Diagnosing Astrophysical Plasmas Using Laser-Driven Nucleosynthesis in Far-From-Equilibrium Plasmas

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This project will study fusion reactions in a hot dense plasma by using ultraintense lasers. All elements of regular matter around us stem from fusing together light elements, starting with hydrogen as the lightest, into successively heavier elements, like carbon, oxygen, aluminum, iron, and nickel, which are synthesized in the cores of stars, like the sun. Hydrogen atoms fuse to form Helium, two helium atoms fuse to form beryllium, and so on. Heavier elements like copper, silver, gold, or uranium, are formed via nucleosynthesis within burning shells of massive stars and in supernova explosions. In almost every case, these nuclear fusion processes happen in a hot, dense plasma environment. Up to now, measurements of the nuclear fusion reactions using accelerators have not included these plasma backgrounds. This may have led to significant observed discrepancies between the expected amount of elements and those inferred from astronomical measurements. These discrepancies also influence our understanding of stars and their evolution as well as the use of these processes in fusion technologies. By using ultraintense lasers, this project will create fusion reactions in a hot dense plasma and measure the fusion processes. For a few trillionth of a second the laser will create a billion-degree hot plasma and accelerate atoms to the required energies to cause them to fuse. By measuring the different escaping particles, it is then possible to understand both the plasma conditions and how they influence the fusion reactions. This data can then be used to improve nuclear and stellar models and improve our understanding of the universe and maybe even help to develop controlled fusion technology here on earth, providing an infinite clean energy source.This project computes and measures plasma-induced corrections to fusion reactions between light nuclei in far-from-equilibrium plasmas with the aim of increasing neutron flux and reaction rate in controlled laboratory conditions. The primary reaction of study, deuteron-deuteron fusion, is known as promising for laser-driven neutron sources and has been shown to carry information about the plasma in the neutron spectrum. The project includes theoretical, computational and experimental efforts. The theory effort will compute corrections to nuclear reaction rates and observables from plasma conditions. Numerical simulations will compare laser and target parameters to optimize energy transfer to deuterons. Simulations will also provide the distribution of electrons and deuterons as inputs to the fusion cross sections and their plasma-dependent corrections, as well as reaction volume and confinement time. The experiment plan begins with improving plasma and neutron measurements at the Texas Petawatt using neutron and plasma diagnostics developed recently. The project will then break new ground by scaling up stepwise to experiments at the Extreme Light Infrastructure-Nuclear Physics (ELI-NP) facility in Romania. The extensive suite of photon and neutron diagnostics available at ELI-NP will enable greater improvements in precision and angular coverage and may allow searching for secondary nuclear reactions. The project will conclude with analysis of the experimental data in light of the theory and simulation progress.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.