andrew.lundgren@LIGO.ORG - posted 13:29, Friday 01 May 2015 - last comment - 17:07, Friday 01 May 2015(18148)
Changing coherence with SRCL
We see some bursts of noise broadly around 200 Hz (first plot - you may need to squint a bit). I guessed that this was due to non-stationary coupling with SRCL, a la Gabriele. The second plot is a coherence spectrogram for the same five minutes. The coherence is indeed changing in bursts. The third plot is the coherence with MICH, PRC, and SRC over the same time. The coherence with MICH especially is extremely high; I think I saw that the feedforward is disabled?
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Yes, we have not yet finished commissioning the MICH and SRCL feed-forward with the better recycling gain. For the sake of robustness, we've decided not to advance beyond "LOWNOISE_ESD_ETMY" to the "LSC_FF" state for the mini run.