Today we followed up on the alignment change we saw yesterday 60408.

The story we understand right now:  Yesterday and this morning we thought that the problem was an alignment shift of ZM4.  We saw that the beam reflected off the beam diverter was reaching the diode on SQZT7, making us believe that alignment of the beam leaving the VIP is not the main problem (still true).  We also saw that the beam was poorly centered on ZM5, which made us think that the shift was in ZM4.  Looking back at the alogs, it is likely that the beam was never well centered on ZM5, and the irses were placed with the beam very off center on ZM5. We believe that ZM5 was bumped or somehow the alignment changed while we were doing beam profile measurements Tuesday mornig.  We attempted to restore our alignment through HAM5 by restoring the alignment to the irses, but this didn't work well.

Details:

This morning after Rahul and Betsy had a close look at ZM4, Rahul and Camilla did a pitch adjustment to get the beam centered on ZM5 (this was about 3200urad according to the osems).  Rahul recentered the osems, then they noticed that the beam was now very far off on the first iris right after ZM5.  After this they adjusted again the pitch of ZM4 to center on the iris, which undid all but 800urad of the original pitch change.  I believe that Rahul never recentered the osems after that because I asked him not to do it right away. 

We tried to align ZM5 using the sliders to center on the second iris, and found that we were saturating.  When we looked at trends of ZM5 osems, we saw a large shift in the osems around 11:30 am on the 26th, which is when we had the beam profiler in the chamber around ZM5.  This seems likely to be what caused our alignment confusion.  Rahul and Betsy moved the ZM5 cage and pitch adjustment on M1, then we used sliders on ZM4+5 to center on the irises.  We were not going through the OFI on the return from SRM, and were high on the SRM iris.  Camilla used the IR viewer to try to get a more precise alignment to the irses, but this still did not get us through the OFI on reflection off SRM. 

We had hoped that these irises would give us an alignment reference that would allow us to restore our path through HAM5 once the chamber is closed, but it seems like we can't rely on them confidently.  We will do another round of alignment tomorow, centering on ZM5.