In relation to Sheila's investigation on the increased noise in the aux length loops, I ran BruCO on the loop error signals LSC-PRCL_IN1, LSC-SRCL_IN1, LSC-MICH_IN1.

SRCL

The BruCo report can be found here:

https://ldas-jobs.ligo.caltech.edu/~gabriele.vajente/bruco_srcl_1159781057/

Beside some expected coherences, there are quite some ASC signals that are coherent in the 10 to 100 Hz region. Of course, it might as well be that the angular signals are polluted by the LSC control.

• as for PRCL, the IMC WFS has significant coherence all over the frequencies(fig 1 and 2)
• ASC-AS_B_RF36_Q_PIT (fig 3) below 70 Hz
• in the region between 10 and 70 Hz, there is coherence with ASC_OMC_B_PIT (fig. 4)
• finally, there is some coherence with LSC-REFL_A_LF (fig. 5)