Kiwamu, Stefan

Using the pr2spotmove script (see alog 28420), we moved the spot on PR2 in lock by almost 1 milimeter.

Conclusions:

- The carrier recycling gain desn't care about the PR2 spot positon.
- The POP beam from PR2 to the invacuum POP diode is fairly close to the edge of the visibility aperture. This might be an issue for LSC aux noise.

Details:

- To be able to explore the full range of motion, we had to switch back to the REFL B WFS for PRC2 / PR3 control. We BTW verified that this WFS also works at 40W (and during the power increase).
- With that, the move-limiting aperture is the path from PR2 to POP. We can move until the POP_A loses the beam. The pitch and yaw min/nominal/max values for PR3 alignment angles are
    Pitch value / delta:
     min: -302.95  / -4.6urad
     nom: -298.35 / 0urad
     max: -275.35 /  +23urad
    Yaw value / delta:
     min: 257.45 / -16urad
     nom: 273.45 / 0urad
     max: 281.45 / +8urad
  Notice how close to the edge we are in pitch - this could be a factor for PRCL/SRCL/MICH auxiliary length noise and scatter coupling. We have to revisit this in low-noise.

- The 27.6urad move in pitch (24urad in yaw) peak-to-peak move corresponds to 0.9mm (0.8 mm) for the PR2 spot position. Note though that for the beam in transmission of PR2 that corresponds to several spot sizes of motion. (The virtual beam waist behind PR2 is 114u, i.e. we moved the spot more than 7 beam waists. As a result the beam completly left the POPAIR camera view.)