Controlled plasma wave generation and particle acceleration through seeding of the forward Raman scattering instability

Trapping and acceleration of background plasma electrons in plasma waves generated by low energy (<0.1 J) laser pulses copropagating with much weaker (1% in intensity) seed pulses that are down shifted in frequency by omega(p) is investigated in the self-modulation regime by one-dimensional (1D) and 2D particle-in-cell simulations. Without the seed, the modulation for pulses of subcritical power is found to develop slowly compared to the interaction time limited by diffraction and dephasing. With the seed, on the other hand, strong primary pulse modulation, wakefield excitation, and particle trapping and acceleration can be achieved reproducibly. Moreover, in contrast to incoherent seeding mechanisms such as ionization, the seed pulse enables coherent control of the excited wakefield. The simulations show that 38 mJ seeded pulses can generate relativistic bunches of similar to0.5 nC. Seeded acceleration by pulses of subcritical power (P=1/2P(c), or 19 mJ) is demonstrated by simulations in a performed plasma channel (C) 2005 American Institute of Physics.