This image, taken with an electron microscope, is of a niobium plate. To investigate the effects of impure particles on superconducting cavities for accelerators, small vanadium particles were deposited on the plate, which was then charged with several kilovolts relative to a nearby electrode. The intense electric fields that formed on the sharp edges of the vanadium particles caused them initiate high voltage breakdown. Plasma was created, and as it expanded and dissipated, it left behind complex starburst patterns on the surface.