Influence of a low-Z thin substrate on a microwire hard x-ray source driven by a picosecond laser pulse for point-projection x-ray radiography

• Published in: Physics of plasmas Vol. 27; no. 12
• Main Authors: Li, Meng-ting, Hu, Guang-yue, Huang, Lin-gen, Zheng, Jian
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 01.12.2020
• Subjects: Bremsstrahlung; Emission; Gamma rays; Hot electrons; Inertial confinement fusion; Particle in cell technique; Plasma physics; Projection; Radiators; Radiography; Short pulses; Substrates; X ray sources; X-ray radiography
• ISSN: 1070-664X; 1089-7674
• DOI: 10.1063/5.0023189

In the point-projection hard x-ray radiography of dense matter, for example, an inertial confinement fusion implosion capsule at stagnation time, a picosecond laser driven gold microwire is used to produce a short pulse point, bremsstrahlung hard x-ray source. The microwire was held by a low-Z CH thin substrate commonly used to promote experimental performance. We explored the influence of the low-Z thin substrate on the microwire bremsstrahlung hard x-ray source via particle-in-cell and Monte Carlo simulations. It was shown that both of the microwires, with or without the low-Z thin substrate, could emit more intense hard x-ray radiation than the radiator buried in the equal-density substrate, which benefited from efficient electron recirculation. The freestanding microwire exhibited further enhanced electron recirculation compared to that with the low-Z thin substrate, while the increased hot electrons were only present for the energetic electrons of >1 MeV. Thus, the freestanding microwire could produce significantly more intense MeV gamma x-ray emission with respect to that with the substrate, but an ignorable increment was exhibited at the softer x-ray emission of 10–200 keV. These results provided valuable insights into the design of backlighter targets in point-projection x-ray radiography, such as a freestanding microwire being preferred in MeV gamma-ray radiography, while the microwire with the CH thin substrate could be used in the 10–200 keV hard x-ray Compton radiography of an implosion capsule.