Mitchell, Disha, Robert
On Friday we finished alignment of the baffles on the +X side of HAM3. This took extra time because we didn’t expect 12 point flange bolts on the PR2 dog clamps that we were moving. Beam spot photos from the BBS showed that we had mitigated retroreflections from the dog clamps and other retro-reflectors that we were worried about, but the brackets for two of the SPI baffles formed strong 2-D corner reflectors with the table top (see figure). We need to hide them with something that is the same height but not normal to the BBS-PR3 beam, and we need to finish aligning the baffles on the –X side. We may also need to treat two of the table baffle brackets on the +X side of HAM3 if they produce retroreflections in PR3 beam spot photos.
Here's some pictures to aide the conversation about "which brackets are SPI bracket retro-reflectors?" These were taken on 2026-06-18 when TJ and I were installing these baffles for the first time (see LHO:90676). Two versions of each photo, one annotated and one not. 2026-06-18_H1SPIH23_ISIK_Baffles_BigPicture_ANNOTATED.jpg shows "looking in the +X direction" big-picture view of the beam splitter from inside the HAM23 mode cleaner tube, and highlights in red which baffles' brackets are the problem. 2026-06-18_H1SPIH23_MinusYSide_Baffles_TopDown_IsometricView_ANNOTATED.png shows a top-down / isometric, "looking in the +X / +Y / -Z direction" view of the -X / -Y corner of the optical table, again calling out the problematic baffle brackets. Saying it out loud -- it's not one baffle's brackets, its both - the -Y bracket of the middle upper panel baffle, and - the +Y bracket of the -Y upper panel baffle. of the ISIK shroud assembly D2400106 Also -- just saying it out loud. Robert shows how shiny these brackets are in the -X view of HAM3 from the beam splitter. "Why aren't these an issue for the -Y view of HAM4 from the beam splitter?" Because HAM4 doesn't have any of these HAM table baffles on its -Y side -- the HAM3 baffles exist because we had to remove the lower panel of the HAM2-HAM3 *mode cleaner tube* baffle on the HAM3 end of the tube (LHO:90138 and LHO:90162) in order to support SPI. But the equivalent panel on the HAM4 end of the HAM4-HAM4 tube baffle is still in place, so these HAM table baffles are not needed.
