Plasma Physics @ Complex Systems

We are the Plasma Physics Group, a part of the Complex Systems Group at the School of Physics at the University of Sydney, Australia. Our research interests include complex (dusty) plasmas, gas discharge plasmas, quantum plasmas, space and astrophysical plasmas, as well as plasma technologies. We carry out theoretical research, laboratory experiments, and numerical simulations.

Our research highlights

Experiment: Dusty plasma afterglow

Superimposition of images taken after the discharge with a dusty plasma had been switched off. Dust particles drift upwards, downwards and to the side due to existing temperature gradients, and they oscillate due to the electrostatic force. Arrows 1 and 2 represent, respectively, the vertical and the horizontal components of the temperature gradient. These experiments allowed us to determine the residual dust charge distribution.

Source: L. Couёdel, A. Mezeghrane, A.A. Samarian, M. Mikikian, Y. Tessier, M. Cavarroc, and L. Boufendi, Contrib. Plasma Phys. 49, 235 (2009)

Theory: Debye shielding in a streaming plasma

Electrostatic potential around a test charge in a streaming cold one-component plasma. The charge is in the centre; the flow is to the right; the dimensions are 40x40 in units of the flow velocity over the plasma frequency. The thick line shows the boundary between the positive and negative potential. This result suggests a possibility of a reciprocal attraction in complex plasmas.

Source: R. Kompaneets, S. V. Vladimirov, A. V. Ivlev, and G. Morfill, New J. Phys. 10, 063018 (2008)

Simulations: Dust particle near a substrate with regular structures

Ion density around a charged insulating dust particle approaching a substrate with regular insulating structures. The distances are shown in units of the electron Debye length. The plot is obtained using particle-in-cell simulations. The obtained results help us to understand the interactions between small objects and structures, which is important for controlling the plasma-aided particle deposition.

Source: W. J. Miloch and S. V. Vladimirov, IEEE Trans. Plasma Sci. 37, 1670 (2009)

Theory: Shielding of a moving test charge in a quantum plasma

Potential around a moving test charge in a degenerate fermion plasma described by the Lindhard dielectric function. The plot shows the potential multiplied by the third power of the distance. The charge is in the centre and moves to the right with the velocity of a half of the Fermi velocity; the plasma coupling parameter is 1.5. The red line shows the boundary between the positive and negative potential; it transforms to the white line if the quantum recoil (tunneling) is neglected. These calculations allow us to understand how the motion of the charge modifies the Friedel oscillations.

Source: D. Else, R. Kompaneets, and S. V. Vladimirov, Phys. Rev. E 82, 026410 (2010)

Theory: Dust particles in the polar summer mesosphere

Distribution of dust particles in the polar summer mesosphere versus altitude, particle radius, and time. Initially nanosized particles (with the bell-shape distribution and mean value of a ~ 5 nm) were distributed in between 90 - 100 km altitude range. Formation of a steady-state dusty structure takes a few days.

Source: S. V. Vladimirov and B. A. Klumov, Adv. Geosci. 21, 429 (2010)

Simulations: Ion flow around two dust grains

Surface plots of the ion density, showing ion focusing, for three different separations between two dust grains immersed in a plasma with ion flow. The plots were obtained using molecular dynamics simulations. The grains create a single wake if the separation between them is small enough.

Source: S. V. Vladimirov, S. A. Maiorov, and O. Ishihara, Phys. Plasmas 10, 3867 (2003)

Experiment: Self-arrangement of two dust particles in a discharge

Structural diagram of the arrangements of two dust particles in a rf discharge vs the peak-to-peak voltage and the pressure. Regions correspond: I to vertically aligned particles; II to horizontally aligned particles; III to the transition region between the vertical and horizontal alignments; IV to horizontal rotation of the upper particle in the vertical alignment; V to circular oscillations of horizontally aligned particles. Triangles and squares correspond to the parameters at the transition (solid symbols stand for VHT, open symbols for HVT): triangles - due to the pressure changing, squares - due to the peak-to-peak voltage changing. Open circles stand for rotation of vertically aligned particles, solid circles stand for circular oscillations of horizontally aligned particles.

Source: A. A. Samarian, S. V. Vladimirov, and B. W. James, Phys. Plasmas 12, 022103 (2005).