Geo,

Moist of these MCA files have nothing in them

50kV, 40, 30 seem ok but 20 have very few counts and 15 has no counts same with all. You are getting no signal below 30

The data are very noisy as I think is due to the skimming and the collimator.

Rerun these using the standard 45 degree shot and use a beam current around 40 or 50 and no narrow collimator. Try for a spot size of about 6mm or larger

Dud

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Theory says Fe and Ca should XRF with quite low energy excitement = "just above the K-edge".
. Fortunately the test was left as-is last night, so it was easy to redo and save example .mca's. so here's a fresh set of .mca that show the reality of this skimming arrangement.?

Note the Ca, Fe and Ba peaks as exemplars. Also remember the possibility of stray "W" L-lines due to the Si-PIN collimator..?

The .mca marked as "ALLkVp" should contain the others too, if not I've included each individual .mca's.

Once I'm able to strike this test, I'll take a repeat this test wiht the standard 45 degree arrangement of exciter and detector angle.
Then a direct Gamma Scan of the beam itself to see how the internal tungsten target characteristic L lines look. If they are being filtered internally that would explain a lot.

Geo