Plasma jet acceleration of dust particles to hypervelocities

A convenient method to accelerate simultaneously hundreds of micron-size dust particles to a few km/s over a distance of about $1m$ is based on plasma drag. Plasma jets which can deliver sufficient momentum to the dust particles need to have speeds of at least several tens of km/s, densities of the order of $1022m−3$ or higher, and low temperature $∼1eV$⁠, in order to prevent dust destruction. An experimental demonstration of dust particles acceleration to hypervelocities by plasma produced in a coaxial gun is presented here. The plasma flow speed is deduced from photodiode signals while the plasma density is measured by streaked spectroscopy. As a result of the interaction with the plasma jet, the dust grains are also heated to high temperatures and emit visible light. A hypervelocity dust shower is imaged in situ with a high speed video camera at some distance from the coaxial gun, where light emission from the plasma flow is less intense. The bright traces of the flying microparticles are used to infer their speed and acceleration by employing the time-of-flight technique. A simple model for plasma drag which accounts for ion collection on the grain surface gives predictions for dust accelerations which are in good agreement with the experimental observations.