Speaker
Description
This work focuses on the experimental characterization of a neutron source driven by the high-energy (between 300 and 700 J), short pulse (700 fs) LMJ-PETAL facility. For this purpose, we have developed two experimental platforms, both operating in a pitcher-catcher configuration [1], but using either a solid target or a gas plasma to generate the primary high-energy particle beam.
Our first approach was to produce neutrons by (p,xn) reactions triggered by a target normal sheath accelerated (TNSA) proton beam. The TNSA target was a 50 μm thick CH foil producing protons up to 50 MeV [2]. The converters were two-layer targets of lithium fluoride (LiF) and lead (Pb), the thicknesses of which were varied to optimize the neutron yield [3].
Our second approach used a supersonic helium gas jet as a target to generate a relativistic electron beam through self-modulated laser wakefield acceleration (SMLWFA) [4]. The accelerated electron reached energies up to 350 MeV and a total charge exceeding 1 μC, a performance comparable with the state of the art [5]. This electron beam was converted into intense Bremsstrahlung radiation in a thick lead (Pb) converter [6], which in turn produced neutrons through (𝛾,xn) reactions.
The properties of the primary protons or electrons, as well as emitted gamma and neutron populations were inferred by a suite of diagnostics, including radiochromic films, imaging plates, magnetic particle spectrometers, nuclear activation, bubble dosimeters and neutron time-of-flight (nToF) detectors [7].
The total number of fast neutrons (above 1 MeV and emitted quasi-isotropically) is estimated to be in the 1010−5×1010 range per shot. Such sources could find applications in nuclear physics and astrophysics [8,9,10], as well as in radiography of high-energy-density environments and fast neutron material characterization techniques [11].
References
[1] W. Cayzac et al., “Experimental capabilities of the LMJ-PETAL facility”, High Energy Density Physics 52, 101125 (2024).
[2] D. Raffestin et al., “Enhanced ion acceleration using the high-energy petawatt PETAL laser”, Matter and Radiation at Extremes 6, 056901 (2021).
[3] B. Martinez et al., “Numerical investigation of spallation neutrons generated from petawatt-scale laser-driven proton beams”, Matter and Radiation at Extremes 7, 024401 (2021).
[4] F. Albert et al., “Laser wakefield accelerator based light sources: potential applications and requirements”, Plasma Physics and Controlled Fusion 56, 084015 (2014).
[5] J. Shaw et al., “Microcoulomb (0.7 ± 0.4/0.2 μC) laser plasma accelerator on OMEGA EP”, Scientific Reports 11, 7498 (2021).
[6] J. Ferri et al., “Electron acceleration and generation of high-brilliance x-ray radiation in kilojoule, subpicosecond laser-plasma interactions”, Physical Review Accelerators and Beams 19, 101301 (2016).
[7] D. P. Higginson et al., “Global characterization of a laser-generated neutron source”, Journal of Plasma Physics 90, 90590308 (2024).
[8] A. Yogo et al., “Laser-Driven Neutron Generation Realizing Single-Shot Resonance Spectroscopy”, Physical Review X 13, 011011 (2023).
[9] S. N. Chen et al., “Extreme brightness laser-based neutron pulses as a pathway for investigating nucleosynthesis in the laboratory”, Matter and Radiation at Extremes 4, 054402 (2019).
[10] V. Horny et. al., “Quantitative feasibility study of sequential neutron captures using intense lasers”, Physical Review C 109, 025802 (2024).
[11] F. Mirani et. al., “Laser-Driven Neutron Generation with Near-Critical Targets and Application to Materials Characterization”, Physical Review Applied 19, 044020 (2023).
