[3dem] contamination...leopard?

[Reinhard Rachel]

I see your point, Wim. 

> On systems with side-entry cryo-holders, the pump-time for holder insertion

> is limited and pressure is not measured by the vacuum system. 

it is measured on our 2100F. 
I doubt that 20 sec is a good time for cryo-transfer. Vacuum always needs
time!
the sample temperature should be kept low enough for quite some time (120 /
180 sec, at least). 
but the vacuum improves quite considerable when going from short pump times
(20sec) up to 180 sec. or even longer. 
this is at least the case for the air-lock/gonio of our 2100F (holder with two
O-rings ...). 
thus: 
- tilting to -30 or -35 degrees is fully sufficient
- pumping up to 120/180 sec (or even longer?) is fine, and the sample looks
fine, too. 

> If a grid 
> contains a lot of frozen ethane (from a fast transfer from ethane into
liquid 
> nitrogen on the plunge freezer), this ethane will sublimate in vacuum: too 
> much ethane and/or short pump time -> column vacuum crashes as the ion
getter 
> pumps see a lot of ethane coming in when the holder is inserted. 

this is the point - thank you, Wim. 
thus, I think Tobias & Co may try longer times for pre-pumping in the
air-lock? 
I do not know this type of air-lock in the Halo -  but it might work. 

kind regards,
Reinhard

-- 
Prof. Dr. Reinhard Rachel
University of Regensburg
Centre for EM / Anatomy
Faculty of Biology & Preclin. Med.
Universitaetsstrasse 31
D-93053 Regensburg - Germany
tel +49 941 943 -2837, -1666
mail reinhard.rachel at biologie.uni-regensburg.de
office: VKL 3.1.29 
member of the IFSM board

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