our COMM noise.  There weren't any surprises, we see the same coherence with the end station PDH control signal around 1kHz that we are used to, ISCT1 accelerometers around 70-100Hz, and a little coherence (-0.7-0.9) with the oplevs at low frequencies (pitch at 0.5Hz, yaw around 0.1).  We don't see much coherence at all with the TMS QPDs, just a small bit at low frequencies.  We lose coherence with the in loop sensor below around 100Hz.  

Chris and I went out to End X to look into the beam quality problems.  We didn't find much that was promising.  We checked rather carefully for clipping on the way into the chamber again.  We also set up the nanoscan again, and we see that there really isn't anything coming back to the WFS when the ITM and the ETM are both misaligned (so it isn't a second beam that is directly reflecting a lens or some optic on transmon.)  

We also tried Daniel's suggestion of closing down an iris in the path.  For WFS B this only made things worse.  WFS A scans will be attached to this alog soon, but we didn't get any improvement there either.  

We came back and tried out some of Rich's blends.  We were able to get relatively low noise once without using WFS, 30z down to 0.02 Hz. The attached plot shows the COMM noise (measured by the IR) with different blends on.  We are curently seeing a lot of noise on ETMX T240s at around 3Hz, (100 times more) Rich is looking into this.