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Entry  Thu Apr 29 11:51:27 2021, Anchal, Summary, LSC, Start of measuring IMC WFS noise contribution in ar cavity length noise 
    Reply  Thu Apr 29 15:11:33 2021, gautam, Update, CDS, RFM  RFM_errs.pngScreenshot_2021-04-29_15-12-56.png
       Reply  Thu Apr 29 17:43:16 2021, Koji, Update, CDS, RFM  
       Reply  Thu Apr 29 17:43:48 2021, Anchal, Update, CDS, F2A Filters double check F2AFiltersON.png
          Reply  Fri Apr 30 00:20:30 2021, gautam, Update, CDS, F2A Filters double check 
    Reply  Thu Apr 29 17:51:19 2021, Anchal, Summary, LSC, Start of measuring IMC WFS noise contribution in arm cavity length noise WFS1_PIT_exc_80-100Hz_Arms_ASD.pdf
       Reply  Fri Apr 30 00:18:40 2021, gautam, Summary, LSC, Start of measuring IMC WFS noise contribution in arm cavity length noise 
       Reply  Mon May 3 09:14:01 2021, Anchal, Paco, Update, LSC, IMC WFS noise contribution in arm cavity length noise WFS1_PIT_Noise_Inj_Test_IMC_unlocked.pdfWFS1_PIT_Noise_Inj_Test_ARM_locked.pdf
          Reply  Mon May 3 17:28:58 2021, Anchal, Paco, Rana, Update, LSC, IMC WFS noise contribution in arm cavity length noise excitationoftheMCanglessothatwecanseesomethingdotpng.pngexcitationoftheMCanglessothatwecanseesomethingdotpngbutthistimeitsMC2.png
             Reply  Tue May 4 11:43:09 2021, Anchal, Paco, Update, LSC, IMC WFS noise contribution in arm cavity length noise ArmCavNoiseContributions.pdfIOO-MC1_PIT_NoiseInjTest2.pdfIOO-MC1_PIT_NoiseInjTest_AWGGUI_Config.png
                Reply  Fri May 7 11:54:02 2021, Anchal, Paco, Update, LSC, IMC WFS noise contribution in arm cavity length noise ITMX-XARM_TF.pdfITMY-YARM_TF.pdfArmCavNoiseContributions.pdf
                   Reply  Mon May 10 18:19:12 2021, Anchal, Paco, Update, LSC, IMC WFS noise contribution in arm cavity length noise, Corrections ArmCavNoiseContributions.pdf
                      Reply  Wed May 12 10:53:20 2021, Anchal, Paco, Update, LSC, PSL-IMC PDH Loop and XARM PDH Loop diagram IMC_SingleArm.pdf
Message ID: 16127     Entry time: Fri May 7 11:54:02 2021     In reply to: 16117     Reply to this: 16129
Author: Anchal, Paco 
Type: Update 
Category: LSC 
Subject: IMC WFS noise contribution in arm cavity length noise 

We today measured the calibration factors for XARM_OUT and YARM_OUT in nm/cts and replotted our results from 16117 with the correct frequency dependence.


Calibration of XARM_OUT and YARM_OUT

  • We took transfer function measurement between ITMX/Y_LSC_OUT and X/YARM_OUT. See attachment 1 and 2
  • For ITMX/Y_LSC_OUT we took calibration factor of 3*2.44/f2 nm/cts from 13984. Note that we used the factor of 3 here as Gautum has explicitly written that the calibration cts are DAC cts at COIL outputs and there is a digital gain of 3 applied at all coil output gains in ITMX and ITMY that we confirmed.
  • This gave us callibration factors of XARM_OUT: 1.724/f2 nm/cts , and YARM_OUT: 4.901/f2 nm/cts. Note the frrequency dependence here.
  • We used the region from 70-80 Hz for calculating the calibration factor as it showed the most coherence in measurement.

Inferring noise contributions to arm cavities:

  • For converting IMC frequency noise to length noise, we used conversion factor given by \lambda L / c where L is 37.79m and lambda is wavelength of light.
  • For converting MC1 ASCPIT OUT cts data to frequency noise contributed to IMC, we sent 100,000 amplitude bandlimited noise  from 25 Hz to 30 Hz at C1:IOO-MC1_PIT_EXC. This noise was seen at both MC_F and ETMX/Y_LSC_OUT channels. We used the noise level at 29 Hz to get a calibration for MC1_ASCPIT_OUT to IMC Frequency in Hz/cts. This measurement was done in 16117.
  • Once we got the calibration above, we measured MC1_ASCPIT_OUT power spectrum without any excitaiton and multiplied it with the calibration factor.
  • Attachment 3 is our main result.
    • Page 1 shows the calculation of Angle to Length coupling by reading off noise injects in MC1_ASCPIT_OUT in MC_F. This came out to 10.906/f2 kHz/cts.
    • Page 2-3 show the injected noise in X arm cavity length units. Page 3 is the zoomed version to show the matching of the 2 different routes of calibration.
    • BUT, we needed to remove that factor of 3 we incorporated earlier to make them match.
    • Page 4 shows the noise contribution of IMC angular noise in XARM cavity.
    • Page 5-6 is similar to 2-3 but for YARM. The red note above applied here too! So the factor of 3 needed to be removed in both places.
    • Page 7 shows the noise contribution of IMC angular noise in XARM cavity.

Conclusions:

  • IMC Angular noise contribution to arm cavities is atleast 3 orders of magnitude lower then total armc cavity noise measured.

Edit Mon May 10 18:31:52 2021

See corrections in 16129.

Attachment 1: ITMX-XARM_TF.pdf  12 kB  Uploaded Fri May 7 13:06:33 2021  | Hide | Hide all
ITMX-XARM_TF.pdf ITMX-XARM_TF.pdf
Attachment 2: ITMY-YARM_TF.pdf  12 kB  Uploaded Fri May 7 13:06:40 2021  | Hide | Hide all
ITMY-YARM_TF.pdf ITMY-YARM_TF.pdf
Attachment 3: ArmCavNoiseContributions.pdf  52 kB  Uploaded Fri May 7 13:06:51 2021  | Hide | Hide all
ArmCavNoiseContributions.pdf ArmCavNoiseContributions.pdf ArmCavNoiseContributions.pdf ArmCavNoiseContributions.pdf ArmCavNoiseContributions.pdf ArmCavNoiseContributions.pdf ArmCavNoiseContributions.pdf
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