Because assuming the cluster size of ALPIDE by particle is related to deposit energy by particle, it is important to calculate deposit energy from initial kinetic energy from source. In this projects, $^{241}Am$ and $^{90}Sr$ are used for obtaining alpha, beta and gamma particles. But there are many factors to disturb knowing exact informations like impurities, so the manufacture process should be researched for calculate impurities effect.
Although their long half-life (432.2y), few Americium elements only exist in the earth, because they generated from Uranium. Recently, Americium has been produced in nuclear reactor, but seperating procedure isn’t easy.
From the search, the purification of Am-241 doesn’t makes critical impurity problem.