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Interferometer_sensitivity_studies (General)

Vajente - 19:02 Monday 02 May 2011 (29263)

Some coherences below 50 Hz

I tried to make a compilation of frequencies that show some coherences below 50 Hz.

There are large regions of coherence with NI and WI tx control below 20-30 Hz, where the coherence can be as high as 0.5.

Here are others frequencies. Last number in each line is the maximum coherence

12.63 Hz Pr_B2_8MHz_ACp 0.74
13.37 Hz Sc_WE_F7_CoilR 0.88

13.12-13.85 Hz Pr_B1p_d1_ACq peaks 0.77 @ 13.61 - 0.87 @ 13.79
14.71-16.30 Hz Pr_B1p_d1_ACq peaks 0.61 @ 15.93 - 0.79 @ 16.24

14.00 Hz Ti_1PPS_Atomic 0.59
14.40 Hz Pr_B2_8MHz_ACp 0.72

18.62 Hz Pr_RFCRef_DC 0.61
26.43 Hz Sc_MC_zCorrR 0.40
28.75 Hz Em_SETONT01 0.58
29.05 Hz Pr_B2_d2_ACq 0.61 + Pr_RFCRef_d1_DC 0.60

30.00 Hz Gc_Al_q81dc 0.43
34.91 Hz Em_SEDBCE15 0.63 + Em_SETODE01 0.61
35.58 Hz Em_SETODE01 0.37
36.44 Hz Pr_6MHz_NE_PhErr 0.81 + Em_MABDCE01 0.59
37.05 Hz Pr_B1_ACq 0.47
37.41 Hz Em_SEDBCE15 0.66
37.66 Hz Em_SETONE01 0.52
37.96 Hz Pr_B1_ACq 0.48
39.98 Hz Bs_PMC_DR_DCHF 0.39
41.99 Hz Sc_IB_IMC_QN_ACv 0.47
42.85 Hz Bs_IMC_QF_DCv 0.46
43.33 Hz Sc_IB_IMC_QN_ACv 0.39
43.95 Hz Em_SEBDCE07 0.44
44.25 Hz Em_MABDWE01 0.67
45.47 Hz Pr_B1p_d1_ACq 0.49
46.39 Hz Pr_B1p_d1_ACq 0.78
49.07 Hz Pr_B1p_q2_ACqv 0.42

Comments to this report:

majorana - 21:50 Monday 02 May 2011 (29264)

It is not clear too clear which are the regions of coherence mentioned in Gabriele's entry. Does it mean that in 20-30 Hz region the contribution of tx control of NI and WI is coherent up to 0.5 and that the coherence with those correction signals is canceled only at :
26.43 Hz (Sc_MC_zCorrR 0.40),
28.75 Hz (Em_SETONT01 0.58)
and
29.05 Hz (Pr_B2_d2_ACq 0.61 + Pr_RFCRef_d1_DC 0.60) ?

fiori - 9:55 Tuesday 03 May 2011 (29268)

About the 44Hz: I can add that this same was present also in VSR3 (27553). So we can at least exclude recent additions like the Chrocc. I add that there is also a bit coherence at its harmonic, around 88Hz. I considered if this could be again fans in the CD crate (Suppression of 44Hz and 88Hz bumps) but I would say no. In fact, differently from that case (see 23483) now the dark fringe noise is coherent with magnetic probes and not coherent (or very tiny) with the mirror coils current. Now the signal is very well visible in fixed magnetometers spectra, indicating for some intense source (a fan?) which might couple noise directly to mirror magnets. We can do some hunting with portable magnetic probes.