The filter cavity is again relocked with the green beam.
Preparatory work
- This morning Luca checked the vacuum level around FCIM tank then open the gate valve
- We recovered the vertical position of SQB1 and SQB2 benches
- FCIM inverted pendulum was put in the same set points of July 2024 (last FC lock)
Realignment of the cavity
- Before closing FCIM local control loop we checked the transmission of the green beam on the camera in transmission from the filter cavity FCEB_GR_Cam. We saw that the beam was too high and clipped thus we have to change the correction of EQB1_GR_M7 from 2 to -5 in order to see the beam completely on the camera and the beam centered also on FCIM external surface (toward SQB2)
- We went to SQB2 and we checked on the viewport the presence of the back reflection
- We left open FCIM _LC_MAR_T{X,Y} and we kicked the input mirror sending DC offset to the marionette. During this oscillation we saw the FCIM reflection passing randomly on SQB2
- We looked the RDS data and we found a moment in wich the back reflection arrived to EQB1_GR__PD_DC . Thus we closed the LC with this set point and we saw immediatlely the reflection coming back up to EQB1
- Once the retroreflection was coming back up to EQB1 we started to move the end mirror in order to find cavity flashes on FCEB_PD_DC photodiode in transmission
- To do it we proceeded similarly as FCIM. This time with the LC closed we moved a lot TX and TY set point and a certain point we saw a small glitch in the transmission PD
- With RDS data we went to the position of the glitch and we found the first flashes
- As soon as we had flashes we aligned the cavity in the standard way but in order to maximize the transmission we had to move in vertical also EQB1_GR_M5 and M7 mirrors
- Once the transmission was higher than 3V we engaged the lock and the autoalignment and it worked at the first attempt
- The maximum value obtained with automation is 4V
- We realized that EQB1_GR_M{5,7}_Y DOFs were saturiating. Thus we went int DET_LAB to discharge them
