Common problems during efficiency determination
Although efficiency determination is almost a trivial task with HyperLab, there may be common problems for the users. One such problem may arise with peak matching.
Using the same measurements for nonlinearity and efficiency
If you want to determine the nonlinearity and the efficiency from the same measurement set, it is advisable to evaluate the measurements twice:
evaluate the measurement with a purely linear energy calibration;
create the nonlinearity calibration, and save it;
load measurements into the peak evaluator again one by one, and assign the new nonlinearity to the energy calibration, then save a new peak list;
load these new peak evaluations into the efficiency evaluator.
Decays not set
If you have selected a measurement, where the sample is not set to a radioactive source, HyperLab is not able to automatically assign decays and their radiations to the measurement. In this case the user should manually assign decays to the measurement.
To add decays, select Input data tab, then click on the Searched decay lines node under the measurement in question.
If you open this node and no decay has been set, click Add decay on the right.
Select proper decay and click OK. HyperLab now loads the decay and its radiations, and performs a fit with the currently identified matching radiation-peak pairs.
Radiations not found
When only a simple linear energy calibration is applied to a spectrum, large discrepancies may exists between the expected and observed peak energies. If this difference is greater than the identification threshold (100 chi by default), radiations will not be identified. Therefore it is very important to apply the precise energy calibration (together with nonlinearity) in the Peak evaluator for the calibration measurements.
To get detailed information about the peak matching, see radiations under the Input data tab, or select File / General info menu item. A detailed listing is provided here about the matching of all searched radiations.
Another reason for missing peak matching is the missing radiation usage flag
. HyperLab uses a gamma line for efficiency determination purposes only if that radiation is equipped with “Use for efficiency” flag. See further details in section Nuclear data library management