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<TITLE>RE: Why FEG?</TITLE>
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<P><FONT SIZE=2>Yes, Uwe is exactly correct. The energy spread is what makes the difference here. Plus low mag and large underfocus. And it applies to the info limit, not to point-to-point resolution. See an example at <A HREF="http://maxsidorov.com/ctfexplorer/science/spatial_coherency.htm" TARGET="_blank">http://maxsidorov.com/ctfexplorer/science/spatial_coherency.htm</A> (two pictures at the bottom).</FONT></P>
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<BR><FONT SIZE=2>Max</FONT>
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<P><FONT SIZE=2>________________________________</FONT>
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<P> <FONT SIZE=2>From: Lucken, Uwe [<A HREF="mailto:uwl@nl.feico.com">mailto:uwl@nl.feico.com</A>] </FONT>
<BR> <FONT SIZE=2>Sent: Friday, April 23, 2004 6:03 AM</FONT>
<BR> <FONT SIZE=2>To: Philip Koeck; 3dem@ucsd.edu; microscopy@sparc5.microscopy.com</FONT>
<BR> <FONT SIZE=2>Cc: Sidorov, Max</FONT>
<BR> <FONT SIZE=2>Subject: RE: Why FEG?</FONT>
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<P> <FONT SIZE=2>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. </FONT></P>
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<P> <FONT SIZE=2>end</FONT>
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<P> <FONT SIZE=2>Sincerely yours,</FONT>
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<P> <FONT SIZE=2>Dr. Uwe Lücken</FONT>
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<P> <FONT SIZE=2>Senior Scientist Application Development</FONT>
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<P> <FONT SIZE=2>FEI-Electron Optics; Building AAE</FONT>
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<P> <FONT SIZE=2>Achtseweeg Noord; 5600 MD Eindhoven</FONT>
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<P> <FONT SIZE=2>The Netherlands</FONT>
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<P> <FONT SIZE=2>tel.:+31-40-2766106; fax:+31-40-2766102</FONT>
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<P> <FONT SIZE=2>mob: +31 40 2791621</FONT>
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<P> <FONT SIZE=2> </FONT>
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<P> <FONT SIZE=2>-----Original Message-----</FONT>
<BR> <FONT SIZE=2>From: Philip Koeck [<A HREF="mailto:Philip.Koeck@biosci.ki.se">mailto:Philip.Koeck@biosci.ki.se</A>]</FONT>
<BR> <FONT SIZE=2>Sent: Friday, April 23, 2004 10:44 AM</FONT>
<BR> <FONT SIZE=2>To: 3dem@ucsd.edu; microscopy@sparc5.microscopy.com</FONT>
<BR> <FONT SIZE=2>Cc: Max.Sidorov@Amd.Com; Lucken, Uwe</FONT>
<BR> <FONT SIZE=2>Subject: Why FEG?</FONT>
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<P> <FONT SIZE=2>Hi,</FONT>
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<P> <FONT SIZE=2> </FONT>
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<P> <FONT SIZE=2>I've been playing around with Max Sidorow's CTFexplorer and I'm finding it hard to see the</FONT>
<BR> <FONT SIZE=2>advantage of FEG microscopes for structural biology.</FONT>
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<P> <FONT SIZE=2>At 61000-times magnification I can't see any major difference between the Tecnai 20T and</FONT>
<BR> <FONT SIZE=2>the Tecnai F20T for example.</FONT>
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<P> <FONT SIZE=2>Only at magnifications beyond 300000 is the F20T clearly superior (due to better spatial</FONT>
<BR> <FONT SIZE=2>coherence).</FONT>
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<P> <FONT SIZE=2> </FONT>
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<P> <FONT SIZE=2>Am I (or is CTFexplorer) missing something relevant?</FONT>
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<P> <FONT SIZE=2> </FONT>
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<P> <FONT SIZE=2>The CTFexplorer can be found at <A HREF="http://clik.to/ctfexplorer" TARGET="_blank">http://clik.to/ctfexplorer</A>.</FONT>
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<P> <FONT SIZE=2>Upon request I can also send a Word file with the CTF-plots.</FONT>
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<P> <FONT SIZE=2> </FONT>
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<P> <FONT SIZE=2>Philip</FONT>
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