Measuring Magnetic Field Dynamics Generated by Laser-Driven Electron Beams in Plasma Channels

Laser-plasma interactions can be used to create bright, directional and ultrashort charged particle beams and high-energy photons that have many potential scientific, technological, and engineering applications. This project will enable experimental measurements of extremely large magnetic fields generated in laser plasma interactions. These magnetic fields often play a critical role in the interactions because they can profoundly alter the behavior of a plasma or charged particle beam. A charged particle-probe set up will be developed and characterized for the National Science Foundation ZEUS laser user facility to make measurements of the dynamic magnetic fields. These measurements will advance our understanding of the complex processes occurring in laser-plasma particle accelerators. The particle-probing diagnostic development will also enhance ZEUS’s overall capabilities for the benefit of the broader ZEUS user community. The goal of the project is to investigate and measure the extremely large magnetic fields generated by electron beams driven in plasma channels. High-intensity laser pulses interacting with low density targets can create a plasma channel, and accelerate forward directed electron beams that self-generate large azimuthal magnetic fields within the channel. These magnetic fields are understood to be crucial for direct laser acceleration (DLA) of electrons, for the generation of bright, directional x-rays and gamma beams, and for the promising ion acceleration mechanism of magnetic vortex acceleration. Measuring the electric or magnetic fields inside a plasma is challenging, particularly when the fields are dynamic and rapidly evolving. However, significant advances have been made in both charged particle probing techniques and the unfolding algorithms, so it is now possible to measure extremely transient fields with femtosecond temporal and micrometer spatial resolutions. Once measured, these magnetic fields may also be configured in a reconnection geometry for future laboratory 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.