[3dem] Elsa 698 : best-practice bake-out procedure

[Tim Gruene]

Dear Wim,

the modern Gatan Controller includes a manual mode, that allows to set
the current. The user friendly menues show temperature to the user, but
most likely, the controller itself uses current, controlled by T.

Best,
Tim


On Mon, 29 Aug 2022 23:07:29 +0200 Wim Hagen <hagen at embl.de> wrote:

> Dear Tim,
> 
> I’m not familiar with current cryo holders but have some old info to
> share. The 626 Gatan cryo holders used zeolite, nowadays carbon packs
> I think, to trap water when cooled down. This improves the vacuum
> around the holder dewar and improves temperature stability which in
> turn improves drift behavior in the microscope. Baking out on the 626
> meant 750 mA starting current to get to 100 degree C. When 100 C is
> reached the current is adjusted to maintain 100 C. As the zeolite or
> carbon gasses out, vacuum improves and less current is needed to
> maintain 100 C. So the current is the spec to watch. On 626 I settled
> for 450 mA to maintain 100 C.
> 
> I figured this out some twenty years ago in the Philips factory: at
> the time bake-out time was fixed to a few hours by the Gatan
> controller. and had to be done once a week according to the Gatan
> manual, but I noticed different behavior on all the new holders I got
> from stock. We however didn’t know when the holders came in to the
> warehouse at Philips…. Multiple bake-out cycles, while measuring
> vacuum, improved holder performance, and this correlated with the
> current-drop needed to maintain 100 C during bake-out. So the
> bake-out time was made a user setting on the Gatan controller. Once a
> 626 holder gets to 450 mA after a bake-out, it was fine. Bake-out
> current is the spec….. But maybe I’m a dinosaur on this currently, so
> I’m happy to be corrected.
> 
> Best,
> 
> Wim Hagen
> 
> > On 29. Aug 2022, at 14:52, Tim Gruene <tim.gruene at univie.ac.at>
> > wrote:
> > 
> > Dear all,
> > 
> > we recently received our Gatan Elsa 698 holder. I would like to
> > gather some recommendations for daily use and bake-out procedure. 
> > - what temperature do you use for bake-out?
> > - how long do you bake-out for?
> > - are there special maintenance procedures?
> > - what would be signs of deterioriation, abd after what period would
> >  they occur?
> > 
> > We use the holder both for room-temperature and for
> > cryo-measurements.
> > 
> > The manual refers to the Gatan pumping station, but ours was
> > delivered with a Pfeiffer pumping station ;-)
> > 
> > Thanks a lot for your time!
> > 
> > Best,
> > Tim
> > 
> > -- 
> > --
> > Tim Gruene
> > Head of the Centre for X-ray Structure Analysis
> > Faculty of Chemistry
> > University of Vienna
> > 
> > Phone: +43-1-4277-70202
> > 
> > GPG Key ID = A46BEE1A
> > _______________________________________________
> > 3dem mailing list
> > 3dem at ncmir.ucsd.edu
> > https://mail.ncmir.ucsd.edu/mailman/listinfo/3dem  



-- 
--
Tim Gruene
Head of the Centre for X-ray Structure Analysis
Faculty of Chemistry
University of Vienna

Phone: +43-1-4277-70202

GPG Key ID = A46BEE1A
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