[3DEM] Why FEG?

[Philip Koeck]

To get similar curves with CTFexplorer I have to select a magnification
Between 300K and 400K. At magnifications between 30K and 60K the
difference
between a FEG and a LaB6 is much smaller according to CTFexplorer.
(Of course I don't know whether the curves given by CTFexplorer are
realistic.)

yours,

Philip

-----Original Message-----
From: owner-3dem at ncmir.ucsd.edu [mailto:owner-3dem at ncmir.ucsd.edu] On
Behalf Of Henning Stahlberg
Sent: 23 April 2004 19:00
To: Philip Koeck
Cc: 3dem at ucsd.edu
Subject: Re: [3DEM] Why FEG?

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Hi,

The biggest difference between a FEG and an LaB6 performance seems to 
me to arise from the effective electron source opening angle, when 
short cryoEM exposure times are considered. I used 0.1 mrad for a FEG 
and 0.7 mrad for a thermal electron source, see also Jong & van Dyck, 
Ultramicroscopy 49, 66-80 (1993).
http://dx.doi.org/10.1016/0304-3991(93)90213-H

Even when only interested in 0.5 nm resolution, the difference is 
significant, see
http://www.amp.ucdavis.edu/index.php?p=download

Those are CTF simulations made with a simple MS-Excel sheet, which is 
also on that server.

Henning.


Henning Stahlberg, Ph.D.,
Molecular & Cellular Biology, Briggs Hall 115B,
UC-Davis, 1 Shields Ave., Davis, CA 95616, USA
Tel: +1 (530) 752 82 82      Fax: +1 (530) 752 30 85
mailto:HStahlberg at ucdavis.edu	
http://www.amp.ucdavis.edu