7th Asia-Pacific Conference on Plasma Physics, 12-17 Nov, 2023 at Port Messe Nagoya

Diffusive transport of magnetized dusty plasma

Aman S. Katariya1, Amita Das1, Bibhuti Bhushan Sahu2, Patrick H. Diamond3
1
Department of Physics, Indian Institute of Technology Delhi, 2Department of Energy Sciences andEngineering, Indian Institute of Technology Delhi, 3University of California San Diegoe-mail (speaker): amansk362@gmail.com
Dusty plasma is a complex plasma system involving
electrons, ions, and charged dust particles. In such aplasma system, the size of the dust particles varies fromnanometers to microns. The plasma electrons get attachedto these dust particles making them highly negative thirdcharge species of the plasma. The charge of these dust
particles typically varies from 100e to 10000e, where ‘e’is the electronic charge.
The dusty plasma medium turns out to be an ideal system
to study strongly coupled behavior of matter. The highcharge of the dust species enables them to be pushed into
strongly coupled regime (where the coupling parameter isdefined as the ratio of inter dust Coulomb interaction
potential to their average thermal energy) even at room
temperature and with reasonable density of the dust
particles. A host of studies on this medium have been
conducted to identify the effect of strong coupling on avariety of physical phenomena (e.g. typical electrostatic
modes [1] instabilities [2, 3] etc.) have been conducted.
The main focus of this work here is to understand thetransport characteristics of the dusty plasma medium inthe presence of external magnetic field. These studies
have been carried out with the help of an open-source
Molecular Dynamics code LAMMPS [4], which involves
charge particles dynamics in the presence of external
magnetic field. The electrostatic repulsion causes the dust
particles to expand. The magnetic field on the other handconfines their motion. It is observed that in the absence ofany collisions the dust particles show radial pulsations but
remains confined within a certain radius. It is observedthat in the presence of dust neutral collisions, diffusivetransport gets triggered. A detailed parametric study has
been conducted to understand the behavior of thediffusion coefficient as a function of magnetic field B andcollision frequency νd-n. The diffusion coefficient is foundto scale as 1/B when the dust cyclotron frequency
is greater than or equal to the dust neutral collision
frequency (ωcd ≥ νd-n). With respect to the dust neutral
collision frequency, the diffusion coefficient scales as 1/νdn for ωcd ≥ νd-n, whereas, a √νd-n scaling is observed when
ωcd < νd-n. For neutral plasmas a theoretical understandingof the scaling of diffusion coefficient has been provided
by Taylor and McNamara [5]. Here on the other hand thesimulations have been carried out for the one component
dusty plasma, for which a theoretical analysis has been
carried out.
The theoretical work has a connection with the depositionof thin films using magnetized plasma device likemagnetron sputtering (MS). Particularly, the growth ofcrystalline microstructure or nanostructure is a criticalrequirement for numerous applications in nanoscience. In
this sense, one can have a similar analogy of nanoparticle
deposition using MS. The nanoparticles or crystalline
films in plasma creates a dusty plasma environment where
they pass through the plasmas in presence of magneticfield. This scenario can be realized as diffusion ofnanoparticles across the magnetic field, and it will be
studied in a MS device later.
References[1] Rosenberg, M., & Kalman, G. (1997). Physical Review
E, 56(6), 7166.
[2] Das, A., & Kaw, P. (2014). Physics of Plasmas, 21(6),062102.
[3] Dharodi, V. S., Patel, B., & Das, A. (2022). Journal ofPlasma Physics, 88(1), 905880103.
[4] Thompson, A. P., et. al. (2022). LAMMPS. Comp.
Phys. Comm., 271, 108171.
[5] Taylor, J. B., & McNamara, B. (1971). The Physics ofFluids, 14(7), 1492-1499.

(a)(b)

Figure 1. The “Mean Square Displacement (MSD)” of dust particles as a function of time has been shown in subplot(a)for various values of the magnetic field B. The straight lines indicate that the transport is diffusive. In subplot (b) thediffusion coefficient D as a function of magnetic field has been plotted which shows 1/B scaling, The coupling parameters
for this case corresponds to a value of 10.