Reports 1-1 of 1 Clear search Modify search
AdV-ISC (Commissioning up to first full interferometer lock)
casanueva - 11:59 Wednesday 29 June 2022 (56300) Print this report
Optical Gain of the PR angular error signals

Using the angular lines that are injected to the PR mirror I have computed the optical gain of the corresponding error signals. The calibration is based on the Local controls readout signals of the PR mirror, which give the information in radiants already. The calibration has been made by making the transfer function between Sc_PR_MIR_T* and the corresponding error signal. We have checked both the 6MHz and the 18MHz signals. The coherence and optical gain is shown in Figures 1 to 8.

IN order to make a comparison with simulation, we have normalized the optical gans by the total power reaching the quadrants and then we have combined the information from both quadrants (sqrt(QD1^2 + QD2^2)), to remove the uncertainty on the gouy phase of the sensors. All the information is summarized in the following table:

H OG [W/urad] OG norm [1/urad] Combined OG [1/urad]
B2 6MHz QD1 8.2e-3 5.5e-2 0.39
B2 6MHz QD2 6e-2 0.39  
B2 18MHz QD1 2.5e-4 1.7e-3 3.4e-3
B2 18MHz QD2 4.5e-4 3e-3  


V OG [W/urad] OG norm [1/urad] Combined OG [1/urad]
B2 6MHz QD1 4.7e-3 2.7e-2 0.93
B2 6MHz QD2 1.7e-1 0.9  
B2 18MHz QD1 3.3e-4 1.9e-3 6.4e-3
B2 18MHz QD2 1.1e-3 6.1e-3  


Images attached to this report
Comments to this report:
boldrini - 15:55 Tuesday 05 July 2022 (56357) Print this report

The measured OGs are expressed in mW/urad, not W/urad.

boldrini - 12:47 Thursday 07 July 2022 (56377) Print this report

The simulated OGs for the angular DoFs are as follows (in \mu rad^{-1})

  • PR_AA (B2_6MHz): 6.1
  • BS_AA (B1p_50MHz): 1.9
  • DIFFp (B1p_56MHz): 258
  • COMMp (B7 + B8): 2.35

They have been obtained by normalizing the each signal by the power impinging on the relative quadrant, and then normalizing on the Gouy phase by taking \sqrt{nf^2+ff^2}, where nf and ff are the original component simulated in the near-field and far-field regime respectively.

casanueva, mantovani, boldrini - 10:49 Friday 08 July 2022 (56384) Print this report

Using these calibration factors we can estimate the residual angular movement of the PR loops: 16 nrad rms for the TY and 3 nrad rms for the TX.

Images attached to this comment
Search Help