Electronic Theses and Dissertations

Ravi Kumar

Date

2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Mechanical Engineering

Committee Chair

Ranganathan Gopalakrishnan

Committee Member

Daniel Foti

Committee Member

Edward Thomas

Committee Member

Yue Guan

Abstract

Dusty plasma, also known as Complex plasma, are ionized gases containing nanometers – to – micrometers sized particles (often referred as dust). The dust particles instantaneously get negatively charged due to high-mobile electrons present in the background plasma. These charged dust particles confined in a planar (two-dimensional) geometry interact through long-range forces (screened-Coulomb) exhibiting strongly coupled behavior, analogous to those in condensed matter and real 2D materials. This makes complex plasmas an ideal experimental platform to investigate the fundamental classical dynamics of strongly coupled many-body systems, such as phase transitions, configurational and thermodynamic properties. In condensed matter the direct observation of atoms/molecules is limited due to high fragility and quantum scales but in 2D complex plasma, micrometer size particles can be directly visualized and tracked using high-speed video microscopy, mimicking ‘atomistic’ behavior. This dissertation presents a comprehensive experimental investigation of two-dimensional (2D) dust clouds and finite clusters in laboratory complex plasmas. A novel mechanical assembly BECAA (Bidirectional Electrode Control Arm Assembly) is invented to enable precise control over density and dimensionality of the dust particles in complex plasma. BECAA offers controlled manipulation of individual particles in an active plasma experiment without perturbing background plasma parameters, unlike conventional passive methods that rely on multiple trials and power modulation. First, strongly coupled finite clusters of size ��=1−50 are studied for static and dynamical properties such as shell structures, crystal configurations, rotation and intershell diffusion. Then, precision laser beams are used to impart momentum on levitated dust particles generating liquid states of the clusters as well as inducing multibody collisions to study kinetic processes and interaction potential between charged particles. The laser induced melting of crystal structures followed by spontaneous recrystallization resulted in identification of ground and metastable states of strongly coupled many-particle system of size ��=1−30. The probabilities of occurrence of each state, configurational entropy is calculated with uncertainties less than <10%. In summary, the dissertation establishes a state-of-the experimental strategy to probe structural, configurational and thermodynamic properties of strongly coupled finite 2D clusters in complex plasmas, with broader implications in understanding classical dynamics of strong correlations in condensed matter, soft matter and material sciences.

Comments

Data is provided by the student.

Library Comment

Dissertation or thesis originally submitted to ProQuest.

Notes

Embargoed until 08-06-2026

Download

Available for download on Thursday, August 06, 2026

Share

COinS