The FSS control loops have been operating with relatively low gain and a UGF of some 20 kHz. We must fix this before any useful beat note can be obtained.
About two weeks ago I was progressing towards this with tuning up the gains of the loops. I found that there were some issues with the offset and the boost being engaged at the time of establishing the lock. Now I am finding that it is impossible to push the UGF above about 10 kHz without the loop breaking down into a ringing mode. I have tuned up the alignment of beams and polarisation for the input chain of optics so the issues now appear to be in the control stage.
Today I was bashing my head against a wall on the why both paths seemed to be glitching as I got close to tuning the laser to resonance for a lock. It turns out that I had two instances of the 'startAcromag' script running in two separate windows of tumux. Weirdly they were able to co-exist without throwing an error in each other. I only found the problem after plugging the slow controls actuation signal into a oscilloscope and deciding that I would progressively restart processes until the problem went away.
It might be better practice, not to mention more efficient, in the long run something like a cron job for each of the PID and EPICS scripts to keep them up and running without manual wrangling with tumux. I think Evan has done this before, it was something along the lines of calling a bash script to check if the process is running and then restarting it if its down. I guess it needs some condition to stop it temporarily.