High current density small divergence electron beam production by laser-induced various-order multiphoton photoeffect

The relative roles of (1) surface and volume type photoelectric effects, (2) slow and fast laser-induced thermionic electron emission, and (3) optical tunnel emission are discussed from the point of view of the production possibilities of efficient high current density, small divergency electron beams. Angular distribution of photoelectrons emitted from gold target surface by high-intensity pulsed laser radiation at wavelengths of 1,060, 343, and 248 nm for the s and p polarization of the grazing incident radiation are investigated experimentally. For the longer wavelengths, where the order of the multiphoton photoelectric emission increases, the ratio of the yields of the surface photoeffect and of the volume photoeffect also increases. The comparative advantages of the surface multiphoton photoeffect of metals as a promising method for the realization of small emittance, high brightness, high current density electron sources are pointed out