From: Anna Ferrari <anna.ferrari_at_lnf.infn.it>

Date: Mon, 6 Jun 2011 13:34:44 +0200 (CEST)

Received on Mon Jun 06 2011 - 17:33:20 CEST

Date: Mon, 6 Jun 2011 13:34:44 +0200 (CEST)

Dear Ertan,

first of all thank you for having resent the summary file of your results

(I put it in attachment).

You wanted to calculate the number of positrons exiting your target.

You correctly did it using two different estimators:

a) with the USRYIELD card you estimated the particle yield calculated

respect to the beam direction, expressed as double differential

distribution (in energy and in solid angle in your case);

b) with the USRBDX card, choosing the scoring of the current you computed

the same quantity, as double differential distribution in energy and in

solid angle and calculated respect to the normal to the boundary surface.

After having run FLUKA you gave the FLUKA output files in input to the

corresponding post-processing programs to finally obtain the summary

output files ([]_tab.lis, []_sum.lis) with the computed distributions.

You have to take care because there are done some integrations.

Let's concentrate only on the total responses.

You must observe (it is written in the []_sum.lis file) that while the

USRYIELD results for the total response have been integrated in energy and

mantained as differential in angle (even if you used a sigle angular

bin they are always given "per steradian"), the USRBDX results are

integrated in energy and in angle (they are given both as "part/cm2 per

primary" and as "part per primary", but not anymore "per steradian").

Results from a) and b) in your []_sum.lis file have therefore a different

normalization.

Total responses from a) are given in part/sr per primary particle.

You get: 1.594 E-2 part/sr per primary.

To obtain the fully integrated total response you have still to integrate

over the solid angle, that for you is 4pi (you considered 1 bin in solid

angle:(0,pi) ).

Then you get 0.200377 particles per primary that is exactly the result in b)

after the integration over the boundary surface.

-----

I saw that you used also the USRBDX card with the fluence scoring. The

fluence estimator has a different physical meaning: you weight in this

case each exiting positron with 1/cos(theta) (where theta is the angle of

the positron track respect to the normal to the boundary surface) because

the fluence at the boundary surface is the density of particle tracks in

an infinitesimal thickness at that boundary (see the first pages of:

https://www.fluka.org/free_download/course/heidelberg2011/Lectures/Scoring0311.pdf

useful also for a comparison of all the estimators).

In this case you obtain therefore a total response a bit higher then in

the case of current scoring (you would obtain the same results only if all

the positron tracks were exiting perpendicularly to the surface).

Hope it helps,

bests regards,

Anna

-------------------------------------

Anna Ferrari

Helmholtz-Zentrum Dresden-Rossendorf

01314 Dresden (Germany)

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*> Hi Fluka experts
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*>
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*> I want to learn relationship between the usrbdx and usryield results
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*>
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*>
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*> in my work the electrons hit on the target and I try to find some
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*> information about the positrons after the target (for example number of
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*> positron etc)
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*>
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*> So I obtained some results but I cannot interpreted
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*>
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*> I remember that the usrbdx and usryield results should be compatible
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*> is it true
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*>
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*> My results attached
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*> May you help me please about the my usrbdx and usryield results
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*>
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*> Thank you so much for your help
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*>
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*> Ertan ARIKAN
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*>
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- text/plain attachment: bdx_and_yield_results

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