EMCCD for pyramid wavefront sensor: laboratory characterization

Electro-Multiplying CCDs offer a unique combination of speed, sub-electron noise and quantum efficiency. These features make them extremely attractive for astronomical adaptive optics. The SOUL project selected the Ocam2k from FLI as camera upgrade for the pyramid wavefront sensor of the LBT SCAO systems. Here we present results from the laboratory characterization of the 3 of the custom Ocam2k cameras for the SOUL project. The cameras showed very good noise ($0.4e^-$ and $0.4-0.7e^-$ for binned modes) and dark current values ($1.5e^-$). We measured the camera gain and identified the dependency on power cycle and frame rate. Finally, we estimated the impact of these gain variation in the SOUL adaptive optics system. The impact on the SOUL performance resulted to be negligible.