A chart which summarizes the data we have or we can estimate.
in orange, the case 1, where we suppose the initial cold Finesse is the one measured by modulation technique in December 2019 (F=20.8k).
and in green, the case 2, where we suppose the initial cold Finesse is the one measured by "zero compensation" technique between transmission and reflection signals during the power-up measurements (F~11k).
clearly, the case which matches better the only one data (written in red) of input power and then of cavity gain, is the Finesse estimated by the "zero compensation" technique. it matches also better the gain of the cavity measured after M1 had its hole and for which the estimated Finesse of 4k, and then estimated gain of 277 by "zero compensation" technique is not so far from the measurement of 185 (the gain is may be higher than 185 as it is possible we had some additional misalignment which reduced the gain).
| Ronic Chiche wrote: |
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the 10th of January, we increased the power of the amplifier to study the cavity transmitted and reflected power signals.
analyzing the noise transfer functions of transmitted and reflected power one could deduce the Finesse of the cavity.
the power of this technic (if it is confirmed) does not depend on the decay time of one signal which depends on the speed of the cut off but on the difference between reflected and transmitted transfer functions,
and then is independant of the cut off speed.
here are 6 analysis of the Finesse when the cavity is cold, depending only on short lock periods.
5 of them agrees on a Finesse around 11k.
the 6th estimation at 40kW stored in the cavity is about 4k but now, we know that the M1 mirror had suddenly a hole for this power... thus the Finesse value is reasonable.
we can then, use the non conservation of TRANS+REF signal to estimate the FInesse decrease when the cavity is hot... to be done
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