However I couldn't close the ALS loop somehow.
Locking activity last night:
It became able to close the ALS loop (beat-note signal was fed back to ETMY).
The UGF was about 60 Hz, but somehow I couldn't bring the UGF higher than that.
Every time when I increased the UGF more than 60 Hz, the Y end PDH was unlocked (or maybe ETMY became crazy at first).
Perhaps it could be a too much noise injection above 60 Hz, since I was using the coarse frequency discriminator.
Anyway I will try a cavity sweep and the successive noise budgeting while holding the arm length by the beat-note signal.
Another thing : I need a temperature feedback in the Y end green PDH loop, so that the PZT voltage will be offloaded to the laser temperature.