Bright and stable betatron beams from various injection schemes in laser-driven plasma wakefield

With the evolution of various injection techniques[1] in laser-driven wakefield acceleration (LWFA) since 2004 [2], we now have more control over our resultant electron beams. This in turn facilitates a bright and stable betatron beam.

By implementing shock-induced density down-ramp injection and by rotating this shockfront with respect to the laser axis simulations show a shift in the injection angle, which was anticipated to be observable in the Betatron radiation. We also produce quasi monoenergetic electron beams with ~40pC charge, <10 mrad divergence and ΔE/E <10% through this scheme. This was achieved by using Jet-Blade assembly (with He+N₂ (95% + 5%) mixture) and by varying the shock profile, position, angle and the blade coverage of the 5mm gas jet.

In a second experiment, Betatron beams from ionisation injection in a gas cell were produced. We observe a peak brightness of ~10²³ [Photons/(s.mm².mrad².0.1%BW)], with ~1 µm source size using the ionisation injection method, outweighing any advantages from the off-axis injection approach discussed above. A gas cell with a 10 mm acceleration length (H₂+N₂ (95% + 5%) mixture) was used. We compare the Betatron characteristics from different injection schemes (shock, ionisation and off-axis shock injection).