Autoresonance laser acceleration of guided "quasineutral" electron-positron beams

A scheme for simultaneous laser acceleration of electrons and positrons to high energies is discussed. The acceleration is based on a cyclotron autoresonance between the particles and a linearly polarized radiation, propagating along an axial magnetic field. The nonlinear dynamics of an electron and a positron in the system is investigated for homogeneous fields and luminous radiation. The energy of the accelerated particles scales asymptotically as 0.82{[Bz(100 kG)/(10 m)]1/2xz(m)}2/3 GeV, where z and Bz are the distance and strength of the guide magnetic field and x=eE/(mc) and are the normalized radiation field amplitude and its wavelength, respectively. It is shown that high-current quasineutral beams (plasmas) can be accelerated to high energies with low radiation losses.