Mechanisms Of Ion Acceleration Via The Interaction Between An Ultra Intense Laser With The Underdense Plasma

Rapid development of laser technology and the realization of TW laser and fs laser pulse have excited a lot of research interest in studying the interaction of ultra-intense lasers with matter. Among these studies, the generation of energetic ion beams by the interaction of ultra-short relativistic laser pulses with plasma is currently an attractive subject. Because these ions will be potentially applied in several aspects such as proton radiography, fast ignitors for laser fusion, tumor therapy, producing high-energy-density matter and so on. Over the past decade, relevant researches both on theoretic and experimentation have made evolutional breakthrough.Various acceleration mechanisms have been discovered and verified through computer simulations and experiments. Most of the researches are focused on the overdense plasmas or solid targets because of the low intensity laser can drive enough electrons out of the target when the target density is high, and therefore the strong charge separate electric field can accelerate the ions. Recently, scientists found that if the intensity of laser pulse is high enough, it also has strong coupling with low density plasmas. It makes the ion acceleration available and may get high quality ion bunches.In this particle, we use2.5D PIC (Particle in Cell) code to simulate the interaction between ultra intense laser pulse and underdense plasmas investing the proton acceleration course and the physical mechanisms. We can clearly see that TNSA, magnetic vortex acceleration, BOA, combined with the wakefield BOA(W-BOA) mechanism worked together in the density n0<nc region and obtain proton bunch with low emittance. Results show that protons undergo a long time and space scale acceleration of about several ps and mm each, at last,1.66GeV proton bunch generates and it demonstrates.In summary, this research on underdense plasma is an development of the theory of laser-plasma interaction to accelerate ion beams. It can be easily achive using gas target in experiments generating good collimated ion bunches. Deeply study on the quasi-monoenergtic proton beams by a laser-illuminated underdense plasmas may lead the practical application of proton beams, such as tumor therapy, fast ignitors for laser fusion.