I am planning to build a cloud chamber to demonstrate alpha decay for a science exhibition. My question is, what amounts of radioactive samples are still safe to handle? My understanding is that small quantities of uranium ores are relatively safe, but what about other elements? Note that I won't need much, merely enough to demonstrate the alpha decay.
Side question: is there enough americium in a smoke detector to use in a cloud chamber?
While I have been studying medicinal chemistry for the past two years, my knowledge of inorganic chemistry is still pretty small.