Fringe wrapping excitations (all made in test_L excitation with 10000 counts amplitude).
- CPY 0.2 Hz longitudnal excitation, 7.6 um peak to peak as measured by the osems, with alignment sliders at 300 P, -325 Y Feb 24 18:01:30-18:06:30 UTC. (ref2)
- CPX 0.2 Hz longitudnal excitation, 7.8um peak to peak, with alignment sliders -300P, -100Y, at 18:09:10-18:14:30 UTC
- CPX 0.2 Hz longitudnal excitation 7.8um peak to peak, with alignment slider 0,0 18:18:28-18:22:28-18:27:49 UTC ref 4
- CPY 0.2 Hz extitation, 7.8 um peak to peak, alignment biases off 18:23:47 UTC
Rough summary: CPX and CPY have similar levels of fringe wrapping from a longitudnal excitation. For CPY, a third shelf appears when I turned off the ailgnment offsets that Robert set to reduce the noise he sees while shaking the input arm.
From Accadia et al the shelf frequency = abs(2*velocity of scatterer/lambda). So our first shelf at 17Hz comes from some path with a velocity of 9 um/second, the second fringe at 33Hz from a path with twice that velocity at 17.5um/second, and the third fringe which only shows up for CPY with no offsets is at three times that velocity at 50Hz (27um/second). The max veolcity of R0 should be 2 *pi*0.2 Hz * 7.7um/2 = 4.8um/second. That's consistent with the first shelf being from some scatter path hits the CP twice, so it scatters out of the cavity by being reflected off one of the CP faces, and also scatters back in by a reflection off the CP.
Side note, the damping signals for the two CPs seem rather different, I will try to come back later to look at why they are so different.
Editing to add after looking at the damping loops with help from Jeff:
ITMY's R0 F2 has a lot of 60Hz noise. Jeff suggests copying the 60Hz notch filter from the main chain damping loops into the oseminf filter banks for the reaction chain, and he recomends doing this for F1,F2, F3 and SD since these are all on the same electronics chain.
At first it seems that we have rather different settings between the R0 damping filters for ITMX + ITMY, but the gains for ITMX are incorporated into filter banks, in the end the damping loops seem to be the same. The attached spectrum comparison shows that the motion of the two reaction chains looks similar on the osems.
