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<p>Hi Shen,</p>
<p>It is also my understanding that the k value is the momentum
transfer.</p>
<p>Sorry, I do not have the time to look into you problem now.</p>
<p>best, Kim</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 2/7/19 4:53 PM, <a class="moz-txt-link-abbreviated" href="mailto:ls8vm@virginia.edu">ls8vm@virginia.edu</a>
wrote:<br>
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<p class="MsoNormal"><span style="font-family:"Times New
Roman",serif">Hi all,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Times New
Roman",serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Times New
Roman",serif"> I checked the
supermirror_m3.rfl file and it ranges from 0 to 0.09
[Angs-1] so I’m really confused with the k value in the
first column of reflectivity file. I thought it represent
the total momentum transferred. Can you explain more on
“better the k values in the reflectivity file to be around
e.g. 1.0 Angs-1.” Does the guide_gravity component have a
different definition on reflectivity file? My actual source
wavelength ranges from 0 to 10 [Angs].<o:p></o:p></span></p>
<p class="MsoNormal" style="text-indent:.5in"><span
style="font-family:"Times New Roman",serif"><o:p> </o:p></span></p>
<p class="MsoNormal" style="text-indent:.5in"><span
style="font-family:"Times New Roman",serif">And
also for Peter, my actual problem is to optimize a polarizer
which is built by stack of supermirror. I’m trying to find a
way to get the most transmission through that setup. So I
want to calculate the ratio neutron_out/neutron_in. Now it
seems that I should just divide the intensity instead of
event numbers?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Times New
Roman",serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Times New
Roman",serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Times New
Roman",serif">Happy Lunar New Year,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Times New
Roman",serif">Lingnan Shen<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<div
style="mso-element:para-border-div;border:none;border-top:solid
#E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal" style="border:none;padding:0in"><b>From:
</b><a href="mailto:pkwi@fysik.dtu.dk"
moz-do-not-send="true">Peter Kjær Willendrup</a><br>
<b>Sent: </b>Tuesday, February 5, 2019 4:20 AM<br>
<b>To: </b><a href="mailto:ls8vm@virginia.edu"
moz-do-not-send="true">Lingnan Shen</a><br>
<b>Cc: </b><a href="mailto:farhi@ill.fr"
moz-do-not-send="true">Emmanuel Farhi</a><br>
<b>Subject: </b>Re: [mcstas-users] Guide_gravity Problem</p>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Hello again, <o:p></o:p></p>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">A better starting point for understanding
Guide_gravity and reflectivity files may be the instrument
file Test_Guides which is included with your McStas
installation, in combination with one of the example
reflectivity files from the data folder - e.g.
supermirror_m3.rdl.<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">Also, for a pencil beam with controllable
divergence, an option is to use Source_div.<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">Hope this helps - otherwise you are
welcome to write again, preferably with a good description
of what exact problem you are trying to solve. :-)<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">Best,<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">Peter<o:p></o:p></p>
<div>
<p class="MsoNormal"><br>
<br>
<o:p></o:p></p>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<div>
<p class="MsoNormal">On 5 Feb 2019, at 10.12, Peter Kjær
Willendrup <<a href="mailto:pkwi@fysik.dtu.dk"
moz-do-not-send="true">pkwi@fysik.dtu.dk</a>>
wrote:<o:p></o:p></p>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<div>
<div>
<p class="MsoNormal">Hello Lingnan, <o:p></o:p></p>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<div>
<p class="MsoNormal">Agree with Emmanuel. <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">Further, the combination of a
pencil-beam, i.e. almost non-divergent source
and using 500 channels in a rotated
Guide_gravity means that transport through the
guide becomes close to impossible. <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">With regard to your second
question you should always consider the
transported intensity I. The event count is
simply a measure of statistics (of "neutron
rays", not “neutrons”).<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">Best,<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">Peter Willendrup<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<blockquote
style="margin-top:5.0pt;margin-bottom:5.0pt">
<div>
<p class="MsoNormal">On 5 Feb 2019, at 10.01,
Emmanuel FARHI <<a
href="mailto:farhi@ill.fr"
moz-do-not-send="true">farhi@ill.fr</a>>
wrote:<o:p></o:p></p>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<div>
<div>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Hello
Lingnan,</p>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Your
reflectivity file is given for k=0 to 0.14
Angs-1. This is very small and covers
neutrons around lambda=60 Angs, which are
not even created by your source. Change
either the lambda setting at the source,
or better the k values in the reflectivity
file to be around e.g. 1.0 Angs-1.</p>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Cheers,
Emmanuel.</p>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><o:p> </o:p></p>
<div>
<p class="MsoNormal">On 2/5/19 7:17 AM,
Lingnan Shen wrote:<o:p></o:p></p>
</div>
<blockquote
style="margin-top:5.0pt;margin-bottom:5.0pt">
<div>
<p class="MsoNormal">Hi all, <o:p></o:p></p>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal"> I was
trying to learn how to use the
guide_gravity component. I tried to
define the reflectivity curve but I
get zero neutrons at the wavelength
monitor in the end of guide. I have
attached my .instr and .rfl file. I
also found that even if the neutron
beam just go through the guide. The
detector at the end still see
nothing.<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> Also
another question about transmission
of certain setup. To calculate the
ratio of neutron_in / neutron_out. I
want to know how much neutron
remained after passing through that
setup. Should I use the flux or the
events count?<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">Sincerely,<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">Lingnan Shen<o:p></o:p></p>
</div>
</div>
<p class="MsoNormal"><br>
<br>
<o:p></o:p></p>
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<pre>-- </pre>
<pre>Emmanuel FARHI, \|/ ____ \|/</pre>
<pre>Spectroscopy Group Institut Laue-Langevin (ILL) Grenoble ~@-/ oO \-@~</pre>
<pre>71 av des Martyrs,CS 20156,38042 Grenoble Cedex 9,France /_( \__/ )_\</pre>
<pre>Work :Tel (33/0) 4 76 20 71 35. Fax (33/0) 4 76 48 39 06 \__U_/ </pre>
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