[mcstas-users] intercomparison between McStas and SIMRES

[Peter Willendrup]

Hello Tom, Jan,


I agree with Jan, you need to perform a scan in 2\theta. I have  
modified Tom's instrument slightly - optimizing it slightly - and  
performed the proposed scan. Please find attached both the  
instrumentfile and the resulting peak profile. It now looks much more  
like your result from SIMRES, but a bit more broad.

A closer study of SIMRES parameters in comparison to the McStas  
component parms will very likely resolve this discrepancy. As Jan also  
mentions, intensity agreement is a bit more complicated. :)


Best regards,

Peter Willendrup

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Peter Willendrup - Development engineer

RISØ DTU
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On 18/08/2009, at 16.14, Jan Saroun wrote:

> I am not an expert in using McStas, but I guess the McStas peak  
> profile has been obtained by the BananaTheta monitor. If so, it is  
> not the angular peak profile, which is measured by scanning the  
> detector angle (and which is simulated by SIMRES). Instead, you only  
> see the angular distribution of neutrons passing through the Soller  
> lamellae in front of the PSD. Instead, you need to make a scan by  
> the sample_out component angle in order to get equivalent results  
> and (hopefully) the same peak profiles.
>
> With SIMRES, you can either simulate the resolution function (as you  
> have done) or to make the THETA scan as suggested above. The results  
> are nearly the same (in contrast to the simulation speeds). I was  
> able to reproduce your results by both the methods.
>
> I am not worried about differences in absolute intensities at the  
> moment, as there are many issues to be checked first (e.g.  
> normalization of the resolution function or physical models used by  
> the two programs for the monochromator and sample components).



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