Single-shot spectrometer with pointing angle correction for laser-driven electron beams featuring pointing instability and transverse inhomogeneity
Year: 2026
Authors: Vlachos S.G., Labate L., Baffigi F., Bandini G., Brandi F., Fulgentini L., Gregocki D., Ktzster P., Palla D., Piccinini S., Salvadori M., Gizzi L.A.
Autors Affiliation: CNR, Natl Inst Opt, Intense Laser Irradiat Lab, Via Giuseppe Moruzzi 1, I-56124 Pisa, Tuscany, Italy; Univ Pisa, Dept Phys, Largo Bruno Pontecorvo 3, I-56127 Pisa, Italy; Natl Inst Nucl Phys INFN, Pisa Sect, Largo Bruno Pontecorvo 3, I-56127 Pisa, Tuscany, Italy.
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.
Journal/Review: NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT
Volume: 1082 Pages from: 171038-1 to: 171038-7
More Information: The authors acknowledge the following fundings: EU Horizon 2020 Research and Innovation Program EuPRAXIA Preparatory Phase, under Grant Agreement No. 101079773; EU Horizon IFAST, under Grant Agreement No. 101004730. This research has been co-funded by the European Union-NextGeneration EU through the italian PNRR MUR projects Integrated infrastructure initiative in Photonic and Quantum Sciences-I-PHOQS (IR0000016, ID D2B8D520, CUP B53C22001750006) , EuPRAXIA Advanced Photon Sources-EuAPS (IR0000030, CUP I93C21000160006) , and Tuscany Health Ecosystem (THE)-Spoke 1:Advanced Radiotherapies and Diagnostics in Oncology (ECS00000017, D.D. MUR No. 1055 23 May 2022) . The authors also acknowledge support from the European Union’s Horizon Europe research and innovation programme and the UKRI guarantee funds through the MSCA, Italy EuPRAXIA Doctoral Network (grant agreement no. 101073480) , and the italian INFN CSN5 funded project FRIDA.KeyWords: LWFA; VHEE; Pointing instability; SpectrometerDOI: 10.1016/j.nima.2025.171038
