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

[Wim Hagen]

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
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