Helpful tip for adjusting the faraday cup parameters

[John Donovan]

Getting the proper configuration settings for reading and setting the beam current on JEOL instruments can be a little work.

If you want to more easily and quickly test the proper INI configuration file settings for setting and getting reliable faraday cup beam current reads, you might consider using the little Faraday.exe utility. It has the complete faraday cup capabilities, including the Calibrate Set Beam Current button in the Analytical Conditions menu.

[John Donovan]

Here is a post on making sure your JEOL faraday cup reads the beam current reliably:

http://probesoftware.com/smf/index.php?topic=80.0

[Malcolm Roberts]

Has anyone noticed this? During automated analyses, the software is recording beam currents less than that set and this is giving very high totals. This effect is random affecting ca 1 in every 15 or 20 analyses overall but has baffled me. I thought that the I was supposed to be read from the PCD at the end of each analysis. Adjacent readings show very consistent values. Now, if I make a copy of the MS access database used for that  run, go in and change the current value, hey presto...nice analysis.
Any idea on why this might be happening and how I can fix it without "fiddling data"?
Cheers,
malc.

[John Donovan]

Yes, don't "fiddle" the data!   

Seriously, the solution to your problem is in this Probe for EPMA board topic...  (even though it is a JEOL specific issue!)

http://probesoftware.com/smf/index.php?topic=80.0

[Malcolm Roberts]

Hi John
I thought it would be as simple as that. I will go and check the parameters and tweak as needed. I had another thought for this and that was to change the sequence of processes to something like counting stops, PCD in, park spectros, measure I, commence new sample. That might give sufficient wait to even out the PCD measuring problem?
Cheers,
Malc.

[John Donovan]

I thought it would be as simple as that. I will go and check the parameters and tweak as needed.

Hi Malc.
You might need to increase the FaradayWaitInTime to 2.2 seconds. For some reason JEOL keeps making this darn picoammeter slower with each new model.

I had another thought for this and that was to change the sequence of processes to something like counting stops, PCD in, park spectros, measure I, commence new sample. That might give sufficient wait to even out the PCD measuring problem?

Sorry that will not work, but increasing the FaradayWaitInTime in the [faraday] section of the Probewin.ini file will fix the read current problem.
john

[Malcolm Roberts]

This thread has disappeared for some reason. Recall the problem with low beam I being recorded during automated acquisition on a JEOL 8530F? Suggestion was to change the waitonfaraday = 2 to 2.2. I have now increased this to 2.3 as the system is still recording values less than the beam current set for the analyses. Eventually I hope to arrive at a value that works!!

Edit by John: Try doing manual beam current acquisitions using the Faraday app. Try a beam measurement both with the cup in and with the cup out and increase the Probewin.ini FaradayWaitInTime until they are within precision- remember to restart Faraday each time you edit the INI file.

[Malcolm Roberts]

Thanks John,
Yesterday I increased the wait on time to 2.3. I have only I spurious reading right at the end. I have now increased it to 2.5 and will see how things go today.
Meanwhile...... the Z matter...remember the issue to do with returning the correct Z values on stage movement I mentioned the other day? I have scanned through probewin.ini then motors.dat. In the latter, I see a Z backlash specified as -0.002 and a JEOL backlash of 5000 for Z. Checking focus on the last acquired sample this morning shows a discrepancy or ca 5 microns. It has been a little greater - up to 15 - I wondered whether fine tuning either of these two values might help, but which? Should I reduce the JEOL backlash to 2000? Questions...questions.......

[John Donovan]

This thread has disappeared for some reason. Recall the problem with low beam I being recorded during automated acquisition on a JEOL 8530F? Suggestion was to change the waitonfaraday = 2 to 2.2. I have now increased this to 2.3 as the system is still recording values less than the beam current set for the analyses. Eventually I hope to arrive at a value that works!!

Edit by John: Try doing manual beam current acquisitions using the Faraday app. Try a beam measurement both with the cup in and with the cup out and increase the Probewin.ini FaradayWaitInTime until they are within precision- remember to restart Faraday each time you edit the INI file.

JEOL EPMA instruments for some reason seem to require a good 2 or 3 seconds for the picoammeter to stabilize after inserting the cup. But the exact "waitin" time value varies from instrument to instrument, and of course we wouldn't want to have it be any longer than necessary. For this reason all JEOL instruments should be tested as described above using the Faraday app, or if testing using Probe for EPMA, please continue reading...

We recently had a user who was trying to adjust the Faraday Cup insert/remove delay times or as we call them, the "WaitIn and WaitOut" times on their new JEOL iHP2100F instrument.  The problem was that they edited the Probewin.ini file for the FaradayWaitInTime value, but did not create a *new* run to properly test the new Faraday "WaitIn" time value. The problem is that Probe for EPMA stores the value read from the Probewin.ini file and then utilizes that every time the old run is re-opened.

Therefore to test the newly edited FaradayWaitInTime (or FaradayWaitOutTime for absorbed current measurements), one should create a new probe run (without using the Load File Setup button!), which then loads these keyword values from the probewin.ini file only.  And each time the FaradayWaitInTime value is edited in the Probewin.ini file, the user should start a new probe run to re-load and test this new value.

That is why using the Faraday app might be the easier way to go for testing these delays.

But that reminded me that there is a to see the current FaradayWaitInTime delay for the current run: and that is to acquire a data point with DebugMode turned on from the Output menu. Then one will see this output when the cup if first removed and measuring absorbed current (if that option was turned on):



After acquisition the cup is closed and the 2nd Faraday cup reading is performed as seen here:



In this case both the FaradayWaitInTime and the FaradayWaitOutTime values are set to 0.2 seconds.

But just to make things even easier, we decided to modify the Count Times dialog and so now both these Faraday delay values are displayed as shown here:



Just use the Help | Update Probe for EPMA menu to update as usual...