Electron accelerators, in addition to important industrial applications, can be used to produce an impressive form of “art”. The acrylic block; 15 cm square and 2.5 cm thick was placed in front of a beam of electrons. The energy of the electrons was chosen so that the beam penetrates roughly half the thickness of the material before stopping and charging up the plastic. (This penetration is the “range of the electrons”). The length of time required for the beam on the target (typically a few minutes) is dependent on the characteristics of the particular accelerator and of the specific plastic used.
Following the irradiation a sharp point, which is electrically grounded, is driven a short way into the plastic with a sharp blow from a grounded hammer and an electrical discharge, very similar to a lightning strike, occurs within the plastic. The discharge paths show up as damage to the plastic and produce the beautiful “trees” seen – each one is unique. The acrylic was then mounted in the wooden base that also houses a small-wattage bulb. This unit was presented to B. Bigham from his colleagues in Accelerator Physics on his retirement in 1992.
