Reports until 14:00, Wednesday 02 April 2014
H1 ISC
alexan.staley@LIGO.ORG - posted 14:00, Wednesday 02 April 2014 (11132)
IMC Noise Measurements

(Daniel, Alexa)

We measured the dark noise and shot noise of the LSC RF PD in the refl path of the IMC.

  1. 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.
  2. 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). 

Non-image files attached to this report