We had problems with the error-signal monitor from the TTFSS board. We thought that something
was wrong with it because the SNR was very small. Before starting the process of nailing down what was
wrong with the electronics I wanted to put some effort to reach a good lock again because I suspected
that the monitor was wrong. We need to check it (later)!
The cavity now it can be stably locked for half an hour.
The cavity was initially easy to lock without the EOM. Few crucial things have been done to make the lock:
With this changes the lock was possible but the control-signal was very noisy;
Thanks to Andrew, he added a lambda/4 before the BB EOM to remove additional circular light (after the PBSO).
The quality improved considerably.
I have then twicked the gain Knobs in order to have a better lock. The lock is satisfying (fo now!). Aidan will
provide us of a feedback on the temperature too. Then the lock will stay longer.