Hypervelocity Dust Storm Launched with a Coaxial Plasma Gun

Abstract

A shower of 50-ptm-diameter carbon dust grains has been accelerated to speeds up to 6 km/s in laboratory for the first time. A coaxial plasma gun is used for dust acceleration. A distinctive feature of this plasma accelerator is that it can use any gas and can operate with microparticles having any shape. Deuterium gas and carbon dust is chosen to be compatible with fusion plasmas as a diagnostic tool. The measured voltages and discharge currents of the plasma gun are up to 10 kV and 230 kA, respectively. The plasma ejected from the gun by JxB forces at speeds of about 28 km/s is well collimated for a distance of about 2 m. A hydrodynamic model, as well as a direct collision model which accounts for direct collisions of ions with the grains, is used to explain the dust acceleration. The drag force depends on the ratio of the plasma density to the dust material density. The plasma density and the electron and ion temperatures in the models are of the order of 10 19 m-3, and about 1 eV, respectively. Possible applications of hypervelocity dust are studies of dust-plasma interaction and magnetic field mapping in fusion plasmas.