Energy deposition of superpinched relativistic electron beams in aluminum targets

Dynamic response data, which traditionally have been used to obtain equation-of-state (EOS) information of materials, were instead used here to study energy deposition of an intense (∼1011 W/cm2) tightly focused relativistic electron beam (REB). Measurements of the REB-induced shock-wave transit time and average rear-surface velocity were compared with two-dimensional hydrodynamic calculations which contain well-known EOS information for 6061-T6 aluminum. The experimental results were consistent with classical electron deposition, i.e., a one-dimensional Monte Carlo transport calculation. In addition, peak pressures in the range 1–2 Mbar (0.1–0.2 TPa) were implied. Two anomalous effects were observed: (i) a low-amplitude (free-surface velocity ∼104 cm/sec) precursor signal, preceding the REB-induced shock wave and (ii) a velocity distribution of material behind the rear surface of the target following the arrival of the REB-induced shock wave.