"Isomer population control via direct irradiation of solid-density targets using a laser-plasma accelerator"*

A small component of spent nuclear fuel is both highly radioactive and long-enough lived to require costly long-term storage. Efforts to accelerate the decay of these species through excitation into the multi-MeV nuclear “quasicontinuum” via nuclear-plasma interactions are underway. In this work we present results using a hundred terawatt laser-plasma accelerator to excite Bromine nuclei through pulsed ultra-fast (<10 fs) direct irradiation of solid-density active LaBr targets. These targets absorb real and virtual 5-30 MeV photons and then immediately de-excite to states with different lifetimes. The population of these excited states provides a sensitive probe of gamma strength and level densities in the nuclear quasicontinuum. Further probing of these nuclear-plasma interactions could have far-reaching impact including decreased storage of long-term nuclear waste and an improved understanding of heavy element formation in astrophysical settings.