Field Emission Gun Problems

[DavidAdams]

Hi, me again.

In the middle of a run this morning PFE gave me the dreaded warning that there was no longer any probe current. In my good-ol-W-Filament days that meant it was time to crack open the gun and put in a new lightbulb. I’m hoping that this doesn’t mean that my Field Emitter tip has decided to go because it’s only four years old right now.

The maintenance window says there’s emission current but I have no current on the stage or in the cup and I also don’t get any electron images. Is there some way that the beam is somehow blanked and if so how do I un-blank it? Or is it likely that my tip is truely gone?

Thanks in advance!
Dave

[Anette von der Handt]

Hi Dave,

Nobody has replied to you yet and it has been a week so you might already have found the problem. However, I want to throw out if it is possible that somehow the gun alignment values could have been messed up? That would explain why you have emission current but nothing arrives at the cup.

[DavidAdams]

Hi Anette,

Thanks for the reply! You're sort of correct in a way.

I discovered that the problem was with the objective lenses, specifically that they had no power at all.

This is the second time I have had power issues with my instrument and the fix comes in the form of opening up the big box that sits behind the console and (very carefully) poking around to discover the problem. Attached are pictures from the diagnostic light/fuse panel on the top of all the power supplies in the box. As you can see on the second panel that lights PD281, PD321, and PD341 are off but the fuses are still good. These lights correspond to the individual power supplies (10-1, 12-1, 12-2) which are the 13v supplies for the objective lenses. Thankfully this time the power supplies were still functional but the connector from those supplies to the lenses had come lose. I suspect it may not have been plugged in fully at the factory and managed to work itself loose over the past 4 years. Plugging that connector back in fully brought the power back to the lenses and thankfully my e-beam reappeared. 

[Probeman]

This is the second time I have had power issues with my instrument and the fix comes in the form of opening up the big box that sits behind the console and (very carefully) poking around to discover the problem. Attached are pictures from the diagnostic light/fuse panel on the top of all the power supplies in the box. As you can see on the second panel that lights PD281, PD321, and PD341 are off but the fuses are still good. These lights correspond to the individual power supplies (10-1, 12-1, 12-2) which are the 13v supplies for the objective lenses. Thankfully this time the power supplies were still functional but the connector from those supplies to the lenses had come lose. I suspect it may not have been plugged in fully at the factory and managed to work itself loose over the past 4 years. Plugging that connector back in fully brought the power back to the lenses and thankfully my e-beam reappeared. 

OK, I am officially impressed with your trouble shooting skills! 

We had a similar problem last weekend when I tried to fire up the Thermo EDS system, but it would not connect to the Thermo hardware.  After re-powering the Thermo electronics  and getting the same result, I mentioned it to our in-house instrument engineer (Steve Wiemholt) and he discovered (after poking around about as you did!), that the network cable had just barely pulled out of the CAT5 socket, because (as Steve explained to me), the cable had apparently been under tension for years and finally gave up last weekend.  So he just pushed the connector back in (after giving the cable some slack) and the Thermo software connected right up!

"Fighting entropy one day at a time" is my instrumentalist's slogan...

[Anette von der Handt]

Agree, excellent sleuthing and problem solving. I had the power supply for the objective lens go once but in my case it went with a giant "pow" while I was in the lab. So it was easy to see what the problem is.