A 1-mm-size cluster composed of 10 dust particles immersed in plasma is rotated by the torque of a pulsed electron beam with energy in the range 8–12 keV. The dust particles are electrically charged spheres with radius 5.9 $\mu \mathrm{m}$ and are levitated in the plasma sheath, forming a round, planar, Coulomb-coupled cluster. The electron beam irradiates the dust cluster passing slightly off its center, and sets the particles in motion by the action of the electron drag force. The total torque at 12 keV is $4.9\pm 0.2\times {10}^{-11}$ Nm at an angular speed $1.41\pm 0.05$ rad ${\mathrm{s}}^{-1}$. The main dynamical features of the cluster such as intershell rotation and itinerancy of the dust particles inside the cluster are simulated by using a molecular dynamics code.

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.

We measured the peak force of the plasma jet produced by a pulsed coaxial plasma gun operated at voltages up to 2 kV, using a home-made ballistic pendulum positioned in two locations, one in the proximity of the gun nozzle at 0.75 cm and the second at a distance of 9 cm from the gun nozzle. The force of the plasma wind is inferred and ranges from 11 to 60 N, which is almost an order of magnitude higher than that of typical ion-based thrusters. The results of various models of self-field magneto-plasmadynamic thrusters indicate that the magnetic component thrust tends to dominate over the thermal expansion, particularly at higher discharge voltages of 1.5 kV and 2 kV. The highest thrust of 60 N is obtained for a 2 kV discharging voltage. The plasma was ignited in CO₂ at pressures between 1 and 5 Torr. The displacement of the pendulum pushed by the plasma wind force was measured using a high-speed camera.

A strongly coupled quasi-two-dimensional dusty plasma confined electrostatically in the plasma sheath of a radio frequency (RF) plasma is irradiated by a collimated and mono-energetic pulsed electron beam (e-beam) with an energy of 13 keV and a high peak current per pulse of 30 mA. A stream of rapidly moving charged dust particles is created inside the dust crystal due to the drag force of the electrons in the e-beam. The dust flow is split into two symmetrical branches when it reaches the boundary of the round dust crystal, each following the limit of the circular confining region. This results in the formation of a double vortex flow pattern with the dust particles being transported along the irradiation direction and then aside, eventually back to the entrance position of the e-beam. The observed flow regime is laminar at all times, with the speed in the central region increasing up to 12 mm s−1 in the first 200 ms and then diminishing gradually to a steady value of about 5–6 mm s−1 during a stress relaxation time period of 360 ms. The vorticity follows a similar trend with peak values −3.8 and 3.8 s−1 and steady state values between −2.5 and 2.5 s−1 in the two symmetrical vortices. Time-resolved particle-image-velocimetry and particle-tracking-velocimetry are used to characterize the flow. Molecular dynamics simulations confirm qualitatively the experimental observations showing dust stream and double vortex formation.