Cyclic patterns in quant data

[Ken Orr]

Hi,

I'm using the polygon extraction tool to extract the quant data from my maps. When I look into the data and start plotting elements up, a cyclic pattern emerges (see attachments). I'm plotting around 40000 points from a single pyroxene grain.
This pattern occurs in all the elements. Does anyone have any ideas as to why this is happening?

Thanks.

[Probeman]

Hi Ken,
Just a wild guess here.

Could the raw counts per pixel be close to small integers, e.g., 1, 2, 3, etc. photons?   In other words were these pixels acquired with a very short dwell time per pixel, so only a few photons were captured?  Take a look at the net intensity maps, and look at the count rate...

By the way, what was the pixel dwell time and beam current?
john

[Ken Orr]

The dwell time was 40 ms with 15 kv and 40 amps. And a 2 µm pixel size. They were 16 hour maps. I don't have net intensity maps as yet. Does 40 ms sound like that might be the issue?

[Probeman]

40 millisec is a pretty short time for that beam current (I assume you meant 40 nano-amps!). It could be simply due to counting statistics, once the background is subtracted.

One will see the same effect on an EDS spectrum when zoomed in (see attached).

Take a look at the net intensity maps and let us know what you see.
john