[3dem] spatial coherence on a Talos Arctica

[Tim Gruene]

Hi Wim,

just a side note: you probably refer to 'current density', the amount
of charge per unit time that flows through a unit area. Dose rate
refers to the quantity of radiation absorbed per unit time, and is
related to radiation damage or radiation safety. In crystallography,
there as been a lot of work (by Elspeth Garman and others) on radiation
damage, and it is confusing how sloppily EM'ists use the term dose
rate, when really they talk about current density.

Cheers,
Tim

On Tue, 23 Jan 2024 12:58:15 +0000 "Hagen, Wim J."
<wim.hagen at thermofisher.com> wrote:

> Hi,
> 
> Spatial coherence depends on gun brightness and dose rate, for
> typical cryo-EM settings on Thermo Fisher FEG systems, one ends up
> with just a few microradians max.
> 
> Best,
> 
> Wim
> 
> From: 3dem <3dem-bounces at ncmir.ucsd.edu> On Behalf Of Morgan, David
> Gene Sent: 22 January 2024 23:02
> To: 3dem at ncmir.ucsd.edu
> Subject: [3dem] spatial coherence on a Talos Arctica
> 
> CAUTION: This email originated from outside of Thermo Fisher
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> 
> Hi,
> 
> Has anyone thought about or even measured the spatial coherence of a
> Talos Arctica at different spot sizes?  We see something odd when
> changing spot size that could be anything from operator error to
> spatial coherence to issues with our FEG...
> 
> --
>     politics is more difficult than physics.
>                                              A. Einstein
> 
>             David Gene Morgan
>         Electron Microscopy Center
>              047E Simon Hall
>              IU Bloomington
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-- 
--
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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