Major ideas
1. Spontaneous transformations in certain atomic nuclei can result in the emission of energetic photons called gamma rays, either directly as high energy internal states transition to lower states following a nuclear decay, or indirectly from annihilation of decay products. The energies of result gamma emissions are signatures of the particular nuclear processes and can be used to identify unknown sources.
2. Gamma rays will interact with matter through three major processes: Compton scattering, the photoelectric effect, and pair production. The cross-section for such interaction depends on the gamma energy. A result of the interaction is transfer of energy that can give rise to processes that may be exploited for gamma detection. These processes can also lead to material damage, for example in biological tissue.
Major equipment
1. Scintillator / photomultiplier / amplifier combination that results in voltage pulses whose peak height is hypothesized to be proportional to energy deposited in the scintillator material. There are numerous physical processes inside scintillators which inform the details of a typical set of data e.g. the backscatter peak at the low energy, the Compton Edge, and the data peak itself. What are these processes and their underlying physics? When low energy (in comparison to the gamma ray) photons strike the face of the PMT, a process begins to amplify the signal. Detail this process. What is a the typical gain of the PMT?
2. Multichannel analyzer for creating pulse height distributions.
Data analysis
1.) Linear regression as it relates to calibration? How is calibration accomplished?
2.) Error propagation. You will be measuring/determining a few factors to measure the energy of the unknown sources’ gamma rays for identification. How do the measured quantities and their uncertainties yield the unknown gamma ray energies and their uncertainties? Which quantity contributes most to the gamma ray energy uncertainty and why?
Here is a link to the attached document containing prelab questions.