BNC 970 Portable Multi-Channel Analyzer (MCA) - Manual (Page 46)

Model 970 Instruction Manual 43
6.5 Create a Regions of Interest (ROI) Set
Prerequisites
This procedure assumes that the detector is attached to the Model 970, the 970 is switched on,
SNAP-MCA software has been successfully started, a radioactive source of known isotopic
composition is on the detector, the 970 Hardware Settings have been set appropriately, and an
Energy Calibration has been performed.
Discussion
An ROI Set must be created in order to perform a detector Efficiency Calibration. You will also be
able to use ROI Set later for performing a Quantitative Analysis of a spectrum.
There are two ways to create an ROI Set. In the first method, a spectrum is acquired and the Find
Peaks
button is pressed from the Peak-Based Panel, edited as desired, then saved as an ROI
Set. The ROI Set can be further edited from the ROI Panel, including adding or removing specific
ROIs to or from the set. In the second method, ROIs are created from scratch by manually
selecting portions of the spectrum.
ROI Sets are based on energy, not channel. This allows an ROI Set to be used with more than
one detector. The channel locations for the starting and ending points are re-calculated from the
stored energy values each time the ROI Set is loaded and when an Energy Calibration is
performed.
ROIs will be sorted by energy, from lowest to highest, when an Efficiency Calibration is
performed.
Procedure: Creating an ROI Set Using Find Peaks (“Automatic Method”)
1. Acquire a spectrum with known peaks. It is usually a good idea to start with a relatively
simple spectrum such as
137
Cs.
2. Click on Peak-Based on the SNAP-MCA Button Panel. This will open the Peak Settings
Panel along the bottom of the Spectrum Display.