Testing new multi-channel analyser PHA capability for Cameca SX

[BenjaminWade]

Ok John, once again you are dead right. There is something weird going on with the increments displayed in Peaksite when running a PHA scan. Its a bit hard to explain but basically when the scan is initiated the first baseline voltage in both PfE debug and Peaksite match perfectly. Following this the voltage displayed in Peaksite will lag behind for two measurements and on the 4th measurement "catch up" with what is displayed in PfE. These "catch up" points correspond to the highs of the spikes in the PHA scan. I made sure I used a long count time of 5 seconds to make sure Peaksite had time to "catch up" but it made no difference. Its hard to explain but hopefully the graphic below makes sense.



So basically if I fit a curve to every 3rd point I would have my nice PHA scan....

I did the same with a Gain scan with similar results:

However this was slightly different in that 90% of the time it was only lagging one measurement behind not two like in the PHA scan. There were ocassions when it was 2 measurements behind but not often. So the plateau bumps are still there which i think is another issue, but some of the small "noise" definitely correlates to when it was lagging and when it "caught up"

I then did the same with a bias scan:

And same as the Gain scan, it was lagging every second measurement however there was no obvious effect I could see in the Bias scan?

So I think I am having two separate problems here probably. Weird call lagging from Peaksite for steps in PHA, and a separate problem with Gain electronics for my bumps in my gain scan.

Cheers

[BenjaminWade]

Ok yet another update. I ran a manual PHA through Peaksite as per John's suggestion, and I get exactly the same problem so I don't think its a "lagging" issue. See below for comparison of PHA acquired throuhg PfE vs manually in Peaksite.



Weirdness was happening in Peaksite when I ran it manually though. Every now and then I would enter a number in for the base line volts, hit enter and within a second I can see the window value changing value of its own accord! I was using 104mV and I would watch it drop 103.102,101, 100… so as soon as I hit enter after changing the window value I have to hit the “Count” button immediately otherwise it would start dropping. Once the counting starts the baseline/window voltages were “locked”. This also happened on the odd occasion for the baseline voltage!

If I let the window value change of its own accord it wanted to go down to 74mV. I might run the manual scan again using that window and see what happens....to be continued

Cheers

[Julien]

I'm not sure what is going on here, but as per John's request, here is the test results obtained on a JEOL-8230.

Edit by John: Thanks Julien. I just wanted to confirm that the PHA issue Ben Wade and Philipp Poeml reported only concerns Cameca instruments. Your and Anette's PHA scan (link below), confirm that JEOL instruments do not suffer from this issue. That is when many PHA points are acquired using a small PHA window. Based on Ben's observations we suspect that the Cameca firmware is trying to adjust the baseline and window values as we acquire the PHA data. The problem does not not occur with the default Cameca MCA PHA method, but only when acquiring lots of small baseline increments using non MCA (traditional) PHA acquisition methods.


https://probesoftware.com/smf/index.php?topic=217.msg9066#msg9066