Energy loss of heavy ions in a plasma target

The energy loss in a plasma target was measured for different heavy-ion species, ranging from ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ to ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ at an energy of 1.4 MeV/u. A discharge tube was used to generate a hydrogen plasma with a high degree of ionization and temperatures between 1 and 2 eV. An on-line diagnostic of the plasma was performed to measure the free-electron density and the electron temperature. Compared to neutral hydrogen of the same particle density, the plasma target shows an enhanced stopping power due to the increased energy transfer to the free plasma electrons, and a higher effective charge of the projectiles inside the plasma target. Theoretical predictions based on the Bethe-Bohr-Bloch stopping theory are in good agreement with the experimental results.