Not sure if this is real (it looked real on DARM spectrum!), but H1 made it up to about 176.7Mpc. And it was in this higher-range state for about 10min. (attached is the last 6hrs of H1 running with first lock on left at 37 W and the last two locks at 35W).
There were multiple ADC overflows in the DARM loop flagged in the database during this period, triggering automated h(t) gates. The DQ times flagged (integer second discreteness) were 1243843959 1243843960 1243843967 1243843969 1243843975 1243843977 1243843981 1243843984 1243843985 1243843988 1243843989 1243843990 1243843991 1243843994 1243843995 1243843996 1243843997 1243843999 1243844000 1243844004 which span 08:12:21 UTC - 08:13:06 UTC.
Andy, TJ, Laura This looks like it was a PI mode ringing up. The broadband monitor (plot 1) sees a nice exponential ringup. The high-bandwidth DCPD channel shows that the line is about 10,430 Hz (plot 2). As Keith posted, the DCPD began to saturate due to the huge line, and plot 3 shows that this looked like a decrease in shot noise on the DCPD which is why the range looked unrealistically high.
From mode identification before the change in test masses https://dcc.ligo.org/LIGO-T1600080 it looks like this could be one of the ~10420Hz mode group. The mechanical eigen-frequency model from this dcc implies this is likely the drumhead mode. No measured mode is within 1Hz of this frequency indicating its probably one of the new test masses. This mode would best be actuated on with the ESD with all four quadrants driven with the same phase. There is also a more complicated mode with a similar frequency, see the 3 and 4th attached figures. And there is also the possibility that this mode is aliased (real frequency 55106) though this is unlikely given there are AMDs.
It looks like this mode also rang up slightly 5th june when the power was increased. It appears that ring heater were not adjusted for this power up. I guess applying some more ring heater will likely avoid this instability.
