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Detector Characterisation (Glitches)
direnzo, longo - 16:12 Wednesday 27 March 2024 (63761) Print this report
Scattered light glitches and larger noise at low frequency due to bad weather conditions

As already happened a few weeks ago, #63420, associated with the bad weather conditions of this morning and the large microseismic noise, there was an increased rate of scattered light glitches, best witnessed by LSC_SRCL, and reproduced by the V1:SBE_EIB_GEO_H2_200Hz channel.

Figure 1: spectrogram of a scattered light glitch in LSC_DARM.

Figure 2: Top: spectrogram of several scattered light glitches in LSC_SRCL. Middle: extracted arch frequency and predicted frequency of the scatterer surface according to the equation f_{\text{fringe}} (t)=2n\frac{|v_{sc}(t)|}{\lambda}, with \lambda the laser frequency, v_{sc} the speed of the scatterer, equals to the time derivative of SBE_EIB_GEO_H2_200Hz channel, and n the number of times stray light gets reflected back and forth between the test mass and the scatterer before it joins the main beam arXiv:2007.14876 . Notice that the y-axis is the same for both the reconstructed frequency of the arches and the predicted frequency. In the box, the value of the Pearson correlation coefficient between the two quantities, 80%.  Bottom: time series of SBE_EIB_GEO_H2_200Hz.

We are currently running an extended analysis to find other correlated sensors, using the list of position, speed, and acceleration channels documented in this git issue.

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direnzo, longo - 18:37 Wednesday 27 March 2024 (63764) Print this report

We have analysed all the raw channels with units of position, speed and acceleration, transforming them to reproduce the frequencies of the arches. The results confirm the V1:SBE_EIB_GEO_* family as the channels that reproduce best the frequency of the arches in LSC_SRCL. Speed and acceleration channels are not good predictors of these arches.

In the attachments, three text files with the most correlated position channels (truncated to Pearson correlation values larger than 0.1), speed and acceleration channels (truncated to 0.04).

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