[Bram, Alberto]
Both the ALS REFL PD and the TMS green QPDs are showing larger counts than before the weekend. It looks like the trend started sometime between Friday and Saturday night.
See attached plots. The REFL PD is set with a negative gain so that it reads 0 when the arm was unlocked, and it beceomes postive when the arm is locked.
Now we read around -4000 cts when the arm is unlocked.
Also the green QPD segments, both A and B read around 2200 cts, vs about 2000 as they did before.
We're not yet sure if this means that there's actually more physical power in the beam going. If that was the case, then it would be quite strange.
Could it be a DAQ artefact?
This maybe have to do someting with the PLL being out of lock, with the intergrator railing both the temp and the PZT feedback. Although I don't know the mechanism, but it may seem that there is more green being generated???
After we disabled the PLL servo and cleared the integrator (in Beckhoff), the pwoer seemed to be fine. When we engaged the temp controller (slow servo and integrator in the Beckhoff), after a little while (2-5 min), the power on the green REFL_PD_DC seemded to 'increase'.
We haven't measured the power levels in the end-station, as we had bigger fish to fry... see a later post.