The Short Pulse Generating And Shaping Research Of Heaven-Ⅰ System Front-End

The KrF excimer laser is used as one of the inertial confinement fusion(ICF) driven source candidates. The findings show that pulse with width of 1-10ns is the most appropriate pulse in ICF experiment. Currently the"Heaven-I"system is the biggest high power excimer laser system. The pulse width of the ASE pulse generated by front-end is more than 10ns and doesn't meet the requirements of the ICF for the drive pulsew. For this reason, we hope to acquire the driven pulse of ICF through compressing, stacking and amplifying for the original KrF ASE to provide the technical support for ICF.In the progress of short bpulse generation, we adopt the technologies of laser oscillation quenching with one mirror at the beginning. The experiment results show that the pulse width can be compressed from 10.6ns to 5.1ns. However the compression of the pulse trailing edge is not completely. So we adopt the technology of laser auxiliary quenching, the pulse width can be compressed from 12.6ns to 4.7ns, however the stability is not satisfied. Finally we apply the method of laser oscillation quenching with two mirrors. The pulse width could be compressed from 12.6ns to 2.5ns, and the stability of short pulse is well improved. What's more, the trailing edge of the output pulse is compressed completely.In addition, we make numerical simulations anpobt the progress of pulse stacking and amplification for the short pulse. The result shows the main factors that would affect the characters of the stacking pulse are the symmetry property of original pulse waveform, the peak power density ratios of each sub-pulse and the delay time among each sub-pulse; It proved that the short pulse can stack nearly flat-top pulse and the driving pulse that shock ignition need, also theoretically proved that the pulse stacking can reshape complex waveform pulse. Meanwhile we ayalyzed the influence of pulse stacking caused by original pulse width fluctuation, and the result shows that the pulse stacking waveform is free from fluctuation when it is less than 5%. Also the simulation about pulse amplification shows that higher the injection pulse energy is, greater waveform distortion will generate after amplification. Finally we prove that the KrF ASE pulse can acquire the driving pulse which ICF needs after pulse compression, stacking and amplification. Based on the short pulse generated, we also reshape the quasi-flat top pulse using two beams and three beams stacking and confirm the symmetry of original pulse waveform, the peak power density ratios of sub-pulse and the delay time among sub-pulse which will affect the pulse stacking in combination with experiments. The study about single beam pulse amplification and multi-beam stacking pulse amplification show that the waveform distortion occurs and the greater the injection pulse energy, the greater the waveform distortion. This research provides the basement for generating the pulses with quasi-flat top or other shapes by changing the shape of stacking pulses before being incidented to the amplifier.