R. Short, J. Oberling

After the NPRO control box was swapped last week and glitches persisted (see alog80566), we decided it would be best to switch back to the original so that signal readbacks for the NPRO would be accurate. I started by bringing down the PSL in a controlled manner (ISS, FSS, PMC, AMPs, NPRO), then went out to the LVEA PSL racks and swapped control box S/N S2200008 for S2200009. Since this is the control box that had previously been in service with this NPRO laser head, no adjustments were needed to set the temperature and current to be correct. I returned to the control room and brought the whole system back up without issue.

Once it was time to lock the FSS, similar to what was needed with the last control box swap, I manually moved the NPRO temperature down about 0.4K (from 0.19 to -0.23) and locked the RefCav so that the SQZ laser would be happy. I then updated the FSS search parameters and accepted them in SDF (see screenshot).

As I noted in the 10-day trends yesterday (see alog80665), PMC REFL has risen over the past week, so I attempted a remote alignment tweak using the picomotors before the PMC. In the end, I wasn't able to make much of any improvement to the PMC alignment. I also attempted a remote alignment tweak for the RefCav, and here I was able to get a slight improvement from 0.80V to 0.81V on the TPD.

Looking for more things to try to impact the laser glitching and hopefully bring down the amount of PMC reflected power, Jason and I returned to the PSL racks to try adjusting the NPRO pump current. We ultimately raised the current from 2.12A to 2.19A, increasing the NPRO output power from 1.82W to 1.91W according to the PD in front of the laser, but not having much of an impact on the PMC. We also tried slightly altering pump diode currents in the amplifiers, but we didn't see any improvement, so these remain as they were.

I concluded our PSL activities today with a rotation stage calibration following the steps in alog79596. The measurement file, new calibration fit, and screenshot of accepting SDFs are attached.