[Yuhang, Eleonora]

We have tried to recover the alignment and the lock of the filter cavity.

The alignment was easily recovered even if we could not use the local control for the telecope. See entry #1139. (We just tweeked a bit the BS position wiith picomotors) 

We optimized the aligment with the input and output mirrors local control and it seems it is quite fine (flashes movie here:https://drive.google.com/open?id=1045raQj_n84CjnnUuYfYBT6Kqngv-id8) nevertheless we could not lock the cavity. We didn't have much time to investigate. Some possibilties:

1) The power is too large (a factor 3 higher than before), so the gain of the loop could be too high (we tried to change the gain value and also put some attenuation but it didn't work)

2) The beam fluctuation it too large since the BS and PR are not controlled (but this should be visible in the flashes).

3) Since the power is higher the camera in transmission could saturate more than before and mask the presence of HOM flashes. (We suspect there coud be a higher mismatching due to change of the beam from SHG)

The initial value of the gain were: input attenuaion = 5 and PZT gain = 4. As mentioned before we tried to change them but still we coudn't achieve the lock.

We will try to go back to the previouse power value and setting configuration to see if we can lock in this condition.