Efficient generation of relativistic electrons in a target irradiated by a pair of femtosecond laser pulses with a nanosecond delay

It is shown experimentally that the mean energy of accelerated electrons generated by irradiating a dense target with a pair of 13-ns-delay femtosecond laser pulses forming radiation with an energy contrast of 100–500 and an intensity of about 10 18 W/cm 2 increases significantly in comparison with the case of high contrast ∼10 6 .