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AdV-AEI Squeezer Integration (external squeezer table)
de laurentis, sorrentino, sequino, eisenmann, bonnand - 2:26 Wednesday 23 May 2018 (41521) Print this report
Alignment and mode matching of SQZ BAB on OMC
Goal of the shift was to align and mode-match the bright beam from the squeezer on the OMC. We started by opening the shutter on SDB1, and by rotating the polarisation of the waveplate on the SDB1 Faraday to increase the power of the beam from SDB1 to the SQZ bench by a factor 2 as in entry 40668.

We then centered the BAB and the ITF beams on two diaphragms with 1 m path separation by acting on the SQZ steering mirror. At this point, we unlocked the IMC and misaligned the IMC end mirror to avoid the ITF beam to reach the detection bench: in such conditions we could see the spot of BAB on the B1p camera (see first attached image).

We scanned the OMC1 temperature and we could detect the different transmission modes of the BAB on the B1s2 camera, see second to fourth attachment.

We spent quite some time in steering the BAB to improve the alignment mismatch, with little success. The best matching we got was of the order of 30%. The last plot shows the total power on the B1s2 during a typical OMC scan (the SNR on the B12s photodiode is not enough to detect transmission modes).

We'll have to continue this work tomorrow morning.

We closed the shutter on SDB1, tuned the SDB1 Faraday for maximum transmission, and relocked the OMC.
Images attached to this report
Comments to this report:
mwas - 9:09 Wednesday 23 May 2018 (41523) Print this report
The B1s2 photodiode shutter was closed and the vbias switched off during this work (see figure), which explains why there was no signal visible on the PD.
Most B1* photodiodes have the shutter closed and vbias switched whenever the ITF is put in the DOWN state, and the PDs need to be enabled manually when the automation is not used.
Images attached to this comment
de laurentis, sorrentino, sequino, eisenmann, bonnand - 17:21 Wednesday 23 May 2018 (41536) Print this report
During yesterday's shift we were unable to move the folding mirror underneath the Faraday isolator on SDB1 because of a communication error with the picomotor controllers.
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