Transcript Nuclear Physics Institute

Nuclear Physics Institute
Doctor V. Wagner
Mitja Majerle
Antonin Krasa
Ondrej Svoboda
Detection of relativistic neutrons by BaF2 scintillators
Simulation on MCNPX
Ludovic BATTISTA
SETUP
25 cm
5.9 cm
view : py=0
view pz=3
Aluminium Separation
Description of the beam
sdef erg 600 dir 1 vec 0. 0. 1. x=d1 y=d2 z=-3.95 par n ccc=2
si1 h -10 10
sp1 d 0 1
si2 h -10 10
sp2 d 0 1
OR
sdef erg 600 dir 1 vec 0. 0. 1. rad d1 pos 0.0 0.0 -3.95 par n ccc=20
si1 h 0 3.5
sp1 -21 1
TALLY Selection
●
F6 : Energy deposition over a cell (in MeV/g)
secondary particles are not taken into account.
●
*F8 : energy deposition created in a detector (in MeV)
not a spectra
●
F8 : Energy distribution of pulses, created in a detector
by radiation (in pulses)
Take into account secondary particles.
Determination of the amount of neutron passing
through the detector without depositing energy
σ=
cross sectionof theBaF2 in thecylinder
cross sectionof thecylinder
21,27cm2

27,34cm²
2,95cm
σ = 77,8 %
25 cm
Determination of the amount of neutron passing
through the detector without depositing energy
tally type 1
number of neutrons
crossing a surface 4.
energy e11 0 499.999999 500
0.0000E+00
1.0000E-06
4.9900E+02
5.0000E+02
5.0000E+02
0.00000E+00
0.00000E+00
4.13000E-02
0.00000E+00
1.00000E+00
0.0000
0.0000
0.0561
0.0000
tally type 1
number of neutrons
crossing a surface 6.
energy e21 0 499.999999 500
BaF2 Cylinder
view : pz=3
0.0000E+00
1.0000E-06
4.9900E+02
5.0000E+02
5.0000E+02
Set up view : py=0
0.00000E+00
0.00000E+00
1.66600E-01
1.25400E-01
2.79500E-01
σ ≈ 30 %
0.0000
0.0000
0.0360
0.0264
0.0161
Determination of the amount of neutron passing
through the detector without depositing energy
F1 : current integrated over a surface (in particles)
tally type 1 particle(s): neutron
surface 31
energy e1 0 399.999999 400
0.0000E+00
4.0000E+02
4.0000E+02
0.00000E+00 0.0000
2.31560E-01 0.0130
1.00000E+00 0.0000
tally type 1 particle(s): neutron
surface 311
energy e11 0 399.999999 400
0.0000E+00
4.0000E+02
4.0000E+02
Setup view : py=0
0.00000E+00 0.0000
4.20900E-01 0.0079
3.02080E-01 0.0068
σ ≈ 30 %
Energy Deposition
on Central Module
Shape of beam 400 MeV nps=5e5
Counts
Energy Deposition in Central Hexagone
with Central Beam 400 MeV
0.1
0.01
0.001
0.0001
0
200
400
600
Energy bins (MeV)
SHAPE OBTAINED BY F8 TALLY IS ACCEPTED
Problem of Normalization ?
F8
tally type 8 particle(s): neutron
surface 311
energy e11 0 1e-6 400
0.0000E+00
1.0000E-06
4.0000E+02
F1
0.00000E+00 0.0000
2.95440E-01 0.0069
6.93760E-01 0.0030
tally type 1 particle(s): neutron
surface 311
energy e11 0 399.999999 400
0.0000E+00
4.0000E+02
4.0000E+02
0.00000E+00 0.0000
4.20900E-01 0.0079
3.02080E-01 0.0068
F8 tally DOES take into account particle
passing through without depositing energy
Fig. 5 : ε=f(EKIN,LTHR)
Efficiency
Neutron efficiency of the BaF2 cluster detector for various values of the
electronic threshold LTHR as a function of EKIN
Fig 5
1
0.9
0.8
THR=0 MeV
0.7
THR=9 MeV
0.6
THR=25 MeV
0.5
THR=45 MeV
0.4
THR=90 MeV
0.3
0.2
0.1
Ekin [MeV]
0
500
1000
1500
Script : beam for (i=200, i<=1500, i=i+50)
Code :
F8:n,e,p,h,/ 1
E8: 0 1e-6 9 25 45 90 1500
Fig. 6 : ε=f(L ,E )
THR
KIN
Neutron efficiency of the BaF2 cluster detector for various incident
neutron kinetic energies EKIN as a function of LTHR
Fig 6
Efficiency
THR [MeV]
1
0
10
20
30
40
1
0
20
40
60
80
100
120
100 MeV
150 MeV
300 MeV
500 MeV
1200 MeV
0.1
0.1
Script : beam for (i=200, i<=1500, i=i+50)
Code : F8:n,e,p,h,/ 1
E8: 0 1e-6 9 25 45 90 1500
Fig 6
Efficiency
THR [MeV]
1
0
10
20
30
40
100 MeV
150 MeV
300 MeV
1
500 MeV
0
1200 MeV
0.1
Fig. 6 : ε=f(LTHR,EKIN)
0.1
20
40
60
80
100
120
Exponential Regression
Efficiency
1
0
50
100
Graph 20 : Exponential Regression of Fig. 6 for 23
different beams:
0.1
Exponential Regression of Fig. 6
for 23 different beams
100 MeV
150 MeV
200 MeV
250 MeV
300 MeV
350 MeV
400 MeV
450 MeV
500 MeV
550 MeV
600 MeV
650 MeV
700 MeV
750 MeV
800 MeV
850 MeV
900 MeV
950 MeV
1000 MeV
1050 MeV
1100 MeV
1150 MeV
1200 MeV
Expon. (200 MeV)
Expon. (250 MeV)
Expon. (300 MeV)
Expon. (350 MeV)
Expon. (400 MeV)
Expon. (450 MeV)
Expon. (500 MeV)
Expon. (550 MeV)
Expon. (600 MeV)
Expon. (650 MeV)
Expon. (700 MeV)
Expon. (750 MeV)
Expon. (800 MeV)
Expon. (850 MeV)
Expon. (900 MeV)
0.7
0.6
0.5
0.4
MCNPX
simulation
Experimental
Results
0.3
0.2
0.1
0
0
500
1000
1500
Neutron Energy
Ekin [MeV]
Slope λ by exponential regression
slope λ (MeV-1)
Energy Thresholds [MeV]
Efficiency
BaF2 Efficiency ε0
by exponential regression
0.03
0.025
0.02
MCNPX
simulation
0.015
experimental
results
0.01
0.005
0
0
500
1000
1500
Neutron Energy
Ekin [MeV]
Fig. 4 : δ=f(EKIN)
Pulse height spectra measured with the BaF2 cluster detector for
neutrons with kinetic energies EKIN =200, 300, 400, 800 MeV
Script :
beam for i in 200 300 400 800
Code : F8:n,e,p,h,/ 1
E8: 0 1e-6 80i 800
Shape of beam 400 MeV nps=5e4 -->
Fig 4
Pulse Height Spectra with coefficents
L [MeV]
200.00
400.00
600.00
800.00
Counts
0.10
0.00
X2,29
0.01
X1,19
Ekin=200
Ekin=300
Ekin=400
Ekin=600
Ekin=800
0.00
MeV
MeV
MeV
MeV
MeV
X1,43
X1,92
BERTINI
LCA J J J
Pulse Height Spectra with Bigger Coefficients
Fig 4
1.00
0
100
200
300
400
500
600
700
0.10
Counts
X5,15
0.01
X3,15
X3,15
X1,82
X1,36
Ekin=200 MeV
0.00
Ekin=300 MeV
Ekin=400 MeV
Ekin= 600 MeV
Ekin= 80 MeV
0.00
L [MeV]
BERTINI
LCA J J J
Pulse Height Spectra
using
CEM2K model
Pulse Height Spectra
using CEM
model
Beam
600
MeV
Beam 600 MeV
L [MeV]
Counts
0.10
0
100
200
300
400
500
600
700
Fig 4
0.01
0.00
CEM
LCA 8J 1
beam 600 MeV
0.10
0
100
200
300
400
500
600
700
Pulse Height Spectra using
PHYS:N J 100 3J -1
beam 600 MeV
Counts
0.01
0.00
0.00
L [MeV]
In output file : warning.
Fig 4
f8 tally unreliable since neutron transport nonanalog
manual extension
Coincidence counting of capture multiplicities and moments requires analog capture: CUT:N 2J
0 0. Calculations must be totally analog, with no variance reduction. Fission multiplicity also is
required: PHYS:N J 100 3J –1. An FT8 CAP tally in an input file automatically will set analog
capture, fission multiplicity, and exit with error messages if variance reduction is used. The
capture multiplicities and moments are stored in 80 cosine bins, which are printed out with the
F8 tally. A much more readable table of capture multiplicities and moments is given in Print
Table 118. The captures and moments can be compared with Print Table 117, which has the
spontaneous-fission source and induced-fission summaries of fission neutrons and moments
(Section 3.3.3).
Dealing with 2ndary particles
BaF2
detector
Neutron beam
800 MeV
Neutron beam
800 MeV
Delimitation
of free path
BaF2
detector
3x bigger
Dealing with 2ndary particles
Pulse height spectra for BaF2 cylinder 3x
bigger with beam 800 MeV
Pulse height spectra for BaF2 cylinder with
beam 800 MeV
1.00
efficiency
0
0.10
200
400
600
800
1000
Efficiency
energy bins [MeV]
energy bins [MeV]
1.00
0
0.10
0.01
0.01
0.00
0.00
200
400
600
800
1000
Adding the polyethylene box
Graph 15 : set up with polyethylene box.
View py = 0
View pz = - 2.05
Graph 16 : pulse height spectra considering polyethylene box
pulse height spectrum simulated in BaF2
detector with polyethylene box infront, for
beam 800 MeV
pulse height spectrum simulated in BaF2
detector with polyethylene box infront, for
beam 600 MeV
0
200
400
600
800
1000
Counts
counts
0.1
Energy bins [MeV]
0.1
0
0.01
0.01
0.001
0.001
0.0001
Energy bins [MeV]
0.0001
200
400
600
800
1000
Fig 7 :
pulse height spectra observed in
(a) central module
(b) the all cluster
Central hits selected by the condition that the maximum
signal occurs in the central module
Fig 7 : 200 MeV
L [MeV]
Counts
1.E-01
0
100
200
300
400
1.E-02
Ekin=200 MeV
1.E-03
central
whole cluster
(a) central module
(b) the whole cluster
Fig 7 : 300 MeV
L [MeV]
Counts
1.E-01
0
100
200
300
400
1.E-02
Ekin=300 MeV
1.E-03
central
whole cluster
(a) central module
(b) the whole cluster
Fig 7 : 400 MeV
L [MeV]
Counts
1.E-01
0
100
200
300
400
500
1.E-02
1.E-03
1.E-04
Ekin=400 MeV
1.E-05
central
whole cluster
(a) central module
(b) the whole cluster
Fig 7 : 800 MeV
L [MeV]
Counts
1.E-01
0
200
400
600
800
1000
1.E-02
1.E-03
Ekin=800 MeV
1.E-04
central
whole cluster
(a) central module
(b) the whole cluster
Conclusions
●
●
MCNPX cannot describe “maximum signal
occurs in the central module”
MCNPX code is designed for integral quantities
determination , doesn’t take into account dead
time of detector.
THANK YOU FOR YOUR ATTENTION