High Totals in CalcImage

[Probeman]

I recently heard that a colleague of ours was seeing slightly high totals in their x-ray maps in CalcImage.

After further inquiries it turned out that they were running both their standards and unknowns using 100 nA of beam current. Now, there is a case to be made that one should generally run their standards using the same conditions as one's unknowns- assuming of course that the standards and unknowns are somewhat similar in their matrices...  one will get similar detector dead times for example. However, when x-ray mapping we generally only dwell on a single pixel for a few hundred milliseconds at most, whereas on our standards we often count tens of seconds on each standard position...

Now, if we are analyzing pure metal standards and metal alloys for unknowns, it probably doesn't matter much. But if our standards are silicates or glasses, we might expect some beam damage at 100 nA over tens of seconds, while our stage or beam scanned unknown will not have as much beam damage.

In cases where our standards have been beam damaged we might expect reduced x-ray counts (not the case for alkali elements in glasses of course, as they will generally migrate as ions deeper into the sample by attraction to the sub surface charge in insulating samples!). In any case, if our standard have reduced x-ray counts and our unknown are not, we will generally observe high totals.

Of course it all depends on the details!

Now, here is the point: to avoid running the same conditions on the standards and x-ray maps, simply run Probe for EPMA and Probe Image separately, or for complete automation of standards, unknowns and x-ray maps, run the standards from Probe for EPMA and the x-ray maps from Probe Image as described here:

http://probesoftware.com/smf/index.php?topic=42.msg3650#msg3650

This post describes the ability to automatically re-run the standards after the x-ray mapping is complete, but within the circled area of the screen shot there is also a PI Setup button.  This button allows one to specify a sample setup for the subsequent x-ray mapping (or one can use the column conditions tab in Probe Image).

Therefore this automation feature allows one to run their standards using whatever conditions are specified in Probe for EPMA, and then just before Probe Image is automatically launched, Probe for EPMA will load a previously specified sample setup with your desired x-ray mapping beam conditions.

This will avoid the problem with high totals from beam damaged standards.
john