Basics about Efficiency Calibration of Gamma Detectors

In this exercise you are to do an efficiency calibration of a Ge-detector. The efficiency to any detector is dependent on quantities such as the [math]\gamma[/math]-rays energy, the geometrical shape and size of the source, and the distance between the source and detector. In order to make an efficiency calibration we use sources with known amounts of activites. The sources are measured and then we can calculate the counting efficiency: If the source activity is A, the number of counts obtained with a given detector is R, then the counting efficiency is given by: [math]\epsilon=\frac{R}{A}[/math]
To calibrate a ã detector we must also take into consideration that a [math]\gamma[/math] ray will not necessarily be emitted every time the source disintegrate. The frequency [math]\gamma[/math] rays are emitted can be found in tables and is given as the ã intensity, usually symbolised with I[math]\gamma[/math]. The formula we use to calculate the efficiency then looks like this: