<!doctype html public "-//w3c//dtd html 4.0 transitional//en">
<html>
Hello Markus and neutron-mc guys !
<p>If we look at the usual formulas for curved guide computation we can
write (for the example given)
<br><tt>m=2 (coating)</tt>
<br><tt>H=0.06 [m] (width)</tt>
<br><tt>Gamma_c = m*0.1 deg/Angs (critical angle)</tt>
<br><tt>r=1640.0 [m] (radius)</tt>
<br>Then the critical wavelength is simply (from Mildner and Coppley papers)
<br><tt>Lambda_c = 180*sqrt(2*H/r)/2/pi/Gamma_c = 1.22 Angs</tt> for <tt>m=2</tt>
(2.45 for <tt>m=1</tt>)
<br>This means that the transmitted intensity versus the wavelength should
vary as Lambda^2 below Lambda_c, tends to be linear after, and then saturates
far away.
<p>I've been running the 'test.instr' given by Markus with mcstas-1.6-ill-alpha,
and new developpment versions. They all give the same result, and it seems
reasonable (see mcstas.ps plot from test2lam.dat with 1e6 neutrons)
<p>I also attach the files for components <tt>Source_flat_lambda</tt> and
<tt>Bender</tt> that I used. There may be differences with your library.
Please check (specially the source).
<p>Cheers, Emmanuel.
<br>
<pre>--
What's up Doc ?
--------------------------------------------
Emmanuel FARHI, <A HREF="http://www.ill.fr/tas/people/Farhi.html">http://www.ill.fr/tas/people/Farhi.html</A> \|/ ____ \|/
CS-Group ILL4/156, Institut Laue-Langevin (ILL) Grenoble ~@-/ oO \-@~
6 rue J. Horowitz, BP 156, 38042 Grenoble Cedex 9,France /_( \__/ )_\
Work :Tel (33/0) 4 76 20 71 35. Fax (33/0) 4 76 20 76 48 \__U_/</pre>
</html>