[Sem] Last Night's Demo Notes

Chris Murphy chrisnoisebridge at gmail.com
Thu May 26 21:56:56 UTC 2011


Last night, we fashioned a wooden camera mount for DSLRs that is  
compaible with the SEM camera bellows system that was made last year.  
Thanks for your help Alan.

After photographing a specimen, we decided to get seriously involved  
in cleaning the electron gun cartridge and replacing the filament. The  
image was wandering on screen and the emmision gauge was occaisionally  
pegging beyond 300 which signaled an aging filament. Also, the image  
has always been ghosting at resolutions higher than 2000x.

The SEM is presently inoperable because the electron gun cartridge was  
not sufficiently clean to warrant returning it into the machine. We  
ultrasonically cleaned it in water along with all of the spare  
electron gun parts but that didn't seem to be enough to get off the  
residue.

The next steps are to use a small diameter wooden stick in the drill  
press and some metal polish to remove more dirt from the parts of the  
electron gun cartridges.

It appears that the electron gun cartridge we had been using had so  
much metalic debris that it had been shorting to ground periodically  
(tested with an ohm meter). The filament was blackened unlike a new  
pristine white filament. When we complete the cleaning we will do  
another demo evening of the SEM to see if the image has improved.

We also dissasembled the vacuum tube era ultrasonic cleaner that Larry  
kindly donated. We repaired it's fan and fuse and generally cleaned it  
up. It works well now.

Thanks everyone!

Chris

Sent from my iPhone



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