Accurate single-shot measurement technique for the spectral distribution of GeV electron beams from a laser wakefield accelerator

Abstract

We present a technique, based on a dipole magnet spectrometer containing multiple scintillation screens, to accurately characterize the spectral distribution of a GeV electron beam generated by laser wakefield acceleration (LWFA). An optimization algorithm along with a numerical code was developed for trajectory tracing and reconstructing the electron beam angle, divergence, and energy spectrum with a single-shot measurement. The code was validated by comparing the results with the Monte-Carlo simulation of electron beam trajectories. We applied the method to analyze data obtained from laser wakefield acceleration experiments performed using a multi-Petawatt laser to accelerate electron beams to multi-GeV energy. Our technique offers improved accuracy to faithfully characterize electron beams with non-neglegible shot-to-shot beam pointing fluctuations, particularly in the state-of-the-art multi-GeV LWFA experiments performed to push the energy frontier.

Strong field physics pursued with petawatt lasers

“…After exiting the magnet, the dispersed electron beam propagated through two other scintillating screens (Lanex2 and Lanex3) for energy measurement. This three-screen setup allowed a correct spectral calibration of electron beam energy [88]. Other diagnostics for plasma (imaging, shadowgraphy, and optical emission spectra) and laser beam profile monitoring were installed outside the vacuum chamber.…”