Experimental demonstration of nonlinear inverse Compton scattering using the 4 PW laser at CoReLS*

Advances in laser wakefield acceleration (LWFA) have enabled production of GeV electron beams from a cm-long plasma. The co-location of these electron beams and high intensity laser pulses at petawatt (PW) laser facilities allows the study of inverse Compton scattering - revealing a new interaction regime, known as strong-field quantum electrodynamics (SFQED) [1].

In this work, we present the experimental demonstration of inverse nonlinear Compton scattering [2], using the CoReLS 4PW laser [3]. We collide LWFA electrons (E<3.5 GeV) [4] with an ultrashort laser pulse (25fs) of intensity I≈4x10 20 W/cm 2 , achieving a quantum nonlinearity parameter χ≈0.5. A single electron can scatter off hundreds of laser photons, converting them into a single gamma-ray photon with unique properties. We characterized gamma-ray beams, showing they can reach mrad divergence, critical energy 50-150 MeV (approaching the GeV range) and exhibiting high brilliances. Furthermore, we investigated the relation between this gamma-ray energy and the electron beam energy, demonstrating the influence of the colliding pulse intensity. Our experiment provides insight into the parameters requiring further investigation and the demands posed by the study of laser-electron collisions at upcoming facilities [5].