Georgia, Sheila

LSC things

• CARM transition
  • We did all the steps from engaging DHARD WFS to CARM 5 PM by hand and measured DARM and CARM (and SRCL) gains at various steps.  We moved the DARM gain reduction which used to happen at at TR_CARM offset of -7 to happen after the offset is ramped to -20, because DARM would have been on the high edge of the phase bubble as the guardian was written. 
  • We left in the increase in TR_CARM gain that Craig and Georgia added last night
  • We changed the TR_CARM offset at which we switch from TR_CARM to TR_REFL 9. Before we improved the recycling gain, we were doing this at a TR_CARM offset of 41, which at the time meant 90-85% of the transmitted arm power that we would have on resonance.  Since we improved the recycling gain we have been doing the transition at the same TR_CARM offset, which is now only about 65% of the final arm build up, so we have been doing it at a larger CARM offset.  Georgia and I move the TR_CARM offset in the final step to 48, which is 88% of the final build up.  
  • We have locked twice since making this change and it has worked both times, so we are leaving it like this in the guardian. 
• CARM gain redistribution
  • In one of our attempts to power up, we saw that there was a large glitch at the time when the common mode board gain was switched, which caused a lockloss.  We have been using a high gain (23dB) on the summing junction and a lower gain than we used to on the CM board, so we decided to increase the CM board gain by 20 dB and reduce the summing junction gain by 20dB.  This worked fine and we updated the adjust power function for this gain.  We added a step to do this gain redistribution in the CARM_TO_ANALOG state, but haven't tested this.  
  • We should re-write the power adjust functions so that there is only one function used in both adjust power and increase power, and so that it checks the current power and gain in the main to use as a basis for calculating the new gain, so we don't have to update the hard coded values every time we change things.  
• Since Georgia and Craig had a lockloss last night during the REDUCE 45 MHz modulation depth state, we have taken it out of the path for now.  

ASC

• Georgia added a convergence checker for SRC_ASC so that once the boosts are engaged the loops will be able to settle before we engage the soft loops.  
• We have been able to turn the CHARD Y gain up to 1 (with a factor of 3 of where it should be to match the UGF from O2), with all the other ASC loops engaged as they are by the guardian. A gain of 2 did not work.
• We have used the ASC as it is engaged by the Guardian (except with teh MICH LP filters turned off) to power up to 8 W.  at 9W we saw a yaw instability similar to what we saw during the day yesterday. 
• Attached are screenshots and dtt files for CHARD  and DHARD Y measured at 8W.
• At 8 W were engaged the DHARD P boost with no problems, but when I tried to engage the DHARD Y boost we lost lock.  
• A2L
  • We made some fixes to the a2L script that were needed because of the changes to ISC_library.  
  • We ran this several times, and it reduced the noise in the DARM spectrum belo 50Hz.  (Screenshot attached, the calibration here is not correct, the lump around 150 Hz could be a calibration error).  
  • The A2L coefficients are large for yaw, I haven't converted them to spot centering but both of the ITM Y coefficients are in the neighborhood of 5.  
  • For ITMX Y there is a very large bilinear coupling which meant that the a2L script failed to set it correctly.  I don't understand why this is only true for one optic while the bi linear coupling of the other optics is much smaller.  
  • We also saw that the Y2L coefficient we need for MICH is large which makes since since the spot seems to be off center on the ITMs.  The coefficient that minimizes the coupling to LSC MICH actually makes the coupling to DARM rather large.