R. Short, J. Driggers

Continuing on from our work Saturday, Jenne and I started by double checking the alignment through Amp2 with the same low power (1.53W) seed beam. We increased the current into Amp2 in steps of 2A, and our power through the amplifier was very comparable to the steps we took on Saturday (measured 59.5W at 8.5A compared to 60.8W on Saturday; we chalked this up to not as long of thermalization time as before, still 1W better than install). At this point we had made no alignment adjustments, so we called our Amp2 alignment good.

Before increasing the seed power into Amp2, we placed a 2W power meter after M07 to be able to monitor the seed beam power using that pickoff while leaving the rover power meter to watch the power through Amp2. With the 1.53W seed beam, the power meter read 2.03mW, so this gave us a rough calibration of 753.69 W/mW to monitor the seed beam as we increased it in steps of 10W. At a maximum calculated seed power of 62W (actual 65.6W) we measured 138W on the power meter after Amp2. We then lowered the seed beam to 1.7W and turned off Amp2 in order to check the alignment onto the high power shutter. It looked good, so with the shutter closed, we brought the Amp2 seed beam back up to maximum and turned Amp2 back on.

To check alignment after the high power beam dump, we used the second High Power Attenuation assembly (HPA02) immediately following the shutter to lower the power, then placed the roving power meter in front of the PMC. Using the IR viewer and cards, we confirmed that all beams had good position on necessary mirrors, lenses, and beam dumps up to the PMC. We then moved the rover to after the PMC, raised the power using HPA02 while watching the PMC_REFL PD signal, and attempted to lock the PMC. It locked without issue, however the transmission was low at around 90W and we could see on the PMC cameras that adjustment was needed. I used the picomotors to adjust the alignment and increased the transmission through the PMC to 104W (there's still more adjustment that could be done here, but we called it good enough for now). We lowered the power after the PMC using the third HPA (HPA03) to again check alignment, this time for the remainder of the I/O side of the table and up the periscope into the light pipe, and removed the roving power meter. Alignment again looked good, so we increased the power and were able to lock the FSS and ISS (refsignal needed adjustment from -2.01 to -1.91 to set the diffracted power).

The PSL is now fully recovered.

Edit: Attaching notes from this morning.