Tube tails

ahhill

I realise this is not strictly a Topas question, but I hope someone may be able to shed some light on this issue.

I am using LaB6 to define my emission profile (Kα₁₁, Kα₁₂, Kα₂₁, Kα₂₂ + a bit of Kβ + some "Kα₃"). I also am including the tube tails. However, on different peaks I seem to have different positions of the tube tails (or else what I think is a tube tail is something else). The following images hopefully show that.

Is the lower angle feature really the tube tail? Why does it (or should it) change position with 2 theta (standard D8 diffractometer - flat plate mode).

Thanks

Adrian

mfisch

Hi Adrian

011 Peak: What about the Ni-absoprtion edge?
Someone please correct me if I'm worng.

Regards
Martin

ahhill

Hi Martin.

Thanks for the tip. I think it may be more likely to be tungsten, it is quite an old tube (an I am new to lab diffractometers).

Would I be correct in saying that W's primary wavelength is 1.47639 Å?

Thanks again

Adrian

ahhill

I think Martin was right (sorry). It is the Ni absorption edge. I assume in the current TOPAS (4.2) there is no way to easily model this?

I seem to remember it being talked about as an addition in v5 though, so I shall wait to see.

Thanks

Adrian

alancoelho

Hi Adrian

If there's a post monochromator then there should be no observable absorption edge. Hard to tell what you have there without looking at the pattern; send me the INP/data file and I will have a look.
cheers
alan