Not sure if your using W or Lab6, but if it W have you tried a new filament? I noticed on the old MAC probe a poor filament would cause problems ( dating myself), but we also made the filaments. Graph indicates not a filament thought.
I will have to check the 8530F+ stability as I have JEOL coming into install the Windows 10 upgrade.
Do you have the latest JEOL software. The 8530F+ crashed with the latest JEOL update so stuck on version 1.14. Service engineer finally replaced the hard drive to get the backup software to work and get us going again.
Good Luck
Keith
From: JEOL-Focused Probe Users List <[log in to unmask]>
On Behalf Of Allaz Julien
Sent: Saturday, July 11, 2020 7:06 AM
To: [log in to unmask]
Subject: [EXTERNAL] Re: [PROBEUSERS] Non linearity of beam current?
Many thanks for the prompt and valuable replies! Greatly appreciated, as usual!
Effectively using the largest beam aperture improves the linearity, although not perfectly (#1; previous measurement were done with aperture #2). I will run more tests next week, notable an independent measure of the current using a separate
ammeter and a faraday cup mounted on the sample holder. The attached PDF shows another comparison with aperture 2 and aperture 1 (beam current vs. relative change in intensity [reference = 20 nA]). All data are averages with a relative SD around 0.5% or better,
except low current values (~1-2% RSD at 2 to 10 nA).
Hopefully something can be improved a bit, as a 4% difference from 20 to 200 nA is quite a lot to my opinion! Or maybe there is a way to implement a sort of software correction or something else (hardware / electronic board of the ammeter)?!?
It is also interesting to notice a slight increase at lower current, notably on spectrometer 1 (PET-J), but here the measurement errors are quite large with a count rate below 10 cps... Our local JEOL engineers will have to come anyway in the next coming month
for the annual maintenance, and I’ll see with them if the Faraday cup can be aligned more properly to improve this. Or this is maybe something I can do myself if this is “just a matter” of turning two screws to (X,Y) align the faraday cup??
I believe that is a reproducibility test performed at installation, not an alignment procedure. The alignment is done while monitoring the board that monitors the beam current.
To build on this there is an alignment procedure for the column faraday cup where you put a faraday cup in the chamber, record it's current, then insert the column one and align it in x and y until you're reading
a similar amount of current. This being said you can't always take the reading from the column cup as a ground truth due to the possibility of it being misaligned.
I’d suggests using a sample as a Faraday cup and measure sample current vs. column Faraday cup. See if they track.
You might also use an independent microammeter to check on linearity.
Joe Geller
Geller MicroAnalytical Laboratory, Inc.
426e Boston St.
Topsfield, Ma 01983 (USA)
978 887-7000, fax 978 887-6671
www.GellerMicro.com
From: JEOL-Focused Probe Users List <[log in to unmask]>
On Behalf Of Allaz Julien
Sent: Thursday, July 9, 2020 11:44 AM
To: [log in to unmask]
Subject: [PROBEUSERS] Non linearity of beam current?
Dear all,
I hope you are all safe and healthy…
Ever since JEOL installed our new 8230 last year, I’m having issues with the count rate at low vs. high beam current. At first, I thought this was a dead time issue (still set to the original value of 1.1 µs), but I can ensure you it is
not...
My most recent test was done from 10 nA to 200 nA, looking at a LOW QUANTITY element (Ti in hornblende ~1.4 wt% TiO2). With this test, even the highest beam current yields a relatively low count rate (around 6000 to 8000 counts per second),
and therefore I can almost for sure eliminate a dead time issue. As you can see from the attached PDF, ALL five spectrometers show the same behaviour, with an increase in count rate with beam current, around 4 to 6% at 70 nA (reference = measure done at 10
nA), and a whooping 8 to 12% at 100 and 200 nA!!!
This result let me think that there is a non-linearity in the beam current measurement (i.e., when the instrument measures 200 nA with the Faraday cup, it is in reality 220 or 225 nA…). Or maybe something else???
Did anyone observe such a behaviour on their 8230 or 8530? Is it possible to adjust this, and if so, how?
I know that Cameca acknowledge this issue; in their case, the “jump” occurs around 50 nA (and there is possibly another “jump” at much lower current; these jumps are due to different “loops” measuring either a low, medium, or high current
or something like this...). Cameca “solves” this issue by adding to the dead time correction a linearity coefficient that is applied beyond a certain current threshold (this factor can be found in the dead time setting of Peak Sight). Does JEOL has the same
thing somewhere (maybe not accessible unless logged in as a JEOL engineer)???
###########################
Dr. Julien Allaz
Head assistant for SEM/EPMA
Inst. für Geochemie und Petrologie
ETH Zürich
NW E 84
Clausiusstrasse 25
8092 Zürich
Switzerland
###########################
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