Summary: scattering evaluation photos of ETMX, the ACB, the cryobaffle and the p-cal periscope show no major problems.

Figure 1 shows approximately what the beam spot on ETMY “sees”. I use these photos to look for potential scattering problems; the camera is placed very close to the center of the optic where the beam spot will be. The flash mimics the wide-angle scattering of interferometer light from the beam spot and lights up regions that will retroreflect interferometer light back to the beam spot, where it can recombine with the main beam to produce scattering noise. Of course the technique is limited by different angular distributions of scattered IFO light and light from the flash, as well as by color differences, but it gives a rough idea. The camera is about 10 cm in front of ETMX, so it sees a little more through the hole in the baffle than the beam spot on the optic will. This is why you can see the baffle walls on either side of the baffle aperture. I think the actual view of the beam spot is just narrow enough that it doesnt see these baffle walls. The "H" at the middle is the sheet metal cover at the spool with an "H"-shaped aperture in it for IAS. The flash is reflecting off of this sheet metal cover. 

I dont see any terrible glints coming from the pcal periscope, though it reflects more than the cryobaffle behind it. I think the lower reflectivity of the cryobaffle is not needed here, but is needed for its twin baffles near the ITMs where the angle is smaller. The white spot at the right of center is one of the periscope mirrors, which is directing the flash to a reflective surface at the port. This is a reminder that we need to be careful about backscattering from the pcal boxes and other equipment at the ports.

Figure 2 is an approximation of what ITMX will see of ETMX. The camera is in the beam path and so the flash is reflecting off of the ETM. Of course the camera is a lot closer than the ITM, so the camera sees more through the baffle aperture of the region around the ETM than the ITM will see. The ETM is covered with first contact, which produces the irregular reflections. The view of everything, except the ACB, is blocked by the cryopump baffles. The ACB looks good, the light spots are the photodiodes.