Corey, TJ, Thomas Vo, Terry, Dan Brown, Alexei, Sheila
Today we swapped the lenses in the squeezer path for a ROC +250mm lens (1st lens) and a +350 lens (translation stage), both were lenses from the enhanced LIGO squeezer (E1000077) which Corey cleaned this morning.
When Terry and I swapped the lenses the beam became very misaligned through the squeezer Faraday, so we spent some time re-aligning and then aligning through the apperatures we had placed on HAM6. To do this we made mechanical adjustments to ZM1 pitch.
After the PSL crew was done for the day Thomas Dan and I co-alinged the squeezer beam to the interferometer beam very roughly. (NB, HAM5 HPI has been tripping all evening, so we will need to redo this with HAM5 isolated.) We were able to close the centering and OMC QPD loops and get a mode scan, results are still being interpreted.
We have removed the apertures we placed in HAM6 this afternoon.
Here are two of the OMC scans taken using the OPO beam last night. The second scan was with the additional apertures removed. If we just take the ratio of the 2nd/0th order peaks it suggests we have around 3-5% mismatch, scan 2 looks slightly better. The model was predicting around 2% so this seems promising. However the high 1st and 3rd order mode content relative to the 2nd and 4th makes us think we could be clipping the beam somewhere. The culprit is likely to be the OPO faraday, as the new lenses mean the aperture is only 3x larger than the beam now.