KAGRA Logbook

PEM (Center)

tatsuki.washimi - 13:19 Tuesday 02 May 2023 (25081)

Accelerometers on the OMC chamber

We put the portable accelerometers on the OMC chamber for the shaker injection test.

CH1: +X, +Y side
CH2: -X, +Y side
CH3: +X, -Y side
CH4: portable (near the shaking points)

CAUTION

The cabling is not appropriate because it is temporal for the measurement on 5/4 and we believe no one will go there during the golden week holiday.

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Comments to this report:

takaaki.yokozawa - 12:19 Monday 08 May 2023 (25140)

I checked the spectrum for setting accelerometers.

Fig.1. ACC1(+X +Y side, horizontal direction) vs ACC2(-X +Y side horizontal direction).
There are large three peaks in 20.3, 21.4 and 23.0 Hz.
Also there several peaks with higher coherence.
Except for the peaks, the coherence is not high, especially above 100 Hz(Even the shape is similar.)
The spectrum shape itself was different between 60 - 90 Hz, this is unknown.

Fig.2. ACC1 vs ACC3(+X -Y side, vertical direction, not a chamber)
Compared the spectrum, many peaks became smaller.
Also, the structure above 200 Hz was changed.
We need to check this is due to the position or direction of accelerometer and/or vibration source.
It may affect to the shake injection test, we need to inject the many position and/or additional direction.

Fig.3. ACC1 vs ACC at AS table
Mostly independent. Some common sound effect may exist, see Fig.5.

Fig.4. ACC1 vs ACC at OMC bellows leg.
Several peaks have coherent, but the amplitude for OMC leg bellows is smaller than chamber (We don't know the position and direction dependence).
Most vibration source may come from the chamber(?)
Some common sound effect may exist, see Fig.5.

Fig.5. ACC1 vs booth MIC
Several peaks have coherent, one interesting is there are three coherence around 20 Hz.

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