Today while locking ALS we had fast glitches in both x and y arms which caused us to lose lock. I had a quick look at the same channels I looked at when we had extra intensity noise on the ALSX laser back in September.

The glitch in the x arm coincided with a jump in a few channels in the laser: the pump diode 2 power, the noise eater, and the IR anf green output powers. We lost lock a few seconds after the glitch. First attached plot shows the glitch in green arm transmission (bottom middle), and other laser-related channels. 

The y arm has glitches much more frequently than the xarm, their frequency and severity comes and goes. Looking at the same channels at the y-end during a period of frequent glitching (second attached plot) shows nothing obvious that is coincident with the glitches. There are some noteworthy things: the RMS noise on the green and IR powers out of the laser is significantly worse for ALSY, compared to X. And there are also frequency glitches in the pump diode 1 noise monitor.

Conclusion: the als-x laser maybe has some kind of intermittent mode-hopping. It's unclear from these plots what is going on with the y-arm.