Ion emission from warm dense matter produced by irradiation with a soft x-ray free-electron laser

• Published in: Matter and Radiation at Extremes Vol. 9; no. 1
• Main Authors: Krása, Josef, Burian, Tomáš, Hájková, Věra, Chalupský, Jaromír, Jelínek, Šimon, Frantálová, Kateřina, Krupka, Michal, Kuglerová, Zuzana, Singh, Sushil Kumar, Vozda, Vojtěch, Vyšín, Luděk, Šmíd, Michal, Perez-Martin, Pablo, Kühlman, Marion, Pintor, Juan, Cikhardt, Jakub, Dreimann, Matthias, Eckermann, Dennis, Rosenthal, Felix, Vinko, Sam M., Forte, Alessandro, Gawne, Thomas, Campbell, Thomas, Ren, Shenyuan, Shi, YuanFeng, Hutchinson, Trevor, Humphries, Oliver, Preston, Thomas, Makita, Mikako, Nakatsutsumi, Motoaki, Pan, Xiayun, Köhler, Alexander, Harmand, Marion, Toleikis, Sven, Falk, Katerina, Juha, Libor
• Format: Journal Article
• Language: English
• Published: United States China Academy of Engineering Physics (CAEP)/AIP Publishing 14.11.2023
• Subjects: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; distance-of-flight spectra; free-electron lasers; ion acoustic wave; ion velocity distribution; time-of-flight ion diagnostics; warm dense matter
• ISSN: 2468-2047

Here we report on an experiment performed at the FLASH2 free-electron laser (FEL) aimed at producing warm dense matter via soft x-ray isochoric heating. In the experiment, we focus on study of the ions emitted during the soft x-ray ablation process using time-of-flight electron multipliers and a shifted Maxwell–Boltzmann velocity distribution model. We find that most emitted ions are thermal, but that some impurities chemisorbed on the target surface, such as protons, are accelerated by the electrostatic field created in the plasma by escaped electrons. The morphology of the complex crater structure indicates the presence of several ion groups with varying temperatures. We find that the ion sound velocity is controlled by the ion temperature and show how the ion yield depends on the FEL radiation attenuation length in different materials.