Lasers for the Observation of Multiple Order Nuclear Reactions

Nuclear reaction rates become nonlinear with respect to flux (1/cm²/s) in extreme environments such as those found during stellar nucleosynthesis and terrestrial nuclear detonations. To observe these effects directly in the laboratory, extremely high particle fluences (1/cm²) are necessary but not sufficient. Reactor-based neutron sources, such as the Institut Laue-Langevin’s high-flux neutron reactor, were the closest to meeting this challenge, albeit over ∼hour time scales. In contrast, multiple rapid reactions occur on a picosecond time scale in ultra-high flux environments, preventing nuclei from returning to their ground states between reactions. Data on the cross- sections of excited nuclear states, which differ significantly from those of ground states due to spin/parity effects, is needed in order to accurately model high-flux environments. In order to replicate these effects in the laboratory, short high-fluence pulses on the order of the lifetime of a typical nuclear excited state (generally <1 ns) are required. Particle beams generated by petawatt lasers are uniquely positioned to meet this need with the potential to produce fluences of 10¹⁷ protons per cm² and 10²² neutrons per cm² over a few pico-seconds or less. In addition to providing a quantitative analysis of the rates of multiple rapid reactions in general, this talk examines a number of laser-based experiments that could be conducted in the near future to observe multiple rapid reactions for laboratory-based astrophysics and the measurement of exotic cross-sections.