Open Access

Sophia Malko, Witold Cayzac, Valeria Ospina-Bohorquez, Krish Bhutwala, Mathieu Bailly-Grandvaux, Christopher McGuffey, Robert Fedosejevs, ‪Xavier Vaisseau, Anna Tauschwitz, Jon Imanol Apiñaniz, Diego de Luis Blanco, Giancarlo Gatti, Marine Huault, Jose Antonio Pérez-Hernández, Suxing Hu, Alexander White, Lee A. Collins, Katarina Nichols, Paul Neumayer, Gérald Faussurier, Jan Vorberger, Giuseppe Prestopino, Claudio Verona, João Jorge Santos, Dimitri Batani, Farhat N. Beg, Luis Roso, Luca Volpe

• Ion stopping in warm dense matter is a process of fundamental importance for the understanding of the properties of dense plasmas, the realization and the interpretation of experiments involving ion-beam-heated warm dense matter samples, and for inertial confinement fusion research. The theoretical description of the ion stopping power in warm dense matter is difficult notably due to electron coupling and degeneracy, and measurements are still largely missing. In particular, the low-velocity stopping range, that features the largest modelling uncertainties, remains virtually unexplored. Here, we report proton energy-loss measurements in warm dense plasma at unprecedented low projectile velocities. Our energy-loss data, combined with a precise target characterization based on plasma-emission measurements using two independent spectroscopy diagnostics, demonstrate a significant deviation of the stopping power from classical models in this regime. In particular, we show that our results are in closest agreement with recent first-principles simulations based on time-dependent density functional theory.