A new and improved spark detector gives a memorable and dramatic demonstration of the ionising properties of alpha particles.
Alpha particles have short range but are very effective at ionizing 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 EHT supply 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.
An EHT power supply capable of providing a negative potential is required. (XPU 080 010) from Scientific & Chemical is recommended.