Patent Number: 
Section: claims

1. An arrangement for producing a proton beam of relativistic protons of 0.5 GeV to 1 GeV of energy, the arrangement comprising:a proton target, anda laser source focused on the proton target, configured to produce a beam of short pulses at an intensity greater than 1023 W/cm2, the laser source comprising:an ultrashort pulse laser pulse oscillator for producing pulses, anda coherent amplification network system comprising a series of successive amplifier stages, each amplifier stage comprising:a bundle of single mode fiber amplifiers for amplifying the pulses produced by the laser pulse oscillator, each fiber amplifier comprising a plurality of optical fibers, the optical fibers being spaced from one another, anda cooling medium flowing between the fibers,wherein a bundle of one of the successive amplifier stages comprises optical fibers obtained by splitting of optical fibers of a preceding stage,the coherent amplification network system further comprising a downward end portion comprising a last amplifier stage comprising:an amplifying fiber section having optical fibers separated from each other to allow cooling of the optical fibers, andan output bundle section comprising a transport fiber section of a smaller diameter than the amplifying fiber section, comprising optical fibers of a loss lower than that of optical fibers of the amplifying fiber section. 2. The arrangement for producing a proton beam according to claim 1, wherein the current is about 20 mA. 3. The arrangement for producing a proton beam according to claim 1, wherein the current is about tens of mA. 4. The arrangement according to claim 1, wherein a duration of each laser pulse is about 30 femtoseconds. 5. The arrangement according to claim 1, wherein an average power is about 20 MW. 6. The arrangement according to claim 1, wherein the proton target is a solid target formed by a film of a substance. 7. The arrangement according to claim 1, wherein the laser pulse oscillator has a repetition rate of about 10 KHz. 8. An installation for transmutation of nuclear waste, comprising an arrangement for producing a proton beam according to claim 1, and a spallation target irradiated by the beam of relativistic protons for producing neutrons of 0.5 GeV to 1 GeV of energy by spallation, said neutrons being directed towards the nuclear waste to be transmuted. 9. The installation according to claim 8, wherein the spallation target is a liquid target. 10. The installation according to claim 9, wherein the spallation target comprises an entrance window of high-stress steel and a cylindrical tube filled by a liquid of Pb—Bi alloy, wherein said liquid alloy flows and circulates in a dedicated hydraulic circuit to cool the installation. 11. The installation according to claim 8, wherein a duration of each laser pulse is about 30 femtoseconds. 12. The installation according to claim 8, wherein an average power is about 20 MW. 13. A method for transmutating nuclear waste, comprising:producing a proton beam, using an arrangement according to claim 1,irradiating a spallation target with said proton beam so that neutrons of 0.5 GeV to 1 GeV are spallated from said spallation target,directing said neutrons spallated from said spallation target towards said nuclear waste so as to transmute said nuclear waste.