(Dan, Alexa)
Since the MC cavity length was adjusted, we repeated the MC cavity length measurement as described in alog 9679.
Data_refl9_short.txt is the data collected using REFL9. ArmCavityLength_v2.m is the script that determines the length given the zero crossing of the projection. The attached plot show the results with a linear regression included.
The cavity length is determined to be L = 16.471698m ± 4um assuming 2 Hz accuracy. The 2 Hz accuracy comes from the accuracy of the IFR plus the extreme rattyness of the transfer function.
Compared to the previous measurement the delta L = L_old - L_new = 0.001914 ± 6um. This is very close to the expected 2mm reduction in length as mentioned in alog 12654.
If desired, we can repeat the measurement and include a zero crossing for REFL45 as well. However, we just wanted to make a measurement and get the result public...
Looking at the PRC length measurement from alog 10642, we can reevaluate the relative length mismatch:
| Parameter | Value | Unit |
|---|---|---|
| FSRPRC | 2.600075 | MHz |
| LPRC | 57.6508 | m |
| FSRMC | 9.100229 | MHz |
| LMC | 16.471698 | m |
| FSRMC / 3.5 - FSRPRC | -5 | Hz |
| (1 - FSRMC / 3.5 FSRPRC) LPRC | 0.1 | mm |
| (1 - 3.5 FSRPRC / FSRMC) LMC | -0.03 | mm |
Right on target! 9.100230 MHz should become the new modulation frequency.
