Off Peak Background Correction Types
Probe for EPMA allows the user to select the off-peak type for the background correction. The default slope calculation is the most accurate, except in cases where the user has moved both off-peak positions to the same side of the analytical peak and adjusted the off-peaks excessively close together resulting in a large extrapolation. The off-peak correction types are as follows :
0. = linear slope interpolation or extrapolation
1. = average of both high and low off-peak counts
2. = use only the high off-peak counts
3. = use only the low off-peak counts
4. = exponential off-peak calculation (based on exponent)
5. = slope-high (based on high off-peak and slope coefficient)
6. = slope-low (based on low off-peak and slope coefficient)
7. = polynomial (based on high and low off-peak and three coefficients)
8. = multi-point (user defined number of background positions on each side of peak)
These off-peak background correction types may be assigned on a sample by sample basis either on or off-line. Note that the actual values of the polynomial fit coefficients are dependent on the absolute magnitude of the count intensities. For this reason it is important to avoid changing the value of the nominal beam current once any polynomial fit coefficients have been assigned to samples in the run. The calculations for linear slope and exponential calculation are shown below :