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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. [ABSTRACT FROM AUTHOR]

Inspired by the outstanding mathematical breakthroughs of Zhukovsky (2016-2018) regarding the exact analytical solutions of heat equations applicable to flash laser-matter interaction and, on the other hand, by huge progress, both experimental and theoretical, in the area of the ultrashort pulse lasers, we discuss in the present paper the limits of the two temperature model (TTM). We try to extend the TTM from thermal effects during laser metal interaction at femtosecond scale to the metal interaction with attosecond laser pulses. The main result of our theoretical work is that the proposed TTM gives us the same results as the very complex quantum interaction models. In other words, the heat equation from femtosecond laser-metal interaction becomes at the level of attosecond scale a quantum interaction model between metal and laser pulses. We present the computational plot of thermal field for 200 as and 2 fs laser pulse interaction with a 20 × 20 μm² Cu surface. The main result of our work is that somewhere between 200 as and 2 fs laser pulse, the TTM breaks-down, even for a very energetic and very powerful laser beam. [ABSTRACT FROM AUTHOR]

The splitting of CO 2 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 × 10 21 particles m -3 . Spectroscopic measurements were carried out in the plasma plume produced at pressures between 1 and 5 Torr, and evidence of CO 2 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.