ELI-NP Thematics - Laser based Nuclear Physics

Nuclear Isomer Production via Laser-Driven Bremsstrahlung Irradiation

Isomeric states are long-lived excited states, lasting from microseconds to even years, that decay to their ground state through gamma emission or internal conversion. Nuclear isomers are essential in the formation of elements in the Universe and in the controlled release of nuclear energy. However, the majority of nuclear reaction measurements are still conducted on nuclei predominantly in their ground state. As a result, the contributions of photoreactions on excited states to the effective stellar nuclear reaction rates are typically estimated from statistical models. The high-intensity and ultra-short pulse lasers, available at ELI-NP facility, have a great advantage for studying isomeric states with lifetimes impractical for conventional accelerator or nuclear reactor experiments. Several nuclear isomers of interest for astrophysical applications are planned for study, including ^26mAl, ^113mCd, ^123mSn.

a) Simulated energy distribution of gamma photons and a generic nuclei level scheme highlighting an isomeric state. b) The electron spectrometer setup, and two sample images for electrons up to 350 MeV; results obtained during the commissioning of E7, 1PW experimental area and In-115 isomer production tests.

Laser-Driven Bright Neutron Sources

The unique characteristics of "laser-based accelerators", such as their ability to produce ultra-short high-intensity particle pulses with high-field gradients, opens up new possibilities for research. The list of potential applications of compact, high-flux neutron sources includes wide areas like medical and biology studies, material structure, nuclear waste transmutation, nuclear research, and many others. The use of the high-power, short-pulse laser systems at ELI-NP to generate such neutron fields is being investigated experimentally and theoretically via various production mechanisms. Examples include light ion (proton or deuteron) or electromagnetic (gamma or electron) beam acceleration by laser-target interaction followed by nuclear reactions in secondary targets. An example of a simulation for such a multi-stage mechanism of neutron generation with intense laser pulses is shown below.

Simulation of neutron generation with high power lasers: (a) PIC simulation of ion acceleration by the laser pulse; (b) Monte Carlo simulation of neutron generation in Be/Pb converter. Figure from reference: Vojtech Horny et al., Scientific Reports 12, 19767 (2022).