Demonstration of a high repetition rate directional MeV laser-driven neutron source*

Neutron beams generated by laser-driven ion sources exhibit promising characteristics including high peak flux and short pulse duration. However, low repetition rates have previously limited these sources' development towards maturity for applications. We present the first demonstration of a high repetition rate (HRR, 0.5 Hz) laser-driven neutron source operating in the pitcher-catcher geometry, producing up to 8x10⁵ neutrons/sr/shot within a 20-degree cone centered on the target normal direction. We implemented an ambient-temperature microjet target¹ producing planar liquid H₂O or D₂O sheets 1 micron thick at the ALEPH laser facility (400 nm, 5 J, 45 fs). We placed a 1.5 mm-thick beryllium converter with an on-axis pinhole behind the liquid target to enable simultaneous ion beam characterization and neutron beam production. In the target normal direction we observed a 17-fold increase in the neutron yield for D₂O targets compared to H₂O targets, confirming a significant contribution from deuteron breakup reactions². This suggests that increased laser energies and intensities, additionally assisted by laser pulse shaping on the fs timescale, will facilitate the production of high-flux, HRR beams of 14 MeV neutrons for studies of neutron-induced damage in fusion materials.

1. F. Treffert and G. D. Glenn et al., Phys. Plasmas 2022

2. A. Alejo et al., Plasma Phys. Control. Fusion 2017