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Probe Software User Forum / Re: Probe Software Forum Newsletters
« Last post by John Donovan on April 15, 2024, 01:33:13 PM »
Here is our Winter 2023-2024 newsletter that went out about 10 days ago...

Here's the winter 2023-2024 Probe Software user forum newsletter (only a couple of weeks late!).

It has been fairly busy this last winter, with over 29 new topics and over 234 new posts in the fist three months of 2024. The forum totals currently stand at 11695 Posts in 1372 Topics by 811 Members... here are some recent highlights:

Dawncruth asks how do Faraday cup delays affect the extrapolation of TDI trends to zero time (when the Faraday cup actually is removed?

John Donovan answers and Sem-geologist chimes in also with some other questions and suggestions.

Rom asks for help with unstable detector counts on his old JEOL 8200 and JonF, Probeman and Anette von der Handt respond with suggestions:

Andrew Locock asks about magnetic specimens and Probeman asks a question:

Amedeo asks about the Kanaya-Okayama expression and Probeman responds:

Dawncruth wishes for several new features and John Donovan grants a couple of her wishes (and explains some alternative approaches for the others):

Sem-geologist brings the Duane-Hunt limit topic to which Probeman, chenderson and Nicholas Ritchie respond:

This discussion goes on for several pages and illustrates some difficulties with using the Duane-Hunt limit to determine the electron beam energy. It may be that Nicholas Ritchie's suggestion to instead measure net intensities of a characteristic line with small steps of overvoltage might be a less problematic method. For example, we could measure the Ti Ka emission (K edge of 4.96 keV), at beam energies of 5.0 keV, 5.1 keV, 5.2 keV, etc., etc. and extrapolate to the zero intensity intercept of the x-axis...

This topic will be explored further at M&M 2024 in Cleveland this summer.

JonF asks about how to create custom .FC palettes for use by CalcImage and Probeman responds:

Barbara Donovan announces the Probe Software January 2024 applications webinar with Anette von der Handt and Julien Allaz presenting high accuracy, high precision EPMA :

Barbara Donovan announces the Probe Software March 2024 applications webinar with Anette von der Handt and John Donovan presenting Time Dependent Intensity corrections (TDI) and Quantitative X-ray Mapping:

You can watch the full videos here on our YouTube channel:

Probing asks how she can utilize the constant k-ratio method to determine her dead time constants without Probe for EPMA and Probeman responds with some helpful suggestions for how to run these dead time calibrations on any instrument with any software:

Ben Buse asks about the epsilon value used in the Alicona Mex software:

JonF posts in the Tips and Tricks for PFE quant and provides a very nice explanation for dealing with unanalyzed elements in the matrix corrections:

Radek_MM wishes for a new feature to allow one to simply "right-click" on a bias scan plot to update the PHA bias value in Probe for EPMA and John Donovan grants his wish and even implements the same feature for gain scans in Cameca instruments (what a guy!):

Andrew Locock brings up a valid point about statistics in heterogeneous x-ray maps and Probe man responds with an example showing that the standard error is the best approach:

Remember, we should not average x-ray intensities (defocused beam analysis is not accurate) to obtain an average composition, instead we must average concentrations.

Anenburg asks about cathodoluminescent materials and crystalgrower responds:

John Donovan posts a tip on using the search function in the user forum:

Mwloewen asks whether a test for regression significance could be implemented dynamically in Probe for EPMA and we are still thinking how it could be implemented:

Probeman posts about the new DAM (Donovan and Moy) backscatter correction in CalcZAF and Probe for EPMA which seems to provide more accurate results for materials with different A/Z ratios:

And just to show everyone that sometimes interesting observations are lost over time here's a paper from 1913 that is a must read:

Scott B. and Dave Adams discuss some JEOL spectrometer maintenance issues:

Dave Adams also asks about JEOL FEG problems and Anette chimes in:

Science humor and leap (light) years:

John Donovan reminds those using the Thermo Pathfinder software to update to the latest Pathfinder version and make sure the ThermoNSSVersionNUmber keyword in the probewin.ini file is correct:

Jarrod Crum asks a great question on tracking instrument drift on long runs and John Donovan responds:

Nicholas Ricthie responds to an apparently overlooked question on what in EDS hardware determines different energy resolutions for the same chip size and jensrafaelsen also responds:

JonF asks about ways to create multiple setups for different minerals in a single automated run, some which may share elements and some which may not and John Donovan responds:

Ben Buse asks if anyone has used the JEOL thin film analysis program xm-27470thin and no one has responded as yet:

John Donovan posted pdfs of his presentations at the Athens 2024 EPMA Workshop:

Anette wishes there was a way to export stage positions from Probe for EPMA to the PictureSnapApp point annotation import format, and her wish was granted (finally!):

Nathan C. asks why in the latest Probe for EPMA the maximum beam diameter is limited to 50 um and John Donovan explains:

Ben Buse has a question about modeling thin films in BadgerFilm which I'm sure Aurelien will respond to as soon as he finishes moving and starts his new job:

Someone pointed out to us that JEOL lists integration with Probe for EPMA on their iHP200F website:

Probeman posts some references explaining some problems with using DBA (defocused beam analysis) for attempting to obtain an average composition in a heterogeneous material:

Short answer: you can't!

Joe Boesenberg asks how one can obtain a "negative" concentration boundary fluoroescence artifact as described in the paper by Llovet et al. (2023) and Probeman explains this quite unintuitive phenomena:

We added 5 presentation videos from the Athens 2024 EPMA Workshop last week by Anette von der Handt and John Donovan to our Probe Software YouTube channel (with permission from Ioannis Baziotis):

John Fournelle asks how to create an empirical PHA calibration file (EMPPHA.DAT) for Probe for EPMA and Probeman referred him to some posts by Ben Buse:

Probeman points out that the secondary boundary fluorescence correction in CalcZAF is now implemented in Probe for EPMA and much easier to use:

However, we are still trying to implement a Bragg defocus correction, so if your modeling demonstrates an SF boundary issue, try to orient your phase boundary pointing towards your spectrometer. In this way, the Bragg defocus will be close to zero as one moves away from the boundary.

John Donovan answers a question about comparing matrix corrections for silicate compositions:

John Donovan grants Anette's wish for a way to export stage positions from Probe for EPMA into PictureSnapApp:
General EDS Issues / Re: Duane-Hunt limit
« Last post by Probeman on April 15, 2024, 07:52:14 AM »
And here is the dataset for Ge Ka:

This plot causes me to suspect that the electron beam energy on my Cameca SX100 at ~11 kV is slightly higher than the nominal value would indicate...  what do you all think?

Again, both the Ti and Ge pure metals were freshly polished and uncoated (though well grounded).
General EDS Issues / Re: Duane-Hunt limit
« Last post by Probeman on April 15, 2024, 07:39:43 AM »
This over voltage curve method is working better than I initially thought possible.

Unfortunately the instrument failed with a vacuum error about halfway through so the second data sets didn't get acquired, but here is the first attempt using 0.04 KV increments just about the TI K edge:

Looking at the counting scatter, this plot shows how reproducible this method is.  One can also conclude that the instrument is producing a fairly smooth curve in the high voltages... so perhaps we can conclude that the electron beam energy on my SX100 is very slightly lower than the nominal value at ~5 kV since the zero intercept is very slightly higher than the Ti K edge energy?
General EDS Issues / Re: Duane-Hunt limit
« Last post by Probeman on April 15, 2024, 07:31:18 AM »
I made some very low over voltage measurements over the weekend on Ti Ka (~ 5 keV) and Ge Ka (~11 keV) and the results are very encouraging.

The Ti K edge energy is 4.964 (or 4.967 in another tabulation), so I started with a beam energy of 4.98 kV and went up from there.  At 4.98 kV, I obtained a count rate of 0.05 cps/nA with a variance of less than 0.0003!

I then increased the beam energy in increments of 0.04 KV, so the next measurement at 5.02 kV I obtained a count rate of 0.33 cps/nA +/- 0.02.

These were at 100 nA and counting 120 sec on-peak and 60 seconds on each off-peak.  I'm plotting them up now...
General EDS Issues / Re: Duane-Hunt limit
« Last post by Probeman on April 15, 2024, 07:20:45 AM »
At the end of the day, reproducibility is more important than accuracy.  While beam energy is an important parameter in our matrix corrections, if the true beam energy is 10.25 keV when we've set it to 10 keV, the difference is probably buried within the uncertainty in the matrix correction so long as all data is collected at the 10.25 keV.

Well, I for one sure would like to know if my high voltage was off by 250V!     :)

As I said previously the whole point of this topic is to determine the accuracy of our electron beam energy.  Yes, I agree that most of the time at sufficiently high over voltages the beam energy accuracy isn't too critical. But we at UofO often run at low over voltages in order to attain high spatial resolution analyses, so the question has concerned me enough to have started a thread to look into this.

And now we've made significant progress in learning about the convolution of the photon "cliff" at the Duane-Hunt limit... which no one had even suspected existed previously! I think this has been a fun and interesting exercise and appreciate all the help and support!    :)

The good news is that the over voltage curve method is also good for determining our beam energy precision/reproducibility...
General EDS Issues / Re: Duane-Hunt limit
« Last post by Nicholas Ritchie on April 15, 2024, 06:08:55 AM »
At the end of the day, reproducibility is more important than accuracy.  While beam energy is an important parameter in our matrix corrections, if the true beam energy is 10.25 keV when we've set it to 10 keV, the difference is probably buried within the uncertainty in the matrix correction so long as all data is collected at the 10.25 keV.
General EDS Issues / Re: Duane-Hunt limit
« Last post by sem-geologist on April 15, 2024, 12:58:49 AM »
Since the Cameca high voltage power supply goes from 0 to 50 KV (is that still true of more recent Cameca probes?) and if it is a 12 bit DAC as SG claims that means 50,000 / 4096 which is 12.2V. 
AFAI am aware SXFive has column control board very similar (practically the same) as in SX100, thus DAC's precission are the same. Cameca designed HV tanks are still designed to go up to 50kV. However, SXFive FE (field emission) uses YPS manufactured HV supply (up to 30kV) and it interface with Cameca hardware with serial interface. I guess internally the supply has 14bit DAC, as HV, heat, extractor, suppressor can be changed in very small steps. Set Values and reported values are in 5 digit precision, and reported values react to very small increase in set values.

As for my previous claim about 12.2V step for Cameca HV, I could be wrong (the notes on schematics then also are not precise - misleading). It is very likely only 4000 bits from 4096 is used to scale from 0 to 50kV, and then it is 12.5V per bit or step. Such approach makes possible setting precise round high voltage instead closest to the set value. so i.e. 15kV would be round-bit 1200 integer. The analog signal created by DAC (0-10V) would not be then 3V, but... 2.93V (It is noted to be 0-10V signals, but in reality then it would be only 0-9.765V). And actually that is what can be observed if measuring on that analog control line with voltmeter (Initially I had freaked out that something is wrong with our cables). As for other vendor HV supplies, I am pretty convinced that it is rather common practice to use round (dividable by 10) fraction from full bitdepth of DACs for HV control: thus for 10bit from 1024 steps only 1000, for 12bits --- 4000, or 3000 (in case max HV is 30kV), for 14bit  probably only 15000 (from 16,384). Minimum 14bit DAC for FE emission is a must, as Schottky FE is designed to be usable even down to 0.2kV (analytically it makes no sense, but HV supplies are not manufactured explicitly for microprobes but for SEM and eventually probes). Actually to get such small energy beam many SEM use higher voltages in column and de-accelerate beam at bottom of column before being focused to the sample.

I doubt Jeol would had used 10bit DAC, if LaB6 fillaments can be mounted. Logically it should be at least 12bit so precise low voltage values could be set.
Probe Software User Forum / Re: EPMA Humor
« Last post by Probeman on April 14, 2024, 01:15:13 PM »

Is this an argument for the Fahrenheit scale?
General EDS Issues / Re: Duane-Hunt limit
« Last post by Probeman on April 14, 2024, 09:10:57 AM »
I agree that when designing a DAC for high voltage control in an SEM/EPMA, there is no need for less than a 12 bit DAC.

Since the Cameca high voltage power supply goes from 0 to 50 KV (is that still true of more recent Cameca probes?) and if it is a 12 bit DAC as SG claims that means 50,000 / 4096 which is 12.2V. 

But what about JEOL instrumemnts?  Does anyone know what bit DACs JEOL uses to control the HV?  I think their high voltage supply is designed to only go from 0 to 30 KV, correct?

The only concern I have is that when we "read" the HV from the gun, how do we know how accurate that number is? It seems to me that only the over voltage curve method is precise and accurate enough, unless one has access to a NIST traceable high voltage voltmeter...
General EDS Issues / Re: Duane-Hunt limit
« Last post by sem-geologist on April 14, 2024, 08:16:04 AM »
At least 12 bit is a standard. What kind of a**h**** would make SEM/EPMA EHT with 10bit DAC? EHT is not (can't be) fast changing as i.e. scanning coils - there is absolutely no excuse using lower resolution. Even my grandma would had used 12bit for that...

Wow, are you trying to pick a fight?  Any design is a compromise.  When you tell your electronics department to make a high-voltage supply that goes from a few kV to 30 or so, then their first question will be "how accurate do you want it to be?" and in our case, we specified "max 1V per step, max 1Vpp ripple".  So I suppose we ended up with a 15V DAC.  But that's just because these components are cheap nowadays (and, as you said - it doesn't need to be fast).

SG sometimes gets a little excited- he means well.    :)

Our effort to find the means for precise beam energy estimation is a first step. It would be a waste of time, if we could not do the second step - do the software offset calibration. I.e. We would know that if we set 15kV we see that in real it is 15.075kV, we could then for 15kV set at our programs controlling the probe or SEM 14.925kV to offset those 75V overvoltage. If DAC is 10bit and have 30V step, then we could set the offset value either to 14.94kV or 14.91kV, which would give 15.015 or 14.985kV in real. I think if we find easy way to measure real energy, the second step is really easy to implement in PfS (I am saying this just as side observer aware of that huge list of different calibrations already there). If DAC is 12 bit we can correct it better, and if DAC is 14bit - that even much more better... And if it is 10bit DAC our correction would be kinda still OK at 15kV. But i.e. for 5kV step of 30V (10bit DAC), which s like 0.7% of the set value, - and that is not OK.

The chose of DAC (type, bitdepth, speed) often is kind of compromise of speed, price, stability. High precision DAC (16 and more bits) needs much better PCB design, else the electronic noise present on the PCB renders those additional bit precision useless. Higher bitdepth DAC tends to have larger delay which is important in example for scanning beam control and image acquisition synchronisation (thus for imaging we see 11-14bit DAC used for scanning beam control, also ADC for imaging is often not the 16bit, but 8bit, 10bit, 12bit for the same speed/real-time reason). Also price-wise 10bit and 12 bit DAC often has like 1-2$ difference (often it comes in the same IC package) when looking to models from same vendor with same technology. It makes a lot of sense price-wise to chose 10bit over 12bit when manufacturing kids-toys, in example making 1000000 toys and using cheaper 10bit instead of 12bit DAC will give very huge profit. However even taking into account bus width and its buffers (i.e. Jeol and Cameca EPMA use VME, and cards for column control have internal parallel buses, and DAC use parallel digital interface, 10 bit bus is smaller than 12 bit bus... and saves few mm of PCB space, in case of serial interface there is no difference) price saving of more less 10$ per unit for few to tens of units (costing 0.5 to few millions per unit) produced per year is really ******* ridiculous, and I mean it when I called it being AH originally. Speed reason is non existent there, HV can't be changed many times per second. The DAC for HV control basically produce stable DC signal. So in case of HV control the choice of DAC (between 10-14bit) has no basis for any compromise, and lower bit DACs there has no pros, but just cons. There is no reason to choose less bits in these cases.
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