Generation of periodic accelerating structures in plasma by colliding laser pulses

A mechanism for generating large (>1 GeV/m)accelerating wakes in a plasma i s proposed. Two slightly detuned counterpropagating laser beams, an ultrash ort timing pulse and a long pump, exchange photons and deposit the recoil m omentum in plasma electrons. This produces a localized region of electron c urrent, which acts as a virtual electron beam, inducing intense plasma wake s with phase velocity equal to the group velocity of the short pulse. Modul ating the pumping beam generates periodic accelerating structures in the pl asma ("plasma linac") which can be used for particle acceleration unlimited by the dephasing between the particles and the wake. An important differen ce between this type of plasma accelerator and the conventional wakefield a ccelerators is that this type can be achieved with laser intensities I much less than 10(18) W/cm(2). [S1063-651X(99)15708-8].