[3dem] Beam drift - Glacios G2

[Farzad]

Dear Piotr,

Beam drift might have two main causes:

*1- Tempetature: *The most plausible cause is changing the temperature,
either ambient, lens or water temperature. The most sensitive parts there
are C2 and Obj. The temperature induced drift is gradual and steady.

*2- Hysteresis: *The second plausible reason might be hysteresis of C2. It
is more problematic in most of the older JEOL microscopes where you could
not change the C2 current abruptly (e.g wobbling for aperture centering
etc.). Glacios also has some considerable hysteresis in its C2 but it does
not end in beam cut offs if you use a proper (big enough) C2 aperture or in
general if you use the microscope in the recommended optical set ups.

For characterizing the true cause of the drift, please change one parameter
at the time. For that reason please go to diffraction and image mode using
hand panel not EPU-D software. EPU-D does some extra steps and corrections
which might be misleading. You can then characterize the responsible
parameter. Monitor the water and ambient temperature using extra sensors
and data loggers. I did it myself. You wont believe how much insight you
might get. You can also read the lens temperature using the engineer's
monitoring software. Ask this from your engineer to give you access to the
microscop's parameters graphs. Change the current of each lens separately.
Doing all these steps you can analyze the situation. Also make sure if the
normalization functions are set up correctly.

I guess according to what you described it is a thermal issue which leads
to a steady beam drift. Specially if it happens in one direction e.g. x or
y or in between. So monitoring lens temperatures are the first thing to go.

And at the end you should not expect the ultimate stability like a Krios.
As mentioned before it has a decent amout of C2 hysteresis. Moreover the
lenses (except the objective) are not constant powers. You should deal with
a bit of instabilities.

Cheers

Ferrie- Halle

Dr.-Ing Farzad Hamdi,
EM Engineer - Staff Scientist
Kastritis Laboratory for Biomolecular Research (KLBR)
Cryo-Electron Microscopy & Computational Structural Biology
__
Institute of Biochemistry and Biotechnology
Martin-Luther-Universität Halle-Wittenberg (MLU)
ZIK HALOmem & Biozentrum, Room A.2.14 & 15
Weinbergweg 22, 06120, Halle (Saale), Germany


Phone:


Office: +49 345 5524984
Glacios Room: +49 345 5524883
JEM-3200FSC Room: +49 345 5524868

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On Tue, Feb 13, 2024, 10:52 Piotr Szwedziak <piotr.szwedziak at zmb.uzh.ch>
wrote:

> Dear All,
>
> We have realised that the electron beam of our Glacios G2 (installed in
> December 2023) is not stable – for instance switching from imaging to
> diffraction and back causes the beam to return to a different position and
> continue drifting for several minutes. More background information:
>
>
>
> -          switching on/off active electromagnetic field cancellation
> system doesn’t make a difference to the beam stability
>
> -          opening/closing the microscope enclosure, disturbing the
> electromagnetic field intentionally doesn’t make a difference to the beam
> stability
>
> -          a lower end EM (Talos 120), which is next door and in similar
> electromagnetic field environment, has a very stable beam that doesn’t
> drift
>
> -          the drift we observe on the Glacios G2 is particularly severe
> after changing microscope magnification/switching to diffraction
>
> -          the beam drift is unidirectional rather than in random
> orientations
>
> Therefore we believe the issue of the unstable beam is system- rather than
> environment-related. Has anyone experienced similar problems?
>
> Best and many thanks,
>
> Piotr
>
>
>
>
>
>
>
>
>
> --
> Piotr Szwedziak, PhD
> Center for Microscopy and Image Analysis
> University of Zurich
> Winterthurerstrasse 190
> CH-8057 Zurich
> Switzerland
>
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