I photographed the recently installed baffles on the EY P-Cal periscope. Figure 1 shows a before/after comparisons of views from the ETMY beam spot with labeled features. The glints in the “before” picture are thought to be responsible for the appearance of raven pecks in DARM (https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=37630).

Figure 2 is a close-up of the reflections on the cylindrical portions of the Cryo and P-cal periscope baffles, suggesting that the light is from the gate valve and so will not be there when the valve is open. However, the gate valve reflections suggest a possibility: since the cryopump-baffle cylinder is not perfect (see reflection in Figure 2), and the cylinder may also be slightly angled, light from the ITM may reach the ETM through shallow-angle reflection off of the inner surface of the cylinder. I think that the ITM can "see" the inner surface so it should probably have been a cone or otherwise baffled.

Figure 3 shows a before/after comparison with much of the light from the gate valve blacked out. The remaining glints are from the finishing grooves on the view port blank-offs, where the lines of the groves are normal to the direction to the beam spot.

The P-Cal periscope baffles have not yet been installed at EX but I took photos to see if there are glints that won’t be covered. Finishing grooves that are deep enough and other linear structures could cause glints (see https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=40454 ) from regions of the periscope that won’t be covered by the new baffles. But Figure 4 shows that there are no such glints that will not be covered up by the current design.