Relativistic plasma expansion with Maxwell-Ju¨ttner distribution

A self-similar analytical solution is proposed to describe the relativistic ion acceleration with the local Maxwell-Ju¨ttner relativistic distribution electrons. It is an alternative to the existing static model [M. Passoni and M. Lontano, Phys. Rev. Lett. 101, 115001 (2008)], which exploits a limited solution for the acceleration potential. With our model, the potential is finite naturally and has an upper limitation proportional to the square root of the electron temperature. The divergent potential in the non-relativistic case is the linear items of the Taylor expansion of that obtained relativistic one here. The energy distribution of ions and the dependence of the ion momentum on the acceleration time are obtained analytically. Maximum ion energy has an upper limitation decided by the finite potential difference. In the ultra-relativistic region, the ion energy at the ion front is proportional to t4/5 and the energy of the ions behind the ion front is proportional to t2/3 since the field there is shielded by the ions beyond them and the field at the ion front is the most intense.