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Entry  Thu Apr 8 10:17:52 2010, Alberto, Update, 40m Upgrading, REFL11 Noise Vs Photocurrent 2010_04_05_REFL11_ShotnoiseVsPhotocurrent.png
    Reply  Thu Apr 8 10:24:33 2010, Alberto, Update, 40m Upgrading, REFL11 Noise Vs Photocurrent 
    Reply  Thu Apr 8 20:53:13 2010, Koji, Update, 40m Upgrading, REFL11 Noise Vs Photocurrent 
       Reply  Fri Apr 9 06:45:28 2010, Alberto, Update, 40m Upgrading, REFL11 Noise Vs Photocurrent 
          Reply  Mon Apr 12 17:09:30 2010, Alberto, Update, 40m Upgrading, REFL11 Noise Vs Photocurrent 2010-04-09_REFL11NoiseMeasurements.png
             Reply  Mon Apr 12 22:44:30 2010, Koji, Update, 40m Upgrading, REFL11 Noise Vs Photocurrent 
Message ID: 2784     Entry time: Thu Apr 8 20:53:13 2010     In reply to: 2782     Reply to this: 2785
Author: Koji 
Type: Update 
Category: 40m Upgrading 
Subject: REFL11 Noise Vs Photocurrent 

Something must be wrong. 

1. Physical Unit is wrong for the second term of "Vn = Vdn + Sqrt(2 e Idc)"

2. Why does the fit go below the dark noise?

3. "Dark noise 4 +/- NaN nV/rtHz"   I can not accept this fitting.

Also apparently the data points are not enough.

Quote:

From the measurements of the 11 MHz RFPD at 11Mhz I estimated a transimpedance of about 750 Ohms. (See attached plot.)

The fit shown in the plot is: Vn = Vdn + sqrt(2*e*Idc) ; Vn=noise; Vdn=darknoise; e=electron charge; Idc=dc photocurrent

The estimate from the fit is 3-4 times off from my analsys of the circuit and from any LISO simulation. Likely at RF the contributions of the parassitic components of each element make a big difference. I'm going to improve the LISO model to account for that.

2010_04_05_REFL11_ShotnoiseVsPhotocurrent.png

The problem of the factor of 2 in the data turned out to be not a real one. Assuming that the dark noise at resonance is just Johnson's noise from the resonant circuit transimpedance underestimates the dark noise by 100%.

 

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