The efficiency curve is commonly used to calculate the response of the ionization chamber for radionuclides not yet measured in the SIR. This is needed for two reasons:
- to calculate the correction for impurities present in a submitted solution;
- to give a point of comparison when a radionuclide is measured in the SIR for the first time.
The contribution to the ionization current of any high-energy -rays emitted is taken into account.
A mathematical solution to the efficiency curve has been completed in cooperation with the NPL, which enables impurities and strong -emitters to be evaluated with smaller uncertainties.
Efficiency curve of the SIR (iterative method):
Influence of impurities on 57Co SIR measurements: