• Instability in pitch rings up when we go to 30W.  Can save the lock by quickly stepping to 25W and then 30W. 
  • Reverted CSOFT input matrix changes from last night (alog 46816), but instability still rings up.
  • There was a sign error in the guardian version of the new input matrix for pitch.  Marie and I have fixed this in guardian, and now the new input matrix works.
• Made a resG at 1 Hz for DHARD_P rather than the boost, so we lose less phase near the dip around 1.5 Hz.  (This 1.5 Hz dip is in the model, and totally expected, we have to deal with it, but it's not a mystery).
  • Able to use this resG, and the ELP17 cutoff, and everything seems stable so far.  We've been at NomLowNoise for 10 min now.
• Measured DSOFT_P, but a few tens of seconds after the measurement ended, something rang up at 2.7 Hz.  That's a little surprising, I was expecting it to have been the 3.3 Hz that we've seen before. 
  • We had been locked at NomLowNoise for 2hrs 38min without ringing up either the 0.4x Hz or 1.1 Hz instabilities that we've been fighting with recently.

Attached are 2 TFs of DHARD Pit, and one of DSOFT Pit. 

In each of the DHARD plots blue is the measured TF (and is the same for both of these 2 plots), and orange is taking that measured TF and applying the gain and filters indicated in the title (during the measurement my DHARD_P gain was -60, rather than the -50 that the guardian would put in, but the orange with the 0.5 gain multiplier puts the gain down to -30, which is where we used to put it at the end of LOWNOISE_ASC).  The DHARD plot with boost_cutoff in the name is what our loop would look like with the 1Hz boost filter and the ELP17 lowpass filter, and it's clear that it's very marginal.  The DHARD plot with resG_cutoff in the name is what the loop would look like with a resonant gain filter at 1Hz that is narrow enough to not eat very much phase near the 1.5Hz dip.  This is the loop that Marie and I put into the guardian this morning, and seems to have worked well for our long lock this morning, except we used a gain of -42 (which, on this plot, would mean a gain multiplier of 0.7 rather than 0.5, so the orange loop should scoot up a little).

The DSOFT plot is just a measurement of the loop that we have, with the DSOFT_P radiation pressure compensation still engaged.  We will likely turn off the RPC for the soft loops.