Haocun, Nutsinee, Sheila, TVo, Dan Brown

After some failed attempts (45474) at doing OMC scans of the squeezer seed single bounce off of ITMX we finally managed to see something today with increased seed power. In summary we are ~99% mode matched on single bounce from ITMX and ITMY. The SNR for the OMC scan was reasonable enough that we could see the astigmatism present in the beam. ITMY and SRM single bounce have a similar astigmatism, however ITMX single bounce doesn't look astigmatic.

Details

First we realigned ZM1/ZM2, going back to the weekends alignments we manage to find a good position that wasn't completely railing ZM2. We then used the new ZM1/ZM2 WF centering and guardian scripts from Haocun to offload to the ZM1/ZM2 sliders. This alignment seems to work well for getting the seed onto SQZT6 camera and the AS A/B, OMC QPD A/B. In this setting ZM1/ZM2 are still nearly saturating so we need to offload these at some point.

Aligning the seed to IFO beam was done with the same procedure outlined in 45375. With the AS air camera with a very long exposure we could see multiple beams from ITMY, ITMX, and SRM. Aligning SRX we saw good fringes on AS A/B. With SRM only we get around ~50 counts, with ITMX/Y ~2 counts on AS A/B.

We then did OMC scans for single bounce off of SRM, ITMX, and ITMY. We couldn't switch on the alignment loops for ITMX/Y single bounce so the first order peaks are still quite high. SRM single bounce we did switch them on but there appears to be an offset. Overall the ITM scans have very small second order peaks, giving ~1-2% mismatch comparing just the TEM20/02 to TEM00. The SRM single bounce is still showing the previous ~8% mismatch in horizontal and ~3% in vertical.

On the astigmatism front SRM single bounce still has the same features we saw previously. The ITMY second order peaks show an astigmatism is present, which is similar to the SRM result. Interestingly the ITMX bounce doesn't show any noticeable astigmatism. After watching the ITMY second order peaks for some time it became apparent that astigmatism was changing, most likely due to alignment drifting as no loops were on. So we are hoping that we can fix this with some more careful aligning soon.

The TCS was in a 50W preloaded state today. TVo is writing a log post about this.