GammaVision
®
v7 (A66-BW) 783620H / 1013
6.2.1.2. GAM32
GAM32 does a preliminary Mariscotti peak search of the spectrum and removes library nuclides for which sufficient energy peaks were not found based on Fraction limit. A library-based peak search is then performed using the reduced library. This analysis engine is used for specialized applications and generally should not be selected. GAM32 overcomes the false-positive weakness of “library-directed” analysis when the sample is completely unknown, and the activityaccuracy weakness of the traditional “matrix” method.
In most cases, the MDA for a nuclide will not be reported because all nuclides without gamma rays in the spectrum will have been removed from the library. In a few cases, the nuclide will be eliminated in the deconvolution step and the MDA will be reported for this case. To remove these possibilities, go to the System tab under Analyze/Settings/Sample Type... and select
Suppress Output from the MDA Type droplist.
For information on library reduction during GAM32 analysis, see Section 6.2.3.
6.2.1.3. NPP32
NPP32 does a preliminary library-based peak search like WAN32. Gain shift corrections can be applied for an accurate determination of peak energy and associated nuclide activity. After the
Library-based analysis is complete, a Mariscotti peak search is used to find any peaks that were not included in the library or did not pass the library peak search criteria. A Directed Fit can also be used to generate negative peak areas to meet environmental reporting requirements for singlet peaks. Standard reports have a “Summary of Peaks in Range” section that displays potential library matches and associated activity concentration for each peak found during analysis.
NPP32 and ENV32 do especially well with Library-Based peak stripping.
For the deconvolution of multiplets in the re-analysis phase, the peaks are allowed to shift in energy, up to two channels. The entire multiplet moves as a group. This gives more accurate peak areas when the energy shifts between the calibration and the sample spectrum. (Note that this is in addition to the recalibration for energy for the entire spectrum.)
6.2.1.4. ENV32
ENV32 does a preliminary Mariscotti peak search of the spectrum and removes library nuclides for which sufficient energy peaks were not found. A library-based peak search is then performed using the reduced library. Gain shift corrections can be applied for an accurate determination of peak energy and associated nuclide activity. A Directed Fit can also be used to generate negative peak areas to meet environmental reporting requirements for singlet and multiplet peaks.
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