NSF-GACR: Study of Gamma-Ray Generation in High-Intensity Laser-Plasma Interactions at ELI Beamlines

University Of California-San Diego, La Jolla CA

Investigators

Abstract

This project will explore efficient gamma-ray generation using ultra-high-intensity lasers. The development of advanced light sources has contributed to significant progress in science and technology across many disciplines. The next frontier are sources of efficient gamma-rays – whose energies are thousands of times higher than those of typical x-rays. Light at these extreme energies can be used in fundamental studies, such as matter-antimatter production and understanding of astrophysical multi-messenger sources, and in applications to nuclear material detection, nuclear waste analysis, and medical isotope production. The aim of this project is to demonstrate efficient gamma-ray generation using ultra-high-intensity lasers at the Extreme Light Infrastructure Beamlines (ELI-Beamlines) facility in the Czech Republic. This collaboration, enabled by the partnership between NSF and the Czech Science Foundation (GACR), combines the required theoretical expertise from UCSD, experimental expertise from ELI-Beamlines, and target fabrication expertise from General Atomics. In addition to graduate student training, the project will also provide dedicated summer internships to undergraduate students from underrepresented groups. The emission of high-energy photons, a million times higher than visible-light, will be achieved by driving a multi-GigaGauss quasi-static azimuthal magnetic field inside a dense plasma that is rendered transparent by an ultra-high-intensity laser pulse. Plasma electrons serve as a mediator in the conversion of laser energy into a dense beam of energetic gamma-rays. The confining azimuthal magnetic field facilitates electron energy gain from the laser, while the electron deflections within the magnetic field cause the electrons to emit MeV gamma-rays in the direction of laser propagation. The extreme magnetic field strength and high electron energy ensure high efficiency of gamma-ray emission. The experiments will be performed at the ELI-Beamlines laser facility in the Czech Republic. The ability of these lasers to reach ultra-high on-target intensity is the key to accessing the desired regime. The experiments will utilize low-mass foam targets to produce a dense plasma whose electron density is well above the classical cutoff density, but below the relativistically adjusted cutoff density for the laser intensities used in the experiments. This choice of target density enables laser propagation through the plasma while also providing efficient generation of MeV photons. 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.