Time-resolved optical shadowgraphy of solid hydrogen jets as a testbed to benchmark particle-in-cell simulations

• Published in: Communications physics Vol. 6; no. 1; pp. 368 - 15
• Main Authors: Yang, Long, Huang, Lingen, Assenbaum, Stefan, Cowan, Thomas E., Goethel, Ilja, Göde, Sebastian, Kluge, Thomas, Rehwald, Martin, Pan, Xiayun, Schramm, Ulrich, Vorberger, Jan, Zeil, Karl, Ziegler, Tim, Bernert, Constantin
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 21.12.2023; Nature Publishing Group; Nature Portfolio
• Subjects: 639/766/1960/1135; 639/766/1960/1137; Benchmarks; Collisional plasmas; Electrons; Expanding plasmas; Fluid mechanics; Hydrodynamics; Hydrogen; Irradiation; Laser beam heating; Lasers; Particle in cell technique; Physics; Physics and Astronomy; Plasma density; Plasma physics; Ray tracing; Relativistic effects; Simulation; Test stands
• ISSN: 2399-3650; 2399-3650
• DOI: 10.1038/s42005-023-01473-w

Particle-in-cell (PIC) simulations are a widely-used tool to model kinetics-dominated plasmas in ultrarelativistic laser-solid interactions (dimensionless vectorpotential a 0  > 1). However, interactions approaching subrelativistic laser intensities ( a 0  ≲ 1) are governed by correlated and collisional plasma physics, calling for benchmarks of available modeling capabilities and the establishment of standardized testbeds. Here, we propose such a testbed to experimentally benchmark PIC simulations of laser-solid interactions using a laser-irradiated micron-sized cryogenic hydrogen-jet target. Time-resolved optical shadowgraphy of the expanding plasma density, complemented by hydrodynamics and ray-tracing simulations, is used to determine the bulk-electron-temperature evolution after laser irradiation. We showcase our testbed by studying isochoric heating of solid hydrogen induced by laser pulses with a dimensionless vectorpotential of a 0  ≈ 1. Our testbed reveals that the initial surface-density gradient of the target is decisive to reach quantitative agreement at 1 ps after the interaction, demonstrating its suitability to benchmark controlled parameter scans at subrelativistic laser intensities. Relativistic laser-solid interactions are simulated via particle-in-cell (PIC) approaches, while subrelativistic regimes rely on radiation-hydrodynamics formulations. To validate the methods at the transition from relativistic to subrelativistic laser intensities, the authors propose a testbed to experimentally benchmark PIC simulations.