[mcstas-users] split neutron into component

[Santiago Miguel Gómez]

On Fri, May 12, 2017 at 1:53 PM, Kim Lefmann <lefmann at nbi.ku.dk> wrote:

> Hi Santiago,
>
> The short answer is that SPLIT is meant to function at the instrument
> level, e.g. for users that will not need to worry about programming
> components themselves.
>
> To make a SPLIT inside a component, much more bookkeeping is needed, in
> particular for the fractional rays that would emerge in the middle of a
> component, and this has only been imagined and never implemented (Peter may
> correct me here if some test fragments exist?).
>
> However, most of the computational work done by the simulation at (almost)
> any given point in the instrument lies in all the rays that were lost
> earlier in the simulation, e.g. in the guide system, the slits, the
> monochromator, and so on. Therefore, in most cases not much actual running
> time would be gained by an in-component SPLIT compared to the existing
> instrument-level SPLIT. This analysis is roughly what lies behind the fact
> that the in-component SPLIT has never been implemented.
>
> best, Kim
>
>
> On 05/12/2017 06:31 PM, Santiago Gómez wrote:
>
>> Hello
>>
>> I would like to split a neutron inside component.
>>
>> As far I see it is possible to split a neutron that reaches a specific
>> component using the SPLIT macro before the component declaration in the
>> instrument file, but it cannot be used inside de component.
>>
>> I would prefer to split the neutron inside my component because if I do
>> the SPLIT outside, a series of calculations already done be my components
>> will be redundant (I would say more than 50% of all the calculation of the
>> component).
>>
>> The idea of the split is to do a variance reduction which optimizes the
>> time, so for my component will be much more better to do that inside the
>> component code.
>>
>> Is it possible to performs it? I think that a similar issue is the
>> possibility to have more than one source component in a single instrument
>> file.
>>
>> Best regards
>>
>>
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-- 
Santiago Miguel Gómez

Si queremos un mundo de paz y de justicia hay que poner decididamente
la inteligencia
al servicio del amor. Antoine de Saint-Exupery
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