This is a continuity of 31381.
For a bookkeeping purpose, I have extended the spot position thing to PRM and MC mirrors. Here is a summary. They all seem fine as expected.
p2l or y2l gain | alpha | spot position from the center [mm] | previous spot position record [mm] (18106, Apr 2015) | |
PRM PIT | +1.23 | +0.059 | -2.5 | N/A |
PRM YAW | + 1.05 | -0.050 | +2.1 | N/A |
MC1 PIT | -1.3 | -0.020 | +0.84 | +4 |
MC1 YAW | +1.6 | -0.076 | +3.2 | +1.9 |
MC2 PIT | -3.8 | -0.18 | +7.6 | N/A |
MC2 YAW | -0.4 | +0.019 | -0.80 | N/A |
MC3 PIT | -1.1 | -0.053 | +2.2 | -3.7 |
MC3 YAW | -2.6 | +0.12 | -5.0 | -2.4 |
The measurement was done with the interferometer fully locked at 25 W in nominal low noise. The measurement precision should be something like 10% or so.
I repeated this for the IMC when the IFO was unlocked, 2W into the vacuum, to see if things are drastically different hot vs. cold. Conclusion: the spots in the IMC are basically the same hot vs. cold, so this probably isn't what is changing our alignment (or something) and giving us the drift down in range as we thermalize after increasing the power into the vacuum.
+2.4
+3.0
+7.6
-0.8
+2.3
-5.1
Some notes on the method, basically transcribing conversations with Kiwamu:
Since the ADS system does not actuate on the IMC mirrors, nor does it read in IMC_MCL, this was done by hand (also by hand by Kiwamu yesterday). I put a 100 count dither line at 20.125 Hz into H1:SUS-MC[1, 2, 3]_M3_DITHER_[P, Y]_EXC using awggui and minimized the appearance of that line in H1:IMC-MCL_OUT_DQ.