Tungsten N lines

[bill]

Hello,

I have a question. Even though there are N tungsten lines, when I simulate pure tungsten, the peak at the N lines is considered to be bremsstrahlung. And then when I try do a quantification with a tungsten carbon material it overestimates the carbon because it thinks the N tungsten lines  are carbon. Is there anything I can do about that?

Thanks a lot!

[Nicholas Ritchie]

I'm not sure that I've ever seen the W N lines.  I imagine that you could see the W N lines with a very low incident beam energy but the fluorescence yield would be tiny.  I suspect that you are actually measuring extra carbon because there really is extra carbon in your system.  Without a heroic effort, it is really hard to eliminate surface carbon contamination.  If you aren't at a low incident beam energy then the absorption correction for C will be huge because tungsten is so opaque to light X-rays.  At low incident beam energies (let's say <5 keV), the correction is smaller but you are much more susceptible to contamination.  Either way, it is a tough measurement.

[bill]

Hello again,

I've attached a pure tungsten (W) simulation generated using NIST DTSA II. I noticed that in the energy range where I usually expect the carbon peak (in spectra that actually contain carbon), the tungsten spectrum also shows a peak. The software indicates that this is due to bremsstrahlung.

Could you please clarify why bremsstrahlung would produce a peak in this region?

Thanks very much for your help!

Best regards,
Bill

[Nicholas Ritchie]

Likely absorption edge structure.  It is likely that the minimal N line intensity is very low due to the fluorescence yield but the structure in the mass absorption coefficient at the W N-lines combined with the increasing Bremsstrahlung intensity at low energies could look like a peak.