Jenne, Sheila, Jeff, Kiwamu, Keita, Terra

Once the laser was back and Corey had finished inital alignment today, we made some progress:

• We followed Koji's suggestion to align the OMC QPDs using OM1 and 2, then picomotored to center on the WFS. The attached screenshot shows the position of the OMs and the movement of the picomotors.  The drives to the OMC suspension are small before we power up now, but we still see large drives as we power up (second attachment shows a comparison of the drives to the OMC suspension from a lock over the weekend to one today).  This must mean that there is a significant difference between the alignemnt of the carrier at the AS port and the sidebands as we power up. 
• We also saw that the OMC QPDs were saturated in full lock, so we turned off 1 stage of whitening (we now have no whitening filters) and reduced the whitening gain from 36 dB to 21 dB. 
• Keita, Kwiamu, Jenne and I followed old alogs with instruction on how to engage both the ISS 2nd and 3rd loops at once (alog 27940).  Today we have been stable enough to turn off the 3rd loop, engage the second loop, and then add the 3rd loop back (we used FM6 and FM9 off, gain of -0.25). We tried to measure the OLG of the 3rd loop in the configuration but could not get a good measurement.  We have added this to the IMC_LOCK guardian, in states called CLOSE_TR_AROUND_SECOND_LOOP and SECOND_AND_TR_LOOPS_CLOSED.
• With both loops closed, the noise in DARM at high frequencies is still dominated by intensity noise, as can be seen from the 3rd attachment. Motivated by this we started some differential TCS tuning with the second loop off so that we are totally dominated by intensity noise.  Our nominal in lock settings have been 0 for CO2 Y and 0.2 for CO2 X, at 2:36 UTC I set CO2Y to 0.1 W, at 3:06 UTC I set CO2Y back to 0, at 3:32 I set CO2 Y to 0.1 and CO2 X to 0.1.  None of these changed the intensity noise, so I tried one more step which caused the rotation stage problem TJ described.  This caused us to be down for 2 and a half hours, but when we relocked the intensity noise coupling was much lower.  The low intensity noise time was at 6:49 UTC, when according to the TCS simulation ITMY substrate defocus was 1.75e-5 diopters, and ITMX was 7e-6 diopters.  I am not sure if we should trust these simulations though, because it looks as though the arm powers may be miscalibrated (?) 
• We sucsesfully in switched the quad coil drivers to the low noise state once using the indiviual coil switching, thanks to Jeff's violin mode damping. 
• We also saw that there was an instability in CSOFT P that was improved by reducing the loop gain.  We reduced the gain in CSOFT pitch, from 0.5 to 0.1, the instability went away but came back and broke the lock when we tried to close the second loop. We have also twice lost lock due to what seems more like the dP dtheta instability after turning on the second and third loops together. We will try to look at these locklosses in the morning.

Note that the DARM spectrum here is not in the low noise state, it is only meant to show that the intensity noise coulping (without the 2nd loop on) changes dramatically with the thermal state of the interferometer.  For now we are leaving the inteferometer in the coil_drivers state, to see what happens with PI.  This means we are at 50 Watts input power, recycling gain of about 23, no ISS second loop, high noise ESD driver, low noise pum states.