Why FEG?

[Philip Koeck]

Hi,

>From your plots it seems that you need a FEG to reach resolutions beyond
about 3 A,
But I can’t see any great advantage up to about 5 A resolution.
Is that correct? (and what is all the excitement about then?)

Philip


		-----Original Message-----
		From: Lucken, Uwe [mailto:uwl at nl.feico.com] 
		Sent: 23 April 2004 15:03
		To: Philip Koeck; 3dem at ucsd.edu;
microscopy at sparc5.microscopy.com
		Cc: Max.Sidorov at Amd.Com
		Subject: RE: Why FEG?

		Dear Philip, for an FEG one can set 0.6eV energy spread
and for and Lab6 one usually has 1.5eV energy spread. As you can see for
–2000nm defocus and 61kx. There is a small mistake in the estimate of
the convergence angle. The parallel beam conditions are C2 diameter/7 in
microprobe and I have included the plots. 

		end
		Sincerely yours,

		Dr. Uwe Lücken
		Senior Scientist Application Development
		FEI-Electron Optics; Building AAE
		Achtseweeg Noord; 5600 MD Eindhoven
		The Netherlands
		tel.:+31-40-2766106; fax:+31-40-2766102
		mob: +31 40 2791621

				-----Original Message-----
				From: Philip Koeck
[mailto:Philip.Koeck at biosci.ki.se]
				Sent: Friday, April 23, 2004 10:44 AM
				To: 3dem at ucsd.edu;
microscopy at sparc5.microscopy.com
				Cc: Max.Sidorov at Amd.Com; Lucken, Uwe
				Subject: Why FEG?

				Hi,
				 
				I’ve been playing around with Max
Sidorow's CTFexplorer and I’m finding it hard to see the
				advantage of FEG microscopes for
structural biology.
				At 61000-times magnification I can’t see
any major difference between the Tecnai 20T and
				the Tecnai F20T for example.
				Only at magnifications beyond 300000 is
the F20T clearly superior (due to better spatial
				coherence).
				 
				Am I (or is CTFexplorer) missing
something relevant?
				 
				The CTFexplorer can be found at
http://clik.to/ctfexplorer.
				Upon request I can also send a Word file
with the CTF-plots.
				 
				Philip
				 
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