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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: 7997     Entry time: Tue Feb 5 02:04:44 2013     In reply to: 7994     Reply to this: 7998
Author: yuta 
Type: Summary 
Category: General 
Subject: rough analysis of aligned PRM-PR2 mode scan 

I redid PRM-PR2 cavity scan using oscilloscope to avoid anti-aliasing effect.
Measured Finesse was 104 +/- 1.

Method:
 1. Splitted POP DC output into three and plugged two into oscilloscope TDS 3034B. Ch1 and Ch2 was set to 1 V/div and 20 mV/div respectively to take the whole signal and higer resolution one at the same time (Koji's suggestion). Sampling frequency was 50 kHz. Sweeping time through FWHM was about 0.001 sec, which is slow enough.
 2. Took mode scan data from the oscilloscope via network.

Preliminary results:
 Below is the plot of the data for one TEM00 peak.
PRMPR2scan.png

 The data was taken twice.
 Measured FWHM was 0.764 MHz and 0.751 MHz. By taking the average, FWHM = 0.757 +/- 0.005 MHz.
 This gives you Finesse = 104 +/- 1, which is OK compared with the expectation.

What I need:
 I need better oscilloscope so that we can take longer data (~1 sec) with higher resolution (~0.004 V/count, ~50kHz).
 TDS 3034B can take data only for 10 ksamples, one channel by one!  I prefer Yokogawa DL750 or later.

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