Zhang, J (reprint author), Chinese Acad Sci, Inst Phys, Lab Opt Phys, Beijing 100080, Peoples R China.
Article; Proceedings Paper
Studies on the fast electrons escaped into vacuum are reported from solid targets illuminated by 150-fs laser pulses with p-polarised oblique incidence at a modest irradiance of 5x10(15) Wcm(-2)mum(-2). The escaping electrons were found to form a jet in the normal direction to the target surface. The fast varying charge separation current can be measured by an LCR circuit, which converts the instantaneous charging current into a slow discharge process during the interaction. The total number of the escaping electrons is, for the first time, accurately determined to be 7x10(9) by direct measurement of the charge separation potential generated during the interaction. The average energy of the escaping electrons was also accurately measured to be around 60 keV The energy conversion from laser to these escaping fast electrons was found to be as high as 1.3% at such a modest irradiance.