Kiwamu, Keita, Filiberto, Rich

Finished installation of all RFPD cabling inside ISCT1.  Received LSC diode by Fedex from Caltech.  Ran through same procedure as Lisa and Matt did when they verified the calibration of the MC length diode in log entry 5277.

Data Taken on LSC-REFL-AIR-A RFPD

System Constants:
LSC Detector Serial Number - S1203919
LSC Detector Frequencies - 9 MHz and 45 MHz
LSC Detector RF Transimpedance - 341 ohms at 45 MHz
LSC Detector DC Transimpedance - 100 ohms at BNC Jack on detector body
LSC Detector Photodiode Responsivity at 980nm - 0.67 A/W
Laser Calibrator Head Serial Number - S1300150
Calibrator Output Power - 4mW at 980nm
Calibrator Head Gain - 13 mW/V (From Lisa and Matt)

Measured Parameters:
RF drive amplitude into calibrator head - 0.1Vp-p at 45.497379MHz
DC Output of RFPD Head (at BNC) - 0.165 VDC
Measured Counts of RFPD DC - 538 Counts (consistent with DC output of head and factor of two differential gain).
I and Q beat note counts - 3400 Counts p-p
Measured RF input to demodulator - 180 mV p-p at 45... MHz

Calculated Parameters:

Responsivity = 538 counts/(1638 counts/V * 200 V/A *4e-3 W) = 0.41 A/W (0.37 A/W by Lisa and Matt)

Expected RF to Demodulator = 341 V/A * 0.41 A/W * 0.013 W/V * 0.1 Vp-p = 182 mVp-p (180 mV measured)

Check of Laser Calibrator Head against LSC RFPD measured parameters:

(This calculation must correct for the amount of light that doesn't hit the RFPD diode.  This is seen in the last calculation:)

Calibrator head gain = 0.180 Vp-p / (0.67A/W * 341 V/A * 0.1 Vp-p)  = 7.9 mW/V

The incident power and observed DC photocurrent requires following correction factor:
4mW * 0.67 A/W * 100 V/A = 268 mVDC vs the actual measured 165 mVDC, therefore the correction factor of 268/165 is applied
Calibrator head gain (corrected for light spillage) = 7.9 mW/V * 268/165 = 12.8 mW/V (vs. 13 mW/V from Lisa and Matt)


Conclusion is that the LSC REFL-AIR-A RFPD and calibrator head seem to be functional within reasonable levels and is in agreement with the measurements taken by Matt and Lisa.