Relativistic Feedback Discharges in Dielectric Solids

The photoelectric feedback processes leading to growth of relativistic runaway electron avalanches are believed to be responsible for extreme fluxes of γ rays produced from very compact regions of space with dimensions on the order of a hundred meters in association with lightning activity in the Earth's natural environment [V. P. Pasko et al., Photoelectric effect in air explains lightning initiation and terrestrial γ ray flashes, J. Geophys. Res. 130, e2025JD043897 (2025)JGREA20148-022710.1029/2025JD043897]. Here, we demonstrate for the first time that the same photoelectric feedback discharges can be realized on centimeter scales in common solid state dielectric materials, like quartz, acrylic, and bismuth germanate. These discharges can serve as new sources of high energy x-ray radiation.