Sheila, Louis, with help from Camilla and TJ

Louis and I have had several locklosses transitioning to the new DARM configuration.  We don't understand why.

This transition was done several times in December, one of these times was 15:15 UTC on December 19th, when the guardian state was used (74977).  Camilla used the guardian git to show us the code that was loaded that morning, which does seem very much the same as what we are using now (the only difference is a ramp time which Louis found was wrong and corrected, this ramp time doesn't actually matter though since the value is only being reset to the value it is already at). 

We also looked in the filter archive and see that the H1SUSETMX filters have not been reloaded since December 14th, so the filters should be the same.  We also looked at the filters and believe that they should be correct.

In the last attachment to 74790 you can see that this configuration has more drive to the ESD at the microseism (the reduction in the ESD RMS comes from reduced drive around a few Hz), so this may be less robust when there is more wind and microseism.  I don't think this is our current problem though, because we are loosing lock due to a 2.6Hz oscillation saturating the ESD.

We've tried both to do this transition in the way that it was done in December, (using the NEW_DARM state) and by setting the flag in the TRANSITION_FROM_ETMX state, which I wrote in Decmber but we hadn't tested until today.  This code looks to have set everything up correctly, but we still loose lock due to a 2.6Hz saturation of the ESD.

Camilla looked at the transition we did on December 19th, there was also a 2.6Hz ring up at that time, but perhaps with the lower microseism we were able to survive this. A solution may be to ramp to the new configuration more quickly (right now we use a 5 second ramp).