Transcript hp.ujf.cas.cz

Simulations on
“Energy plus Transmutation”
setup, 1.5 GeV
Mitja Majerle, V Wagner, A Krása, F Křížek
[email protected]
This document can be downloaded in form of report at :
http://ojs.ujf.cas.cz/~mitja/articles/ept.pdf
What was studied ?
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INFLUENCE OF
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simplifications of the setup description
different parts of the setup
beam geometry
inserted detectors
reactions with protons
intra-nuclear cascade model used in calculations
PARAMETERS OF THE SETUP
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the number of produced neutrons (spallation, fission, ..)
k (criticality)
heat production ...
Code, setup parameters
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MCNPX 2.4.0
plots, photos of the setup will follow
estimation of some parameters
(aluminum shielding, density of polyethylene,
dimensions and material of holders, wooden
plates, nuclear structure, ..)

position of detectors (input data !)
Control detectors for studying the
setup
1E+00
1E-01
Nneutrons
1E-02
on the target
under Cd
outside box
1E-03
1E-04
1E-05
1E-06
1E-07
1E-10
1E-08
1E-06
1E-04
1E-02 1E+00 1E+02 1E+04
Energy [MeV]
- with (n,g) we study LE
neutrons (flat part) – odd
numbers
-(n,4n) threshold is 23 MeV –
even numbers
The simplifications of the blanket
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No influence
on high
energy
neutrons (even
numbers)
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Box has no
influence on
HE neutrons !
Box blurs
differences.
40%, 10%
Comparison of HE part of spectra
Polyethylene, Cd layer
1,15
1,1
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Last winter V Wagner presented
these spectra.
The spectra were taken inside
the 1st and 3rd gap.
No influence on HE neutrons.
Ratio
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1,05
w ith Cd/all
1
w ith box/all
0,95
0,9
0,85
0,1
1
10
100
1000
Neutron energy [MeV]
3rd gap, 3 cm from axis
1st gap, 3cm from axis
1E-01
1E-01
1E-02
1E-02
1E-03
1E-03
without Cd
without Cd
without box
1E-04
without box
whole_setup
whole_setup
1E-04
1E-05
1E-05
1E-06
1E-10
1E-06
1E-08
1E-06
1E-04
1E-02
1E+00
1E+02
1E+04
1E-07
1E-10
1E-08
absorption done by 238U
resonance capture
1E-06
1E-04
1E-02
1E+00
1E+02
1E+04
Aluminum and iron holders,
upper iron plate
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Two simulations with and
without Al, Fe components.
The results do not differ
outside the limits of
statistical error - (HE 3%, LE 10%)
The upper iron plate reduces
the number of neutrons for
2%.
The wooden plate
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Wooden plate under the
target(1+2cm,0.5kg/l).
Without box.
Detectors from top to
bottom.
Asymmetry 5% =>
negligible wood influence.
5E-5
4E-5
Production rate

3E-5
Au-198
Au-194
2E-5
1E-5
0E+0
-10
-5
0
Radial foil position [cm]
5
10
Beam parameters influence
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Beam profile is approximated with Gaussian
distribution (good only near the beam center !).
We must always count with beam displacement.
Experimentally determined beam profiles and
displacement (V Wagner using monitor and track
detector data – for profile mainly I Zhuk data):
Experiment
(Energy)
Beam
integral
[1013]
700 MeV
1 GeV
1.5 GeV
2.0 GeV
1.47(5)
3.40(15)
1.14(6)
1.25(6)
Beam
integral
on lead
target
[1013]
1.04(8)
3.25(14)
1.10(5)
1.07(10)
FWHM
(vertical)
[cm]
FWHM
(horizontal)
[cm]
5.91(21)
4.1(3)
3.7(5)
5.4(3)
same
2.5(3)
2.4(5)
3.8(3)
Fraction Position
Position
of beam (vertical) (horizontal)
outside
[cm]
[cm]
Pb target
[%]1)
< 27
-0.4(9)
0.2(2)
<6
0.2(2)
0.0(2)
<6
0.1(2)
0.3(2)
<20
0.3(2)
-1.4(2)
Beam profile
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6
4
beam/3cm-1 (in %)
2
0
1
2
3
4
5
6
7
-2
8
9
10
3mm/3cm-1
gauss/3cm-1
-4
-6
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-8
-10
Foil and reaction number

Simulations with
3mm, 3cm
homogenous beams
and with a beam with
gaussian profile
(FWMH=3cm).
Differences only for
few percents.
Not important.
Beam displacement

Beam displaced for
3,5,8, and 10 mm.
Differences between
results up to tens of %
Displacement must be
measured as accurately
as possible !
70
Displaced beam/center beam-1 (in %)

60
50
3 mm
5 mm
8 mm
10 mm
40
30
20
10
0
1
2
3
4
5
6
Foil and reaction
7
8
9
10
Beam hits uranium
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Badly focused beam also
hits uranium blanket.
The influence of few
percents of beam hitting
uranium was not seen in
simulations.
Gaussian distribution is not
valid for the tails and in
reality we don’t know how
much big is this influence.
The influence of protons
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Activation detectors could also be
activated by protons.
Cross-sections for reactions with
protons are not included in MCNPX.
Estimations from Phasotron experiment
and neutron/proton ratio : in gaps, near
the central axis ca. 10% of activation is
due to protons.
The influence of detectors on
neutron field
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Metal plate on top reduces the number of
neutrons only for 2%. Our detectors are
much smaller.
Golden strap (2mm, 4mm) in the first gap has
no influence on detectors in other gaps.
Only 0.1 mm thick golden strap is an obstacle
for thermal neutrons : it can reduce the
production rates of reactions with thermal
neutrons inside the same gap for 20%.
The influence of plastic foils for
detectors on neutron field
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The 4mm and 8mm
polyethylene on
which were placed
the detectors for 1.5
GeV experiments
had effect on LE
neutrons.
Au in sandwich of 2
Bi foils => no
influence.
1E+0
1E-1
1E-2
1E-3
nothing
1E-4
4mm polyeth foil
full poly
1E-5
1E-6
1E-7
1E-8
1E-10
1E-7
1E-4
1E-1
1E+2
1E+5
Intra-Nuclear Cascade models
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In MCNPX are 3 models (above 150 MeV):
Bertini
CEM
Isabel
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The differences are up to 50% (standard, our detectors).
30
60
25
50
40
-10
8
9
10
0
-10
-15
-20
-20
-30
-25
-40
Foil and reaction
Foils and reactions of the Rez group
61
7
56
6
51
5
46
4
41
3
36
2
31
1
26
-5
CEM/BERTINI-1
ISABEL/BERTINI-1
10
21
0
20
16
cem
isabel
11
5
30
6
10
1
15
model/BERTINI-1 (in %)
model/bertini-1 (in %)
20
Neutrons per proton,
criticality,..
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Experimentally we cannot
measure these.
For 1.5 GeV experiment,
neutron production :
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29 in nuc. Interactions
8 in (n,xn)
14 prompt fission.
Together 54 neutrons per 1
proton.
Without box 49 neutrons,
box reflects back 10% of them.
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KCODE calculations for
criticality :
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k=19.2%
k was calculated also by
S.R. Hashemi-Nezhad 22%.
If we add polyethylene
wall at the back, k stays
the same.
Comparison with experiment

The Greek group
measures the ratios
of neutrons inside
and outside the box.
Calculated results do
not agree with
experiment.
1E+00
1E-01
1E-02
Nneutrons

on the target
under Cd
outside box
1E-03
1E-04
1E-05
1E-06
1E-07
1E-10
1E-08
1E-06
1E-04
1E-02 1E+00 1E+02 1E+04
Energy [MeV]
Density of polyethylene ?
density 0.7 kg/l
1E+0
1E+0
1E-1
1E-1
1E-2
1E-2
on the target
under Cd
outside box
1E-3
1E-4
Nneutrons
Nneutrons
density 0.35kg/l
1E-4
1E-5
1E-5
1E-6
1E-6
1E-7
1E-7
1E-10
on the target
under Cd
outside box
1E-3
1E-8
1E-6
1E-4
1E-2
Energy [MeV]
1E+0
1E+2
1E+4
1E-10
1E-8
1E-6
1E-4
1E-2
Energy [MeV]
1E+0
1E+2
1E+4
Group from Poland
Radial
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No comparison with
experiment yet.
Cross-sections only for
2 reactions (+2 stable
isotopes).
Y detectors at places :
1.00E-04
n,gamma
1.00E-05
n,2n
1.00E-06
1
2
3
4
5
Longitudinal
1.00E-04
The numbers on the drawings agree witch those in table 1.
7
2
5
6
4
8
3
1.00E-05
11
9
10
n,gamma
n,2n
1
1
1.00E-06
2
3
4
5
1.00E-07
1
2
3
4
5
Group from Řež
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4 detector types
A lot of cross-section
libraries
Trends in ratios
experiment/simulation
are seen
3 GeV experiment
would confirm these
trends
194Au
196Au
2.5
2.5
a)
b)
2.0
2.0
1.5
exp/sim
exp/sim
Longitudinal distribution
Comparison between experiment and simulations
1.0
1.0
0.5
0.5
Au194 1.0 GeV
0.0
-10
Au194 1.5 GeV
Au194 0.7 GeV
0
10
20
30
40
Position along the target X [cm]
Au196 1.0 GeV
0.0
-10
50
2.5
Au196 1.5 GeV
Au196 0.7 GeV
0
10
20
30
40
Position along the target X [cm]
50
2.5
c)
d)
2.0
2.0
exp/sim
exp/sim
Radial distribution
1.5
1.5
1.0
0.5
1.5
1.0
0.5
Au194 1.0 GeV
Au194 1.5 GeV
Au194 0.7 GeV
0.0
Au196 1.0 GeV
0.0
0
5
10
15
Radial distance from the target axis R [cm]
0
Au196 1.5 GeV
Au196 0.7 GeV
5
10
15
Radial distance from the target axis R [cm]
Experiment: Ep = 1.5 GeV
0.7 GeV, 1.0 GeV - the similar shape of radial distribution
for experiment and simulation
1.5 GeV -different shape of radial distribution
for experiment and simulation
Clear dependence on reaction energy threshold ↔ on the neutron energy
Radial direction
Longitunidal direction
6
2.5
6 MeV
2
8 MeV
11 MeV
23 MeV
23 Mev
1.5
1
24Na
196Au
194Au
206Bi
58Co
EXP/CEM
EXP/CEM
23 MeV 23 MeV
11 MeV
5
24Na
4
8 MeV
3
196Au
194Au
206Bi
2
6 MeV
0.5
58Co
1
0
0
10
20
30
40
50
l [cm]
60
0
0
5
10
15
r [cm]
ratios normalized on first foil
Longitudinal distribution – small differences, maybe done by not included protons
Radial distribution – big differences, description is worse for neutrons with higher energy
Radial distribution for 0.7 GeV and 1.0 GeV
Radial distribution 1.0 GeV
1.50
1.40
1.30
1.20
1.10
1.00
0.90
0.80
0.70
1.50
1.40
1.30
196Au
194Au
EXP/SIM
EXP/SIM
Radial distribution 0.7 GeV
1.20
196Au
1.10
194Au
1.00
0.90
0.80
0.70
0
2
4
6
8
10
12
0
2
4
6
Conclusions:
1)
2)
8
10
12
r [cm]
r [cm]
Very small differences of shape
Maybe increase with energy?
Necessary systematic of experiments with different beam energy
Dependence of EXP/SIM ratios for first
radial foil on beam energy
1.2
EXP/SIM
1
Very important: 1) To analyze 2 GeV experiment
2) To make 3 GeV experiment
0.8
196Au
0.6
194Au
0.4
0.2
0
0
500
1000
Beam energy [GeV]
1500
2000