Femtosecond laser-induced plasma filaments for beam-driven plasma wakefield acceleration.

We describe the generation of plasma filaments for application in plasma-based particle accelerators. The complete characterization of a plasma filament generated by a low-energy self-guided femtosecond laser pulse is studied experimentally and theoretically in a low-pressure nitrogen gas environment. For this purpose, we adopted a spectroscopic methodology to measure the plasma density and electron temperature. In addition to this, we also employed a side-imaging technique to retrieve the plasma column sizes (length and diameter). The measurements show the stable generation of a ≈4-cm-long plasma filament with ≈300µm diameter. The peak plasma density and temperature are n_{e}≈10^{16}cm^{-3} and T_{e}≈1.3eV, respectively, with a decay time of approximately 8 ns. We show that the experimental results are in agreement with numerical simulations in terms of filament size and density decay time.