New irradiation and performance requirements applicable to ELSA call for an evolution of the photocathodes in operation. The previous Cs₃Sb photocathodes have been replaced by new Cs₂Te photocathodes and the frequency of the laser illuminating them has been doubled accordingly, shifting the wavelength of the latter from the green to the UV range. The choice of a new cathode emissive material enables an extension its lifespan while maintaining comparable beam currents in spite of the lower laser power resulting from the frequency doubling.

Thanks to a 15 % postproduction quantum efficiency (QE) and a 10 % laser frequency conversion efficiency, we obtained a 5-fold increase of the electron beam current, thus meeting the needs of the users. The most significant achievement was the extension of the cathode lifespan: we managed to keep the very same Cs₂Te photocathode in operation for a duration of 6 months whereas the previous Cs₃Sb technological solution would have required at least ten replacements over the same period of time.