In the efficiency calibration, the energy-dependent parameter ε is determined. The measurement setup is schematically depicted in the figure below. The point-like calibration source is installed on the side of the cylindrical container facing the detector at half the height. The detector, aligned radially to the container, is located at the same height at a distance S from the calibration source.
Note:
- The efficiency calibration must cover the entire energy range for which the evaluation of the measurement data is to be performed. The number of support points must be sufficiently large.
- It is assumed that the efficiency is independent of the angle at which the gamma radiation strikes the detector, i.e., a quasi-spherical detector is assumed (see derivation).
- The measurement times for the calibration measurements must be sufficiently long to obtain good statistics.
Note:
If these assumptions are (largely) met and all other parameters are known with sufficient accuracy, then the activities calculated in this way lie within the uncertainties of the calibration sources used. Deviations from the assumptions, however, can lead to significant errors in the calculated activities.
