We successfully aligned the X arm. No big deal. Nothing to write in giant colorful letters about. If we thought it was tricky, we'd be excited. But since we're rockstar grad students, we can do this anytime, with one hand behind our back.
Earlier this evening, Kiwamu put a PD at the dark port. After starting with the usual steering beams around and approximately centering them by finding the beam on the SUS tower, we saw that we could see the fringes on a 'scope hooked up to the dark port's new PD. We could make the dip in the scope trace go away by misaligning the ETM, so we were confident that it was due to some kind of resonance in the arm. We then fine-tuned our beam centering by moving the optics in either pitch or yaw until the fringe went away, wrote down the number, then moved the other direction until the fringe went away, and then put the optic back in the middle of those two numbers. We did the ETM first, then the ITM (because the beam on the PD is sensitive to the ITM pointing, so we didn't want to have to move the ITM very far). We saw that the cavity had a visibility of ~56% when we had finished with this method.
We then went to look for the flashes transmitted through the ETM. We were not able to see them on a card, but when we looked with an IR viewer at the back face of the ETM, we could see the flashes. We stole a spare CCD camera found on the PSL table, and the camera power supply from the RefCav Refl camera, and set up a CCD camera with telephoto lens on the ETMX Trans table, looking directly at the back of the ETM. We hooked the camera up to the regular ETMX camera cable, so we can see the flashes in the control room. You can see them here:
While the cavity was aligned, here were the slider positions: