Date: Fri, 29 Sep 2023 14:04:08 +0300
Dear experts,
I am going to analyse W resonances using flow of neutrons
after Wnat foil : 0.2 mm width.
I want to define self-shielding corrections for this foil,
using FLUKA.
For this I do small experiment:
I analyze 2 W resonances for E-region : 2-9 eV (see fig-E-3-9-sigma.png)
-------------------
I introduce E bins with E-step = 0.010 eV
and for each Ebin I use rndm points with K= 1000 entries.
Each neutron starts from X=0,
Wnat foil is disposed at X=11 m
N counter is disposed at X= 13 m (to be close to some experiments ...)
Each E-point is translated into T-points according to the expression:
T= 72.29 * L / sqrt(E), (mks, m, eV)
replace air by VACUUM.
FLUKA suggests 2 variants of Wnat : ordinary and self-shielded, 300 K,
So, I run 2 jobs (2 cases) :
a) no shield, see W5.inp
------
b) WITH self-shielded W : W5sh.inp
---------
and use 5 cycles.
RESULTS
========
1) FLUKA *.out files does not show any comments about self-shielded mat.
see fig-FLUKA-T.png ,.... comparing 2 cases ===> no any differences
---------------
it looks like that FLUKA uses the same input data for both cases
..... or I missed something in self-shielding definition ?
2) I fill also my own array for E, T data using C4 counter
look at the entries for E- T- distributions:
fig-my-E-entry.png , fig-my-T-entry.png
------------------ ------------------
...there is no any difference for these 2 cases... why ?
3) Q: is it possible to define self-shielding resonance correction
using FLUKA ?
4) Q: ..or I should use the expression for capture flow after the foil: ?
Ycap = ( 1 -exp(-n*d*SIGtot) ) * SIGcap/ SIGtot
where expression in brackets can be treated as self-shielding
correction,
SIGtot - total cross section
SIGcap - capture cross section
n - atoms density, according to FLUKA it is equal to
6.3222E-02 ( at/(cm barn) )
d = 0.02 cm
---------------------------------
thank you,
sorry for the long e-mail
Vladimir
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(image/png attachment: fig-E-3-9-sigma.png)
(image/png attachment: fig-FLUKA-T.png)
(image/png attachment: fig-my-E-entry.png)
(image/png attachment: fig-my-T-entry.png)
- application/x-fluka attachment: W5.inp
- application/x-fluka attachment: W5sh.inp