Dust collisions in protoplanetary disks are one means to grow planetesimals, but the destructive or constructive nature of high speed collisions is still unsettled. In laboratory experiments, we study the self-consistent evolution of a target upon continuous impacts of submm dust aggregates at collision velocities of up to 71 m/s. Earlier studies analyzed individual collisions, which were more speculative for high velocities and low projectile masses. Here, we confirm earlier findings that high speed collisions result in mass gain of the target. We also quantify the accretion effciency for the used SiO_2 (quartz) dust sample. For two di erent average masses of dust aggregates (0.29 μg and 2.67 μg) accretion effciencies are decreasing with velocity from 58 to 18 and from 25 to 7 at 27 m/s to 71 m/s, respectively. The accretion effciency decreases approximately as logarithmic with impact energy. At the impact velocity of 49 m/s the target acquires a volume filling factor of 38. These data extend earlier work that pointed to the filling factor leveling off at 8 m/s to a value of 33. Our results imply that high speed collisions are an important mode of particle evolution. It especially allows existing large bodies to grow further by scavenging smaller aggregates with high effciency.
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