Here is a much simpler detector: A bottle of Corona (or any other beer in a long-necked, clear bottle) makes a workable cloud chamber. Chill well in the freezer, and watch the neck closely as you open it. You may see the streak of a cosmic ray passing through just as the cloud of condensation forms. Of course, as a bonus, it may take more than one try…. It's not an ideal project to do with your teen-aged child—a soda doesn't get cold enough, it has to be a beer. And yes, it really does work.