Neutron beams driven by the Texas Petawatt laser*

Intense laser-driven ion beams produced in the relativistically-induced transparency regime have been used to generate intense $\gamma $-ray and neutron beams [1]. For neutrons, a laser-driven deuteron beam is directed at a Be disk ``converter'', where deuterons split producing mainly forward-directed neutrons. The aforementioned experiments have been done at the Trident laser using a 0.5 ps laser pulse of 1 $\mu $m wavelength focused up to 10$^{\mathrm{21}}$ W/cm$^{\mathrm{2}}$ onto nanofoils of deuterated-plastic (CD$_{\mathrm{x}}$ where x$=$1$-$2), making 1x10$^{\mathrm{10}}$ neutrons/sr at $\sim $ MeV average energies [2]. Here we report on the first experiments to explore the same regime at the Texas Petawatt (TPW) laser facility. With one plasma mirror, TPW delivers high-contrast laser pulses as short as 0.15 ps at intensities up to 2x10$^{\mathrm{21}}$ W/cm$^{\mathrm{2}}$. CD and Al/CD multilayer targets of thickness in the range of 50 -- 750 nm have been used. This setup has delivered up to 5x10$^{\mathrm{9}}$ neutrons/sr. The dependence of neutron yield on target composition and thickness, and on laser pulse length is presented and discussed. . . . . . . . . . . . . . [1] J.C. Fern\'{a}ndez et al$.$, \textit{Laser-plasmas in the relativistic-transparency regime: Science and applications, }Phys. of Plasmas \textbf{24}, 056702 (2017) [2] M. Roth et al., \textit{Bright Laser-Driven Neutron Source Based on the Relativistic Transparency of Solids,} Phys.Rev. Lett. \textbf{110, }044802 (2013)