[3DEM] 626 cryoholder pin

Bill Tivol tivol at caltech.edu
Tue May 2 16:12:47 PDT 2006

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On May 2, 2006, at 5:32 AM, Lisa Craig wrote:

>  Sorry to hear about your troubles but thanks for sharing with the 
> rest of us. I will soon be purchasing a cryoholder and would like to 
> know more about this potential problem. Do you know why the pin 
> breaks? Do you think its from uncontrolled withdrawal of the stage? 
> Its been a while since I've used a cryoholder but I know that some 
> users of the non-cryo single tilt holder end up ripping the holder out 
> of the microscope once they've freed it of the vauum lock and this 
> seems to be pretty hard on the pin. Also, what happens if the pin 
> breaks when the holder is in the microscope? Can the holder be 
> repaired?
Dear Lisa,
	In a few of my recent posts to this list I have speculated that 
something about the temperature either of operation or cycling might 
play a role, but this is just speculation on my part.  I have 
instructed our users to hold one or two fingers against the blue plate 
of the compustage--recommended procedure per FEI to prevent damage to 
the stage--and to push with the other hand (holding the cryoholder 
dewar) against the first in order to have a more controlled withdrawal 
of the holder past the vacuum lock.  If the pin breaks off in the 
scope, there are two possibilities depending on whether it happened on 
putting the holder in or when taking it out.  In the first case, the 
airlock will be open, and if one rotates the holder to the position to 
withdraw it, the airlock will remain open, so if the holder is then 
withdrawn, room air will rush into the scope and, I'd guess, blow the 
filament as well as shutting down the scope and likely causing 
additional damage.  In the second case, the airlock will be closed, so 
the only problem will depend on where the pin ends up--it could damage 
the compustage.  The holder can be repaired, and the cost for our last 
repair was ~$3500.
Bill Tivol, PhD
EM Scientist and Manager
Cryo-Electron Microscopy Facility
Broad Center, Mail Code 114-96
California Institute of Technology
Pasadena CA 91125
(626) 395-8833
tivol at caltech.edu
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