Measurement of hot electron energy spectrum in femtosecond laserplasma

This paper reports the results of the measurement of hot electron energy spectrum during the interaction of femtosecond laserplasmas. First, there is a depression of hot electron fluence at the energy of around 40keV. Second, there is a local plateau of electron fluence at energies of 100~350keV, which is produced by the several acceleration mechanisms, and a rapid reduction of electron at energy greater than 350keV. In the range of 1~5.4MeV, the number of hot electrons decays approximately by an exponential function. Fitted with Maxwellian distribution, the temperature of hot electrons is much lager than those from the known temperature scaling, which is due to runup of the energy spectrum at its tail and the selffocusing or channeling of laser.