Measurement of angularly dependent spectra of betatron gamma-rays from a laser plasma accelerator with quadrant-sectored range filters

Measurement of angularly dependent spectra of betatron gamma-raysradiated by GeV electron beams from laser wakefield accelerators (LWFAs) are presented. The angle-resolved spectrum of betatronradiation was deconvolved from the position dependent data measured for a single laser shot with a broadband gamma-ray spectrometercomprising four-quadrant sectored range filters and an unfolding algorithm, based on the Monte Carlo code GEANT4. The unfolded gamma-rayspectra in the photon energyrange of 0.1–10 MeV revealed an approximately isotropic angular dependence of the peak photon energyand photon energy-integrated fluence. As expected by the analysis of betatronradiation from LWFAs, the results indicate that unpolarized gamma-raysare emitted by electrons undergoing betatronmotion in isotropically distributed orbit planes.