[mcstas-users] curved guide

[Peter Link]

Hi Christoph,

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.

Best regards

Peter

Am 18.07.2019 um 14:07 schrieb Christoph Frommen:
> Dear Peter,
>
> 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.
> I am following a procedure described in by V.M. Pusenkov et all in "Nucl. Instrum. Meth. A 492 (2002) 105-116".
>
> 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.
>
> ------------------------------------------------------------
> *gLength: [m] length of individual guide pieces
> *gGap: [m] gap between guide pieces
> *gReflect0: guide reflectivity
> *gQc: [AA-1] critical wave vector
> *gAlpha : [deg] slope of reflectivity curve
> *gW, gH : [m] guide entrance/exit widths/heights
> *R_curv_m : [m] radius of curvature for bent guide section
>
> component bent_section_1 =  Guide_gravity(w1=gW, w2=gW, h1=gH, h2=gH, l=gLength,
> R0=gReflect0, Qc=gQc, alpha=gAlpha,
> m=2, nslit=3, d=0.0025) at (0, 0, gGap+gLength)
> relative previous rotated (0, gLength/R_curve_m*180.0/PI, 0) relative previous
> ---------------------------------------------------------------
>
> Maybe someone has a more elegant solution?
>
>
> Best regards
> Christoph
>
> -----Original Message-----
> From: mcstas-users <mcstas-users-bounces at mcstas.org> On Behalf Of Peter Link
> Sent: 18 July 2019 13:25
> To: mcstas-users at mcstas.org
> Subject: [mcstas-users] curved guide
>
> Dear friends,
>
> just to avoid some double developpment: to my knowlegde there are the following components or ways to simulate a standard curved neutron guide:
>
> 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)
>
> Guide_curved; only one reflectivity definition for all sides, geometrically correct definition
>
> polygon of Guide_gravity elements; allows for a polygonal approximation only, has numerous options
>
> 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.
>
> Bets regards
>
> Peter
>
>
> --
> Dr. Peter Link
> Leiter Neutronenoptik
> Technische Universität München
> Heinz Maier-Leibnitz Zentrum (MLZ)
>
> Lichtenbergstr. 1
> 85747 Garching
>
> Tel.: +49 (0)89 289 14622
> Fax: +49 (0) 89 289 11694
>
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-- 
Dr. Peter Link
Leiter Neutronenoptik
Technische Universität München
Heinz Maier-Leibnitz Zentrum (MLZ)

Lichtenbergstr. 1
85747 Garching

Tel.: +49 (0)89 289 14622
Fax: +49 (0) 89 289 11694