Study of electromagnetic pulses with frequencies exceeding 10 GHz at the kilojoule sub-nanosecond laser facility PALS

In this contribution, we present the results of a long-term study on radiofrequency and microwave electromagnetic pulse (EMP) emission, a phenomenon that is still not satisfactorily explained, performed at the PALS iodine laser system (1315 nm, 0.3 ns, up to 700 J on target). Using a comprehensive set of broadband diagnostics, including double ridged horn antennas, target current probe, along with special low-loss cables and oscilloscopes with sampling rates up to 100 GS s −1 , we observed an unprecedentedly broad EMP spectrum with frequencies significantly exceeding 10 GHz. Moreover, scaling experiments revealed a dependence of the spectral shape and its central frequency on the laser intensity, and this was further correlated with electron emission. This dependence indicates that in addition to the well-known influence of the eigenfrequencies of the experimental hardware (e.g. target, stalk, and chamber), processes associated with the expanding plasma can also play a dominant role, as demonstrated in this study. We believe that these new findings will not only contribute to EMP mitigation and deepen our understanding of fundamental physics, but also support high-tech applications such as EMP hardening, biomedical research, and defense technologies.