  Particle-in-cell (PIC) simulation results of sustained acceleration of
electron-positron (e+e-) plasmas by comoving electromagnetic (EM) pulses are
presented. When a thin slab of overdense e+e- plasma is irradiated with
linear-polarized ultra-intense short laser pulses from both sides, the pulses
are transmitted when the plasma is compressed to thinner than ~ 2 relativistic
skin depths. A fraction of the plasma is then captured and efficiently
accelerated by self-induced JxB forces. For 1 micron laser and 1021Wcm-2
intensity, the maximum energy exceeds GeV in a picosecond.
