Experimental Comparison of TNSA and LWFA Schemes for Neutron Generation on ALLS 150 TW

Neutron beams allow performing non-destructive analysis as they give unique access to elemental composition with better contrast for low atomic number (Z) materials, complementing higher Z material analysis from standard X-ray investigations. Laser-based neutron sources have recently enabled short bunch duration (ps to ns) with energies up to a few tens of MeV and record peak brightnesses. Nevertheless, applications like studying neutron-induced damage in fusion reactor designs would benefit from a higher flux neutron sources. The upscaling of laser-based neutron sources has been recently studied numerically for the two most promising experimental schemes using high-power lasers, either through the Target-Normal Sheath Acceleration (TNSA) of proton beams and then converting protons to neutrons in a converter, or through the Laser WakeField Acceleration (LWFA) of electrons sent into a high-Z converter for producing high-energy Bremsstrahlung photons followed by photonuclear reactions releasing neutrons within the same converter. In this work at the Advanced Laser Light Source (ALLS), we experimentally compare the two schemes using the same 150 TW laser (3.3 J, 22 fs, 800 nm), and find at least 2 to 3 orders of magnitude higher neutron yield for the LWFA scheme, as recently predicted. This is the first direct experimental comparison of the two schemes using the same laser beam in nominal conditions. Moreover, the source operates at 2.5 Hz reaching the 10⁹ n/s level, and runs for hours with good stability.