WDS Bragg defocus

[Probeman]

I'm attempting to characterize the degree of Bragg defocus on my Cameca SX100 by acquiring a low mag beam scan for a specific x-ray on the pure element or oxide.  This could be useful when performing a Bragg defocus correction for secondary fluorescence effects from nearby grains as described here:

https://smf.probesoftware.com/index.php?topic=1545.msg12853#msg12853

I've noticed an error in the past when acquiring low mag images using the Sx100 mapping command (an error not seen when using the video imaging system), but now I'm curious if there is a way around this mapping error I'm getting back from the Cameca instrument when attempting a low mag beam scan, e.g., Fe Ka at magnifications lower than say ~800x (~450um FOV).



Could it have anything to do with the drift compensation in the mapping command?

[Probeman]

Just FYI, this low mag beam scan mapping (not video imaging) error is confirmed on other Cameca instruments and also in Peak Sight.

I understand that for WDS there is a major Bragg defocus issue (which I'm trying to document the exact extent of!), but even if one is only mapping SE or BSE signals this error occurs still occurs!

Why I wonder does the Cameca EPMA care about SE or BSE signals when mapping?

[sem-geologist]

Just FYI, this low mag beam scan mapping (not video imaging) error is confirmed on other Cameca instruments and also in Peak Sight.

Sorry to bother. How exactly to replicate that error? If I understood correctly you want to beam scan to see brag defocusing, and for that you need low mag. I remember doings something like that and never came up with error (on SXFiveFE peaksight >=6.2v). Or maybe I used "video" mode. What is "video" mode exactly? Is it that pixel data is polled from video/display boards so they are 8-bit? and so intensities does not go out from 0-255 range per pixel?

[Probeman]

Just FYI, this low mag beam scan mapping (not video imaging) error is confirmed on other Cameca instruments and also in Peak Sight.

Sorry to bother. How exactly to replicate that error? If I understood correctly you want to beam scan to see brag defocusing, and for that you need low mag. I remember doings something like that and never came up with error (on SXFiveFE peaksight >=6.2v). Or maybe I used "video" mode. What is "video" mode exactly? Is it that pixel data is polled from video/display boards so they are 8-bit? and so intensities does not go out from 0-255 range per pixel?

You must have used video imaging mode.  Yes, I want to document the amount of Bragg defocus for specific WDS elements on various spectrometers because the degree of Bragg defocus depends on the boundary orientation (and the location of the analytical points relative to that), to the spectrometer crystal:

https://smf.probesoftware.com/index.php?topic=1545.msg12853#msg12853

If you want to try and reproduce this error, you'll need to use the x-ray mapping mode where one specifies the number of millisec per pixel. I can't remember exactly where this is in the PeakSight software (I think it's in Settings/Acquisition), but this same error in PeakSight has been confirmed by several others.

"FYI, PeakSight limits the FOV of a beam map to a maximum X distance of ~400um, which is ~1200x mag on this system."