[3dem] spatial coherence on a Talos Arctica

[Hagen, Wim J.]

Hi Joaquin,

I am only assuming TEM mode parallel illumination.

Best,

Wim

From: Joaquín Otón <joton at cells.es>
Sent: 23 January 2024 14:53
To: Hagen, Wim J. <wim.hagen at thermofisher.com>; Morgan, David Gene <dagmorga at indiana.edu>; 3dem at ncmir.ucsd.edu
Subject: Re: [3dem] spatial coherence on a Talos Arctica

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Hi Wim,

there's another factor contributing to coherence: from the image formation point of view, the ratio between numerical apertures of condenser and objective lenses defines a coherence degree. It leads to partial coherence imaging process even for totally incoherent sources. If source is partially spatially coherent, then both effects add.

Best,

Joaquín




On 1/23/24 13:58, Hagen, Wim J. 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><mailto:3dem-bounces at ncmir.ucsd.edu> On Behalf Of Morgan, David Gene
Sent: 22 January 2024 23:02
To: 3dem at ncmir.ucsd.edu<mailto:3dem at ncmir.ucsd.edu>
Subject: [3dem] spatial coherence on a Talos Arctica

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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...

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