Influence Of Target Density Distribution On Laser-plasma Proton Acceleration

With the development of science and technology, high-energy ion beam, especially high-energy proton beam demand in scientific research and technological applications is increasing rapidly, such as high-energy particle physics reaction, proton imaging, cancer therapy, therefore how to produce high-quality ion beams has become a hot issue in modern science and technology research. In the past 20 years, physicists have been exploring new scheme of accelerated particles, is expected to accelerate the particles to a even higher energies in a much shorter distance. With the rapid development of chirped pulse amplification(CPA) technology, the femtosecond ultrashort laser pulses are available. Such laser field is much larger than the field inside the atom, which laser intensity is up to GV/ m~ TV/ m magnitude of strong longitudinal electric field is achievable, these electric fields can be used to accelerate electrons, protons or ions for the development of miniaturized particle accelerators. Laser plasma acceleration of protons in the laboratory has been established, but due to the relativistic effects, the group effect, turbulence and other factors, the accelerated proton beam quality is not high, so there is still much work to be done.Based on the one-dimensional Particle-In-Cell(PIC) computer simulation, the influence of target density distribution on the laser-plasma proton acceleration is studied by changing the target density distribution. In the simulation, ROOT software is employed for large data analysis and results are patterned, so the underlying mechanism could be understood more clearly. In this article, firstly we determine the most appropriate laser waveform, then the shape of the initial target. It is found that the sin2 type laser pulse produces the best result, and a convex target produced the best proton beam quality. So we focus on the sin2 laser and convex target interaction. The results shows that a right-handed circularly polarized laser interacts with a convex target can produce a high energy mono-energetic proton beam up to 316.92 MeV, One-dimensional PIC simulation shows the favorable target density distribution for laser-plasma proton acceleration, these results would provide theoretical guidance for further experimental study.