The high power laser (HPL) turned off at the weekend because the power watchdog was triggered. The system was running over a couple of day very stable, but on Saturday the output power started smoothly to decrease until the threshold for turning off the pump diodes was reached. The decrease was caused by setteling of the birefringence compensation lenses inside the oscillator as one can see by analyzing the signal at the DC channel of the photodiode downstream of the Brewster window (PDBP, misalignment of the birefringence compensation lenses corresponds to an increase of the voltage for this channel).
This effect is already known from the LLO system and the reference system as well: A couple of days after delivery the components start to settle and need to be tuned.

We realigned the corresponding lenses and and ended up with 185 W outside the laser box so far (205 W at the powermeter inside the expernal shutter). This is about 7 W less than we had directly after installation of the system and can potentially be improved.