Suppose for Bi-214 609 keV gamma line:
- The number of channels for lower and upper background region (m) = 10
- The number of channels for background under the peak (n) = 25
- The integral = 126533
- The live time = 46600 sec
1. OK its easy to calculate total count (peak area) by adding each channel count under your peak in sec with subtracting Bg from each channel separate (net area under peak).
2 its statistical uncertainty for Gamma Spectroscopy. using Sqrt (total cont under peak+total bg under peak)/[total cont under]
Thank you very much. I will attach you a file containing equations for calculation of a- peak area b- its uncertainty c- MDA d- uncertainty of concentration in a sample (propagation of error), could you please review these equations?
It appears you have the answers to the questions you asked.
The detection limit equation is standard. I suggest you consider revising the numerator using the formula in
Poisson-based detection limit and signal confidence intervals for few total counts.
Joseph L Alvarez
that can be downloaded from RG.
The sample weight is used for a calibrated volume. A point source should not be used to determine the efficiency. The efficiency should be determined for the same type of material, in the same volume, and at the same distance from the detector.
If you cannot obtain a standard of the same volume and material, you could submit a sample to an accredited laboratory for characterization as a standard. If you cannot find an accredited laboratory make your own standard using a well-mixed radionuclide in the sample matrix. If you must use the point source, place the point source at many known locations in the sample matrix and perform an average calibration.
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