Beam diameter now limited to 50um after version upgrade?

[Nathan C.]

We recently upgraded to Probe for EPMA v13.7.3 on our JEOL 8530 and are now getting an error when trying to set the beam diameter to 100um as we have in past runs.  Is this able to be adjusted somewhere in the software or .ini files?  I did some searching on the forum but am not having any luck locating an answer.  Appreciate any guidance - I'm a fairly new user of the system and software.

[John Donovan]

We recently upgraded to Probe for EPMA v13.7.3 on our JEOL 8530 and are now getting an error when trying to set the beam diameter to 100um as we have in past runs.  Is this able to be adjusted somewhere in the software or .ini files?  I did some searching on the forum but am not having any luck locating an answer.  Appreciate any guidance - I'm a fairly new user of the system and software.

The current version of PFE is 13.8.2, please update when you get a chance.

The reason is that beam diameters larger than say, 15 or 20 um, will experience severe Bragg defocusing resulting in bad quantification. I pray that you are not attempting "defocus beam analysis"!  Please see the poster:

https://smf.probesoftware.com/index.php?topic=44.msg145#msg145

It doesn't work. One must average the concentrations, not the x-ray intensities, because x-ray physics is non-linear.  Acquire high resolution x-ray maps and then average the concentrations as in here:

https://smf.probesoftware.com/index.php?topic=1151.0

I think we did this a while back when a customer defocused the beam too much and got bad analyses and asked that we not allow so much beam defocus.  But if you really insist, you can check the "Do not set conditions" checkbox in the Acquisition Options dialog and then it won't try to set any beam (voltage, current, size) conditions.

[Alejandro Cortes]

We recently upgraded to Probe for EPMA v13.7.3 on our JEOL 8530 and are now getting an error when trying to set the beam diameter to 100um as we have in past runs.  Is this able to be adjusted somewhere in the software or .ini files?  I did some searching on the forum but am not having any luck locating an answer.  Appreciate any guidance - I'm a fairly new user of the system and software.

The current version of PFE is 13.8.2, please update when you get a chance.

The reason is that beam diameters larger than say, 15 or 20 um, will experience severe Bragg defocusing resulting in bad quantification. I pray that you are not attempting "defocus beam analysis"!  Please see the poster:

https://smf.probesoftware.com/index.php?topic=44.msg145#msg145

It doesn't work. One must average the concentrations, not the x-ray intensities, because x-ray physics is non-linear.  Acquire high resolution x-ray maps and then average the concentrations as in here:

https://smf.probesoftware.com/index.php?topic=1151.0

I think we did this a while back when a customer defocused the beam too much and got bad analyses and asked that we not allow so much beam defocus.  But if you really insist, you can check the "Do not set conditions" checkbox in the Acquisition Options dialog and then it won't try to set any beam (voltage, current, size) conditions.

Hi John,

For EDS systems, there is no problem with Bragg defocussing but I guess very big areas are also not desired when quantifying using EDS. Do you recommend a limit for areas being analysed by EDS. I know one of the limiting factors with the size is that the area to be analysed must be homogeneous. Any more comments on this issue?

[John Donovan]

Yes, the interaction volume must be homogeneous and yes, EDS has a much larger useful FOV than WDS, though it's worth keeping in mind that WDS does NOT suffer Bragg defocus in directions perpendicular to the Bragg crystal orientation in the spectrometer.

See here for more on why this defocus matters on the question of interaction volumes, because there is the electron interaction volume and then there's the x-ray interaction volume:

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