This morning we optimized the injection of the pickoff on the laser bench (fig. 1). However, the power at WEB was not recovered and we were still not able to close the PSTAB loop.
General checks:
| check on | NEB | WEB | ||
| ALS NEB/WEB PD IR PSTAB CALI | 18:01 UTC PSTAB open at NEB | 2.3mW | 1.3mW fiber connections to be checked (next maintenance) at WEB we do not have power enough to close the PSTAB --> |
|
| GREEN power | 38 mW | 39mW | ||
| ALS WEB/NEB PD GREEN I/Q | err signal demod phase WEB/NEB_ALS_fast.phi0 | 4.7 | 4.7-->4.9 | |
| VCO offset | vco ramp set | 0.0 | 0.25--> 0 | |
| check of the triggers | they were ok | |||
| check of the lock threshold | in the past week sometimes metatron did not realize that the green was not locked (the lock threshold should be the same value as the trigger high) | 0.5-->0.45 | 0.55-->0.45 |
Measurement of the OLTF: white noise 1, colored noise 1, select colored noise 1. WEB_fast.noise_sensing_noise_rtpc.noise=1e-8
The UGF were both 1kHz. We increased the gains by 1,5 times for the west (als gain 0.35--> 0.55 -fig.2- ) and 2 for the north (0.45-->0.9), in order to increase the UGF
Check of the modulation at 70kHz
NEB and WEB look very similar. In fig.3 pink is with the new gains 0.55 at web and 0.9 at neb, and in blue is with 0.55 at web and 0.45 at neb (preivous gain), to check if with the new gains we do not have strange behaviours.
In conclusion, the two green at the end were fine in terms of alignment, demodulation phases, thresholds, amplitude of modulation. The only thing that we've changed and that in the past could have caused some problems was the lock threshold, which was slightly too high and could make metatron believe that the green was still locked while it wasn't.
We wanted to run the automatic alignment on the EIB since the values of the beatings are too low, but we did not manage to move the piezo.
To be still checked during next maintenance:
- the power at web (now the soa is working close to its max and it is still not sufficient to close the PSTAB. Fiber connections must be checked)
- check with Alain why the alignment on EIB did not work
We left the ITF locking in LN3.
