[mcstas-users] About Silicon analyzer

[Jesús P. de Vicente]

Dear Erik,

Thank you very much. I appreciate your help.
I would like to attach you the *.instr file and the *.lau file.

My objective is to simulate the backscattering reflections from the 111 and
311 peaks from silicon.

Thank you.
Kind regards.


*Jesús P. de Vicente.-*

2014-09-09 12:51 GMT+02:00 Erik Bergbäck Knudsen <erkn at fysik.dtu.dk>:

> Dear Jesus,
>
> I believe there could be something wrong with your definition of unit
> cell vectors for Si. For instance, in your case, the angle between a and
> b is 60 deg. which does not fit with the cubic structure that Si
> generally exhibits. I'm not sure about the lengths of the unit cell
> vectors either: |a| = 3.84 Å does not seem right.
>
> To simply exclude the .lau file from the crystal definition will have
> the effect of completely disregarding coherent scattering in the
> simulation - you will therefore only see the contribution from
> incoherent scattering, which is probably not what you intended.
>
> To tell you exactly what the _right_ way to use Single_crystal as an
> analyzer is very difficult, as there are many ways. We'd be happy to
> help you find the right way for you, but to do so, we will need more
> details on what it is you're actually trying to do. If you attach a copy
> of the .instr file and whatever extra files that are needed to run your
> simulation we may be able to help you accomplish your task.
>
> kind regards and happy simulating
> Erik B Knudsen
>
> On 09/08/2014 05:13 PM, Jesús P. de Vicente wrote:
> > Dear McStas team,
> >
> > I am trying to perform simulations with a silicon analyzer.
> >
> > I use the *Single_crystal* component. For graphite material everything
> > works fine:
> > // *PG* *************************
> >   mosaic = 48,
> >   reflections = "C_graphite.lau", barns=0,
> >   ax=0,      ay=2.14,   az=-1.24,
> >   bx = 0,    by = 0,    bz =  2.47,
> >   cx = 6.71, cy = 0,    cz =  0,
> >   sigma_abs = 0.014, sigma_inc = 0.004,
> > //**************************
> >
> > But I do not get to work with silicon material. I use the following
> syntax:
> > // *Si* *************************
> >  reflections = "Si.lau", barns=0,
> >  mosaic = 0.1, delta_d_d = 3.10e-4,
> >  sigma_abs = 0.171, sigma_inc = 0.004,
> >  ax = 2.715, ay = 2.715, az = 0.0,
> >  bx = 0.0, by = 2.715, bz = 2.715,
> >  cx = 2.715, cy = 0.0, cz = 2.715,
> > //**************************
> >
> > I built a Si.lau file from the a Si.cif file using Crystallographica
> > software.
> > I have tried lot of configurations, but I got always lot of peaks with
> > the backscatteing configuration. I tried also the simulation without the
> > reflection *.lau file but I have no peaks.
> >
> > Do you know what would be the right way to perform a simulation with a
> > silicon analyzer using the Single_crystal component?
> >
> > Thank you very much for your help.
> > Kind regards.
> >
> >
> >
> > *Jesús P. de Vicente.-*
> >
> >
> > _______________________________________________
> > mcstas-users mailing list
> > mcstas-users at mcstas.org
> > http://mailman.mcstas.org/cgi-bin/mailman/listinfo/mcstas-users
> >
>
> --
> Erik Bergbäck Knudsen, Research Engineer         | DTU | morituri
> NEXMAP, DTU Fysik, DK-2800 Kgs. Lyngby, Denmark  |<>-<>|    te
> phone: (+45) 2132 3151, mobile: (+45) 3123 6184  |<>-<>| salutant
>
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