Author Topic: Cameca digital noise issues  (Read 42 times)

Probeman

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Cameca digital noise issues
« on: May 27, 2020, 09:48:43 am »
Recently we were acquiring some quant maps on our SX100 using stage scanning and upon close examination we are seeing some single photon count artifacts (vertical stripes) on one of the spectrometers (Sp2, LTAP):



The above image is the raw data on-peak acquisition at 100 nA, 10 keV and 60 msec per pixel. We do not seem to see this artifact on the other channels, but this particular spectrometer was tuned to F Ka on TAP and so the count rate is very low.  It may be that the artifact is "buried" in the background on the other spectrometers.

Since these artifacts reproduce at the same stage X interval, maybe it's related to the stage movement? This is the Cameca fast scan direction.  The scan is 900 um wide using 1 um pixels and there's 21 "bands" so the vertical artifacts appears every 42.8 um in the X direction.

Does anyone have any ideas as to what might be the cause of these artifacts?  I guess the next step would be to tune up F Ka on several TAP spectrometers and see if we see the same thing on these other spectrometers...
« Last Edit: July 04, 2020, 12:02:27 pm by John Donovan »
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sem-geologist

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Re: Cameca digital noise issues
« Reply #1 on: June 05, 2020, 10:43:57 am »
is your sx100 electronics new or old type?

Probeman

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Re: Cameca digital noise issues
« Reply #2 on: June 05, 2020, 11:04:59 am »
is your sx100 electronics new or old type?

The instrument was bought in 2006, and when we upgraded a few years ago to PeakSight 6.1 (to be able to run PeakSight under Win 7), we found that the stage mapping no longer worked. That is, it would acquire the first map set, but after that the instrument would be in a "locked up" mode and not able to respond anymore. Details are described here:

https://probesoftware.com/smf/index.php?topic=1171.msg8354#msg8354

After much discussion and negotiations with Cameca we ended up sending two of the electronics boards back to France so they could have their firmware updated (~$2K).  After we got the updated boards back, everything seemed to work OK again.

What I want to do next is acquire a bunch of maps using several spectrometers tuned to F ka, all on TAP crystals, and see if we see the same vertical stripe artifacts on the other spectrometers.
« Last Edit: June 05, 2020, 06:40:18 pm by Probeman »
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sem-geologist

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Re: Cameca digital noise issues
« Reply #3 on: July 03, 2020, 09:48:20 am »
Lets wait first for a second experement (with F ka on other spectrometer). I would not blame resistors - no way a resistor could  (linear analog component which is even not used for any logic, but only for voltage drop) cause this. I would rather suspect digital side. I would bet either on VME crosstalk (false count impulse generated by nearby VME address bus (24-31 bits)... or FPGA on WDS card is programmed with bugs.
« Last Edit: July 04, 2020, 11:56:20 am by John Donovan »

Probeman

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Re: Cameca digital noise issues
« Reply #4 on: July 03, 2020, 10:12:29 am »
Not sure if this is the best topic for this issue, but recently we were acquiring some quant maps on our SX100 using stage scanning and upon close examination we are seeing some single photon count artifacts (vertical stripes) on one of the spectrometers (Sp2, LTAP):

Does anyone have any ideas as to what might be the cause of these artifacts?  I guess the next step would be to tune up F Ka on several TAP spectrometers and see if we see the same thing on these other spectrometers...


I did not, but the material is AlN so pretty robust. Did not view in SE though.
« Last Edit: July 04, 2020, 10:05:58 am by Owen Neill »
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Probeman

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Re: Cameca digital noise issues
« Reply #5 on: July 03, 2020, 10:19:06 am »
Lets wait first for a second experement (with F ka on other spectrometer). I would not blame resistors - no way  resistor could  (linear analog component which is even not used for any logic, but only for voltage drop) cause this. I would rather suspect digital side. I would bet either on VME crostalk (false count impulse generated by nearby VME adress bus (24-31 bits)... or FPGA on WDS card is programmed with bugs.

I'm out of the lab for an extended period of time, but I will see if my lab manager can do this test.  I would tend to agree that is more likely some sort of bus noise. 

On what might be a related or unrelated topic, we have for many years seen a sort of digital noise on our electron imaging monitor, mainly in the lower 1/3 of the display, but it doesn't show up in the data.  Our engineer has tried to track down the source of this noise "hash" but so far been unsuccessful.
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Owen Neill

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Re: Cameca digital noise issues
« Reply #6 on: July 04, 2020, 10:03:32 am »
Apologies for my ignorance - I've deleted my post so as not to give others bad info. Please let us know how the next test goes.
« Last Edit: July 04, 2020, 10:06:24 am by Owen Neill »

sem-geologist

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Re: Cameca digital noise issues
« Reply #7 on: July 04, 2020, 11:04:50 am »
If your sx100 has old type of electronics (visualisation board), the composition (adding texts, lines, applying LUTS, overlaying a scalebar) of video is done on visualisation board, which have its own memory, and old memory can get corrupted. I .e. our old visualisation board has faulty LUT memory, and random bits flips adding colors randomly (off course that is not seen in acquired and saved image), reloading luts fix issue (temporary).

In your case it can be faulty memory of overlay layer (texts, markers...) or memory for temporary storage of signal (as 8bit gray data). Anyway that is not VME bus issue, as else you would see the same patterns on acquired image to PC (which bypass, or more precisely - that process does not include visualisation board at all). With new gen powercquicc II processor (which replaces old Motorola 68030) and new electronics (actually scanning, visualisation and acquisition in the single pack) the RGB composition is done (I am near certain, but not 100% sure) in PowerQuicc II processor, and same image is sent to PC and physical monitor (tailored with additional elements overlayed).

We have such configuration on SXFive, and we are getting vertical stripes on all images (phys. monitor and PC) - I cant find where that noise is coming from, and this actually could be bus related, indeed.
« Last Edit: July 04, 2020, 11:58:08 am by John Donovan »

John Donovan

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Re: Cameca digital noise issues
« Reply #8 on: July 04, 2020, 12:01:01 pm »
Apologies for my ignorance - I've deleted my post so as not to give others bad info. Please let us know how the next test goes.

As SEM Geologists notes above, the other issue probeman has been seeing (digital hash on the electron image display, but not in saved data), could be bus noise.

Julie is going to try and run a test (on all spectrometers) for the vertical stripe issue (originally described) in a few weeks when she finishes a dozen or so maps for a customer. In fact I'm moving this thread to a new topic as it seems we may be able to find a solution and it isn't stage related apparently.
« Last Edit: July 04, 2020, 12:03:13 pm by John Donovan »
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