The primary goal of the shift was to invetigate the offset seen on the PMC error signal and the "weird" slave error signal (42906).
It turns out that the issues were related to some misalignment of the master beam in the crystal providing the 14 MHz for both slave and PMC systems.
It likely induces some RAM which features an offset at PMC and some efficiency reduction at the slave laser level.
- With a proper alignement we have raised the PDH of the slave from 1.4 V to 4 V pp. it seems also that we have noticeably increase the injection locking range which may have an impact on the IMC_OLTF. (data coming soon)
- the offset at the PMC error signal has disappeared and we have recovered a more "orthodox" shape.
--> this may impact the Freq-to-RIN coupling seen when we engage the SSFS: it couples SSFS features at the PMC_TRA
- we have checked that we are now able to reduce the Freq-to-RIN coupling with a dedicated offset on the error signal. ie with - 0,2 V offset wrt the PDH_pp = 2.5 V
- we have realigned the seeder vs the neoVAN, the power raise from 85 W to 94 W but with a larger pedestal
Seen at the PMC: the modal content (rough) is 79 %, the TEM02 is < 1,3 %
The power at the PMC_TRA = 62,9 W when we left (~ 17h00mn LT)