Beam Deflection Acquisition

[Ben Buse]

Hi John,

It seems to work really well. I've tried it at 1 micron and I can do beam deflection without jog called.

Would it be possible to include this in probeimage?

Also I've tried doing a linescan again - not measuring beam current - but it still takes the cup in and out for each point, which for 100 points 1 second each adds a lot of time - anychance of disabling it? - I've just found 'blank beam after move and acquistion' - but unckecing this does not seem to do it

Thanks

Ben

[John Donovan]

It seems to work really well. I've tried it at 1 micron and I can do beam deflection without jog called.

Would it be possible to include this in probeimage?

Hi Ben,
Yes. I will speak to Brian.

Also I've tried doing a linescan again - not measuring beam current - but it still takes the cup in and out for each point, which for 100 points 1 second each adds a lot of time - anychance of disabling it? - I've just found 'blank beam after move and acquistion' - but unckecing this does not seem to do it

OK, so this is a question on PFE?  I will check the behavior.

Note that the beam blank and read faraday are two separate operations.
john

[John Donovan]

Also I've tried doing a linescan again - not measuring beam current - but it still takes the cup in and out for each point, which for 100 points 1 second each adds a lot of time - anychance of disabling it? - I've just found 'blank beam after move and acquistion' - but unckecing this does not seem to do it

Hi Ben,
I found the place where it was inserting the faraday cup when it didn't need to. That is now fixed in the latest version.

Just make sure the "Do not set beam conditions" checkbox is checked.
john

[John Donovan]

Normally when you deflect the beam in the Acquire! | Imaging window, the beam stays deflected until you acquire another image or the Imaging window is closed. 

The reason being that you can utilize the imaging window to select small phases using the acquired image for manual point acquisition in the Acquire! window even if the phase isn't visible in the optical monitor.  Of course you want to be sure you aren't deflecting the beam more than 20 microns or so to avoid Bragg defocusing (unless of course you are only acquiring EDS spectra in Probe for EPMA).  In this mode one can see the beam deflection spot in the Acquire! window acquisition displayed as a small yellow circle.

In addition, the actual stage position of the deflected beam is recorded in the acquisition parameters and can also be displayed in the acquired image (assuming you saved it to the PFE database).

Recently Julien Allaz asked if we could add a button to re-center the beam without closing the Imaging window and rather than add yet another button I added a beam re-center call to the toggle beam/stage button as seen here:



Hopefully this will work for everyone.  Available in PFE 12.2.0.

[John Donovan]

Version 12.2.0 contains optimized code for Beam Deflection acquisition both manually from the Acquire! window and automated from the Automate! window.

Beam deflection acquisition is useful for analyzing small phases that are not easily visible in the light optics display, where precise positioning of the beam spot is essential.  But of course one needs to be careful to not deflect the beam outside the Bragg defocus limit which is usually about 20 - 30 um.

As a reminder, manual beam deflection acquisition is performed using the Acquire! window. Basically one acquires an image in the Imaging window, then using the mouse they click on the image.  The beam is deflected to that pixel.  Note  that one can observe the beam position in the Acquire! window display as seen here:



The stage coordinates of the deflected beam are displayed.  Then one simply acquires manual acquisition points from the Acquire! window for the current beam deflected position, and the beam deflected stage coordinates are recorded.  If you saved the image to your probe run database from the Imaging window, one can also display the beam deflected positions on the saved image just as one does for stage movement acquisition.

For automated beam deflection acquisition (say a very small step size traverse across a small inclusion), one uses the Digitize Image option from the Automate! window. First one creates a new std, unk or wavescan position sample using the Digitize (button) window, then one clicks the Digitize Image button and acquires an image of the appropriate sample area, and using the mouse, one clicks on the image to digitize selected beam spots.

For automated acquisition of these beam deflected positions, one then simply checks the Use Beam Deflection for Position checkbox in the Automate window, and the software will move the stage to the center of the position sample image and then deflect the beam as digitized.   For subsequent position samples, the software will then again move the stage to the center of each position sample, and again deflect the beam based on the image extents of each digitized image position sample.

[John Donovan]

We don't usually post about bug fixes, but this one is worth explaining a bit.

For those who don't know, Probe for EPMA has a beam deflection feature in which one can specify an amount of beam deflection from a centered beam position in order to perform fine scale (micron to sub micron) WDS and EDS point analyses. However, if one is acquiring WDS intensities one should limit the maximum beam deflection from the center to around 20 um or so, to avoid Bragg defocus effects.

But such beam deflection analyses can be very useful when attempting to acquire high spatial resolution data, where the stage movement to each point might be too coarse or unreproducible.

There are two ways such beam deflection acquisitions can be acquired: first using the Imaging window in the Acquire! window where one can acquire points by manually deflecting the beam on a newly acquired image, as seen here:

https://smf.probesoftware.com/index.php?topic=70.msg6833#msg6833

or one can use the Digitize Image option for digitizing points on an acquired image from the Automate! window as seen here:



The basic steps are:

1. Create a new positions sample and open the Digitize Image window.

2. Acquire an image using BSE, SE or CL.

3. Save the image to your probe database.

4. Select the Single Point(s) (or Traverse or Grid Points) option.

5. Digitize the single points(s) (or traverse or grid) on the image by clicking the image with the mouse.

Then, to run the points using beam deflection, simply check the Use Beam Deflection checkbox option (and position sample types), to acquire the point data using beam deflection in an automated fashion as shown here:

https://smf.probesoftware.com/index.php?topic=70.msg6849#msg6849

For each position sample, Probe for EPMA will automatically drive to the center of the saved image for that position sample, then deflect the beam for each digitized positions, and then acquire the data.

Once the data is acquired you can see the beam deflection analysis positions by selecting the sample in the Run | Display, Export and Annotate Analog Signal Images menu dialog as seen here:



To display the points for a specific sample, double-click the image list and select the specific sample.

Thanks to Ben Buse for spotting the issue (the software wasn't always recognizing the correct image magnification) and testing the fix. Update as usual from the Help | Update Probe for EPMA menu or downloading from our Resources web page here:

https://www.probesoftware.com/resources/

[John Donovan]

A colleague of ours recently contacted us with questions about the beam deflection feature in Probe for EPMA for quantitative analysis of very small features.

It occurs to me that I should probably explain better the differences in behavior between the beam deflection feature available from the Imaging button in the Acquire! window and the beam deflection feature available from the Automate! and Digitize! windows as described in the previous post in this topic.

1. Beam deflection from the Imaging button in the Acquire! window.

When the Imaging button is clicked in the Acquire! window, the Imaging and Stage Move or Beam Deflection window opens as seen here:

https://smf.probesoftware.com/index.php?topic=70.msg6833#msg6833

From this window one can acquire digital images and save them to the current run, but then one can also click the Beam Deflection or Stage Move buttons to select the beam deflection or stage move mode, and then click the image to move the beam or stage at the pixel clicked on.

When beam deflection is utilized, the beam will be deflected to that pixel and the beam position in the Acquire! window will also indicate the pixel position.  One can then acquire sample data manually from the Acquire! window using this beam deflection position.

When Stage Move is selected, the stage will move to the pixel clicked on, though the pixel to stage accuracy depends on the stage to beam scan calibration accuracy:

https://smf.probesoftware.com/index.php?topic=831.msg13077#msg13077

Of course, one must be careful to not attempt to deflect the beam by more than the Bragg defocus, which is usually around +/- 10 or 15 um from the beam center position.

2. Beam deflection from the Automate! window.

When the Digitize Positions button in the Automate! window is clicked, the Digitize Sample Positions window is opened, then when the Digitize Image button is clicked, the Digitize Sample Positions on Image window is opened.

https://smf.probesoftware.com/index.php?topic=70.msg13372#msg13372

This window is similar to the Imaging and Stage Move or Beam Deflection window opened from the Acquire! window, but is only utilized to digitize sample positions on an acquired image for subsequent point automation. That is, clicking on the image in the Digitize Sample Positions on Image does not actually move the stage or deflect the beam, it merely records the stage positions of the pixels clicked in the Automate! position sample list.

Then once the positions are recorded, these stage coordinates can be acquired using the automation procedures. The default in the Automate! window is to move the stage to each position to maintain Bragg defocus for WDS elements.  But if the Use Beam Deflection for Position checkbox is clicked, the automation will move the stage to the image center and then use beam deflection to perform the acquisition on that pixel.

The advantage of this automated beam deflection acquisition is that the beam will move to exactly the pixel clicked on, regardless of the accuracy of the stage to beam scan calibration. Therefore, very useful for fine scan features. Again, one must be careful to not attempt to deflect the beam by more than the Bragg defocus which is usually around +/- 10 or 15 um.

In the Acquire! beam deflection method it is highly recommended, and in the Automate! beam deflection method it is required to save the image to your current run, for documentation and/or automated beam deflection acquisition.