A system for generating a spatially localised high-intensity laser beam comprising: - a laser source adapted to generate a burst of N laser pulses, where N is a natural integer higher than 1, the N laser pulses having a first repetition frequency (f 1 ), the laser pulses being ultra-short laser pulses having a duration lower than or equal to 1 picosecond and the first repetition frequency (f 1 ) being higher than or equal to 0.5 gigahertz, - a resonant optical cavity adapted to receive and store said burst of N laser pulses, the resonant optical cavity being adapted to focus the burst of N laser pulses to an interaction area of the resonant optical cavity , a round-trip distance in the resonant optical cavity being equal to c/f 1 , where c is the speed of light, and - a servo control system adapted to control the first repetition frequency (f 1 ) with respect to the round-trip distance in the resonant optical cavity so that the N pulses of the burst are temporally and spatially superimposed to each other by constructive interferences in the interaction area to form an ultra-short and high-energy giant pulse, characterized in that : - the resonant optical cavity comprises two spherical mirrors (M3, M4) and two planar mirrors (M1, M2) arranged in a planar configuration, the resonant optical cavity being adapted for propagating the burst of laser pulses following an X-shape folded loop, the two spherical mirrors being arranged in a concentric configuration, the interaction area being located on the optical axis between the two spherical mirrors (M3, M4), each spherical mirror being mounted on a support , each support comprising an opening adapted to the passage of a charged particle beam so that the charged particle beam propagates in the interaction area in synchronism with the ultra-short giant pulse under an incidence angle lower than or equal to 5 degrees with respect to a direction of propagation of the burst of laser pulses in the interaction area . - a laser source adapted to generate a burst of N laser pulses, where N is a natural integer higher than 1, the N laser pulses having a first repetition frequency (f 1 ), the laser pulses being ultra-short laser pulses having a duration lower than or equal to 1 picosecond and the first repetition frequency (f 1 ) being higher than or equal to 0.5 gigahertz, - a resonant optical cavity adapted to receive and store said burst of N laser pulses, the resonant optical cavity being adapted to focus the burst of N laser pulses to an interaction area of the resonant optical cavity , a round-trip distance in the resonant optical cavity being equal to c/f 1 , where c is the speed of light, and - a servo control system adapted to control the first repetition frequency (f 1 ) with respect to the round-trip distance in the resonant optical cavity so that the N pulses of the burst are temporally and spatially superimposed to each other by constructive interferences in the interaction area to form an ultra-short and high-energy giant pulse, - the resonant optical cavity comprises two spherical mirrors (M3, M4) and two planar mirrors (M1, M2) arranged in a planar configuration, the resonant optical cavity being adapted for propagating the burst of laser pulses following an X-shape folded loop, the two spherical mirrors being arranged in a concentric configuration, the interaction area being located on the optical axis between the two spherical mirrors (M3, M4), each spherical mirror being mounted on a support , each support comprising an opening adapted to the passage of a charged particle beam so that the charged particle beam propagates in the interaction area in synchronism with the ultra-short giant pulse under an incidence angle lower than or equal to 5 degrees with respect to a direction of propagation of the burst of laser pulses in the interaction area . <EOS>