Abstract
Parallel intense laser beam ω0, k0 and ω1, k1 shone on a plasma with frequency separation equal to the plasma frequency ωp is capable of creating a coherent large electrostatic field and accelerating particles to high energies in large flux. The photon beam excites through the forward Raman scattering large amplitude plasmons whose phase velocity is equal to (ω−ω1)/(k0−k1), close to c in an underdense plasma. The plasmon traps electrons with electrostatic field EL=γ1/2⊥ mcωp/c, of the order of a few GeV/cm for plasma density to 1018 cm−3. Because of the phase velocity of the field close to c this field carries trapped electrons to high energies: W=2mc2(ω0/ωp)2. Preaccelerated particles (ions, for examples) coherent with the plasmon fields can also be accelerated. The (multiple) forward Raman instability saturates only when a sizable electron population is trapped and most of the electromagnetic energy is cascaded down to the frequency close to the cut‐off (ωp).
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