Spectrometry using BrilLanCe detectors

Figure 1:  Fit of peaks in the Ho-166m multiplet around 700-750 keV. Measuring time: 301seconds only.

The SODIGAM program “knows” the physical shape of the baseline (i.e. the background under peaks), the correct peakshape and systematics of various parameters for modern BrilLanCe detectors. Therefore even strongly overlapping peaks can be analysed correctly and quantitatively. Figure 1 shows the deconvolution with SODIGAM of the multiplet around 700-750 keV. Different peaks of Ho-166m are plotted in various colours, the sum function of all peaks is the white line going through the experimental histogram data.

Individual Ho-116m activity values are calculated from the area of each peak and the weighted mean activity value <A> for Ho-116m is then calculated from these individual activities. The result is shown in the following graph.

The activity calculated from the small 3.1% - peak around channel 522 (Literature energy: 778.8 keV) is outside of the ± 2s range, but the areas of the 54.0%, 12.2%, 57.8% and 9.8% peaks are very well and consistently deconvoluted.
The reason for the discrepancy of the 5.4% - peak around channel 450 is unknown; spectrometric data do not support a peakarea that is 44% larger than the actually fitted peak. (see fit in spectrum above)

The SODIGAM program can correctly analyse even strongly overlapping peaks in spectra from BrilLanCe detectors. Thus, these new detectors with good resolution can now be used for quantitative gamma-ray spectrometry at room temperature. Using portable spectrometers, one is able to make in-situ measurement and high-precision on-the-spot spectrum analysis for substantiated decisions.