What we're seeing is Lichtenberg Figures form from an electron beam getting zapped into an acrylic prism. The electric trail of the lightning strike is so badass. It's like trapping a lightning bolt in a glass box forever, a force of nature on display.
Lichtenberg Figures can be created within solid insulating materials, such as acrylic or glass by injecting them with a beam of high speed electrons from a linear electron beam accelerator. Inside the accelerator, electrons are focused and accelerated to form a beam of high speed particles. Electrons emerging from the accelerator have energies up to 10MeV and are moving an appreciable fraction (95 - 99+ per cent) of the speed of light (relativistic velocities). If the electron beam is aimed towards an acrylic specimen, the electrons easily penetrate the surface of the acrylic, rapidly slowing down as they collide with molecules inside the plastic.