A device for generating a high-energy particle pulse is provided which comprises a laser system producing laser pulses with pulse length shorter than 100 fs (femtoseconds), and capable to be focused to peak intensities greater than 10A18 W/cmA2, preferred greater than 10A20 W/cmA2 (watts per centimeter squared), a device for shaping the temporal intensity profile accompanying said at least one laser pulse for increasing the laser contrast above 10^5, preferably above IL 0A7, especially 1OA10, and a target capable of releasing a high-energy particle pulse, particularly an electron or a proton pulse, upon irradiation with at least one of said laser pulses. A. corresponding method using the device is also described.