Prof. Dino Jaroszynski FRSE FInstP, Director of the Scottish Centre for the Application of Plasma-based Accelerators, SCAPA, University of Strathclyde

"Ultra-high charge beams from a laser wakefield accelerator driven by a petawatt laser"

Abstract: Over the past three decades significant progress has been made in developing laser wakefield accelerators (LWFAs), which can now produce femtosecond duration electrons bunches with pC-level charge, 10 MeV - 10 GeV energies and kilo-ampere peak beam current. However, in addition to the high-energy, low-divergence electron beam emitted in the direction of laser propagation, a wide-angled beam is produced by the electrostatic forces by a “sling-shot” action that ejects a portion of the electrons forming the sheath of the accelerating structure. These wide-angle electron bunches can have high charge and carry away a significant portion of the laser pulse energy deposited in the plasma. Here I will discuss measurements of these side electron beams, which have unprecedented high charge and energies in the MeV range, produced by a 17 J, PW laser (at CLPU in Salamanca), with high efficiency. I will present evidence of filamentation instability that occurs in the sheath current of the LWFA. The ultra-high charge beams with kA peak currents are produced with high efficiency. This makes them suitable for pulsed radiolysis, imaging and material processing. The interacting converging/diverging beams provide an interesting model system for studying astrophysical phenomena in the laboratory.