Experiments with alpha radiation
Teaching Guidance for 14-16
If you do not have a plutonium-239 source, you can use americium-241. However, you need to be aware that it gives off gamma radiation as well as alpha radiation. Therefore, if you use a Geiger-Muller tube to detect the radiation, you will find that the source still produces a count at long range or when you try to block it with paper. This is due to the gamma radiation that it is emitting.
With advanced students, you could try accounting for this radiation (i.e. treat it as a background count). However, the most effective method of demonstrating the properties of alpha radiation is to use a spark counter. The spark counter responds only to alpha radiation so you do not need a pure source. You can use radium-226, plutonium-239 or americium-241. There is the added benefit that the spark counter makes for an impressive and captivating demonstration.