Wave Propagation and Ionization Efficiency in High-Density Helicon Plasmas

This award supports a study of a novel method to accelerate particles to very high energies using plasma as the accelerating medium. Accelerating elementary particles to high energies entails creating high electric fields in which these particles can reach velocities near the speed of light. In this project, a plasma - an ionized gas of electrically charged particles - creates very strong electric fields that can accelerate particles to such high velocities. The technology to create this plasma with the right features is unique and involves controlling the plasma column to make it very uniform for several hundred meters by utilizing radio-frequency waves known as Whistler waves. The same plasma generation mechanism is at play in the Earth’s ionosphere, where it creates a charge mantle around our home planet. Thus, the research is both of applied interest to high-energy particle physics and of fundamental interest in the study of Earth's ionosphere. The award supports graduate and undergraduate students, including collaborative student travel to the European Organization for Nuclear Research, known as CERN. This project aims to qualify the helicon plasma source technology for application in wakefield particle acceleration as the next-generation particle accelerator technology. Advanced, laser-based spectroscopic methods to measure plasma density will be established and used together with state-of-the-art finite element modeling of the wave propagation and measurements of these characteristics using a microwave interferometer and magnetic probes. These efforts will establish the basis for designing a plasma source prototype for the Advanced Proton Driven Plasma Wakefield Acceleration Experiment (AWAKE) project at CERN. If successful, the plasma source will reduce the length of next-generation linear particle accelerators by a factor of 20 to 30. Hence, it may enable reducing system complexity and cost for future accelerator-based high-energy particle physics studies. A study of the underlying physics of helicon plasma generation will also shed light on our understanding of plasma generation in the ionosphere. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.