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July 2020

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JEOL-Focused Probe Users List <[log in to unmask]>
Date:
Tue, 14 Jul 2020 15:49:14 -0400
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JEOL-Focused Probe Users List <[log in to unmask]>
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From:
William J Mushock <[log in to unmask]>
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Julien,

FYI, the charging could also be the result of a poor connection somewhere
between your sample and the ammeter.
Doesn't have to be the sample. A cold solder joint or a dirty contact etc...

Best of Luck,
Bill


On Tue, Jul 14, 2020 at 1:50 PM Allaz Julien <[log in to unmask]>
wrote:

> Thanks for the additional suggestion!
>
> The W filament is actually pretty new with less than 100 hours, and I’ve
> seen this behaviour of change in count rate with beam current (not purely
> related to a bad DT correction) with other filament.
>
> We have the LaB6 option, and I have yet to load such a crystal on this
> EPMA. We just received a bunch and I will likely load it after the next
> maintenance.
>
> We have the JEOL PC-SEM and PC-EPMA on Windows 10 with the following
> versions:
> - PC-SEM 3.0.1.26
> - PC-EPMA 1.16.0.2
> - EOS sub system 1.15.3.0
>
> I believe these where the version accessible to JEOL Germany as of April
> 2019 (update at installation).
>
> So far it’s running smoothly beside some known software and other minor
> hardware issues. However, I should say that I prefer Probe for EPMA for
> most of my analysis and mapping, and only use the JEOL software for beam
> alignment, imaging, combined EDS-WDS mapping, and leave most of my quant
> analysis and complex cases to PfE. However, all test I sent so far were
> exclusively run with the JEOL software.
>
> I’ll try to hook my ammeter we have at the SEM later this week if I have
> time (and when the SEM is not in use)…
>
> I’ll also check the DH limit on the EDS at high current, although I have
> observed this issue in many samples (test shown here made on our permanent
> standard block, other sample tested are several thin sections freshly
> coated).
>
> Best,
>
> J.
>
>
> On 14 Jul 2020, at 19:31, William J Mushock <[log in to unmask]>
> wrote:
>
> Hi Julien,
>
> Is it possible your sample is building a charge at the higher currents. If
> you have an EDS detector you
> might be able to verify this by monitoring the Dwayne-Hunt limit.
>
> Cheers,
> Bill
>
> On Thu, Jul 9, 2020 at 11:44 AM Allaz Julien <[log in to unmask]>
> wrote:
>
>> 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)???
>>
>> Best,
>>
>> Julien
>>
>>
>>
>> ###########################
>>
>> *Dr. Julien Allaz *Head assistant for SEM/EPMA
>> Inst. für Geochemie und Petrologie
>> ETH Zürich
>> NW E 84
>> Clausiusstrasse 25
>> 8092 Zürich
>> Switzerland
>>
>> Tel: +41 44 632 37 20
>> Fax: +41 44 632 16 36
>> Email: [log in to unmask] <[log in to unmask]>
>> ###########################
>>
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