[3dem] beam blank versus beam shutter

[Tim Gruene]

Dear all,

In 1975, Unwin and Henderson used a beam shutter instead of the beam
blank (JMB 1975, 94, 425-440) to avoid specimen drifts.

When I collected ED data with the EIGER detector, i.e. at 100Hz
(10.1002/anie.201811318), we used a beam blank. I had to inspect each
data set individually, because the beam was creeping towards its final
stable position, which took 50-75images, i.e. 0.5-0.75s. This seems a
lot to me. Those data were measured with a Tecnai F30, which
is less than 46 years old, but not the latest model either.

Personally, I would prefer a mechanical shutter over a beam blank. What
is the current situation with modern TEMs? Does the beam find its
position within a ms when using the beam blank? Are there reasons NOT
to use a mechanical shutter? For crystallographic purposes, the opening
of the shutter to trigger the detector for data recording seems quite
plausible.

I look forward to your experience and opinions.

Best regards,
Tim

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

Phone: +43-1-4277-70202

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