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If you are about to acquire an X-ray map from your sample
but are unsure whether to use a long (optimised for quantitative
analysis) or short process time (to maximise the acquisition
rate) synthesising spectra at different process times allows
you to monitor when peak overlaps may become significant.
If you want to verify the presence of an unexpected element
that has been identified in a spectrum, you can also use synthesised
spectra. For example you can add differing amounts of the
unexpected element to the composition, to test whether the
changes in the synthesised spectrum are consistent with the
peak shapes you see in the real spectrum you have collected.
Alternatively, you can predict if a trace element is detectable
under certain analysis conditions. For example, at a probe
current of 1nA what is the shortest acquisition time needed
to accurately measure 0.2wt% Al in a sample of Haynes Alloy
230?
The estimated composition can be entered as either a formula
or the weight/atomic percent for each element. In this example
the estimated weight percent of the alloy has been entered.
The synthesised spectrum for 50 seconds acquisition is displayed
below.
If the spectrum is quantified using the quant step the +/-
weight % error can be used to approximate the likely detection
limit (the element should be reliably detected if its concentration
is more than 3 times the +/- weight % error or 3 sigma). In
this example, it can be shown that an acquisition time of
at least 10 seconds is necessary for accurate quantitative
analysis of aluminium in the alloy at 1nA probe current. Similarly,
the effects of varying the probe current at a fixed acquisition
time or changing the sample geometry could also be investigated.
| Acquisition time (secs) |
Al content(wt%) |
±s |
| 50 |
0.19 |
0.03 |
| 30 |
0.20 |
0.04 |
| 20 |
0.20 |
0.05 |
| 10 |
0.17 |
0.05 |
| 7 |
0.18 |
0.08 |
|
