== Comprehensive analysis of the cavity scan held on the last Thursday ==
Here I report the results from the automatic peak finding and fitting of them for the cavity scan we did the other day.
From the fitting results and some mathematics, the cavity length, transverse mode spacing, and roundtrip Gouy phase are obtained:
L = 2999.990(2) [m] <=> FSR = 49.96557(4) [kHz]
TMS = 34.79(5) [kHz]
ζGouy = 4.375(5) [rad] = 250.7(3) [deg]
Here I put the two plots, one of which shows the fitting results of the cavity scan and the other of which shows the fitting for the transverse mode spacing.
Note that the error for TMS is evaluated from the systematic error you can see in the bottom plot showing the residual error.
I also attach the code I used.
= Some notes =
* On radii of curvature of ITMX/ETMX.
According to Hirose-san's report, R_ETMX = 1907.83 +/- 2.14 [m], R_ITMX = 1904.54 +/- 2.08 [m].
From these numbers, TMS should be
TMSfrom RoC = 34.703(24) [kHz].
This is not consistent with the value obtained from the cavity scan.
Note that TMS value obtained from the cavity scan we did on Saturday gave us almost the same number, 34.78(5) [kHz]
There is some discrepancy between the measured Gouy phase and that expected from the characterization of the coated test mass. Why???
This dicrepancy corresponds to ~ 5-10 [m] change of the radii of curvature.
