Figure 2, that noise coupling seems real. In blue is the DARM spectrum, in green the projected coupling, and in red the projection where the coherence of the bilinear signal is higher than 20%.
In particular the double peaks at 114Hz and 162 Hz are coherent. Note that if we look at just SSFS_B4_Err_Q_unnorm_10kHz or DAQ_Atomic_Clock_phi there is no coherence at these peaks, and the atomic clock signal is coherent only at the 50Hz harmonics.
Figure 3, to understand where the double peaks come from shown are the spectra of DAQ_Atomic_Clock_phi, SSFS_B4_Err_Q_unnorm_10kHz and their product.
Clearly the double peaks at 114Hz and 162Hz are sidebands of lines present in the atomic clock signal modulated by the MICH error point.
Figure 4, the issue is that the atomic clock noise is ~1 order of magnitude higher than during O2 or last February.
The 2018-04-06 a new DaqBox PLL setup was put in operation to reduce the 10-20Hz Timing noise bump.
For the Daq_Atomic_Clock signals, the operation was done at 2018-04-06-11h57m22-UTC
- 2018-04-06-11h57m22-UTC info process:LNFS_dbox_rack stopped
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2018-04-06-11h57m34-UTC info process:LNFS_dbox_rack started
The following plot shows that the Daq_Atomic_Clock_phi noise increase with the new DaqBox PLL setup .
Investigations inprogress
