[3dem] contamination...leopard?

[Tobias Furstenhaupt]

Dear all,

thanks alot to you all for your replies. I got a wealth of info and thoughts that I will follow up:

1) 20sec pumping time seems way too low (although working for the 626 holder reasonably well). We start to test 50sec and monitor the temperature of the tip. 
2) at the sime time I will buy alternative O-Rings and exchange the ones from the holder (RT and Cryo) and see if this also has influence on the vacuum-crashes
3) I try to somehow measure the temperature of the Cryobox - It is imperative that the box is the coldest part in the microscope
4) last not least I will also check about the vacuum of the transferchamber during pumping and see if the turbo has problems or if we reach a reasonable vacuum around the holder after the 50sec.

#3 has to be done in close cooperation with FEI/TFS but in the end it would put everybodies mind at rest if we could read the temperature.

Probably we were too paranoid with our (only) 20sec pumping time. But as usual one is forced to revise the procedures once you get problems.

Thanks alot again for all your help - much appreciated and I guess we got a good handle now on our contamination problem :)

cheers 
Tobias 



----------------------------------- 
Tobias Fürstenhaupt, PhD 
head of Electron Microscopy 
Max Planck Institute of Molecular Cell Biology and Genetics (MPI-CBG) 
Pfotenhauerstrasse 108 
01307 Dresden, Germany 

phone: (+49) (0)351 / 210-2690 
cell: (+49) (0)176 / 44498706 (NEW!)

----- Original Message -----
From: "Tobias Furstenhaupt" <furstenh at mpi-cbg.de>
To: 3dem at ncmir.ucsd.edu
Sent: Wednesday, 5 January, 2022 10:23:05
Subject: [3dem] contamination...leopard?

Dear colleagues,

although we dont get a high samplethroughput on our Titan Halo, we tested the Gatan ELSA holder and imaged 3 days and nights straight to get data for SPA.
I heard that side-entry TEMs (like our Halo) are more prone to contamination build up over time but we could not see a clear increase in contamination over time.
But our images suffered badly from contamination (see attached images). We see images with fuzzy contamination and also images with darker, more well defined blobs. Probably just two stages in the course of contamination buildup - or what do you think?
We also sometimes see the contamination in in two phases (attachment liquid_border). 

Am I right in assuming that we see the notorious leopard ice that is humidity contamination from a bad vacuum or slow/suboptimal handling after plungefreezing? Indeed our vacuum crashed more often than not when inserting the holder (despite greasing the O-Ring in advance)...so this could explain it. What is your opinion when you see the images?

thanks alot in advance :)
Tobias 


----------------------------------- 
Tobias Fürstenhaupt, PhD 
head of Electron Microscopy 
Max Planck Institute of Molecular Cell Biology and Genetics (MPI-CBG) 
Pfotenhauerstrasse 108 
01307 Dresden, Germany 

mail: furstenh at mpi-cbg.de 
phone: (+49) (0)351 210-2690 
cell: (+49) (0)176 / 44498706 (NEW!)

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