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Message ID: 1480     Entry time: Tue Aug 19 10:35:07 2014
Author: Evan 
Type: DailyProgress 
Category: RefCav 
Subject: South cavity finesse 

I swept the south NPRO PZT with a 2 Vpp, 5 Hz triangle wave and watched the transmission of the south cavity using a PDA100A. I saved three such transmission sweeps from the oscilloscope, and then performed Lorentzian fits on each of them in order to get the cavity pole.

From the Lorentzian fits along with the 4.4(2) MHz/V calibration found earlier [and FSR = 4070(30) MHz], I find the following:

  • Lower resonance: cavity pole of 135(3) kHz, corresponding to a finesse of 15100(340). This gives the total round-trip loss as 417(10) ppm.
  • Upper resonance: cavity pole of 139(9) kHz, corresponding to a finesse of 14600(1000). This gives the total round-trip loss as 429(28) ppm.
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