Gnistdetektor

This apparatus gives a memorable and dramatic demonstration of the ionising properties of alpha particles. Alpha particles have short range but are very effective at ionising air. In this apparatus a number of fine wires are supported above a metal plate to form two electrodes separated by a small air gap. 4mm terminals allow an powersupply to be connected and when the potential across the gap reaches about 4500V occasional ionised particles cause a visible and audible spark to occur. If an alpha source is brought near, the sparking dramatically increases showing the presence of ionised particles. The short range and poor penetrating properties of alpha radiation can be easily demonstrated.