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Environmental Monitoring (Environmental Monitoring)
paoletti, fiori, menendez, romero - 14:41 Monday 11 February 2019 (44824) Print this report
Seismic and acoustic injections

Today we did a seismic injection in the PR tower as well as an acoustic injection in the laser lab.

The seismic injection was made activating a small shaker that does not work below 10Hz. This was a coloured injection that started at 10:20a.m. and finished at 11:26a.m . We started with an amplitude of 1e-6, whose effect was not noticeable in the V1:ENV_B4_GHOST_ACC_Z channel. That is why we began to increase the amplitude of the injections progressively, until we reached 5e-3, which was noticeable in the aforementioned channel.

As for the acoustic injection, it was done thanks to a loudspeaker placed in the laser lab from 11:50a.m. to 12:20a.m. In order to analize its effect, we focused on V1:ENV_EIB_MIC, which is a microphone placed in the laser lab. Just as we had previously done with the shaker, we progressively increased the amplitude of the signal until we reached 2e-4. The loudspeaker does not work below 50 Hz, so we needed to change the band width with respect to that chosen for the seismic injections.

We must keep in mind that the sensitivity of the interferometer was very low below 100Hz, so all the effects regarding frequencies below 100Hz should not be seen as totally correlated to our injection.

It must be noticed that at 11:34a.m. we had to unplug the cable coming from the shaker and plug the one corresponding to the loudspeaker. It was at this moment that a bump and a reduction of the noise could be noticed.

Analysis will follow.

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fiori, menendez, romero - 18:01 Tuesday 19 February 2019 (44931) Print this report
Today we have computed the noise projection of the acoustic injections in the laser labs for different auxiliary channels, among which we have ENV_EIB_MIC and BsX_TX. We have found out that the noise projection corresponding to ENV_EIB_MIC, BsX_TX and BsX_TY make sense, given that the projection is below the quiet noise. However, in the case of BsX_X and BsX_Y we have seen that at 622 Hz, the projection goes above the quiet time, which is something we don't quite understand. Still, in order to check whether the program was computing everything correctly, we computed the noise projection for 622 Hz by hand . For that purpose, we looked for the following data:
1) Value of Hrec during injection at the given frequency: 7.65e-23 (1/sqrt(Hz))
2) Value of BsX_Y during injection at the given frequency: 9.5e-04 (1/sqrt(Hz))
3) Value of BsX_Y during quiet time at the given frequency: 6.5e-04 (1/sqrt(Hz))
With this we could compute the transfer function at that frequency, which resulted in: 8e-20, which is precisely what the program calculated. Then, the noise projection ends up being: 5.2e-23 (1/sqrt(Hz)), which was also in agreement with the program's output.
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