Generation of A High-Density, Axially Homogeneous Helicon Plasma for the AWAKE Wakefield Accelerator Project

This award supports a study of a novel method to accelerate particles to very high energies using plasma as the accelerating medium. Acceleration of elementary particles to high energies entails creating high electric fields in which these particles can reach velocities close to the speed of light. In this project, a plasma - an ionized gas of electrically charged particles - is used to create 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. The project aims to develop this technology and provide it for the design process for a new type of particle accelerator at the European Organization for Nuclear Research, known as CERN. The award supports graduate and undergraduate students, including collaborative student travel to the CERN facility. The plasma generation for the planned particle accelerator entails utilizing radio-frequency waves known as Whistler waves. This approach, called helicon plasma generation, was developed several decades ago and is known to create plasma with very high efficiency. In this project, the helicon plasma source technology is qualified for application in wakefield particle acceleration as a next-generation particle accelerator technology. Advanced, laser-based spectroscopic methods to measure plasma density are 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 establish the basis for the design of a plasma source prototype for the Advanced Proton Driven Plasma Wakefield Acceleration Experiment (AWAKE) project at CERN. The axial plasma density profile for the AWAKE project has to be homogeneous within 0.25%, an unprecedented goal to reach with this plasma source. If successful, the plasma source will reduce the length of next-generation linear accelerators by a factor of 20-30, and hence may have a major impact on system complexity and cost for future accelerator-based high energy particle physics studies. 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.