Characterizing Plasma Arc Velocity in a Jacob’s Ladder Using Shadowgraph Imaging
Luke Keating
Co-Presenters: Individual Presentation
College: Hennings College of Science Mathematics and Technology
Major: BS.SCI/TEC/CHEM
Faculty Research Mentor: Belony, Paul
Abstract:
A Jacob’s Ladder is an electromagnetic device constructed by connecting a high-voltage power supply to two wires arranged in vertical positions that mimic the shape of the letter V. When the power supply is turned on, an electric arc is formed between the two wires and is observed to climb to the top. The arc extinguishes at the top and a new one forms at the bottom, creating a continuous cycle. The arc produced is considered a plasma because it is the result of the high-voltage power source ionizing the air around the wire, thus creating a conductive path for electrons to travel. The arc produces heat that reduces the local air density, generating a buoyant force that drives the plasma upward. In addition to buoyancy, electromagnetic forces arise from the interaction between the current-carrying plasma and its self-generated magnetic field, further contributing to the upward movement of the arc as it travels along the diverging electrodes. The purpose of this investigation is to use optical lenses to produce a shadowgraph of the upward movement that can be utilized to characterize the plasma speed under buoyant and electromagnetic forces. The production of the shadowgraph is possible as the ionized air surrounding the arc creates strong refractive index gradients that deflect light, producing measurable intensity variations on an imaging plane. Measuring the plasma speed allows for analysis of the relative contributions of buoyant and electromagnetic forces to the observed motion. These results provide insight into the fundamental behavior of current-driven plasmas and have direct implications for magnetohydrodynamic plasma propulsion, where controlled plasma acceleration under electromagnetic forces is critical for efficient thrust generation.