عنوان مقاله [English]
نویسندگان [English]چکیده [English]
In this paper, the effect of plasma density ramp and laser pulse length on the energetic particle generation and pulse scattering were investigated in an under- dense plasma for short and long pulse lengths, of τL = 60 fs, and τL = 300 fs, respectively. In our simulations, we used a kinetic particle in cell simulation 1D-3V code. It is found that the laser pulse length and density ramps play an important role on the energetic particles generation and pulse scattering in plasma. So that, the simulations of the laser pulse length impact indicate that, in the case of short pulse interaction with the under-dense plasma, electrons are accelerated to the higher energy level. Furthermore, among the three different ramps: step-like, ramp 1 with a steep slope, and ramp 2 with a gentle slope, in the case of the step-like density ramp, electrons accelerate to high energies, in comparison with two other ramps. A fourier analysis of the total radiation spectrum indicate that in the case of the step-like density profile, the growth rate of the electromagnetic modes have maximum regular picks and minimum growth rate obtained in the case of the smooth ramp. Meanwhile, the time evaluation analysis of the energy distribution function shows that with the time increment of the pulse propagation, in the shorter pulse case, and for the step density scale length, plasma particles can reach a high energy level.
3. C.D. Zhou and R. Betti, Laser-plasma interactions and applications, Phys. Plasmas, 14, 072703 (2007).
4. Y. Sentoku, et al. High energy proton acceleration in interaction of short laser pulse with dense plasma target, Phys. Plasmas, 10, 2009 (2003).
5. B.S. Paradkar, et al. Numerical modeling of fast electron generation in the presence of preformed plasma in laser-matter interaction at relativistic intensities, Physical Review E 83, 046401 (2011).
6. C.J. McKinstrie and R. Bingham, Stimulated Raman forward scattering and the relativistic modulational instability of light waves in rarefied plasma, Phys. Fluids B 4, 2626 (1992).
7. J.F. Drake, Parametric instabilities of electromagnetic waves in plasmas, Phys. Fluids 17, 778-785 (1974(.
8. W.L. Kruer, The Physics of Laser Plasma Interactions, Reading, MA: Addison Wesley (1988).
9. W.B. Mori, Raman forward scattering of short-pulse high-intensity lasers, Phys. Rev. Lett. 72, 1482-1485 (1994).
10. A.S. Sakharov and V.I. Kirsanov, Theory of Raman scattering for a short ultrastrong laser pulse in a rarefied plasma, Phys. Rev. E 49, 3274–3282 (1994).
11. C. Joshi, Ultrahigh gradient particle acceleration by intense laser-driven plasma density waves, Nature 311, 525-529 (1984).
12. S.V. Bulanov, V.I. Kirsanov, and A.S. Sakharov, Limiting electric field of the wakefield plasma wave, Pis’ma Zh.´Eksp. Teor. Fiz. 53, 540-544 (JETP Lett. 53, 565–569), (1991).
13. R.M.G.M. Trines, Generation of fast electrons by breaking of a laser-induced plasma wave, Phys. Rev. E 63, 026406 (2001).
14. C.I. Moore, Electron trapping in self-modulated laser wakefields by Raman backscatter, Phys. Rev. Lett. 79, 3909-3912 (1997).
15. R.M.G.M. Trines, On the effect of laser and plasma parameters on stimulated Raman scattering, J. Plasma Physics. 71, part 4, 411-433 (2005).
16. J. Yazdanpanah and A. Anvary, Time and space extended-particle in cell model for electromagnetic particle algorithms, Phys. Plasmas. 19, 033110 (2012).
17. J. Yazdanpanah and A. Anvari, Effects of initially energetic electrons on relativistic laser-driven electron plasma waves, Phys. Plasmas. 21, 023101 (2014).