Since the ring heater power for EY was raised(82962) in order to move away from PI8/PI24, whose noise seemed to be coupling into DARM (82961), the change in ring heater power has caused PI31 to become elevated as the detector thermalizes(ndscope1). PI31 RMS, which usually sits around/below 2, starts ringing up about two hours into the lock and by four hours into the lock, it reaches its new value that it sits at for the rest of the lock, around 4(ndscope2). Once it's at this new value, every so often, it'll start to quickly ring up before being damped within a minute. The first couple of locks after the ring heater change, this ringup was happening every 1 - 1.5 hours, but then it shifted to ringing up every 30 - 45 minutes.

The channels where we see the RMS amplitude increases and the quick ringups are the same channels (well the PI31 versions) where we were seeing the glitches in PI24 and PI8 that were affecting the range(PI8/PI24 versus PI31). So changing the EY ring heater power shifted us away from PI8(10430Hz)/PI24(10431Hz), but towards PI31(10428Hz). Luckily it doesn't look like these ringups, nor the higher RMS that PI31 sits at after we thermalize, have an effect on the range (comparing range drop times and glitchgram times to PI31 ringup times and the downconverted signal from the DCPDs). They also don't seem to be related to any of the locklosses that we've had since the ring heater change.