(Daniel, Alexa)
We measured the dark noise and shot noise of the LSC RF PD in the refl path of the IMC.
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Dark noise: We blocked the PD and confirmed this by looking at the H1:IMC_REFL_DC_OUT which went down to about 0.02 counts. The noise was measured to be approx 80nVrms/sqrtHz from the SR785. For greater accuracy, we took the power spectrum of H1:IMC-I_OUT using DTT. The result is deipcted in (REF2) -- this measurement is in counts and must be calibrated using 20/2^16 V/cnts conversion with a factor of 100 to take into account the whitening filter.
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Shot noise: We placed a light bulb in front of the PD and read back 8705 counts at DC (again, using H1:IMC-REFL_DC_OUT). The noise was measured to be approx 280nVrms/sqrtHz from the SR785. We also took a power spectrum of H1:IMC-I_OUT (the same calibration above must be applied).
From this measurement we calculated the AC transimpedance of the PD to be 2.1kOhm (with a 100 Ohm DC transimpedance).