TJ, Ryan S, Elenna
Today we (once again) took some time to try to commission the PRM ASC loop in PRMI ASC.
We locked PRMI, and I engaged the beamsplitter ASC. I was able to see by moving PRM pitch around, and watching the buildups, that the "old" error signal, REFL A RF9 I, was a great error signal and only required a sign flip.
However, PRM yaw was harder. I checked REFL A and B RF9 I and neither signal worked. I checked POP X I next, and saw that the signal worked just fine. This doesn't make a lot of sense, but it works. I updated the guardian accordingly.
To test that the guardian changes work, we brought the ISC_DRMI guardian down, which unlocked PRMI, and re-requested PRMI ASC. We fixed a few guardian errors and tried again. It worked fine.
These are the changes made:
- edited the input matrix for PRC1 pitch and yaw as stated above
- edited the PREP PRMI state to engaged DC centering on POP (DC6)
- edited LSCparams to have PRC1 set to True in PRMI ASC
Loaded and tested!
Rereading this, I realized that saying it "didn't work" is very vague.
More words:
I stepped around with the PRM slider, watching both the POP18 and POP90 buildups. While watching the buildups, I looked to see when various signals crossed zero. For PRM pitch, REFL A 9 I clearly had a good zero crossing at the maximized buildup. The difference was the sign flip, which I tested by turning on the loop and seeing the error signal go the wrong direction (away from zero), and then the right direction (towards zero) when the gain sign was flipped. To maintain the gain sign as set by the guardian, I flipped the sign on the input matrix value from positive (pre-vent value) to negative.
For PRM yaw, the REFL signals did not cross zero when the buildups were maximized. However, the POP X RF signal did cross zero. I also watched the POP QPDs, which are sensitive to PRM, but also require some offset. I decided setting some offset and trying to use the REFL WFS was probably a bad idea, so I chose POP X RF yaw as the error signal. I calibrated it by measuring the signal difference in counts compared to the sliders steps I took, which are in urad. I checked the overall sign using the similar loop engagement test I described above.