It is shown that large amplitude Langmuir waves, produced as a wake by short electromagnetic pulses in a plasma, can be generated effectively by a series of short pulses. The nonlinear nature of the Langmuir waves means that a given total energy in the electromagnetic wave is much more effective when delivered in a series of pulses than in a single short pulse. The present analysis treats the generation of the Langmuir wave in both electron-proton and electron-positron-proton plasmas. A plot of phase trajectories shows that the correct phasing of the pulses leads to a dramatic improvement of the wake-field amplitude. For maximum amplification, the pulse maximum of each of the trailing pulses should be spatially coincident with the minimum of the wake-field potential.
- Langmuir waves
- plasma wakefield
- electron-positron-proton plasmas