ENHANCED WAKEFIELDS FOR THE 1D LASER WAKEFIELD ACCELERATOR

The amplitudes of wakefields generated by the ponderomotive force of i ntense pulses much longer than lambda(p)/2 are determined using nonlin ear, relativistic envelope equations and found to be significantly lar ger than predicted by linear theory. This is relevant to the self-modu lated laser wakefield accelerator; under suitable experimental conditi ons enhanced wakefields should be large enough to act as the dominant source for seeding Raman forward scattering induced ''beam breakup.'' Consequently the use of other seeding mechanisms Such as Raman backsca ttering, which is unpredictable, can be avoided. The enhancement mecha nism is attributed to in effective bandwidth increase of the laser pul se due to nonlinearities in the response of the plasma to the ponderom otive force.