Absolute charge calibration and degeneration studies of various scintillation screens used in laser Wakefield acceleration

Scintillation screens are generally used as the electron beam diagnostics in Laser Wakefield Accelerators. We present an absolute charge calibration of the electron detector i.e. a scintillating screen with a layer of powdered rare earth phosphor (Gd2O2S:Tb). The calibration was designed to investigate the absolute light/charge–ratio and saturation effects of various screens used in current laser–electron accelerators. The scintillation screens show a linear photon response to the applied charge up to an upper boundary caused by saturation effects. We also report about degeneration studies of some of these screens which were excited with a similar condition compared to Wakefield experiments.