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Entry  Sun Feb 3 13:20:02 2013, Koji, Summary, General, Hypothesis mode_density_PRC.pdfmode_density_PRC.zip
    Reply  Mon Feb 4 10:45:51 2013, Jamie, Summary, General, rough analysis of aligned PRM-PR2 mode scan scan-labeled.pdf
       Reply  Mon Feb 4 11:10:59 2013, Koji, Summary, General, rough analysis of aligned PRM-PR2 mode scan 
          Reply  Mon Feb 4 19:33:19 2013, yuta, Summary, General, rough analysis of aligned PRM-PR2 mode scan 3peakdata.png
             Reply  Tue Feb 5 02:04:44 2013, yuta, Summary, General, rough analysis of aligned PRM-PR2 mode scan PRMPR2scan.png
                Reply  Tue Feb 5 03:16:51 2013, Koji, Summary, General, rough analysis of aligned PRM-PR2 mode scan 
                   Reply  Tue Feb 5 10:09:08 2013, yuta, Summary, General, rough analysis of aligned PRM-PR2 mode scan 
                      Reply  Tue Feb 5 11:30:19 2013, Koji, Summary, General, rough analysis of aligned PRM-PR2 mode scan 
                         Reply  Wed Feb 13 01:26:08 2013, yuta, Summary, General, rough analysis of aligned PRM-PR2 mode scan unbiased.png
       Reply  Wed Feb 6 15:20:55 2013, yuta, Summary, General, FWHM was wrong 
    Reply  Mon Feb 4 15:06:56 2013, Koji, Summary, General, Hypothesis 
    Reply  Mon Feb 4 19:48:32 2013, Jamie, Summary, General, arbcav recalc of PRC with correct ITM transmission mode_density_PRC_2.pdfmode_density_PRC_3.pdf
Message ID: 7994     Entry time: Mon Feb 4 19:33:19 2013     In reply to: 7991     Reply to this: 7997
Author: yuta 
Type: Summary 
Category: General 
Subject: rough analysis of aligned PRM-PR2 mode scan 

[Jenne, Yuta]

We redid PRM-PR2 cavity scan because last one (elog #7990) was taken with the sampling frequency of 2 KHz. We have also done TMS measurement.

Method:
 1. Align input TTs and PRM to align PRM-PR2 cavity.
 2. Sweep cavity length using C1:SUS-PRM_LSC_EXC.
 3. Get data using Jamie's getdata and fitted peaks using /users/jrollins/modescan/prc-pr2_aligned/run.py
 4. Calculated cavity parameters

Results:
 Below is the figure containing peaks used to do the calculation.

3peakdata.png

 From 11 MHz sidebands, calibration factor is 462 +/- 22 MHz/sec (supposing linear scan around peaks)
 FWHM is 1.45 +/- 0.03 MHz.
 TMS is 2.64 +/- 0.05 MHz.
 Error bars are statistical errors of the average over 3 TEM00 peaks.

 If we believe cavity length L to be 1.91 m, FSR is 78.5 MHz.
 So, Finesse will be 54 +/- 1 and cavity g-factor will be 0.9944 +/- 0.0002. 0.9889 +/- 0.0004   (Edited by YM; see elog #8056)
 If we believe RoC of PRM is exactly +122.1 m, measured g-factor insists RoC of PR2 to be -187 +/- 4.
 If we believe RoC of PR2 is exactly -600 m, measured g-factor insists RoC of PRM to be 218 +/- 6.

Discussion:
 1. Finesse is too small (expected to be ~100). This time, data was taken 16 KHz. Cut-off frequency of the digital antialiasing filter is ~ 5 kHz (see /opt/rtcds/rtscore/release/src/fe/controller.c). FWHM is about 0.003 sec, so it should not effect much according to my simulation.

 2. I don't know why FWHM measurement from the last one is similar to this one. The last one was taken 2 KHz, this means anti-aliasing filter of 600 Hz. This should double FWHM.

 3. Oscilloscope measurement may clear anti-aliasing suspicion.

ELOG V3.1.3-