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A novel laboratory platform has been designed and built for the irradiation of a plasma crystal (PC) with an electron beam (e-beam) having an energy around 10 keV and a current of tens of milliamperes. The pulsed e-beam collimated to a few millimeter-size spot is aimed at a crystal made of dust particles levitated in a radio-frequency (RF) plasma. The platform consists of three vacuum chambers connected in-line, each with different utility: one for generating free electrons in a pulsed hollow-anode Penning discharge, another for the extraction and acceleration of electrons at $$\sim 10$$ ∼ 10 kV and for focusing the e-beam in the magnetic field of a pair of circular coils, and the last one for producing PCs above a RF-driven electrode. The main challenge is to obtain both a stable e-beam and PC by insuring appropriate gas pressures, given that the e-beam is formed in high vacuum ($$\lesssim 10^{-4}$$ ≲ 10 - 4 Torr), while the PC is produced at much higher pressures ($$\gtrsim 10^{-1}$$ ≳ 10 - 1 Torr). The main diagnostics include a high speed camera, a Faraday cup and a Langmuir probe. Two applications concerned with the creation of a pair of dust flow vortices and the rotation of a PC by the drag force of the e-beam acting on the strongly coupled dust particles are presented. The dust flow can become turbulent as demonstrated by the energy spectrum, featuring vortices at different space scales.

The splitting of CO2 was studied in a pulsed plasma discharge produced in a coaxial gun at voltages between ~1 and 2 kV and peak discharge currents of 7 to 14 kA. The plasma was ejected from the gun at a speed of a few km/s and had electron temperatures between 11 and 14 eV with peak electron densities ~2.4 × 1021 particles m−3. Spectroscopic measurements were carried out in the plasma plume produced at pressures between 1 and 5 Torr, and evidence of CO2 dissociation into oxygen and CO was found. An increased discharge current led to the observation of more intense spectra lines and the presence of new oxygen lines, which implies more dissociation channels. Several dissociation mechanisms are discussed, the main candidate being the splitting of the molecule by direct electron impact. Estimates of dissociation rates are made based on measured plasma parameters and interaction cross-sections available in the literature. A possible application of this technique is in future Mars missions where the coaxial plasma gun running in the atmosphere could be able to produce oxygen at a rate of the order of over 100 g per hour in a highly repetitive regime.

The interest in complex plasmas is increasing due to the multiple applications they target (astrophysics, plasma fusion, industry, etc.). A crystal with two vortexes made of spherical microparticles that levitates in an rf plasma interacts with a gas jet. The crystal is displaced in the jet propagation direction due to the neutral pushing force, maintaining its vortex structure. The crystal shift also involves a change of its shape, especially at the level of the two vortexes. One vortex is stretched, and the other one is compressed. During the three phases of modification of the shape of the crystal, its length is approximately constant, about 12.5 mm, this being a consequence of the fact that electric forces and ion drag forces are preserved. The orderly structure of the crystal lasts until the particles begin to fall on the bottom electrode. The changing of the vorticity in the crystal regions can be attributed to the neutral push force.

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