Publications associated with Intense X-ray-Matter Interactions

Saturated ablation in metal hydrides and acceleration of protons and deuterons to keV energies with a soft-x-ray laser.

Phys Rev E Stat Nonlin Soft Matter Phys 83 (2011) 016403-

J Andreasson, B Iwan, A Andrejczuk, E Abreu, M Bergh, C Caleman, AJ Nelson, S Bajt, J Chalupsky, HN Chapman, RR Fäustlin, V Hajkova, PA Heimann, B Hjörvarsson, L Juha, D Klinger, J Krzywinski, B Nagler, GK Pálsson, W Singer, MM Seibert, R Sobierajski, S Toleikis, T Tschentscher, SM Vinko, RW Lee, J Hajdu, N Tîmneanu

Studies of materials under extreme conditions have relevance to a broad area of research, including planetary physics, fusion research, materials science, and structural biology with x-ray lasers. We study such extreme conditions and experimentally probe the interaction between ultrashort soft x-ray pulses and solid targets (metals and their deuterides) at the FLASH free-electron laser where power densities exceeding 10(17) W/cm(2) were reached. Time-of-flight ion spectrometry and crater analysis were used to characterize the interaction. The results show the onset of saturation in the ablation process at power densities above 10(16) W/cm(2). This effect can be linked to a transiently induced x-ray transparency in the solid by the femtosecond x-ray pulse at high power densities. The measured kinetic energies of protons and deuterons ejected from the surface reach several keV and concur with predictions from plasma-expansion models. Simulations of the interactions were performed with a nonlocal thermodynamic equilibrium code with radiation transfer. These calculations return critical depths similar to the observed crater depths and capture the transient surface transparency at higher power densities.

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