Physics

Session I

Zachary Barnet, "Dual Species (He Rb) Magneto Optics in RF Excited Plasma"

Helium plasmas have several import research and industrial applications including materials processing, astronomy, and nuclear fusion reactors. This experiment seeks to develop a non invasive measurement of the magnetic field inside of helium plasma to facilitate more accurate control of sensitive plasma parameters. We use a technique called nonlinear magneto optical rotation (NMOR), a phenomenon which rotates the polarization of light as it passes through a medium in a magnetic field. By measuring this rotation, we characterize the strength of the field experienced by the helium atoms. In order to validate this measurement, rubidium vapor is introduced into the plasma environment. NMOR in rubidium is well studied so comparing measurements in both species will transfer the confidence in the rubidium measurement to helium or highlight any effects unique to helium plasma. 

Student Major(s): Physics and Applied Mathematics Major

Advisor: Dr. Eugeniy Mikhailov

Marcus Galland, "Laser-Plasma Driven X-Ray Emission From Unstructured Targets"

The last several decades have seen a dramatic rise in laser intensities, allowing scientists to accelerate electrons close to the speed of light. With this capability, one can blast a solid target with an ultraintense laser pulse, transforming the target into a plasma and generating x-rays. We use 2D computer simulations to model this system. The x-ray beams that are generated from this process have wide-ranging applications in cancer treatment, fusion energy, plasma optics, and astrophysics. This laser-plasma method can create higher energy x-rays and is more compact than other methods, which can require facilities larger than a football field. However, generating focused x-rays is difficult due to instabilities in the laser-plasma interaction, i.e. the laser will veer off course. We mitigate these instabilities by designing a target with a rapidly oscillating density profile. We also explore the limitations of modeling this system with 2D rather than 3D simulations.

Student Major(s): Physics and Mathematics Major

Advisor: Dr. David Stark

John Hargis, "Using Temperature-Dependent Upconversion Nanoparticles to Determine Local Aqueous Heating in a 976 nm Optical Trap" 

Optical trapping can generate localized heating in aqueous environments, but directly measuring temperature within the micron-sized trapped region presents experimental challenges. This work investigates the use of temperature-dependent upconversion nanoparticle (UCNP) luminescence to estimate local temperature within a 976 nm optical trap. UCNP emission peaks near 525 and 545 nm were measured over a 30–50 °C calibration range and used to establish the emission ratio as a function of temperature. Measurements performed at varying laser powers demonstrated an approximately linear increase in estimated temperature with increasing laser power. The highest estimated temperature was 317.99 ± 2.49 K (44.84 ± 2.49 °C). However, temperature determination was sensitive to UCNP position, particle drift with increasing temperature, nanoparticle heating, and relatively low signal-to-background ratios following spectral filtering. These results demonstrate the potential of UCNP luminescence for local thermometry in optical traps while highlighting the need for improved experimental stability.

Student Major: Physics Major

Advisor: Dr. Bjorg Larson

Joss Hempel, "Dynamic Calibration & Control of Optical Tweezers"

Optical tweezers use a focused laser beam to trap and manipulate microscopic particles. This requires accurate calibration of the output signals for reliable force and position measurements. This project implemented active power spectral density (PSD) calibration for the optical tweezers at William & Mary that does not rely on prior knowledge of a particle's size or the fluid's viscosity. In addition, the previous passive PSD calibration method was improved, reducing the coefficient of variation from 53.1% to 9% and from 49.3% to 7.3% for position and stiffness calibration respectively. Alongside this, a more automated and user-friendly control and data acquisition system was designed, including a new desktop application for controlling the piezoelectric actuators, as well as a field-programmable gate array (FPGA)-based joystick control for the actuators to trap particles more efficiently. This control system also forms the base infrastructure for introducing future calibration methods. 

Student Major: Engineering Physics Major

Advisor: Dr. Bjorg Larson

Jamison Hines, "Development of Topological Data Analysis Techniques for Noisy and Sparse 2D Time-Dependent Datasets"

Hurricanes and tornadoes are examples of the self-organization of turbulence into so-called meso-scale structures. While we have high-fidelity data and modeling to help predict these phenomena and protect human lives, this is not valid for other phenomena where measurements are more challenging and sparser. In this project, we explore whether Topological Data Analysis (TDA) can provide insights into transitions from random turbulence to meso-scale structures using high-speed visible camera data of plasmas on the Large Plasma Device (LAPD). Prior work has shown that TDA can reveal interpretations of physical systems while being made resistant to noise based on simulation results. To continue the previous findings, we first assess whether TDA can identify transitions on LAPD from the camera data. We then test what happens to the TDA results as we artificially reduce the resolution of the measurements, and lastly, apply TDA techniques to camera measurements from the Solar Observatory.

Student Major(s): Physics and Computational Applied Mathematics & Statistics Major

Advisor: Dr. Saskia Mordijck

Eric Johnson, "Laser Ablation in Drosophila Larvae Cold Sensing Neurons"

Humans react to temperature in a way at a neuron level, which scientists still fail to fully map. The complex nervous system is challenging and tedious to navigate. Drosophila larvae, the common fruit fly, provide an excellent model organism due to their relative simplicity, lots of prior research, and clear body when in the larval stage. Through the use of tools coming from physics and study methods from biology and neuroscience, one can gain an understanding of the neural networks that make up the cold sensing behaviors in Drosophila. By dissecting this network and performing behavioral studies, one can address, at a neuron level, how these creatures make decisions. 

Student Major/Minor: Physics Major, Mathematics Minor

Advisor: Dr. Mason Klein

Session II

Hayden Greene, "iRays: Computational Dual-Spectrum Pupillometry for Objective Pre-Hospital Neuro-Triage" 

This project will explore the design and development of a pupilometer, a medical device used to detect traumatic brain injuries in demanding field environments. The research question centers on how integrated electronic systems, custom-designed printed circuit boards (PCBs), and rugged enclosure design can be combined to create reliable, user-focused hardware for first responders and medical professionals. Computer-aided design (CAD) tools will be used to explore enclosure geometry and material choices, including resin and metal components, with close attention to the practical needs of end users such as emergency medical technicians, firefighters, police officers, and sports medicine officials. The broader impact of this work lies in improving the reliability and usability of field-deployable devices, potentially enhancing safety, response efficiency, and decision-making in critical real-world scenarios.

Student Major/Minor: Physics Major (Engineering and Applied Design Concentration), Computer Science Minor

Advisor: Dr. Ran Yang

Eli Groenert, "Adjusting a Statistical Model of Energy Distribution in Neutrino Collisions"

The properties of the subatomic particles known as neutrinos are an active area of study. In light of this, the Fermilab particle accelerator laboratory maintains a statistical model of neutrino collisions. It is important to ensure this model is accurate, as it represents our current understanding of neutrino behavior and it must be kept in line with reality. This project examines several parameters of the model, focusing on different aspects of the correlation between neutrino energy and position of neutrino collisions within the Fermilab collision detector. It then makes a series of comparisons to actual accelerator data, and finally develops a set of adjustments to the model in order to make it more closely reflect actual data.

Student Major: Physics Major

Advisor: Dr. Patricia Vahle

Ava Rogers, "The Roles of Plasma Composition on Laser-Driven Ultra-Strong Magnetic Field Generation"

From the invention of the laser in the mid 1900’s, with primary applications in studying light molecules, the laser has been further developed to expand in its scientific domains. This light-beam technology can be used with high precision to deposit extreme amounts of energy onto a tiny, targeted area; in particular, a plasma. This fourth state of matter, characterized by its highly unstable state, creates fascinating and somewhat unpredictable reactions when met with extreme energy stimulation. For example, when a plasma is met with these conditions, it reaches a super-heated state and seeks to distribute this energy into other forms, such as an ultra-strong magnetic field — around 10,000x stronger than an average MRI machine! Furthermore, modifications of the shape and composition of the targeted plasma can lead to greater control, strength, and longevity of these powerful magnetic fields. In this project, we perform large-scale laser-plasma simulations using particle-in-cell technique, which captures individual particle trajectories. With this tool, we can explore how changing plasma compositions alter magnetic field strengths and durations in these systems in attempt to explain the deeper physics behind it.

Student Major/Minor: Physics Major, Mathematics Minor

Advisor: Dr. David Stark