Ultra-high brilliance multi-MeV ${\hat{I}}^3$-ray beam from non-linear Thomson scattering

Abstract

We report on the generation of a narrow divergence ($\hat{I}¸\approx 2.5$ mrad), multi-MeV ($E_{\text{MAX}}=18$ MeV) and ultra-high brilliance ($\approx 2\times 10^{19}$ photons s${}^{-1}$ mm${}^{-2}$ mrad ${}^{-2}$ 0.1\% BW) ${\hat{I}}^3$-ray beam from the scattering of an ultra-relativistic laser-wakefield accelerated electron beam in the field of a relativistically intense laser (dimensionless amplitude $a_0\approx 2$). The spectrum of the generated ${\hat{I}}^3$-ray beam is measured, with MeV resolution, seamlessly from 6 MeV to 18 MeV, giving clear evidence of the onset of non-linear Thomson scattering. The photon source has the highest brilliance in the multi-MeV regime ever reported in the literature.