Descrizione
S.G. Vlachos, L. Labate L. Labate, F. Baffigi, G. Bandini, F. Brandi, L. Fulgentini, D. Gregocki, P. Koester, D. Palla, S. Piccinini, L.A. Gizzi
Nuclear Inst. and Methods in Physics Research, A 1082 (2026) 171038
Abstract
Electron beams produced via laser wakefield acceleration (LWFA), can be notoriously affected by a non negligible pointing instability, which makes the retrieval of the energy spectrum via magnetic dipole-based spectrometers prone to energy miscalculations. This is of particular interest for beams generated in the range of Very High Energy Electrons (VHEE), which are currently being examined for novel radiotherapy modalities. For this reason, various spectrometer configurations have already been suggested to correct spectra for the actual pointing angle. Here, we experimentally demonstrate an improved scheme of a previously published concept employing two scintillating screens and a magnetic dipole in between. The first screen is placed upstream of the dipole and provides the pointing angle, while the second one is set behind the dipole for energy measurements. A collimator is placed right in front of the dipole, allowing a portion of the beam to be detected, resulting in an improved energy resolution. For the electrons entering the collimator, a numerical procedure is laid out to retrieve the exact entrance angle of each transverse vertical beamlet on the dipole, which in turn allows a weighted sum procedure to be carried out to retrieve the final spectrum. Since the first scintillator screen used in our setup results in the impinging electrons being scattered, thus ultimately acting as an energy dependent attenuator, we performed Monte Carlo simulations to account for this effect, and finally corrected the observed spectrum accordingly. The effect of such a procedure on the lower energy detection threshold for the proposed scheme is discussed.
