Date of Award:

8-2024

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Physics

Committee Chair(s)

Jeong-Young Ji

Committee

Jeong-Young Ji

Committee

Eric D. Held

Committee

J. Andrew Spencer

Committee

James Wheeler

Committee

Som Dutta

Abstract

Studying strongly coupled plasmas can be effectively accomplished using molecular dynamics (MD) simulations. We have developed an advanced MD simulation code that can analyze plasmas with various coupling parameters. This code employs a spherically symmetric cut-off Coulomb force verified through convergence tests by modulating the cut-off and minimum force ranges. Additionally, it incorporates a new algorithm for optimizing the initial positions of particles at a given temperature. This method maintains the temperature constant and the velocity distribution unchanged. As a result, we eliminate the unphysical initial rises and oscillations in temperature that a random distribution of positions causes. The code also utilizes the Monte Carlo method to achieve the desired velocity distribution with a given initial moments. The computational efficiency of the MD simulations is significantly enhanced by using graphics processing units (GPUs) for parallel computing.

By employing these advanced initialization methods for particle positions and velocities, we can measure the relaxation times of various non-Maxwellian moments across different coupling parameters. The collision coefficients obtained from these measurements are then compared with theoretical values. Furthermore, the code investigates the oscillations of higher-order moments in a magnetized plasma. By applying an appropriate linear combination of moment components, we can extract eigenmodes with single frequencies from these oscillations.

This work provides a cornerstone for studying strongly coupled plasmas by presenting a intuitive method for constructing the fundamental characteristic of collisions in a many-body system, the collision matrices.

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Physics Commons

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