Yield of hot electrons and conversion efficiency of laser energy in femtosecond laser-foil targets

The energy spectra of hot electrons have been measured using the magnetic spectrometers, fitted with the LiF thermoluminescent dosimeter (TLD) which were calibrated using Cs~(137) γ-ray sources, in the interaction of a 130 mJ, 60 fs, 800 nm, 1∶10~(-6), 7.0×10~(17) W·cm~(-2) P-polarized laser incidence on Cu foil target at an angle of 45° with respect to the target normal without any prepulse. The yield of hot electrons and the conversion efficiency of laser energy to energy of hot electrons are 1.19×10~(10)/sr and 4.55%/sr at the normal of target and are 1.83×10~9/sr and 0.76%/sr at the specular direction of laser, which were deduced from the energy spectra of hot electrons. They were different at various direction because of the hot electrons produced in the interaction of laser-plasma constituted an anisotropy distribution.