Collisional heating and adiabatic expansion of warm dense matter with intense relativistic electrons.

Adiabatic expansion of a warm dense Ti plasma has been observed after isochoric heating of a 100-μm-thick Ti foil with an ∼100-ns-long intense relativistic electron bunch at an energy of 19.8 MeV and a current of 1.7 kA. The expansion fits well with the analytical point-source solution. After 10 J is deposited and the plasma rapidly expands out of the warm dense phase, a stable degenerate plasma (T∼1.2eV) with n_{e}>10^{17}cm^{-3} is measured for >100 ns. This is the first temporal measurement of the generation and adiabatic expansion of a large volume (3×10^{-4}cm^{3}) of warm dense plasma isochorically heated by intense monochromatic electrons. The suite of diagnostics is presented, which includes time-resolved plasma plume expansion measurements on a single shot, visible spectroscopy measurements of the emission and absorption spectrum, measurements of the beam distribution, and plans for the future.