Craig, Georgia

This afternoon we had some problems locking the X arm in green. We found it would acquire, lock briefly, then lose lock after a few seconds, similar behaviour to what I saw back in January. We spent a while adjusting alignment, tried toggling the noise eater, locking without the WFS, finally Craig adjusted the PDH locked gain. When he set it back to its nominal value (4), a few things happened within a second:

• the arm acquired, and locked (grey trace in attached figure)
• the laser power from diode 2 dropped by 9 mA (brown trace)
• the IR and green power jumped (green and red traces, sorry for the unintuitive colour scheme)

I don't understand why locking would cause the power from one of the laser diodes would change, or why this particular lock worked out. Is it a coincidence and the laser just happened to hop out of a mode-hopping region?