Evolution of the energy distribution of ions moving in aluminum targets

The dynamics of ions moving in thin foils and underdense foams will play a key role in the design of future warm dense matter experiments. Using the SRIM code, we estimate that for initially mono-energetic 2.8 MeV Li+Li+ ions hitting a solid density Al foil, the induced energy spread due to stochastic effects is 10% at a depth of 3.4μm. In contrast, for 400 keV K+K+ ions hitting an Al foam of 10% solid density, stochastic effects induce a nearly 100% energy spread. At these beam energies, the nuclear stopping effects are negligible for the Li beam, but not for the K beam. We estimate this stochastic energy spread leads to almost no change in uniformity of temperature for the target heated by the Li beam, but leads to a factor of two of non-uniformity in temperature of the target for the K beam over a depth of 3.4μm. One application of these new results for temperature profiles with realistic beam energy distributions is as input to hydrodynamic simulations of the evolution of the target.