After Gabriele's CHETA tests with the Hamamatsu Detectors in CIT#612 . We compared to our CO2X VIGO PWM 10.6 diodes.
The coherence is much worse between the two IN and OUT diodes (in the same path, separated by a 50/50 BS), we have no coherence above 600Hz, which is opposite to what Gabriele sees.
Attached are plots with our slower and faster channels.
- H1:TCS-ITMX_CO2_ISS_IN_AC_OUT = H1:IOP-OAF_L0_MADC2_TP_CH10
- H1:TCS-ITMX_CO2_ISS_IN_DC_OUT = H1:IOP-OAF_L0_MADC2_TP_CH11
- H1:TCS-ITMX_CO2_ISS_OUT_AC_OUT = H1:IOP-OAF_L0_MADC2_TP_CH12
- H1:TCS-ITMX_CO2_ISS_OUT_DC_OUT = H1:IOP-OAF_L0_MADC2_TP_CH13
Even looking at the coherence between the DC and AC channels on the same PD is similarly bad, attached, where green is the CO2X OUT PD, Purple is the CO2X IN PD. Gabriele suggests this could be shot noise or dark noise or electronics noise or saturation in the PD electronics as he saw at CIT.
We already know that the DC signal is dominated by dark noise, e.g. plot from 82187 so that's probably what we're seeing reducing the coherence here.
