Jorge Carmona Reyes

Crystallization Dynamics of a Single Layer Complex Plasma

We report a series of complex (dusty) plasma experiments, aimed at the study of the detailed time evolution of the recrystallization process following a rapid quench of a two-dimensional dust liquid. The experiments were accompanied by large-scale (million-particle) molecular dynamics simulations, assuming Yukawa-type interparticle interaction. Both experiment and simulation show a ∝t(α) (power-law) dependence of the linear crystallite domain size as measured by the bond-order correlation length, translational correlation length, dislocation (defect) density, and a direct size measurement algorithm. The results show two stages of order formation. On short time scales, individual particle motion dominates; this is a fast process characterized by α=0.93±0.1. At longer time scales, small crystallites undergo collective rearrangement, merging into bigger ones, resulting in a smaller exponent α=0.38±0.06.

Slow Plastic Creep of 2D Dusty Plasma Solids

We report complex plasma experiments, assisted by numerical simulations, providing an alternative qualitative link between the macroscopic response of polycrystalline solid matter to small shearing forces and the possible underlying microscopic processes. In the stationary creep regime we have determined the exponents of the shear rate dependence of the shear stress and defect density, being α=1.15±0.1 and β=2.4±0.4, respectively. We show that the formation and rapid glide motion of dislocation pairs in the lattice are dominant processes.

Dust as probe for horizontal field distribution in low pressure gas discharges

Using dust grains as probes in gas discharge plasma is a very promising, but at the same time very challenging method, as the individual external control of dust grains has to be solved. We propose and demonstrate the applicability of the RotoDust experiment, where the well controlled centrifugal force is balanced by the horizontal confinement field in plane electrode argon radio frequency gas discharges. We have reached a resolution of 0.1Vcm −1 for the electric field. This technique is used to verify numerical simulations and to map symmetry properties of the confinement in dusty plasma experiments using a glass box.

Simple experiment on the sputtering rate of solids in gas discharges

We present a very simple and sensitive method to measure the sputtering rate of solid materials in stationary low-pressure gas discharges. The method is based on the balance of the centrifugal force and the confinement electric force acting on a single electrically charged dust particle in a rotating environment. We demonstrate the use and sensitivity of this method in a capacitively coupled radio frequency argon discharge. We were able to detect a reduction of 10 nm in the diameter of a single dust particle.

Diffusion in single layer quasi-magnetized strongly coupled dusty plasmas

Summary form only given. Using the “rotodust” experimental setup [1] at the Hypervelocity Impacts and Dusty Plasmas Lab (HIDPL) of the Center for Astrophysics, Space Physics, and Engineering Research (CASPER) at Baylor University we have realized effective magnetization of single layer dusty plasma systems in the strongly coupled state up to thousands of Teslas of magnetic induction. The self-diffusion in these ensembles of 300 to 400 particles was derived by measuring the cage correlation function [2] in the central region and utilizing the recently found connection between the variation of particle environments (cages) and the diffusion coefficient [3]. Systems parameters (Γ coupling and κ screening in the Yukawa OCP model) were determined using the pair distribution and the velocity autocorrelation functions [4]. The experimental values show good agreement with molecular dynamics simulations.