A single detector can measure alpha/beta/gamma ray energy spectra simultaneously (previously, three different detectors had to be used to measure them individually). (a) The alpha particles emitted from ²⁴¹Am source, (b) beta particles emitted from ⁹⁰Sr–⁹⁰Y source, and (c) gamma rays emitted from ¹³⁷Cs source. The gamma rays also deposit energy in the first layer. Therefore, counts can be confirmed in the beta region as well.