[3dem] Insertion of Holder 626
Tobias Furstenhaupt
furstenh at mpi-cbg.de
Mon Feb 24 05:55:01 PST 2020
Dear Ariel
you are pumping your cold 626 for 3 mins before inserting? Most people
(including us) only use 20-30 seconds(!) to pump and then insert it. This
way the sample does not warm up so much. Its more risky to crash the column
vacuum but in reality this happens not too often.
Also cleaning/exchanging the O-Ring of the 626 helps to maintain a good
vacuum. Actually the O-Rings are reasonably cheap and probably we will
exchange them every two months as a preventive measure. Of course the O-Ring
has to be greased properly (not too much, not too little) and has to be
without damage, dust, fibres etc. And make sure that it is not cold when
inserting the 626 or the Ring does not seal properly.
Do you also do the 'trick' of rotating the stage to -60 degrees so that you
can insert the 626 with its dewar pointing to the right (or left) instead of
straight down? This way you keep a bit liquid nitrogen in the dewar which
also stabilises the temperature.
If your cryo _and_ roomtemperature holder do crash the vacuum too often then
it might be a good time for a service. Especially the roomtemperature holder
should be 'safe' for the vacuum. Generally you get more crashes with the
cryoholder (its heavier, less balanced and normally used cold and with short
pumping times) but again if you crash your vacuum more than 50% of the
insertions then something is wrong.
Hope this helps. Feel free to ask if you have more questions
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
-----Original Message-----
From: 3dem [mailto:3dem-bounces at ncmir.ucsd.edu] On Behalf Of TALAVERA PEREZ
Ariel
Sent: 24 February 2020 14:13
To: 3dem at ncmir.ucsd.edu
Subject: [3dem] Insertion of Holder 626
Dear all,
I am using a Gatan 626 holder on a side entry TALOS microscope. I am getting
problems with very frequent crystalline ice formation on the grids. Some
times I get a mix of vitreous and crystalline water, but must of the time I
only get crystalline water. I have been extra careful during sample
preparation, and transferring the grind on to the holder, and I have done 48
hours holder bake out before insertion, but I still get ice on the grid.
I monitored the temperature of the holder during the insertion process,
including 3 minutes for the Airlock pump. During those 3 minutes the
temperature rises up to -152.2. Can this be the reason of the unwanted ice
formation? How high can be the temperature of the holder to ensure a nice
vitreous water?
I am also getting vacuum problems while inserting the holder. This process
has resulted to be extremely, extremely sensitive. After the 3 minutes
Airlock pumping (I cannot give longer time because of the aforementioned
temperature issue) as soon as I open the column port the vacuum either rises
to 99 Log or completely crashes the column vacuum.
This has happened with two different holders either cooled with liquid
nitrogen or at room temperature. So, my question: Is this insertion process
always that picky or it can be that there is something wrong with the
holders/Airlock pump?
Thanks a lot in advanced.
Best regards.
Ariel
--
Ariel TALAVERA PEREZ, PhD
Center for Microscopy and Molecular Imaging (CMMI) Laboratory of Microscopy
Université Libre de Bruxelles Rue Adrienne Bolland, 8
B-6041 Gosselies, Belgium
Phone +32 (0)26509866
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