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2. GETTING STARTED
13
Figure 11. EASY-MCA MDA Preset Tab.
Marking the Overflow checkbox terminates acquisition when data in any channel exceeds 2
31
!
1
(>2×10
9
) counts.
2.3.5. MDA Preset
The MDA preset (Fig. 11) can monitor
up to 20 nuclides at one time, and
stops data collection when the values
of the minimum detectable activity
(MDA) for all of the user-specified
MDA nuclides reach the specified
value. Presets are expressed in Bq,
and are evaluated every 40 seconds.
The detector must be calibrated for
energy in all spectroscopy applica-
tions, and for efficiency in all appli-
cations but MAESTRO.
The MDA presets are implemented
in the MCB (i.e., the entries you make
on this screen are saved in the MCB memory), and have no direct link to MDA methods selected
in the analysis options for applications such as GammaVision, ScintiVision, ISOTOPIC, etc. The
MDA preset calculation uses the following formula:
where:
a, b, and c are determined by the MDA criteria you choose.
Counts is the gross counts in an ROI that is 2.5×FWHM around the target peak energy.
Live time is evaluated in 40 second intervals for the MDA presets.
CorrectionFactor is the product of the calibration efficiency at the specified peak energy
and the peak’s branching ratio (yield) as listed in the working (active) library.
NOTE
MAESTRO does not support efficiency calibration. The efficiency component in
the CorrectionFactor is set to 1.0; the preset field is labeled Correction instead of
MDA; and the preset is based on counting activity (cA) instead of becquerels.
