Author ORCID Identifier

https://orcid.org/0000-0001-7574-8193

Semester

Spring

Date of Graduation

2026

Document Type

Dissertation

Degree Type

PhD

College

Eberly College of Arts and Sciences

Department

Physics and Astronomy

Committee Chair

Earl Scime

Committee Member

Paul Cassak

Committee Member

Weichao Tu

Committee Member

Fabien Goulay

Abstract

In this work, we investigate ion heating in two plasma systems (helicon plasmas and flux rope plasmas) using the PHAse Space MApping (PHASMA) experiment. Our studies rely on high-resolution laser diagnostics, specifically laser-induced fluorescence (LIF), to measure ion velocity distribution functions (IVDFs). The temperature and bulk flow of each species are inferred from their respective VDFs. This dissertation is organized into three main parts: the study of ion heating in helicon plasmas, pulsed LIF modeling and diagnostic development, and the study of ion heating in flux rope plasmas. Helicon plasma sources efficiently generate high-density plasmas and are widely used to study basic plasma physics. The exact mechanism by which ions are heated in helicon plasmas is still under debate. Here we present evidence that ion heating results from the damping of the Trivelpiece-Gould mode, which has a resonance near the antenna operating frequency used to generate the plasma (i.e., the lower-hybrid frequency). Laser-induced fluorescence (as with many spectroscopic techniques) is susceptible to a variety of broadening mechanisms, which can obscure temperature and flow measurements. A model of the LIF lineshape was updated and used to simulate broadened LIF lineshapes. The model successfully reproduced anomalous LIF lineshapes and showed that they arise from a combination of saturation broadening and the laser’s spatial and temporal beam profiles. Broadening mechanisms were analyzed and mitigated, enabling accurate IVDF measurements using pulsed LIF. Magnetic reconnection is studied in PHASMA through plasma-gun-generated flux ropes. Magnetic reconnection is a highly dynamic process that converts magnetic energy into par- ticle energy and occurs in many plasma systems, such as the Sun (where it is associated with solar flares and coronal mass ejections), Earth’s magnetosheath, and fusion devices. PHASMA flux rope plasmas involve a type of magnetic reconnection known as electron-only reconnection, in which ions lack sufficient time or space to fully participate in the recon- nection process. Many open questions remain in both electron-only and standard magnetic reconnection. For the first time, the ion temperature and flow were measured in electron-only reconnection in a laboratory plasma. Ion and electron VDFs were measured both before and after the onset of reconnection. Following the onset, the IVDF broadened significantly, and the flow speed approached the characteristic outflow speed (i.e., the Alfvén speed) of ions in standard reconnection. These results are unexpected, and further research is needed to draw concrete conclusions about the role of ions in electron-only reconnection in PHASMA.

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