Enhanced relativistic-electron-beam energy loss in warm dense aluminum

Energy loss of relativistic electron beams in warm-dense aluminum is measured in the regime of ultra-high electron beam current density over 2x10^11 A/cm2 (time-averaged). The samples are heated by shock compression. Comparing to undriven cold-solid ones, the roles of the different initial resistivity and of the transient resistivity (upon target heating during electron transport) are directly highlighted by the experimental data, reproduced by a comprehensive set of simulations, describing the hydrodynamics of the shock compression, and electron beam generation and transport. We measured a 16% increase in electron resistive energy loss in warm-dense compared to cold-solid samples of identical areal mass.