I apologize for resurrecting this topic but I am really at my wits end and about to give up trying to quantify WDS elements on these highly magnetic samples.
Here's what I've learned over the last year:
1. One can completely demagnetize these magnetic samples and they will re-magnetize in the instrument.
I checked this by demagnetizing the samples in a de-magnetizer setup as shown here:
https://probesoftware.com/smf/index.php?topic=354.msg6656#msg6656Then once the newly demagnetized sample is in the instrument, I first navigate over to the steel sample (H13 and 4140 in the most recent effort), and place the beam over epoxy but just adjacent to the steel sample and when I unblank the beam it burns a spot right where it is supposed to.
2. The sample remagnetizes over time. But here's the interesting part: the re-magnetization appears to occur *not* from the sample sitting in the instrument (though there may be some effect from this), but mostly from the time when the beam is impinging on the steel sample.
My febrile hypothesis at the moment is that at these currents (~50nA for getting good quant for light and trace elements), it is the current *flow* that is that is re-magnetizing the sample.
I have two line of evidence for this.
First when I am imaging the sample, the image is slowly drifting as soon as I am imaging the sample. The longer the beam is imaging the sample, the greater the drift. But if I blank the beam and wait a minute, then unblank the beam, the image drift starts again as before, but it starts *exactly* where it previously left off when the beam was blanked!
Second, I noticed that on these samples I had applied conductive tape on the top of the sample, on the edge away from the edge I am analyzing. And the beam is being deflected only in the Y direction and towards the copper tape. My completely crazy idea that the current flow of electrons towards the grounded side of the sample is inducing a magnetic field that deflects the beam in the direction of the current flow.
So now the even more crazy idea is that instead of grounding the sample on the opposite side, perhaps I could ground *both* adjacent sides of the sample and the current flow might be balanced enough that they might cancel each other out?
Well after an hour of acquisition I checked the beam, again by unblanking it on some nearby epoxy, and indeed the deflection was now much smaller and only in the direction of one of the adjacent sides.
Crazy I know.
But here's my question: can anything else be done? I mean besides running the sample above it's Curie temperature!
The beam deflection we are seeing in these 5 mm sized samples is indeed smaller than the 5 centimeter sized sample we were previously struggling with, so would cutting the sample down even further help? What about plasma fibbing them out? We only need a 600 um traverse distance from the edge. Has anyone tried plasma fibbing out small samples to reduce induced magnetism?
What do people in the steel industry do? Where is Les Moore when you need him?