I continued working on the PRMI alignment (see alog 13592) today and finally obtained good alignment. This should be good enough for proceeding with the next steps.

With the new alignment, the PRMI flashes without loosing the POP beam at ISCT1. In fact, one can now see PRMI fringing in the POP camera.

We are almost ready for some locking activity.

(Next steps)

• Re-configure the POP path on ISCT1. (Right now, an analog camera is blocking the beam and no beam is on the POP photodiodes.)
  • POP is necessary for triggering the LSC feedback.
• Setup a digital camera in the ASAIR path.
• Align and lock MICH
  • We can now use the AS demodulated signals !
• Lock PRMI

(alignment)

From the experience yesterday, I learned that a combination of PR2 and PR3 did not improve the POP/PRMI alignment situation for some reason. In fact, it made the forward propagating beam hit the west side of the PR3 suspension cage. Therefore, I wanted to move the input pointing in order to introduce a translation in the cavity axis in the downstream after PR2 while keeping the POP beam angle (almost) the same. To do so, I touched IM4 in yaw. This then required re-alignment of PRM in order to maintain the beam at the REFL port. Also, every time I changed the alignment of IM4, I compensated it by steering PR2 such that I keep the POP beam at ISCT1. I repeated this process multiple times. This was successful. I could eventually obtain an alignment setting where the PRMI flashes with the POP still visible at ISCT1. The attached is the new alignment settings.

After the PRMI alignment, I re-adjusted the PR3 alignment such that the beam reaches HAM6 and ISCT6. I did not check the beam centering on the SR mirrors.

(fun locking)

Since I was running out my energy, I decided not to try the PRMI locking tonight. Instead, I locked PRX for fun. I just used REFL_A_RF45 for now. The ASAIR_LF signal was used to check if it is locked on the carrier or rf sidebands. The attached is time series of some DC signals at the AS port when locking PRX. It is locked on the carrier.