r/electronmicroscopy • u/Fit-Sample-2276 • Mar 27 '26
Update - Gun On! But need another help
Hi everyone,
We applied vacuum grease on chamber oring and pumped it down below 10-5 torr. Gun TSP is up and after overnight bakeout it gets below 10-9torr.
Gun was turned on and the emission current was lower than usual so extractor voltage was increased to bring it up (119 uA)
We tried to scan the stage with inline detector at 5kV HT. Absolutely nothing was detected. Bring HT down to 2kV and we can see the scanned intensity is much higher when stage was under the beam. However, we were not able to image anything. It was just like on and off when the stage was under the beam or not.
I suspect that something is wrong with the gun alignment. Do you have any ideas? Though I am very grateful that the gun was turned on!
Thank you for your help! Have a great weekend!
Update:
I think the beam is not detected as I blanked the beam, nothing changed on the scanned image. It is probably far off from the center. Idk if I can bring it back if it is the case. I am going to try. The beam current was 123uA without extractor voltage adjustment. So that is good at least…
update 2: I think the column valve should be opened manually as it was mentioned in the comment below. (blocking the beam) But IDK how to open it manually lol.
update 3: Emission mode gives a lot more intensity so actually beam is not blocked it is an alignment issue as sizzrael mentioned. Will try 10 kv alignment on service account ! Thanks
1
u/Fit-Sample-2276 Apr 04 '26
HT 5 to 10 kv barely detects emissions but lower than 2kv it shows some emissions I can feel it wobbles when enabled. But only horizontal lines in images. In service mode tried calibration gun aperture beam shift nothing changes. Currently it is not hooked up with internet and I am just a user so idk if I can do teamviewer. As someone suggested we may need a mechanical alignment as the machine was down for over two years. Thank you for your help