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AdV-COM (AdV commissioning (1st part) )
swinkels - 13:59 Friday 04 August 2017 (39039) Print this report
Identification of drum modes
By comparing 10 days of data from the new server to track the drum mode frequencies with the temperature sensors on the ring heaters, it is finally possible to identify who is who. Fig 1 shows all temperatures plotted vs all frequencies, with the winning combinations on the diagonal. The temperature dependence is close to 0.9 Hz/Kelvin for all peaks. The fifth peak cannot be reliably correlated to a mirror temperature. The frequency of this peak could be either stationary, or the measurement could be too noisy to identify a mirror for now. Fig 2 shows the family portrait, with the NI, WI, NE and WE frequencies at respectively 7808, 7810, 7811 and 7812 Hz. Fig 3 shows that there is currently no risk that any of the frequencies will cross, if the mirror temperatures are kept close to where they are now.

I tried to make the usual etalon plots of B7_DC/B4_DC and B8_DC/B4_DC versus the ITM drum mode frequency, but it seems too early to see anything interesting. The north arm should have done only 0.2 fringe. The west arm should have done half a fringe, but the SWEB alignment issue caused changes of the B8_DC power independent of the etalon effect. I also tried to make a similar plot using the finesse calculated using the calibration lines, but also this was not successful.
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