Target experiments with high-power proton beams

At the Karlsruhe Light Ion Facility KALIF a pulsed high-power proton beam ( 50 ns, 0.15 TW/cm
²
, 8 mm fwhm focus diameter, 1.7 MeV peak proton energy) is used to generate short, intense pressure pulses or to ablatively accelerate 10–100-µm-thick targets to velocities > 10 km/s. The velocity history of the rear target surface is recorded by line-imaging laser Doppler velocimetry with high spatial (≥10 µm) and temporal (≥200 ps) resolution, and provides information on proton beam parameters, and on the state of the matter at high energy densities and intense loading. Utilizing the bell-shaped power density profile we have demonstrated a new straight-forward method for measuring the shock pressure that leads to material melting in the rarefaction wave. For the first time, the dynamic tensile strength was measured across a crystal grain boundary, and using targets with a 1D periodic structure, the growth rate of a Rayleigh Taylor instability could be measured for the first time in direct drive experiments with an ion beam.