[mcstas-users] intercomparison between McStas and SIMRES

[Jan Saroun]

Dear Tom,

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).

All the best,
Jan

wokaoyan1981 wrote:
>
> Hello colleagues,
>
> SIMRES, a new program for neutron ray-tracing simulations, is now 
> available at http://neutron.ujf.cas.cz/restrax/. It¡¯s capable of 
> simulating any user-defined instrument layout such as strain 
> diffractometer, three-axis spectrometer equipped with advanced 
> components like focusing crystals (both mosaic and elastically 
> deformed), radial collimators, benders. etc.
>
> In order to test reliability of the code, a strain scanner is 
> simulated by SIMRES and McStas respectively. (See enclosure) The 
> results show intensities and resolutions are distinct.(Peak 
> reflectivity r0 for McStas is calculated by NOP). Will anyone explain 
> the difference?
>
> 	
>
> Intensity / s^-1
>
> 	
>
> FWHM / ¡ã
>
> 	
>
> Deviation (84¡ã) / ¡ã
>
> SIMRES
>
> 	
>
> 10.980
>
> 	
>
> 0.71087
>
> 	
>
> 0.0074441
>
> McStas
>
> 	
>
> 108.959
>
> 	
>
> 0.23471
>
> 	
>
> -0.003
>
> Best wishes,
>
> Tom
>
>

-- 
-----------------------------------------
Dr Jan Saroun 
Nuclear Physics Institute
Academy of Sciences of the Czech Republic
25068 Rez near Prague
phone: 420-2-66173140 phone/fax: 420-2-20940141
mailto:saroun at ujf.cas.cz


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman2.mcstas.org/pipermail/mcstas-users/attachments/20090818/5dd37dfa/attachment.html>