Date Thesis Awarded
7-2024
Access Type
Honors Thesis -- Access Restricted On-Campus Only
Degree Name
Bachelors of Science (BS)
Department
Physics
Advisor
Saskia Mordijck
Committee Members
Irina Novikova
Pierre Clare
Abstract
Changes in the parallel velocity of plasma, or its flow speed parallel to a mag- netic field, can suppress drift-wave turbulence, a phenomenon that reduces the ef- ficiency of plasma fusion reactors and that may heat the sun’s corona. This thesis compares changes in parallel plasma velocity to the spatial gradient of plasma pres- sure along the magnetic field at the Large Plasma Device (LAPD). The force balance equation in the plasma-only magnetohydrodynamic (MHD) model predicts that par- allel plasma acceleration is directly proportional to the parallel pressure gradient. Experiments were conducted to test the force balance equation in plasmas at LAPD. Langmuir and Mach probes were placed at various parallel locations in the plasma to measure changes in pressure and parallel velocity as the plasma flows. The par- allel plasma acceleration was consistently lower than predicted based on the parallel pressure gradient, with zero or negative acceleration despite steep parallel pressure gradients. The significantly lowered parallel acceleration indicated that non-plasma forces such as neutral gas drag or neutral pressure gradients may oppose parallel plasma motion. In addition, the plasma pressure and density decreased more steeply than expected along the magnetic field, which further implicates non-plasma forces, potentially suppresses drift-wave turbulence, and makes the technique of interferom- etry probe calibration inaccurate under certain conditions at LAPD.
Recommended Citation
Murphy, Leo, "Causes of changing parallel plasma velocity in the Large Plasma Device" (2024). Undergraduate Honors Theses. William & Mary. Paper 2239.
https://scholarworks.wm.edu/honorstheses/2239
