Experimental Results for Multiphoton Nonlinear Photoemission Processes on Phil Test Line

One of the prerequisites for the next generation high luminosity light sources is the availability of the short electron bunches. It also has several applications in other domains, including medical diagnostics and high-resolution imaging. In principle, using photoelectric effect a short electron bunch can initially be generated by illuminating a photocathode with an ultra-short light pulse of appropriate wavelength. Strong EM fields from a RF gun or similar accelerating structures, synchronized with the incoming laser pulses, are then used to accelerate these electron bunches initially up to an energy of tens of MeV. We present our preliminary results on the experimental investigation of two-photon nonlinear photoemission processes for the generation of picosecond, low-charge electron bunches conducted at PHIL photoinjector facility. A comparison of the emission efficiency and bunch characteristics with the single photon emission process is also made.