Jennie W, Sheila, Francisco

11:30 am - ish

After many previous efforts we are trying again to move input yaw pointing in the IMC (via IM1 and IM3) and measure if this has any effect on our jitter coupling.

See first image for where the sliders were before we made changes.

We orginally started by taking a reference jitter coupling measurement, brown traces in the two attached graphs, first one is pitch, second is yaw.

The graphs show the DARM spectra on the top left, the coherence with two jitter witness channels on the top middle and right, and the transfer functions of these witness channels to DARM on the bottom row of graphs.

IM 1 and 3 were stepped in yaw down by 20 and we waited for IM4 and PRM motion to level off before moving again to make sure the IFO stayed lock.

We did three steps to go down a total of 60 counts where we took the green traces in the attached graphs.

After this we reverted the alignment changes.

I then took this ndscope screenshot showing the steps down and then back up.

It is not clear to me that the build-ups are better.

2pm -ish

We took another reference for jitter before moving. This is coloured blue.

We made more steps on IM1 and IM3 till we had gone twice as far as earlier (ie. down by 120 counts on IM1 and IM3). This made the build-ups noticeably bigger as the change is easier to see when we are thermalised.

We took another jitter measurement shown in red.

We are not sure why the PSL-ISS_SECONDLOOP_PDSUMOUTER chnages as we change the input pointing but we could be clipping somewhere between IM4 and ISS array.

We left the IMs where they were and then lost lock a couple of minutes after, probably due to wind (60mph!) The IFO still relocked with these yaw changes.