Observation of Radar Echoes From High-Energy Particle Cascades

Understand

We report the observation of radar echoes from the ionization trails of high-energy particle cascades.

• These data were taken at the SLAC National Accelerator Laboratory, where the full electron beam ($\sim$10$^9$ e$^-$ at $\sim$10 GeV/e$^-$) was directed into a plastic target to simulate an ultra high-energy neutrino interaction.
• This target was interrogated with radio waves, and coherent radio reflections from the cascades were detected, with properties consistent with theoretical expectations.
• This is the first definitive observation of radar echoes from high-energy particle cascades, which may lead to a viable neutrino detection technology for energies $\gtrsim 10^{16}$ eV.