Standby for FE probes?

[JohnF]

In FE probes, we need to avoid the focused, blowtorch beam landing on materials that may be damaged by it. For overnight periods or weekends or whatever long periods of no use, how do you leave the FE probe???

On the Cameca SXFive FE, there are apparently a couple of options. You do NOT want to leave the beam in the Faraday "cup" (annulus)...damage, contamination etc. Some people apparently leave it sitting on the metal holder (e.g. the 'reference' position). Also, you do not want to have the main valve between the chamber and gun (EP6) closed and blast it with the beam, as who knows what damage that ultimately might cause. Rather, my approach (following suggestions from Cameca personnel) is to set the "gun focusing coil" XHI value to 1000 (whereas the normal value is say 21). Then there is no beam down the column and the possibility of damage/contamination.

I don't know if Jeol FE probes have the same option in terms of gun focusing coils...

[John Donovan]

In FE probes, we need to avoid the focused, blowtorch beam landing on materials that may be damaged by it. For overnight periods or weekends or whatever long periods of no use, how do you leave the FE probe???

On the Cameca SXFive FE, there are apparently a couple of options. You do NOT want to leave the beam in the Faraday "cup" (annulus)...damage, contamination etc. Some people apparently leave it sitting on the metal holder (e.g. the 'reference' position). Also, you do not want to have the main valve between the chamber and gun (EP6) closed and blast it with the beam, as who knows what damage that ultimately might cause. Rather, my approach (following suggestions from Cameca personnel) is to set the "gun focusing coil" XHI value to 1000 (whereas the normal value is say 21). Then there is no beam down the column and the possibility of damage/contamination.

I don't know if Jeol FE probes have the same option in terms of gun focusing coils...

On W guns there are several options in PFE for setting the gun into a "standby" mode as defined by the FilamentStandbyType keyword in the Probewin.ini file as seen here:

FilamentStandbyType=0      ; 0 = reduce heat only, 1 = reduce heat and keV, 2 = reduce keV only

But currently there are no "standby" options for FEG instruments, though I would be pleased to implement a method in Probe for EPMA if we can figure out what it is that we want.

I would also mention that Philippe Pinard and I have asked JEOL to provide an API function to close/open the gun valve for JEOL FEG instruments, but maybe setting the gun tilt/shift as John mentions above is a better way to perform a "standby" mode for both JEOL and Cameca FEG instruments...?

What do you all think should be the "standby" mode for JEOL and/or Cameca FEG instruments?

[John Donovan]

On JEOL FEG probes, JEOL recommends that the gun isolation valve (V1) be left closed when the machine is not in use, so the procedure with our machine is to simple close V1 and walk away. We have had no issues with damage to V1 since 2008 outwith some initial problems with faulty O-rings, which JEOL resolved in early 2009, and were not due to damage from electrons. Unless someone else has horror stories about V1 getting holes blasted in it (and if someone does, please share), for leaving a JEOL probe on "standby", I would recommend simply closing V1 and leaving the gun alignment alone.

On the 8500F, V1 can only be controlled via the "V1 Close" button on the column - it cannot be controlled through the JEOL software, so I would doubt that an API exists for that instrument. On the 8530F, V1 can be closed from the JEOL software ("Obsevation On"/"Observation Off"), so I assume such an option could be implemented if the API were available. That said, I don't remember being able to open or close V1 from anywhere else in the JEOL software - I don't remember being able to close V1 at the end of an automation, for example - so it may not be that simple.

Hi Owen,
Thanks for the interesting comments.  Good stuff to have documented here.

However, given that we're never going to get an API for the 8500 to close the gun valve through software, what do you think about me implementing a set gun shift or tilt to the maximum value as a proxy for closing the gun valve for the purposes of an instrument "standby" mode?

Yes, on the 8530 JEOL has said they will eventually provide a call through the EIKS interface to allow software control of the valve, but if the Cameca thinks setting the XHI gun shift to the max value is appropriate for this purpose, might it be worth doing the same for the 8500?

I'm willing to implement it in PFE if someone is willing to use it...  question: on the JEOL should it be setting the gun shift or gun tilt to maximum for this purpose?
john

[John Donovan]

I'm willing to implement it in PFE if someone is wiling to use it...  question: on the JEOL should it be setting the gun shift or gun tilt to maximum for this purpose?
john

Short answer: no.

Long answer: I'll let the 8530 users speak for themselves, but for the 8500, I think you're better off forgetting the whole thing. Even if the feature were implemented, I can't say I'd use it. I would be very apprehensive about misaligning the gun after every automation.

If someone really wanted a standby mode, I suppose you could set the current to something very small (like 1nA) at the end of an automation, so at least you wouldn't be hammering the PCD after a high-current mapping run or something. The cup on the 8500 is between the objective aperature and the OL, so the beam is at least partially defocused when it hits the PCD, and if the beam is defocused, the FEG is no more of a spot welder than a W or LaB6 at a given current.

Maybe I'm underestimating long-term wear and tear on the Faraday cup, but I don't think kludging together a "standby" mode for the 8500 is worth the effort.

Well of course I would read the current gun shift value and save that (for taking the instrument out of "standby" mode), before setting it to a max value...

[John Donovan]

Well of course I would read the current gun shift value and save that (for taking the instrument out of "standby" mode), before setting it to a max value...

Still can't say I'd use it. Again, I may well be underestimating just how badly the PCD gets beaten up, but this seems like a lot of hassle for no reward. If Eric or Gareth H. or any of the other 8500 users out there really want something like this, that changes things. Until then, the V1 Close button covers my needs.

To be clear, I'm just talking about the 8500 here. Given John F.'s post, it sounds like SXFive users would have a real need for such a feature.

Hi Owen,
I'm still not quite understanding you.  You say that closing V1 "covers your needs", but since it can't be controlled by software I don't see how.  Unless you sleep in the probe lab...   

I'm talking about automatically putting the instrument into a "standby" mode after an overnight or weekend automation is completed.
john

[John Donovan]

For these reasons (again, speaking strictly about the 8500) this seems like a solution in search of a problem. Moreover, this function will take time and effort to implement, and that is time and effort that would not go towards things like standby mode for the SXFive, for which there is a demonstrated need.

Hi Owen,
I don't have a FEG myself and so it's difficult for me to know what FEG users feel about an issue such as this, but I think you make excellent points and I concur.

For the SXFive FEG only then.
john