Wed afternoon Nergis and I went to SQZT7 to get a couple of beam profiles after the ZM4 preload was adjusted, before the ZM5 swap. 

We took two measurements with the same psams settings but different centering on ZM2, based on what Camilla and Madi did in 90946 .  The data labeled as  nominal position is for these sliders where Camila reports that the beam on ZM2 is 5.85" off the table, and the data labeled raised is for these sliders where the beam is actaully lowered to 5.75".  The center of ZM2 should be 5.5" off the table.  M^2 went from 1.35 to 1.28 horizontal and 1.25 vertical with the improved centering, and the relative astigmatism also improved from 0.13 to 0.02 Ryan found the definition of relative astigmatism on page 122 (pdf page 129) of the BC207 manual here.

ZM4 strain guage was saturated when the PZT was much above 100V, so this morning Daniel came to SQZ racks with Ryan and I and changed some resistors, Daniel will add the details.  ZM4 strain guage is now working well, with values between -4.1V to 2.7V, and Ryan turned the servo back on. 

Yesterday morning, I noticed that for some psams settings, the beam was clipping on the top periscope mirror and that then we measured quite high M^2 values.  I wondered if clipping on that persicope could explain more of our M^2 measurements.  Today Ryan Short and I carefully aligned the psams to get the beam centered on the two irises on SQZT7.  We raised the top periscope mirrors, and Ryan adjusted both periscope mirrors to get the beam well centered on the irises again.  When we did this, we noticed that only one of the bolts that holds the top periscope mount to the periscope structure was tight.  

After this Ryan and I did another round of profile measurements with the new preload and working strain guage on ZM4.  We took 5 points over the range of ZM4 with ZM5 PZT at 100V, with the ZM5 strain guage not working, then took 3 points with ZM5 at a strain guage of -4.5V which is 20V on the PZT, because the ZM5 strain guage is working there we can compare these to measurements taken before ZM5 stopped working.  

Unfortunately, even after moving the periscope mirror the M^2 values are in the range of 1.4 to 1.23, so the clipping on the periscope mirror wasn't the explanation for the high M^2