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PEM (Center)
tatsuki.washimi - 12:32 Thursday 30 June 2022 (21330) Print this report
Drilling work test

We performed the drilling test toward the new pylon.

During drilling, the vibration of the nearby ground became larger than the normal about order 2 over 100Hz.
However, we can't see any significant increase in the accelerometers on the optical tables nor in the microphones in the clean booth.

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Comments to this report:
tomotada.akutsu - 12:59 Thursday 30 June 2022 (21331) Print this report

It sounds like the noise spectra got increased due to the drilling 100 times, but, is the "nominal" spectrum level well above the noise floor of the instrument?

tatsuki.washimi - 15:41 Thursday 30 June 2022 (21333) Print this report

In these measurements, the "nearby ACC" was not amplified (gain=0dB) to avoid saturation. So the "nominal" spectrum was occupied by the ADC noise except for around 200-300Hz. 
The correct sentence for the drilling effect was "more than 100 times".

For the accelerometers and microphones, the amplifiers (gain=20dB) were engaged and the "nominal" spectrums were enough larger than the ADC noises.

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