Upward-Detector a1 and a2


The Upward Detector a1 and a2 calibration tool calculates the "a1" and "a2" coefficients required by the upward-looking detector method for estimating atmospheric radon. The tool requires background-corrected spectra of the ground, which can be acquired in two ways:

    1. A series of Offshore-Onshore Lines can be split to enable the offshore parts to be used to estimate the backgrounds, and
    2. A survey flown over land can be used to estimate a ground spectrum using an Along-Line Differencing technique. Background is effectively removed by subtracting average spectra from an adjacent section of the same line.

After removing all background components, the resulting spectrum should be a ground spectrum due to K, U and Th radioelement sources only. The a1 and a2 coefficients model the contribution of the downward U window (a1) and downward Th window (a2) to the upward-looking detector's U window. To use this tool:

    • Set the aliases and parameters – File|Set Aliases and Parameters;
    • Use the Select buttons to select the calibration and corresponding over-water lines from the database (Offshore-Onshore Lines method);
    • Click Run to run the tool once all the inputs are set as indicated by the checkBoxes in the top-right control panel.
    • View the log file – File|View User Log File to see the results.

See Tutorial 9: Upward-Detector a1, a2 Calibration for a tutorial on the use of this tool.