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PEM (Center)
tatsuki.washimi - 22:07 Friday 29 March 2024 (29020) Print this report
OMC vibration study

See also
https://klog.icrr.u-tokyo.ac.jp/osl/?r=18434
https://klog.icrr.u-tokyo.ac.jp/osl/?r=18495
https://klog.icrr.u-tokyo.ac.jp/osl/?r=27364
https://klog.icrr.u-tokyo.ac.jp/osl/?r=28985
https://klog.icrr.u-tokyo.ac.jp/osl/?r=28999

 

[YokozaWashimi]

We located a 3-axial accelerometer below the OMC chamber, near a seismometer.
Used channel names are 

K1:PEM-PORTABLE_OMC_RACK_OMC1_ADC0_DSUB13_OUT_DQ
K1:PEM-PORTABLE_OMC_RACK_OMC1_ADC0_DSUB14_OUT_DQ
K1:PEM-PORTABLE_OMC_RACK_OMC1_ADC0_DSUB15_OUT_DQ

and the signal unit is calibrated to m/s2. 

 

Plots attached here are reference data (21 JST,) no one inside the mine.

The shape and value of the Geophone's ASD is similar to the seismometers at 40-130 Hz and to the accelerometers at 50-130, and 160-250 Hz.
From these results, the in-vac table may not reduce the ground vibration.

The peak around 30 Hz is only found in the geophone signal and is larger than the seismometer and accelerometer.
Something inside the vacuum makes amplification?
For this peak frequency, the coherence with SEIS Z is very large.

 

Images attached to this report
Comments to this report:
tatsuki.washimi - 22:45 Friday 29 March 2024 (29021) Print this report

We generated the ground vibration noise by continuously tapping the PC table outside of the OMC booth.

We need more investigations, but just for memo.

Images attached to this comment
tomotada.akutsu - 8:28 Saturday 30 March 2024 (29024) Print this report

Thank you for the detailed follow-up. By the way, when I had a discussion with R. Takahashi-san regarding the noise level of a usual geophone, the geophone's intrinsic noise might be larger than the usual gounrd motion in the ~100Hz freq region. Do you have any idea about the noise level of your measurement?

tatsuki.washimi - 9:05 Monday 01 April 2024 (29033) Print this report

I'm not sure what is "the usual gounrd motion" you and Takahashi-san say, but if it is an f^{-\alpha} exploration from ~1 Hz, the actual (local) ground vibration over 20 Hz should be larger than it.

tatsuki.washimi - 8:35 Tuesday 02 April 2024 (29043) Print this report

Yesterday I prepared many accelerometers for the OMC study.

Channel manes are the followings:

  • 3-axial Seismometer (Trillium Compact) on the ground
    • K1:PEM-SEIS_OMC_GND_X_OUT_DQ
    • K1:PEM-SEIS_OMC_GND_Y_OUT_DQ
    • K1:PEM-SEIS_OMC_GND_Z_OUT_DQ
  • Geophone on the in-vac table
    • K1:PEM-ACC_OMC_VACTABLE_OMC_Y_OUT_DQ
  • Accelerometer (TEAC710) by a bellows leg
    • K1:PEM-ACC_OMC_CHAMBER_OMCLEG_Z_OUT_DQ
  • Accelerometer (TEAC710) on the AS table
    • K1:PEM-ACC_OMC_TABLE_AS_Z_OUT_DQ 
  • 3-axial Acellerometer (TEAC710Z) on the ground
    • K1:PEM-PORTABLE_OMC_RACK_OMC1_ADC0_DSUB13_OUT_DQ
    • K1:PEM-PORTABLE_OMC_RACK_OMC1_ADC0_DSUB14_OUT_DQ
    • K1:PEM-PORTABLE_OMC_RACK_OMC1_ADC0_DSUB15_OUT_DQ
  • Accelerometer (TEAC710) on the Top range neck
    • K1:PEM-PORTABLE_OMC_RACK_OMC1_ADC0_DSUB16_OUT_DQ
  • Accelerometer (TEAC710) for portable usage
    • K1:PEM-PORTABLE_OMC_BOOTH_OMMT_BNC1_OUT_DQ
    • K1:PEM-PORTABLE_OMC_BOOTH_OMMT_BNC2_OUT_DQ
    • K1:PEM-PORTABLE_OMC_BOOTH_OMMT_BNC3_OUT_DQ
    • K1:PEM-PORTABLE_OMC_BOOTH_OMMT_BNC4_OUT_DQ
       
Images attached to this comment
tomotada.akutsu - 9:36 Tuesday 02 April 2024 (29045) Print this report

Hmmm, so the invac geophone's spectral hill around 20-40 Hz range does not have coherence with the outer sensors...

takaaki.yokozawa - 15:04 Tuesday 02 April 2024 (29046) Print this report
Past measurement
https://klog.icrr.u-tokyo.ac.jp/osl/?r=18557
https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=13361
tatsuki.washimi - 21:43 Tuesday 02 April 2024 (29052) Print this report

We tapped the top flange of the OMC chamber to evaluate how mechanical vibration is propagated from the chamber to the in-vac table.

Fig.1 shows the ASDs of the accelerometer and the geophone, and their coherence. The geophone signal is converted from um/s/√Hz to m/s2/√Hz by multiplying 1e-6 * 2πf.
The unique structure around 20-30 Hz and 200-400 Hz in the geophone signal was not found in the accelerometer signal.
The coherence between these sensors was not so large except for some frequencies.

Fig.2 shows the transfer function from the accelerometer to the geophone, evaluated as CSD/PSD_ACC for coherence > 0.5.
The amplitude > 0 dB at the chamber's resonant?
 

Images attached to this comment
tatsuki.washimi - 22:27 Tuesday 02 April 2024 (29054) Print this report

We checked the effect of the trench (縁切り, we are not sure whether it actually exists) on the OMC chamber floor, using two accelerometers located on the outer and inner floors.

Fig.1 is tapping the outer floor and Fig.2 is the inner floor tapping.
For both cases, large coherence was found and the transfer functions from a tapped floor to another floor were about -10 dB at 10-100 Hz.

To distinguish whether a trench actually exists or not, we need to perform the same at another place where surely a trench exists.

Images attached to this comment
tatsuki.washimi - 22:38 Tuesday 02 April 2024 (29055) Print this report

Same work for the -Y side.

Images attached to this comment
tatsuki.washimi - 20:03 Wednesday 03 April 2024 (29068) Print this report

[Tomaru, YokozaWashimi]

We performed shaker injection tests for each bellows leg and evaluated the transfer functions from the witness accelerometers to the geophone.
(Single line injections for 25-40Hz and broad band injections for 40-600Hz)

Fig.1~3 are each result (ASDs, coherence, and transfer function).
Fig.4 is the comparison of each transfer function. They are roughly similar but the details are different.
The magnitude of the TF is largest at the "Leg5". (the injected vibration measured by the witness accelerometer for this leg was somehow smaller than that for the others.)
The magnitude of the TF is almost similar for all legs and any signature-flip was not found. (If the vibration (Y direction) on the in-vac table was tilt motion, the signatures for the "Leg1" and the "Leg5" are expected to be flipped. )

 

Images attached to this comment
tatsuki.washimi - 20:14 Wednesday 03 April 2024 (29069) Print this report

[Tomaru, YokozaWashimi]

We performed acoustic injection tests for the OMC booth and evaluated the geophone signal.

Fig.1 is ASDs and coherence for the geophone and the microphone signal.
Fig.2 is the estimated transfer functions.
Fig.3 is the comparison of the geophone signal and its acoustic noise (TF * MIC signal) for the non-injected data.

Images attached to this comment
tatsuki.washimi - 9:01 Friday 05 April 2024 (29099) Print this report

I moved the portable accelerometers to the OMC chamber body (top range neck)

+Y side, Z direction : K1:PEM-PORTABLE_OMC_RACK_OMC1_ADC0_DSUB16_OUT_DQ
+X side, Z direction : K1:PEM-PORTABLE_OMC_BOOTH_OMMT_BNC1_OUT_DQ
+Y side, Y direction : K1:PEM-PORTABLE_OMC_BOOTH_OMMT_BNC2_OUT_DQ
-X side, X direction : K1:PEM-PORTABLE_OMC_BOOTH_OMMT_BNC3_OUT_DQ
-X side, Z direction : K1:PEM-PORTABLE_OMC_BOOTH_OMMT_BNC4_OUT_DQ
 

Fig.2 is the reference plots and Fig.3 is the plots during tapping the chamber.

Images attached to this comment
tatsuki.washimi - 17:56 Wednesday 01 May 2024 (29367) Print this report

I plotted the high-resolution (3-hour data, 128s FFT) ASDs and Coherences for the geophones and ACCs on the OMC chamber, for the night time before vacuum breaking.

Images attached to this comment
tatsuki.washimi - 17:59 Wednesday 01 May 2024 (29368) Print this report

sorry, the legend was clipped.

It is same for all plots.

Images attached to this comment
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