Devices and methods for producing relativistic particles are provided. The devices and methods involve collision of a thin collimated plasma layer from opposite sides with two counter-propagating ultra-intense laser (UL) electromagnetic (EM) pulses. The plasma layer is sufficiently thin so that the pulses penetrate and conjointly propagate through the plasma layer. The Lorenz force between induced skin currents and the magnetic field of the propagating pulses accelerates a number of "in-phase" plasma particles to relativistic velocities.