On saturday night we made some measurements in the attempt to characterize the power budget before replacing the IMC payload and change the faraday polarizers on EIB.

In orer to measure round trip losses we manually unlocked the PMC a few times to have the decay time of the IMC cavity (see first plot). Data strech from 19:25 to 19:32 UTC of Nov 21. Data were not as "clean" as we collected back in september, analysis is ongoing (see second plot for a close-up on one of the unlock). In particular, as for september measurements, the photodiode on IMC_TRA (thorlabs commercial) shows a decay time that is too long and is not compatible with the upper limit of decay time set by the dihedron transmittance, so we use PSTAB_PD2_DC to estimate the decay time instead.
Results will be posted soon. By the way, for this kind of measurements it would be good to acquire with faster sampling PSTAB_PD2_DC and IMC_REFL_DC (at least around 100KHz, at least in the raw_full).

Also, we tried to measure the power at the input and output of the EIB with the same powermeter head (see pictures: first at the input of  EIB, second after EIB_M5, diagram summarizes the positions of the Ophir powermeter). The measurements were performed with the EIB blocked, so we can have some residual misalignment of the bench, with a little impact on the overall output. Results are: 50.1W at the input of EIB, 39.5W at the output after EIB_M5, so around 20% of losses while we expected less than 10%.
This discrepancy is being analyzed and will be further checked when we replace the polarizers for the Faraday isolator on EIB.

Finally, no green light coming from the EOM was spotted, but the image spoiling the EIB_ALS_Camera was found to come from something coming back from SIB1, to be further investigated.