<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Hi Peter,<div class=""><br class=""></div><div class=""><br class=""></div><div class="">I believe the situation is close to what you sketched - apart from the availability of Guide_four_side from PSI (and its even more complex siblings with 2 or 10 layers), which does however have a slightly complex interface to master. - Comes with an example instrument though…</div><div class=""><br class=""></div><div class=""><br class=""></div><div class="">Otherwise, as I understand the problem, the easiest alternatives would indeed be to either</div><div class=""><br class=""></div><div class="">1) Modify Guide_gravity with curvature (non-trivial if not to be implemented like Bender)</div><div class=""><br class=""></div><div class="">2) Modify Guide_curved with multiple, independent reflectivities (and live with the fact that this then doesn’t include gravity)</div><div class=""><br class=""></div><div class=""><br class=""></div><div class="">There is also a further approximative solution to use Elliptical_guide_gravity (which adds a transverse component to gravity to implement the curvature), but this has a linear appearance in mcdisplay as well…</div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div><div class="">Cheers,</div><div class=""><br class=""></div><div class="">Peter</div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><div><blockquote type="cite" class=""><div class="">On 18 Jul 2019, at 14.12, Peter Link <<a href="mailto:Peter.Link@frm2.tum.de" class="">Peter.Link@frm2.tum.de</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="">Hi Christoph,<br class=""><br class="">this is just the point: I'm producing real neutron guide elements, which are "truly curved" 2m long pieces of glass, which are really bent on radii between 30m and several thousands of m. Usually I use the same approx. as you, but I'm thinking about a more realistic way to simulate my guides.<br class=""><br class="">Best regards<br class=""><br class="">Peter<br class=""><br class="">Am 18.07.2019 um 14:07 schrieb Christoph Frommen:<br class=""><blockquote type="cite" class="">Dear Peter,<br class=""><br class="">I usually try to model curved guides realistically, meaning with a "short section approximation" of individual straight segments each having a certain gap between each other.<br class="">I am following a procedure described in by V.M. Pusenkov et all in "Nucl. Instrum. Meth. A 492 (2002) 105-116".<br class=""><br class="">Below is an example for one segment of a multichannel guide (3 channels) with 2.5 mm walls in between. You can still have different m coatings since it is a gravity_guide. You could use the COPY statement to generate the necessary number of those segments.<br class=""><br class="">------------------------------------------------------------<br class="">*gLength: [m] length of individual guide pieces<br class="">*gGap: [m] gap between guide pieces<br class="">*gReflect0: guide reflectivity<br class="">*gQc: [AA-1] critical wave vector<br class="">*gAlpha : [deg] slope of reflectivity curve<br class="">*gW, gH : [m] guide entrance/exit widths/heights<br class="">*R_curv_m : [m] radius of curvature for bent guide section<br class=""><br class="">component bent_section_1 = Guide_gravity(w1=gW, w2=gW, h1=gH, h2=gH, l=gLength,<br class="">R0=gReflect0, Qc=gQc, alpha=gAlpha,<br class="">m=2, nslit=3, d=0.0025) at (0, 0, gGap+gLength)<br class="">relative previous rotated (0, gLength/R_curve_m*180.0/PI, 0) relative previous<br class="">---------------------------------------------------------------<br class=""><br class="">Maybe someone has a more elegant solution?<br class=""><br class=""><br class="">Best regards<br class="">Christoph<br class=""><br class="">-----Original Message-----<br class="">From: mcstas-users <<a href="mailto:mcstas-users-bounces@mcstas.org" class="">mcstas-users-bounces@mcstas.org</a>> On Behalf Of Peter Link<br class="">Sent: 18 July 2019 13:25<br class="">To: <a href="mailto:mcstas-users@mcstas.org" class="">mcstas-users@mcstas.org</a><br class="">Subject: [mcstas-users] curved guide<br class=""><br class="">Dear friends,<br class=""><br class="">just to avoid some double developpment: to my knowlegde there are the following components or ways to simulate a standard curved neutron guide:<br class=""><br class="">Bender; allows for different reflectivities on top/bottom inside outside; can have multiple channels; but behaves geometrically as straight guide element (mcdisplay, coordinates of subsequent elements)<br class=""><br class="">Guide_curved; only one reflectivity definition for all sides, geometrically correct definition<br class=""><br class="">polygon of Guide_gravity elements; allows for a polygonal approximation only, has numerous options<br class=""><br class="">Having a number of truly curved guides in my simulations I would prefer to have a component, which has the possibilities as it has Bender or Guide_gravity but is a geomentrical correct implementation of truly curved guide. If someone has done this or can tell me where I have overseen it, I would be grateful.<br class=""><br class="">Bets regards<br class=""><br class="">Peter<br class=""><br class=""><br class="">--<br class="">Dr. Peter Link<br class="">Leiter Neutronenoptik<br class="">Technische Universität München<br class="">Heinz Maier-Leibnitz Zentrum (MLZ)<br class=""><br class="">Lichtenbergstr. 1<br class="">85747 Garching<br class=""><br class="">Tel.: +49 (0)89 289 14622<br class="">Fax: +49 (0) 89 289 11694<br class=""><br class="">_______________________________________________<br class="">mcstas-users mailing list<br class=""><a href="mailto:mcstas-users@mcstas.org" class="">mcstas-users@mcstas.org</a><br class="">https://mailman2.mcstas.org/mailman/listinfo/mcstas-users<br class=""></blockquote><br class="">-- <br class="">Dr. Peter Link<br class="">Leiter Neutronenoptik<br class="">Technische Universität München<br class="">Heinz Maier-Leibnitz Zentrum (MLZ)<br class=""><br class="">Lichtenbergstr. 1<br class="">85747 Garching<br class=""><br class="">Tel.: +49 (0)89 289 14622<br class="">Fax: +49 (0) 89 289 11694<br class=""><br class="">_______________________________________________<br class="">mcstas-users mailing list<br class=""><a href="mailto:mcstas-users@mcstas.org" class="">mcstas-users@mcstas.org</a><br class="">https://mailman2.mcstas.org/mailman/listinfo/mcstas-users<br class=""></div></div></blockquote></div><br class=""><div class="">
<div style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; text-decoration: none;">Best regards / Mvh</div><div style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; text-decoration: none;"><br class=""></div><div style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; text-decoration: none;">Peter Willendrup</div><div style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; text-decoration: none;"><a href="mailto:pwillendrup@gmail.com" class="">pwillendrup@gmail.com</a></div><div style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><br class=""></div><br class="Apple-interchange-newline">
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