Gamma gamma coincidences occur from radioactive materials decaying into more stable nuclei and can only be seen with specific lab equipment. These coincidences are interactions between various particles, like electrons, photons, and positrons, that, in very small amounts of time, can produce multiple gamma rays which can be detected. These gamma rays are primarily produced through decay mechanisms and matter anti-matter annihilation, which all originate from the radioactive sample. Clearly there is a lot going on in a small sample. This experiment wouldn’t be possible without my Sodium-Iodide crystal (NaI(Tl)) detector. The crystal in the detector acts as a scintillator, sending photons to the Photomultiplier Tube(PMT). The PMT converts high energy photons into photoelectrons which are accelerated and amplified to create an electronic pulse that is more measurable.