daniel.sigg@LIGO.ORG - posted 17:14, Wednesday 16 November 2016 - last comment - 10:42, Friday 18 November 2016(31554)
Frequency Noise Spectra
The attached plots show the frequency noise seen by the reference cavity (green), the IMC (red), the REFL port (blue) and the POP port (brown). The first plot also shows the estimated in-loop suppressed noise in a lighter color as well.
The second plot shows uncalibrated traces but with a 30 kHz bandwidth. The peaks at ~7250 Hz and at ~13.6 kHz are already present in the IMC spectra when the interferometer is unlocked, and, therefore, are not introduced by the REFL servo. The I' channels are the DAQ sensor channels closest to true in-phase signals.
Non-image files attached to this report
Comments related to this report
A few notes to the calibrations:
- The reference cavity calibration is based on the PZT sensitivity of the Innolight laser. It will be good up to the FSS crossover.
- The in-loop curve is based on an FSS servo model which assumes a nominal ugf, but with a crossover a factor of 2 low. This in turn produces gain peaking around 2 kHz which is required to explain the coherence with MC_F.
- The MC_F calibration is based on the VCO calibration.
- The in-loop curve is derived from an IMC length model with an ugf of 64 kHz.
- The LSC REFL calibration is based on alog 30549. It agrees with the IMC model and the VCO calibration.
- The in-loop curve is derived from a interferometer REFL model with a ugf around 20 kHz.
- The PRC calibration is based on a simple scaling so that it agrees with in-loop REFL at 7 kHz. This is motivated by a coherence of 100% at this frequency.