Creation of persistent, straight, 2 mm long laser driven channels in underdense plasmas

The experimental study of the behavior of deuterium plasma with densities between 2×1018 and 2×1020 cm−3, subjected to a 6 TW, 30 ps, 3×1018 W cm−2 laser pulse, is presented. Conclusive experimental proof that a single straight channel is generated when the laser pulse interacts with the lowest densities is provided. This channel shows no small-scale longitudinal density modulations, extends up to 2 mm in length and persists for up to 150 ps after the peak of the interaction. Bifurcation of the channel after 1 mm propagation distance is observed for the first time. For higher density interactions, above the relativistic self-focusing threshold, bubblelike structures are observed to form at late times. These observations have implications for both laser wakefield accelerators and fast ignition inertial fusion studies.