Experimental Study of Nanosecond Laser-Generated Plasma Channels

Generation of plasma-channels by interaction of gas targets with nanosecond laser beams was investigated experimentally. Such laser-generated plasma channels are very promising for subsequent guiding of high peak power femtosecond laser pulses, over several tens of centimeters, as required in laser wake field electron-acceleration (LWFA). The experimental setup was based on the use of a cylindrical lens (100 mm of focal length) with the aim of proposing a technical solution easy to be integrated into a compact experimental setup for acceleration of multi-GeV electron beams using high peak-power laser systems. A pilot experiment, showing production of asymmetric plasma channels over a length of several millimeters in N and Ar targets with initial neutral-gas atomic density around 5 × 1019 cm−3, is reported. Plasma effective threshold formation was estimated, along with future optimization of the optical setup for a symmetrization of such plasma channel. Scalability of this concept to several tens of centimeters is preliminarily discussed, along with the corresponding critical requirements for an optimal LWFA scheme.