Laser Beat-Wave Accelerator for Ultra-High Energies

Parallel intense laser beams ¿0, k0 and ¿1,k1 shone on a plasma with frequency separation equal to the electron plasma frequency ¿pe is capable of creating a coherent large longitudinal electric field EL = ¿¿¿ mc ¿pe/e of the order of 1-10GeV/cm for plasma density 1018-20 cm-3 through the forward Raman scattering. A concept of applying this process to an ultra-high energy (100-1000 TeV range) accelerator is considered. Associated physics questions such as the laser beam propagation, self-trapping, filamentation, the longitudinal dephasing etc. are discussed. As a method to overcome the longitudinal dephasing, the relativistic forward Brillouin scattering process is proposed, where the frequency separation of two lasers is now ¿pi with ¿pi being the ion plasma frequency.