[Jax, Aidan, Thomas]

I've run an initial analysis on the cavity scan data from last night. The setup was as follows.

1. Cavity scans were run every 90s or so. We scanned over the range [36,56] kHz every 20Hz. The amplitude and phase response of the injected frequencies were averaged over 1000 oscillations.

2. After 10 minutes of cavity scanning, we started the ETM RH at 3.255W per segment (or a requested power of 315mA)

3. The cavity scans were left running for 15 hours or so before we switched off the RH.

4. The frequency of the LG10 mode was determined for each cavity scan. The attached plot shows the frequency shift of this mode vs time. The LG10 mode shifts by 2x the HOM spacing.

Notes

(a) the WFS feedback coupled with the thermal lensing started to drive the cavity away from resonance after ~2hrs of heating. We lost lock and spent about an hour trying to recover. Hence there is no data shown from [t=2hr to t=3hr];

(b) I've also plotted the COMSOL estimate of the frequency shift for 6.5W of heating. The model predicts a frequency shift ~90% of the size of what we measured.

(c) For reference, change in the ROC is ~76m/kHz * the change in frequency of the LG10 mode (or delta ROC = 151m/kHz * the change in the HOM spacing).