[3dem] 914 Synopsis
Cindi Schwartz
Cindi.Schwartz at Colorado.EDU
Mon Oct 13 10:26:56 PDT 2008
Dear 3DEMers,
I got a lot of response about the 914 holder and thought I would try
and give a synopsis of what's been said:
1. Try and leave the cryo-shield in place at least 20min after
inserting the holder into the scope. We're not sure on this one, but
in general, I would say that almost all of us open the shield as soon
as the column vacuum recovers (less than 5-10 min). However, we do
the same thing with the 626 and have no cauliflower at all.
2. Try to look at a grid in the 626 first, then transfer to the 914.
We haven't done this, although it was on my list to try.
3. Other labs (3) reported similar issues and after tomography see
that this cauliflower (or cobblestone) appearance is only on one
surface. This suggests that maybe the cryo-shield is the culprit as
there is a small gap between the cryo-shield and the tip.
4. One suggestion was to open the cryo-shield quickly, check to make
sure there was something worth looking at, then close the cryo-shield
and wait 30min.
5. Others who wait at least 20min before opening the cryo-shield also
have cauliflower ice when using the 914.
6. A similar phenomenon happened with the old CT3500 design (1996). It
was solved by cooling the holder down, letting it frost up, put into
the Gatan cryo-pumping station to maintain vacuum, and then after
opening the cryo-shield, noting that frost was building up on the
edges of the specimen. We don't have a way to do this in our lab, so
someone else should volunteer for this :)
7. At least one person has reported to Gatan this issue, but no one
else has complained until now. I think that we now have enough
anecdotal evidence at least for Gatan to take this as a serious issue
and look at their design.
Thanks for your input!
Cindi
**********************************
Cindi L. Schwartz
University of Colorado, Boulder
Dept. MCDB
BL3DEMC
O: 303-492-7980
F: 303-735-0770
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