<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">
<div style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">
<div style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">
<span style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" class="">Dear Tim,</span>
<div class="" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);"><br class="">
</div>
<div class="" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);">the speed of the blanker varies a lot between TEMs and their configuration. On our TF20 STEM, where blanking is achieved by mis-adjusting the beam tilt, it was in the few seconds range (hence
unusable for our ED experiments) originally. However, this was remedied by replacing a specific electronics board<span class=""> </span><font color="#000000" class="">(with what is essentially a dummy plug) that filters the gun deflector currents, at the expense
of somewhat reduced STEM resolution due to jitter. It is now of the order of 10 ms, so would be acceptable for your ED collection. We actually can trigger our Medipix detector from the shutter signal then, though mostly we go vice versa. </font><span class="">Titans,
on the other hand, have a dedicated beam blanker which is ms-range without influencing beam jitter or drift.</span></div>
<div class="" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);"><font color="#000000" class="">In our JEOL 2100 we get 10 ms or so by default, but pushed it to sub-µs using a custom electro-static blanker (which might be overkill for most use cases).
There is also beautiful work by the Antwerp group on a fast magnetic blanker that sits on the C2 aperture (Appl. Phys. Lett. 108, 093103).</font></div>
<div class="" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);">That said, I see no real reason against well-engineered (that is, no magnetic stray fields, charging, long-term reliability…) mechanical shutters, even though I’d rather stick to magnetic
or electric.</div>
<div class="" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);"><br class="">
</div>
<div class="" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);">Cheers,</div>
<div class="" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);">Robert</div>
<div class=""><br class="">
</div>
<div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">
--<br class="">
Dr. Robert Bücker<br class="">
Centre for Structural Systems Biology // University of Hamburg</div>
<div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">
Notkestraße 85 // 22607 Hamburg // Germany</div>
<div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">
<a href="mailto:robert.buecker@cssb-hamburg.de" class="">robert.buecker@cssb-hamburg.de</a></div>
<div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">
+49 157 70210628<br class="">
</div>
<br class="">
<div class=""><br class="">
<blockquote type="cite" class="">
<div class="">Am 14.05.2021 um 13:50 schrieb Tim Gruene <<a href="mailto:tim.gruene@univie.ac.at" class="">tim.gruene@univie.ac.at</a>>:</div>
<br class="Apple-interchange-newline">
<div class="">
<div class="">Dear all,<br class="">
<br class="">
In 1975, Unwin and Henderson used a beam shutter instead of the beam<br class="">
blank (JMB 1975, 94, 425-440) to avoid specimen drifts.<br class="">
<br class="">
When I collected ED data with the EIGER detector, i.e. at 100Hz<br class="">
(10.1002/anie.201811318), we used a beam blank. I had to inspect each<br class="">
data set individually, because the beam was creeping towards its final<br class="">
stable position, which took 50-75images, i.e. 0.5-0.75s. This seems a<br class="">
lot to me. Those data were measured with a Tecnai F30, which<br class="">
is less than 46 years old, but not the latest model either.<br class="">
<br class="">
Personally, I would prefer a mechanical shutter over a beam blank. What<br class="">
is the current situation with modern TEMs? Does the beam find its<br class="">
position within a ms when using the beam blank? Are there reasons NOT<br class="">
to use a mechanical shutter? For crystallographic purposes, the opening<br class="">
of the shutter to trigger the detector for data recording seems quite<br class="">
plausible.<br class="">
<br class="">
I look forward to your experience and opinions.<br class="">
<br class="">
Best regards,<br class="">
Tim<br class="">
<br class="">
-- <br class="">
--<br class="">
Tim Gruene<br class="">
Head of the Centre for X-ray Structure Analysis<br class="">
Faculty of Chemistry<br class="">
University of Vienna<br class="">
<br class="">
Phone: +43-1-4277-70202<br class="">
<br class="">
GPG Key ID = A46BEE1A<br class="">
<span id="cid:1D7DA05CABD3814AABFD572E1D46C9AB@um.gwdg.de" class=""><OpenPGP digital signature></span>_______________________________________________<br class="">
3dem mailing list<br class="">
<a href="mailto:3dem@ncmir.ucsd.edu" class="">3dem@ncmir.ucsd.edu</a><br class="">
<a href="https://mail.ncmir.ucsd.edu/mailman/listinfo/3dem" class="">https://mail.ncmir.ucsd.edu/mailman/listinfo/3dem</a><br class="">
</div>
</div>
</blockquote>
</div>
<br class="">
</div>
</div>
</body>
</html>