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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]

It is demonstrated numerically that a 1-D plasma crystal made of micron size cylindrical dust particles can, in principle, work as a photonic crystal for terahertz waves. The dust rods are parallel to each other and arranged in a linear string forming a periodic structure of dielectric-plasma regions. The dispersion equation is found by solving the waves equation with the boundary conditions at the dust-plasma interface and taking into account the dielectric permittivity of the dust material and plasma. The wavelength of the electromagnetic waves is in the range of a few hundred microns, close to the interparticle separation distance. The band gaps of the 1-D plasma crystal are numerically found for different types of dust materials, separation distances between the dust rods and rod diameters. The distance between levitated dust rods forming a string in rf plasma is shown experimentally to vary over a relatively wide range, from 650 μm to about 1350 μm, depending on the rf power fed into the discharge. [ABSTRACT FROM AUTHOR]

In the present work we investigated the thermal field distributions obtained by low intensity laser irradiation of layers with variable sizes: from nano to bulk size. We selected Fe as bulk materials and Au for the underlying material with variable size at nano-scale. We find out a method in order to decrease the sample temperature: to put between the Fe bulk surface and incident laser beam a nanoscale Au thin film. On the other hand, we can choose to irradiate the face of Fe bulk, especially when we have a much unpolished Fe surface, which leads us to an increase of the total bulk thermal field. The mathematical models based on the Green function and integral transform technique where employed. The main conclusion is that at low laser intensity in the ultraviolet (UV) range using the proposed method we can decrease the thermal fields with about 10 to 15%. We choose the scale of study to be 20 to 500 nm because 20 nm is the lower limit of Fourier equation validity and 500 nm is the upper limit like theoretical definition of nanoscale materials. The experiment data are in concordance with our theoretical predictions and other data from literature. From theoretical point of view, we obtain an analogue equation for the temperature variation of the nanosized thin film-bulk metal system in 'comparison' with the simple bulk metal situation. It is important to mention from the very beginning that we are dealing with nanosized materials and not with nanomaterials. Only the scale of the materials changes in an important way the heat conduction. [ABSTRACT FROM AUTHOR]

In the present work we investigated the thermal field distributions obtained by low intensity laser irradiation of layers with variable sizes: from nano to bulk size. We selected Fe as bulk materials and Au for the underlying material with variable size at nano-scale. We find out a method in order to decrease the sample temperature: to put between the Fe bulk surface and incident laser beam a nanoscale Au thin film. On the other hand, we can choose to irradiate the face of Fe bulk, especially when we have a much unpolished Fe surface, which leads us to an increase of the total bulk thermal field. The mathematical models based on the Green function and integral transform technique where employed. The main conclusion is that at low laser intensity in the ultraviolet (UV) range using the proposed method we can decrease the thermal fields with about 10 to 15%. We choose the scale of study to be 20 to 500 nm because 20 nm is the lower limit of Fourier equation validity and 500 nm is the upper limit like theoretical definition of nanoscale materials. The experiment data are in concordance with our theoretical predictions and other data from literature. From theoretical point of view, we obtain an analogue equation for the temperature variation of the nanosized thin film-bulk metal system in 'comparison' with the simple bulk metal situation. It is important to mention from the very beginning that we are dealing with nanosized materials and not with nanomaterials. Only the scale of the materials changes in an important way the heat conduction. [ABSTRACT FROM AUTHOR]

Multiple laser irradiations of solids are currently of great importance in quantum electronics. In the present paper we determine the semi-analytical solution of a thermal field in a semiconductor under simultaneous multiple lasers irradiations. To describe the lasers-semiconductor interaction we use the Volkov "non-perturbative" method. We consider three laser beams acting along three perpendicular Cartesian coordinates with different intensities and frequencies. [ABSTRACT FROM AUTHOR]

High-speed imaging is a powerful tool for studying dusty plasmas. The recorded trajectories of dust particles can provide direct information about the physical processes involved in dust-plasma and dust–dust interactions. A review of some experiments and their imaging techniques employed for tracking dust particles immersed in low-ionized gases and in high-density plasma jets is presented. Digital cameras are used to record the motion of slow or hypervelocity dust particles dragged by plasma jets, or to evidence single or collective dust particle oscillations and vibrations in the plasma sheath. [ABSTRACT FROM AUTHOR]