Using A Cloud Chamber to Measure The Energy Of An Alpha Particle Source

We studied the energy of alpha particles emitted during the decay of a 300 source using a cloud chamber. Tracks appearing in the chamber were recorded and measured using Kinovea video analysis software for 246 events over approximately 38 minutes. In the analysis, the source is modelled as an isotropic point source and full track lengths are calculated from the projections of the full 3-dimensional tracks into the XY plane in the cloud forming region. Applying a Gaussian fit to the data, the average track length was 1.68±0.04 cm. Using a stopping power of 1.1425MeV/cm and the same conversion factor used to determine the expected path length projection, the average value for the energy of the alpha particles was calculated to be 5.25±0.2MeV, which is within two standard errors of the accepted value of 5.49MeV.1 This shows cloud chambers can be an effective method of detecting alpha particles and accurately measuring energies.