LB Thesis Theory Section

PAA Theory

General PAA Method

Photon activation analysis is a method used to analyze the isotopic composition of a sample by exploiting the characteristic decays of certain radioactive isotopes. The sample is activated using a Linear Accelerator (LINAC) which accelerates electrons that eventually hit an aluminum radiator that produces Bremsstrahlung radiation when the electrons slow down within the radiator. These Bremsstrahlung photons are then able to knock out nucleons from within the target nuclei in the sample of interest. After the nucleons have been removed from the nucleus, the nucleus becomes unstable and starts to undergo gamma decay. Nuclear gamma decay lines are characteristic to each isotope which can be used as a compositional fingerprint, but one must prove that energy lines of interest are indeed the assumed isotope. Typically High Purity Germanium Detectors are used to count the photons and create energy spectra for the sample of interest. A sample of a full energy spectrum as seen by the HpGe detector is shown below