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AdV-TCS (Wavefront sensing)
bersanetti nardecchia rocchi ruggi - 0:38 Thursday 28 September 2017 (39599) Print this report
NI RH test
During this shift some tests turning ON the NI RH with the ITF @dark fringe have been performed. The goal was to evaluate the position of the DET-HWS beam on the NI TM in preparation to the NI absorption measurement.
16.02 UTC: RH ON, P_{applied on the RH}=2 W
16.33 UTC: P_{applied on the RH}=4 W
After the increase of power, Paolo noticed an improvement of the sensitivity, in particular a decrease of the peak at 20 Hz and at 155 Hz have been observed.
After  half an hour a worsening of the sensitivity curve has been observed and the RH power has been reduced to 2W (17.22 UTC).
To be investigated.
The RH has been turned OFF at 17.44 UTC.
We analyzed the HWS wavefronts and the RH curvature is clearly visibile in the maps, this means that we are enough centered on the TM (see image in attachment).
The measurement of the NI absorption is postponed to tomorrow morning shift, because of the unlock of the IMC (see operator report).
Images attached to this report
Comments to this report:
nardecchia - 13:17 Thursday 28 September 2017 (39605) Print this report

In the plot you can see the comparison between the two sensitivity curves:

-Purple: the reference one (RH OFF)

-blue: NI RH ON.

Images attached to this comment
fiori, chiummo - 18:50 Thursday 28 September 2017 (39618) Print this report

Figure 1 is one Hrec spectrogram covering the time of the noise reduction.

Here a list of the peaks which reduced in Hrec:

Note that also calibration lines of the PR mirror (62.3 and 357.3Hz) reduced

18.5 Hz (Fig 2)

20 Hz 

62.3 Hz  PR calib

97.3 Hz (Fig.3)

100 Hz

107Hz

155 Hz bump

345 Hz bump (Fig.4)

357.3 Hz  PR calib

375 Hz bump

400 Hz bump

550 Hz bump

 

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ruggi - 23:10 Thursday 28 September 2017 (39621) Print this report

Some of peaks present just before the noise reduction were the ones related to MICH accuracy. The analysis of Hrec brms at 75 Hz compared to MICH rms (fig 2) shows that the strange coupling was not there anymore during the good period.

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fiori - 15:49 Monday 02 October 2017 (39640) Print this report

here the correct plots for 39618:

the first attached here replaces Figure 1 of 39618, the second replaces Figure 3 of 39618.

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