Sheila, Matt T, Mayank, Jennie W

tl;dr: After previous PR2 moves last week, we measured the spot clipping on scraper baffle (and exiting HAM3 viewport) to be 8mW in lock. After measuring this we unlocked for unknown reason and so team PR2 moved 6mm towards the centre of PR2 in yaw while unlocked. We estimate we are roughly centred on PR2 now.

Today Sheila and I measured the spot coming out of the HAM3 viewport as was done by Robert in this entry. The process is replace the black glass guillotine with lexan guillotine, take off the illuminator, clip a lens on a stalk to the top of the guillotine and align this with the beam coming out of the viewport. Not all the light is now captured by the lens as the spot is now more a semi-circle of a clipped beam. We moved the power metre behind the lens till we found the max power we could get on the power metre. This was 8mW and the PR3 yaw slider was at around -74 microradians.

After we came back to control room the IFO lost lock so it was decided to move towards the centre of PR2 which had been measured by Sheila using an A2L measurement at the start of the commissioning period.

Matt tuned down on PR3 yaw in 3 microradian steps to -232.4 microradians. Each step he tuned the 8X picomotor to bring back the DIFF and COMM ALS beatnotes. Every so often it is also neccessary to step up the pitch on PR3 to compensate for the cross-coupling of yaw to pitch. The ndscope image for the moves is here. Matt left the picomotor like this and the sliders like this.