Heavy-ion-induced hydrodynamic motion in lead targets

The hydrodynamic response of metal targets to volume heating by energy deposition of intense heavy-ion beams was investigated experimentally. Recent improvements in beam parameters led to a marked increase in specific deposition power: 2·10^{10 40}Ar¹⁸⁺ ions of 300 MeV/u focused to a spot size of 300 μm (σ) × 540 μm energy in solid lead of approximately 1 kJ/g in the Bragg peak, delivered within 250 ns [full width at half maximum (FWHM)]. This value allowed us for the first time to observe heavy-ion-beam-induced hydrodynamic expansion of metal volume targets. Measurements comprise expansion velocities of free surfaces of up to 290 ± 20 m/s, surface temperatures of ejected target matter of 1600-1750 K, and pressure waves in solid metal bulk targets of 0.16 GPa maximum absolute value and 0.8 μs FWHM. The experimental results agree well with the results of a 2D hydrodynamic code. Inside the interaction zone, which can only be accessed by simulation, maximum temperatures are 2800 K and maximum pressures are 3.8 GPa.