L3CCD results in pure photon counting mode

Theoretically, L3CCDs are perfect photon counting devices promising high quantum efficiency ($\sim$90%) and sub-electron readout noise ($\sigma$<0.1 e-). We discuss how a back-thinned 512x512 frame-transfer L3CCD (CCD97) camera operating in pure photon counting mode would behave based on experimental data. The chip is operated at high electromultiplication gain, high analogic gain and high frame rate. Its performance is compared with a modern photon counting camera (GaAs photocathode, QE $\sim$28%) to see if L3CCD technology, in its current state, could supersede photocathode-based devices.