I was hoping to do an OMC scan today and it's tantalizingly close with the angular loops closed but it seems like the both OMC_DC are saturating even though I've turned off the all the gains and whitening(de-whitening). The attachment shows the scans going negative at 2 Watts into the IMC.
So I turned down the power into the IMC to about .1 watts and things got better but it was still very unclean scan data so I'm a little confused because Dan Hoak's OMC scan was able to handle about 4 miliamps on OMC_DCPD Sum.
I've misaligned SR2 so that the OMC isn't flashing and returned the DCPD whitening filters to their nominal observe state (1 whitening + 1 dewhitening). Also I've turned off the OMC ASC and the AS WFS DC loop so that if the IMC loses lock the optics don't go crazy.
I turned down the power to the IMC to .1 Watts and misaligned SRM to get rid of the SRM flashing and there's some decent, clean OMC resonances.
Attached are 3 OMC scans with SR3 at 0, 0.5, and 1.0 Watts. Before I take more data at higher SR3 heater power, I'll see if these results make sense. The columns are time in seconds, PZT offsets in Volts, and OMC_DCPD output in Amps.
Once we lock DRMI, we can try this again.
I've ran your scans through through my code. The plots are attached below. The "mismatch" (i.e. ratio of the average of all second order peaks to the average of all zeroth order peaks) is 0.08 +/- 0.02, 0.09 +/- 0.02, 0.083 +/- 0.005 for 0W, 0.5W, and 1W respectively. The uncertainties came from the standard deviation of the height of the peaks. Most of the uncertainty came from fluctuations in the height of the zeroth order peak. As it stands now I can't really draw any conclusion about the SR3 heater. It could be that the pzt is scanning too quickly, or the beam/cavity could be fluctuating in time. I can't say for sure. There's also this weird thing where the resonances on the upward pzt ramp appear in different locations to the ones on the downward ramp, even though they should correspond to the same length changes in the cavity. Could be some hysteresis in the pzt response. For the analysis I only used downward ramp on the pzt. Driving the pzt with a sawtooth waveform should get rid of hysteresis (since it would only ramp one way), but there might be some artifacts from the sudden voltage change.
