Generation of Quasi-monoenergetic High-energy Electron Beam by Plasma Wave

We have demonstrated an acceleration of a quasi‐monoenergetic electron beam by trapping electrons in a plasma wave. Experiments were performed by focusing 2‐TW (50 fs) laser pulses on supersonic gas jet targets. An intensity was 5 × 1018W/cm2(a0 = 1.5). An electron density was estimated to be 1.3 × 1020cm−3. The quasi‐monoenergetic electron beam at 7 MeV was observed with a peak to foot ratio of 10. An appearance of a Stokes Raman satellite in the forward scattering well correlated with the quasi‐monoenergetic electron beam. A frequency shift of the satellite coincided with a plasma frequency at the measured plasma density. Appearance of the Raman satellite coincided with appearances of a fishbone structure in a side‐scattering image. Supposing the fishbone structure originated from the plasma wave, an acceleration length was estimated to be 200 to 500 microns.