Dear Vladimir,
you want to get the total outgoing yield of neutrons from the target
but in the USRBDX you are scoring Fluence and not Current.
Fluence will be normalized with the cosine of the direction vs surface normal
and this is not what you want.
USRYIELD with the proper normalization should give you identical results
with USRBDX
Making a fast test with your input and using current I get a value of 80
close to your measured one.
Vasilis
________________________________________
From: owner-fluka-discuss_at_mi.infn.it [owner-fluka-discuss_at_mi.infn.it] on behalf of babintsev [babintsev_at_ihep.ru]
Sent: Tuesday, January 15, 2019 13:35
To: fluka-discuss_at_fluka.org
Subject: [fluka-discuss]: Neutron output - big difference in results
Dear experts,
I need to get total number of neutrons from the body (lead)
to compare FLUKA results with those published in articles.
For this I use 2 cards : USRBDX and USRYIELD
I observed that output of N total is very different
and depends on the size of taget !
I have got the following results for the "small" geometry:
Tuto-lead-3.5.inp
Lead, R= 5 cm, L = 9 cm, beam - P , E= 3.5 GeV
-----------------------------------------------
*) USRBDX: N Fl from Pb into Air : Area: 1 cmq,
Tot. resp. (Part/cmq/pr) 27.26922 +/- 0.5661705 %
( --> (Part/pr) 27.26922 +/- 0.5661705 % )
*) USRYIELD: Fl from Pb into Air : linOmega LogE (0-5)
Tot. response (integrated over x1) 3.654836 +/- 0.7171366 %
( --> Tot. response without normaliz. 3.654836 +/-
0.7171366 % )
Ntot= 3.654836 * 5 = 18.27418
*) USRYIELD: Fl from Pb into Air : LogE LinOmega (0-4pi)
Tot. response (integrated over x1) 1.819517 +/- 0.7171366 %
( --> Tot. response without normaliz. 1.819517 +/- 0.7171366 % )
Ntot= 1.819517 *4*3.14156 = 22.864487
------------------------------------------------------
Then I use bigger volume :
accoring to the article: N.SOBOLEVSKY :
"Monte Carlo Calculation of Neutron Yield from Extended
Iron and Lead Targets Irradiated by 1 and 3.65 GeV/u Ion Beams"
where for Ep = 3.5 GeV Ntotal = 65 - 77 neutrons
----------------
So, I use :
Lead, R= 10 cm, L = 60 cm, beam - P , E= 3.5 GeV --
Tuto-lead-3.5-Big.inp
-----------------------------------------------
Results:
*) USRBDX: N Fl from Pb into Air : area = 1
Tot. resp. (Part/cmq/pr) 125.0001 +/- 0.2880751 %
( --> (Part/pr) 125.0001 +/- 0.2880751 % )
*) USRYIELD: N Fl from Pb into Air : linOmega LogE (0-5)
------------------
Tot. response (integrated over x1) 16.10910 +/-
0.2112415 %
( --> Tot. response without normaliz. 16.10910 +/- 0.2112415
Ntot = 16.10910 * 5 = 80.545
*) USRYIELD: N Fl from Pb into Air : LogE LinOmega (0-4pi)
Tot. response (integrated over x1) 8.019730 +/-
0.2112417 %
( --> Tot. response without normaliz. 8.019730 +/- 0.2112417
Ntot = 8.019730 *4*3.14156 = 100.777
---------------------------------------
Questions:
- are there large leakage from "small" target even for this
small energy ?
- the presented results are very different from the published ones.
How to get "right" number of the output neutrons from a body
with FLUKA ?
Summary: measured N : 70 +- 7
simulated : a) 125
b) 80
c) 100
thank you
Vladimir
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Received on Fri Jan 18 2019 - 12:33:36 CET