An imaging alpha detector

A prototype self-triggering spark chamber for alpha contamination monitoring and imaging is described. The contamination can be viewed directly, electronically counted, or integrated over time as a picture with a camera. High efficiency and good spatial resolution make it useful, coupled to a camera, to determine if a source is uniform or consists of hot spots. The instrument is transparent and can be made portable. The charged particles enter through a thin window rather than the source being placed in the gas chamber. It uses an argon-isobutane mixture which can be pre-mixed. It will be useful as a plutonium wound monitor and transuranic decontamination instrument. (author)