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Environmental Monitoring (Environmental Monitoring)
fiori, paoletti, tringali - 18:53 Saturday 28 March 2020 (48846) Print this report
ENV activity: acoustic injections DET lab and DET cryotrap

This morning we countinued the activity of thursday (Acoustic injections in CEB hall) performing more injections:

  1. we did white and band limited injections with one speaker inside the DET lab SAS --> we se the bumps at 50Hz and 160Hz can be easily excited
  2. Marco Vardaro disengaged the squeezer and closed the SQZ shutter, and we repeated similar injection --> the bumps at 50Hz and 160Hz are NO MORE excited
  3. we moved the same speaker next to the SR south flange (see picture) and together with the other speaker that was left on CEB north terrace we produced a beating at 180Hz with 50s modulation (LIGO technique) --> we create a location depended modulation pattern, the data of CT accelerometer and Hrec have to be correated
  4. we performed some band limited and 180Hz line injection with the shaker attached at DET cryotrap --> seems the shaker cannot excite the 180Hz bump, the 180Hz line yes, data to be analyzed
  5. performed some tapping (quick and blind) in some locations of SR and cryotrap (see log file) --> data to be analyzed

Attached is the log file with gps details

Analysis and figures about each item above will follow.

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Paoletti, Fiori, Tringali - 20:00 Monday 30 March 2020 (48865) Print this report

Here we report in more detail the points 1) and 2) of log entry #48846

We use as reference the time slots when a white noise (nominally 10 to 990 Hz) was generated with the loudspeakers in SAS DET room:

08:53:00 UTC + 420s Noise ON and SQZ ON (plot GOLD)

09:13:30 UTC + 360s Noise OFF and SQZ ON (plot BLUE)

09:55:30 UTC + 420s Noise ON and SQZ OFF with also shutter closed (plot PURPLE)

(the noise level was not exactly the same for GOLD and PURPLE injections, the latter being a higher factor 2, but this is not relevant for this analysis)

The overall plot shows that there are:

  • a first "bump" (green circle, 11 to 16 Hz) which depends only on the SQZ shutter position (no acoustic noise has actually been generated below 20Hz, see the central part of the plots);
  • a second "bump" (first red arrow, around 27 Hz) which is clearly excited by the acoustic emission and disappears when the latter is off or when it is on but the SQZ shutter is closed;
  • a "volcano" structure centered on 48 Hz (second red arrow), as above;
  • a high frequency bump centered on 163 Hz (third red arrow), as above.

We have made some detailed graphs for a better visualization of the very low frequency part (from 10 to 30Hz), of the volcano area and of the bump at 163 Hz.

In all cases where it was possible to excite the DET room with acoustic noise, we can see an increase in the seismic motion of the SQZ bench (lower part of the plots).

It is important to note that some of these bumps appear and disappear with the SQZ shutter position even when no acoustic injection is performed (see this plot attached to log entry #48855).

 

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