<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><meta http-equiv=Content-Type content="text/html; charset=utf-8"><meta name=Generator content="Microsoft Word 15 (filtered medium)"><!--[if !mso]><style>v\:* {behavior:url(#default#VML);}
o\:* {behavior:url(#default#VML);}
w\:* {behavior:url(#default#VML);}
.shape {behavior:url(#default#VML);}
</style><![endif]--><style><!--
/* Font Definitions */
@font-face
{font-family:Helvetica;
panose-1:2 11 5 4 2 2 2 2 2 4;}
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:DengXian;
panose-1:2 1 6 0 3 1 1 1 1 1;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:"\@DengXian";
panose-1:2 1 6 0 3 1 1 1 1 1;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri",sans-serif;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:#954F72;
text-decoration:underline;}
pre
{mso-style-priority:99;
mso-style-link:"HTML Preformatted Char";
margin:0in;
margin-bottom:.0001pt;
font-size:10.0pt;
font-family:"Courier New";}
span.HTMLPreformattedChar
{mso-style-name:"HTML Preformatted Char";
mso-style-priority:99;
mso-style-link:"HTML Preformatted";
font-family:"Courier New";}
.MsoChpDefault
{mso-style-type:export-only;}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{page:WordSection1;}
--></style></head><body lang=EN-US link=blue vlink="#954F72"><div class=WordSection1><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">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">Lingnan Shen</a><br><b>Cc: </b><a href="mailto:farhi@ill.fr">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">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">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><pre>_______________________________________________</pre><pre>mcstas-users mailing list</pre><pre><a href="mailto:mcstas-users@mcstas.org">mcstas-users@mcstas.org</a></pre><pre><a href="https://mailman2.mcstas.org/mailman/listinfo/mcstas-users">https://mailman2.mcstas.org/mailman/listinfo/mcstas-users</a></pre></blockquote><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></div><p class=MsoNormal>_______________________________________________<br>mcstas-users mailing list<br><a href="mailto:mcstas-users@mcstas.org">mcstas-users@mcstas.org</a><br><a href="https://mailman2.mcstas.org/mailman/listinfo/mcstas-users">https://mailman2.mcstas.org/mailman/listinfo/mcstas-users</a><o:p></o:p></p></div></blockquote></div><p class=MsoNormal><o:p> </o:p></p><div><div><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:9.0pt;font-family:"Helvetica",sans-serif'><br>Peter Kjær Willendrup<br>Forskningsingeniør, Specialkonsulent<br>Næstformand for DTU Fysik LSU<br><br>DTU Physics<o:p></o:p></span></p></div><p class=MsoNormal><span style='font-size:9.0pt;font-family:"Helvetica",sans-serif'><br><image001.gif><br><br><br>Technical University of Denmark<br><br><br><image002.gif><br><br><br><br>Department of Physics<br>Fysikvej<br>Building 307<br>DK-2800 Kongens Lyngby<br>Direct +45 2125 4612<br>Mobil +45 2125 4612<br>Fax +45 4593 2399<br><a href="mailto:pkwi@fysik.dtu.dk">pkwi@fysik.dtu.dk</a> </span><o:p></o:p></p></div><p class=MsoNormal><o:p> </o:p></p></div></div></div></blockquote></div><p class=MsoNormal><o:p> </o:p></p><div><div><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:9.0pt;font-family:"Helvetica",sans-serif;color:black'><br>Peter Kjær Willendrup<br>Forskningsingeniør, Specialkonsulent<br>Næstformand for DTU Fysik LSU<br><br>DTU Physics<o:p></o:p></span></p></div><p class=MsoNormal><span style='font-size:9.0pt;font-family:"Helvetica",sans-serif;color:black'><br><img border=0 width=400 height=1 style='width:4.1666in;height:.0104in' id="_x0037_F2B9384-5B9D-4EB7-89FC-07916BD8CDEA" src="cid:b6339554-7f28-441d-9f31-5944f811397c@win.dtu.dk" alt="cid:b6339554-7f28-441d-9f31-5944f811397c@win.dtu.dk"><br><br><br>Technical University of Denmark<br><br><br><img border=0 width=36 height=53 style='width:.375in;height:.552in' id=E6FBFD88-6E07-4AB2-AEDD-6E71B78B1972 src="cid:e108e480-fcab-46e2-9531-b38165079572@win.dtu.dk" alt="cid:e108e480-fcab-46e2-9531-b38165079572@win.dtu.dk"><br><br><br><br>Department of Physics<br>Fysikvej<br>Building 307<br>DK-2800 Kongens Lyngby<br>Direct +45 2125 4612<br>Mobil +45 2125 4612<br>Fax +45 4593 2399<br><a href="mailto:pkwi@fysik.dtu.dk">pkwi@fysik.dtu.dk</a> </span><o:p></o:p></p></div></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>