J. Oberling, R. Short, C. Compton, T. Guidry, J. Driggers
Continuing from yesterday, this morning Camilla and Ryan began First Contact cleaning the lenses for our chosen mode matching solution. I met with Tyler and he modded the spacer plates for us. Once that was done I went into the enclosure to begin building the new lens mount stack and place the rail for it. While in there also looked at exactly where on the table our new lens would be going. In checking this I found a discrepancy in the As Built layout; the NPRO was placed in the wrong position, 1/2" back from where it's actually sitting. Seeing this, I left the enclosure and re-ran the mode matching to account for this change in distance to Amp1's input beam waist location. The solution stayed the same but the lens locations changed slightly. I finished this as Ryan and Camilla were finishing up the lens cleaning, and it was almost lunch time so we broke for lunch.
After lunch, Ryan and I went into the enclosure to start installing the mode matching lenses. While in the enclosure Jenne (from the CR) and Ryan worked to find the script that Varun wrote back during the '21 laser upgrade to quickly do a Gaussian fit to beam propagation measurements, which will really speed up checking the results of our mode matching; they found the script and it lives in /ligo/gitcommon/labutils/beam_scans. We then installed L01, an f = +222mm lens, and recovered the beam alignment. With the new L01 in place we then re-installed the EOM and aligned it. Next was installing the new lens, an f = -334mm lens now known as L21. We roughly placed it, then used a scale to measure back from M03 to place it more accurately. It was at this point we discovered yet another discrepancy in the As Built layout; I had not put the beam path from mirrors M03 and M04 on the correct row of holes, which added 2" to our NPRO to Amp1 distance. So once again we left the enclosure to take yet another look at mode matching (we have now discussed talking with CDS about getting JamMT on one or both of the computers in the Laser Room; this requires an installation of the Java Runtime Environment); the lenses did not change but their positions did (as expected), see attached. This done, we went back into the enclosure to install the last 2 lenses in the proper locations for our mode matching solution.
We had to remove WP02, as L21 now sits where WP02 once did (not a big deal, the position of WP02 is not critical). This done we installed L21 and aligned it; during alignment we had to drive the lens to the furthest extent of the lens mount to align the beam, which should not be the case if our M02 to M03 alignment was good. Turns out we were checking the alignment at a bad point, beyond M03. M03 and M04 are used to align the beam into Amp1, so the beam won't be exactly on a row of holes there, but the alignment jig we use (one of the tall posts with pinholes in it at beam height that we stick a power meter behind, then adjust the optic being aligned until power is maxed) sit on a row of holes. By aligning L01, the EOM, and L21 to a point beyond M03 we were steering the beam off of our previous M02 to M03 alignment. So we moved the alignment post to in front of M03 and re-aligned L01, the EOM, and L21; things looked much better after that. Finally we installed and aligned the new L02, an f = +222mm lens. We stopped for the day at this point. The final attachment is the new layout between FI01 and M03.
On deck for tomorrow, in order (likely to bleed into the weekend/next week at this point):
- Beam propagation measurements (done with the leakage beam through M03) and any required adjustments to get the input beam waist and position correct for Amp1
- Begin recovering Amp1
- Check everything is still OK between Amp1 and Amp2
- Begin recovering Amp2
- Check everything is still OK between Amp2 and the PMC
- Recover PSL stabilization systems
