Ultrashort Laser Plasma Interaction In Proton Emission Experimental Study

During the interaction of ultra-short and ultra-intense pulse laser with plasma, energetic proton beams will emit in the form of pulse. Especially, the proton beams that emit in a sarnll cone angle in the direction of target normal have some excellent advances, such as small source size , short pulse duration, high degree of collimation which will enable those protons be applied widely in the future. Additionally, the production of the protons is closely collected with hot electrons whose production and transportation are key processes in both the interaction of ultra-short and ultra-intense pulse laser with plasma and the fast ignition of Inertial Confinement Fusion. We can obtain the information about the production and transportation of hot electrons by investigating proton beams. So, this thesis mainly study the experiments of protons emitting in the interaction of ultra-short and ultra-intense pulse laser with plasma, in particular paid attention to the characteristics of the protons emitting in the target normal direction , including the relation between the yield, the spatial distribution, the energy distribution and the thickness of targets.Firstly, the thesis simply introduced the model and significances of the fast ignition, and the research development of the protons produced in the interaction of ultra-short and ultra-intense pulse laser with plasma. Secondly, we expatiated in detail the theory of three aspects: the process of the interaction of laser with plasma; the process of the interaction of the ultra-short and ultra-intensity laser with plasma; and the acceleration mechanisms of protons. At last and most importantly, we introduced the experimental research, and then analyzed and discussed the results.Our experiments were carried out at the ultra-short and ultra-intense laser facility in the China Academy of Engineering Physics. In the experiments, keeping the laser intensity invariable (5x1017 Wcm-2), we used CR39 and Thomson ion spectrometer to measure the yield, the angle distribution and the energy spectrum of the protons in the interactions of the laser with cuprum targets of different thickness (from 5 to 30 urn). We found that there were high-energy protons produced in the interaction of the ultra-short and ultra-intensity laser with plasma, and drew an important conclusion that the protons emit about 105 ~ 106a.um shot along the normal direction of the target strictly, being independent of the direction of the incident laser. There is a small emissive cone angle of the proton beam which will benefit the application of the proton beams. As far as the energy distribution is concerned, the proton beams cut-off in a certain energy relates closely to the thickness of the target. All results were in good agreement with the acceleration mechanisms of protons.