Hybrid capillary discharge waveguide for laser wakefield acceleration

A hybrid capillary discharge waveguide formed by injecting low-pressure hydrogen (< 3.8 Torr) into a pure ablative capillary is presented to supply the stable guiding for multi-GeV laser wakefield acceleration. The injected low-pressure gas only provides the seed plasma for ablative discharge breakdown, like the adsorbed gas in the inner wall of the ablative capillary. With this hybrid capillary, a stable discharge with low jitter (~ 5 ns) can be achieved in a simple way, and the plasma density inside can also be controlled in a range of ~0.7 x 10¹⁸cm^-3-1.2 x 10¹⁸cm^-3 within a 150-ns plasma channel temporal window. Furthermore, the hybrid capillary can also be easily extended to a longer length by adding multiple segments, and femtosecond laser pulses can be well guided both in the single and multiple segments mode. With these advantages, the hybrid capillary may provide an attractive plasma channel for multi-GeV-scale laser wakefield acceleration.