[neutron-mc] detector output files

[Emmanuel Farhi]

Hello Timur,

When you simulate -n 1e6 neutrons, these are not exactly neutrons, but neutron packs, associated to a
weight which is given usually by the source. The weight IS the intensity. DO NOT use the number of
events. It has NOTHING to do with the neutron flux or intensity, nor with the transmission. The
'strange units' you are talking are the intensities.
If you want to simulate the transmission, place a monitor before and after a section, and look for the
intensity ratio (not N).

Bye, Emmanuel.


Timur Elzhov wrote:

> On Thu, Jul 31, 2003 at 12:26:47PM +0200, Emmanuel Farhi wrote:
>
> > The 'N' data has no physical sense. It is a number of simulation events
> > for a given data bin. You basically should not use that data, except if
> > you wish to study the simulation statistics and efficiency (see Manual, p
> > 41).
> > In McStas, a simulation event may be regarded as a pack of neutrons,
> > containing 'p' particules. When this event propagates, its 'filling'
> > decreases, and the total weight of the pack is the intensity 'I' when
> > stored in monitor bins, even if the event is still there (and counts for
> > '1' in 'N').
> OK! Bu, let's have a look at the exec string of my program:
>
>     ./dn2-guide.out --ncount=1e+06   S=3.0  R0=1.00 ...
>
> and at the output:
>
>     Detector: detect_inc_I=6.77255e+09 detect_inc_ERR=1.1166e+07 detect_inc_N=999931 "inc0003.0.dat"
>     Detector: detect_out_I=1.98277e+08 detect_out_ERR=856286 detect_out_N=446104 "out0003.0.dat"
>
> "detect_inc" is detector at the guide entrance, and all the incoming neutrons
> are directed to them. But, "detect_inc_N" is likely to correspond to the total
> counts of neutrons, not "detect_inc_I". "detect_inc_I" expressed in the
> strange units and have values of order of 7-8, while I've simulated 1e+6
> neutrons... I obviosly misunderstand something, excuse me please :-)
>
> --
> WBR,
> Timur.
>
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--
What's up Doc ?
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Emmanuel FARHI, http://www.ill.fr/tas/people/Farhi.html   \|/ ____ \|/
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