Summarize Geophone measurement

[YoshinoriFujii]

To do

• [ ] summarize the measurements which was done in the KAGRA tunnel in FY2018.

• [ ] upload the data.

  • [ ] here
  • [ ] to JGW wiki

• [ ] reproduce this page to JGW wiki

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• [ ] anyway collect the tips.

[YoshinoriFujii]

anyway collect the tips.

• Measurement notes in Evernote (y0419fujii_at_gmail):

  • 2018 July 29th: https://www.evernote.com/l/AoNALeMv7FhFUbfx66OfPZznqhQ8jdGBAjc/

  • 2018 November 9th and 11th: https://www.evernote.com/l/AoNALeMv7FhFUbfx66OfPZznqhQ8jdGBAjc/

  • 2018 November 17th: https://www.evernote.com/l/AoMJp0TFVFVENpMV857WkJUKx0FmdmDfcsc/

  • 2018 November 25th: https://www.evernote.com/l/AoMDPv1fIu5DPJwqPfjIfFhj_vrTrFSL2CQ/

  • 2018 November 29th: https://www.evernote.com/l/AoNLjeZ29SVFrJKLoaq5plfUvylBFrBfzqQ/

  • Notes in the klog.

  • [ ] collect the information first.

[YoshinoriFujii]

summarize the measurements which was done in the KAGRA tunnel in FY2018.

Brief summary

• the calibration is done with either already-calibrated geophone (one used in ETMX) or the seismometer Trillium120QA at IXV.
• [ ] confirm if which geophones are calibrated with the already-calibrated geophone etc.

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• The noise floor is estimated with the 3-channel correlation analysis.
  • result: geophone_noise_spectra_summary.pdf
    • valid below ~10 Hz.
    • compared to the measurement by T. Sekiguchi: https://granite.phys.s.u-tokyo.ac.jp/svn/LCGT/trunk/VIS/SuspensionControlModel/noise/GEOnoiseproto_vel.dat (please check README.txt as well in the above dir)
    • [ ] summarized the scripts

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• For a sanity check, for a few cases, the noise floors are measured with a configuration where the proof mass is fixed to the frame.

  • result: geo_noise_comp_ETMY.pdf

    • valid below ~10 Hz.

    • (top): geophone noise floor with the 3-channel correlation analysis.

      • geo_18115_1240pm_corr_disp.txt

    • (bottom): geophone noise floor with fixed-mass measurement.

      • geo_monitor_fixed_181128_1616pm.txt

=== Under construction ===
# geo18:  Column 1   K1:VIS-ETMY_IP_ACCINF_H1_IN1    As is 
# geo21:  Column 2   K1:VIS-ETMY_IP_ACCINF_H2_IN1    As is
# geo23: Column 3   K1:VIS-ETMY_IP_ACCINF_H3_IN1    As is

# unit: counts
# calibration: preamp_gain = 375.53*5, cal = 40.0/(2**16)
# disp = cal/preamp_gain*data

#  geo-18: #18 ---------------------# 
Ge_18  = 271.81915 #[V/(m/s)]
f0_18  = 1.0854036 #[Hz]
eta_18 = 0.6596832
w0_18  = 2*np.pi*f0_18
Q_18   = 1./eta_18

#  geo-21: #21 ---------------------# 
Ge_21 = 273.399 #[V/(m/s)]
f0_21 = 1.34161315 #[Hz]
eta_21 = 0.51474033
w0_21 = 2*np.pi*f0_21
Q_21  = 1./eta_21

#  geo-23: #23 ---------------------# 
Ge_23 = 249.245298 #[V/(m/s)]
f0_23 = 1.01841884 #[Hz]
eta_23 = 0.6285111
w0_23 = 2*np.pi*f0_23
Q_23  = 1./eta_23

# ---------------------------------# 

    - [ ] summarized the scripts

[YoshinoriFujii]

Comments to the measurements:

• noise floor (in displacement) is proportional to f^-3.5?:

  • f^-2 is for conversion form the output voltage to the proof mass velocity.

  • f^-1 is for conversion from velocity to displacement

  • the geophone output voltage (in ASD) seems to have f^-0.5 component at frequencies below the resonance frequency (~ 1Hz).

    • geo_monitor_181128_fixed_1616pm.pdf
      • the spectra of geophone output voltage in counts.
      • limited by ADC or pre-amp circuits, or else?

  • In total, the geophone noise (in displacement) is proportional to ~ f^-3.5.