[3dem] Thinner ice question

[Cindi Schwartz]

We have both a TF20 and TF30 with cryo-boxes (not cryo-blades) and we  
found our contamination was due to a design flaw on our 914 holder. We  
also have the 626 holder for about 5-6 years and no real problems.

We have 2 methods for inserting cryo-holders. One person swears by  
cooling the holder in the scope while cooling down the cryo-box at the  
same time and waits about an hour before removing the cryo-holder to  
load a sample. Most of us just cool down the cryo-box right away, do  
the alignments, tune the GIF, take gain references, cool down the  
holder at the bench and by that time the cryo-box seems to be quite  
cold enough. For me, that's about 20-30min time from cooling the cryo- 
box to cooling the cryo-holder.

I'm also apparently not a patient person, because I just wait for the  
vacuum to go down before opening the shield. This is like 5 minutes,  
but I really don't see any issues. Maybe it's because Boulder is so  
dry (especially in winter).

I don't know what to say, but how does your vacuum behave when  
inserting the cryo-holders? Does it spike crazy high and then you have  
to wait forever for it to drop down? If so, maybe you do have a bit of  
a gas bubble and/or leak that works itself out on the first go.

As for cryo-cycle, it's critical to save your IGP pumps. Trust me, you  
don't want FEI to have to change your IGP pumps all the time--1/2 of  
them are bad when they come from the factory.  During cryo-cycle, the  
IGP pumps shut down and the turbo pump sucks out all of the stuff you  
introduced into the column. I tell people that if they work all night,  
they shouldn't run the cryo-cycle unless there is at least 5 hours  
between when they start it and when the next person comes on (we do a  
3 hour cryo-cycle, so that gives us 2 hours to come back to normal).

Good luck!
Cindi

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Cindi L. Schwartz
University of Colorado, Boulder
Dept. MCDB
BL3DEMC
O: 303-492-7980
F: 303-735-0770
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