Experimental investigation of effect on hot electron produced by various wavelength laser

The interactions of two kinds of wavelength ultra-short pulse (744 nm/120 fs/12 mJ, 248 nm/420 fs/35 mJ) laser with solid (Cu) plasma targets were experimentally investigated, and the hot electron spectra and angular distribution were measured by electron magnetic spectrometer and imaging plate (IP) detectors in laser incident plane. At the conditions of pre-pulse free and P polarization and 45° incidence, the temperatures of hot electron fitted by Maxwellian are 46 and 19.4 keV, respectively, and the hot electrons are emit ted mainly along the normal direction of targets. The dominant mechanisms of hot electron generating are vacuum heating (VH). It is experimentally validated that the scaling law of VH is T_h ≈ 4.11 × 10^-2 (Iλ²)^1/2.54 (keV). The charge separation potential of plasma are about 70 and 45 keV, respectively. (authors)