The Reseach Of Laser-proton Acceleration

During the interaction of ultra-short and ultra-intense pulse laser with solid target, proton beams with energies of several MeV per nucleon will emit in a small cone angle in the direction of target normal. Such proton beams exhibit unprecedented characteristi -cs: short pulse lengths, small source size and low transverse emittance, which can be applied widely in ion acceleration, proton imaging,"fast ignition",cancer therapy and so on. In order to realize the characteristics of protons emitting in the interaction of ultra-short and ultra-intense pulse laser with plasma, this thesis mainly studies laser-proton acceleration, emphasizing on the cut-off energy and yield of proton beams at the rear side of target, and introduces preliminary research of proton imaging.The thesis began with simply introduction of the"fast ignition"and high field physics, and the research development of the protons produced in the interaction of ultra-short and ultra-intense pulse laser with plasma. And then we expatiate in detail the theory of the process of the interaction of ultra-short and ultra-intensity laser with plasma and the acceleration mechanisms of protons. At last and most importantly, we introduce the experimental research of laser-proton acceleration and proton imaging.The experiments were carried out at the ultra-short and ultra-intense laser facility——SILEX-I in the China Academy of Engineering Physics. We get the exponential energy spectrum by measuring the parabola of proton track on CR39. According to the theory of laser-proton acceleration, the cut-off energy of proton beams is estimated. The estimation according to the rear side mechanism agrees well with experimental data. Besides the influence of prepulse to the accelerating field is estimated by Multi2005 code and it can be neglected when Signal-to-Noise is better than 108:1 in our experiment. We calculate the yield of protons with given spectrum basing on the OD change of RCF. About 1010 protons with energy greater than 0.2MeV were accelerated in the experiment. The result agrees well with the result gained from CR39. Additionally, it's also shown that copper target plated CH can significantly increase the yield of proton, compared with barely copper target.In proton imaging experiment, high spatial resolution and high contrast proton radiography for metal grid and hollow plastic pellet was demonstrated. The proton source is about 250±100μm before the rear side of target,according to point-imaging model , and the proton fluence changes greatly at the sharp outlines. We also performed preliminary experiment on proton radiography of laser-produced plasma. The results need farther analyses.