Spark detector for alpha particles

This video documents a simple but surprisingly effective detector for alpha radiation. (I’m indebted to Tim Raney of Richmond, Virginia for the hard work of re-discovering this concept from old technical literature, and for preliminary efforts to optimize its practical construction using modern techniques.) Alpha particles and other ionizing particulate radiation of high linear energy transfer leave a dense wake of ionization following their passage through the air, which can trigger electrical breakdown (i.e. sparking) in the presence of suitably strong electric fields. In this detector, a close relative of the Geiger “point counter,“ an array of four thin tungsten wires at ground potential passes over an aluminum plate that is biased at ~6-8 kV negative with respect to ground. The wire-to-wire spacing is 0.2 inches, the wire-to-cathode spacing is 0.1 inches, and the tungsten wire is standard, unstraightened () diameter. A current-limited power supply must be