Ionization and stopping of heavy ions in dense laser-ablated plasmas

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Abstract
Enhanced plasma stopping and enhanced projectile ionization in plasma are considered within the framework of the standard stopping model (SSM), the most economical extension to plasmas of the standard cold-matter formalism. The main goal of this work is to check quantitatively the SSM predictions using the setup SPQR1 (stopping plasma quantitatively reinforced) developed at Bruyères-le-Chatel. It consists of a laser-ablated C or Al plasma synchronized with a 50-MeV Cu ion beam bunched out of a tandem Van de Graaff accelerator. A combination of a Thomson parabola spectrometer and an ionographic tube provides charge-state distribution and energy-loss data. Plasma expansion is modeled and yields electron-temperature and density-profile-matching diagnostics performed in the interaction chamber. In agreement with theoretical expectations, charge-distribution maxima at the plasma exit are shifted toward higher ionization compared to the equivalent results in cold matter. The distribution width is smaller than its cold-target homologue. Energy losses in partially ionized C and Al targets are several times larger than in the respective cold solid. The relevance to heavy-ion-driven inertial fusion is emphasized.