nuclear physics institute
DESCRIPTION
Detection of relativistic neutrons by BaF2 scintillators Simulation on MCNPX. Nuclear Physics Institute. Doctor V. Wagner Mitja Majerle Antonin Krasa Ondrej Svoboda. Ludovic BATTISTA. SETUP. 25 cm. 5.9 cm. view pz=3. view : py=0. Aluminium Separation. Description of the beam. - PowerPoint PPT PresentationTRANSCRIPT
Nuclear Physics Institute
Detection of relativistic neutrons by BaF2 scintillators
Simulation on MCNPX
Doctor V. WagnerMitja MajerleAntonin KrasaOndrej Svoboda
Ludovic BATTISTA
SETUP
view : py=0 view pz=3
5.9 cm
25 cm
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=2si1 h -10 10sp1 d 0 1si2 h -10 10sp2 d 0 1
sdef erg 600 dir 1 vec 0. 0. 1. rad d1 pos 0.0 0.0 -3.95 par n ccc=20si1 h 0 3.5sp1 -21 1
OR
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 = cylinder theofsection cross
cylinder in the BaF2 theofsection cross
2,95cm
25 cm
²34,27
27,21 2
cm
cm
σ = 77,8 %
tally type 1 number of neutrons crossing a surface 4.
energy e11 0 499.999999 500
0.0000E+00 0.00000E+00 0.0000 1.0000E-06 0.00000E+00 0.0000 4.9900E+02 4.13000E-02 0.0561 5.0000E+02 0.00000E+00 0.0000 5.0000E+02 1.00000E+00
tally type 1 number of neutrons crossing a surface 6.
energy e21 0 499.999999 500
0.0000E+00 0.00000E+00 0.0000 1.0000E-06 0.00000E+00 0.0000 4.9900E+02 1.66600E-01 0.0360 5.0000E+02 1.25400E-01 0.0264 5.0000E+02 2.79500E-01 0.0161
σ ≈ 30 %Set up view : py=0
BaF2 Cylinder view : pz=3
Determination of the amount of neutron passing through the detector without depositing energy
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 0.00000E+00 0.0000 4.0000E+02 2.31560E-01 0.0130 4.0000E+02 1.00000E+00 0.0000tally type 1 particle(s): neutron surface 311 energy e11 0
399.999999 400
0.0000E+00 0.00000E+00 0.0000 4.0000E+02 4.20900E-01 0.0079 4.0000E+02 3.02080E-01 0.0068
σ ≈ 30 %Setup view : py=0
Energy Deposition on Central Module
SHAPE OBTAINED BY F8 TALLY IS ACCEPTED
Shape of beam 400 MeV nps=5e5
Energy Deposition in Central Hexagone with Central Beam 400 MeV
0.0001
0.001
0.01
0.1
0 200 400 600
Energy bins (MeV)
Co
un
ts
Problem of Normalization ?
F8 tally DOES take into account particle passing through without depositing energy
tally type 1 particle(s): neutron surface 311 energy e11 0
399.999999 400
0.0000E+00 0.00000E+00 0.0000 4.0000E+02 4.20900E-01 0.0079 4.0000E+02 3.02080E-01 0.0068
tally type 8 particle(s): neutron surface 311 energy e11 0 1e-6
400
0.0000E+00 0.00000E+00 0.0000 1.0000E-06 2.95440E-01 0.0069 4.0000E+02 6.93760E-01 0.0030
F1
F8
Fig. 5 : ε=f(EKIN,LTHR)
Script : beam for (i=200, i<=1500, i=i+50)
Code : F8:n,e,p,h,/ 1E8: 0 1e-6 9 25 45 90 1500
Neutron efficiency of the BaF2 cluster detector for various values of the electronic threshold LTHR as a function of EKIN
Fig 5
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 500 1000 1500Ekin [MeV]
Eff
icie
nc
y
THR=0 MeV
THR=9 MeV
THR=25 MeV
THR=45 MeV
THR=90 MeV
Fig. 6 : ε=f(LTHR,EKIN)
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
Neutron efficiency of the BaF2 cluster detector for various incident neutron kinetic energies EKIN as a function of LTHR
Fig 6
0.1
1
0 10 20 30 40
THR [MeV]
Eff
icie
ncy
100 MeV150 MeV300 MeV500 MeV1200 MeV
0.1
1
0 20 40 60 80 100 120
Fig. 6 : ε=f(LTHR,EKIN)
Fig 6
0.1
1
0 10 20 30 40
THR [MeV]E
ffic
ien
cy
100 MeV
150 MeV
300 MeV
500 MeV
1200 MeV
0.1
1
0 20 40 60 80 100 120
Exponential Regression
0.1
1
0 50 100
Energy Thresholds [MeV]
Eff
icie
ncy
100 MeV150 MeV200 MeV250 MeV300 MeV350 MeV400 MeV450 MeV500 MeV550 MeV600 MeV650 MeV700 MeV750 MeV800 MeV850 MeV900 MeV950 MeV1000 MeV1050 MeV1100 MeV1150 MeV1200 MeVExpon. (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)Expon. (950 MeV)Expon. (1000 MeV)Expon. (1050 MeV)Expon. (1100 MeV)Expon. (1150 MeV)Expon. (1200 MeV)
Graph 20 : Exponential Regression of Fig. 6 for 23 different beams:
Exponential Regression of Fig. 6 for 23 different beams
BaF2 Efficiency ε0 by exponential regression
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 500 1000 1500
Neutron Energy Ekin [MeV]
Eff
icie
nc
y
MCNPXsimulation
ExperimentalResults
Slope λ by exponential regression
0
0.005
0.01
0.015
0.02
0.025
0.03
0 500 1000 1500Neutron Energy
Ekin [MeV]
slo
pe
λ (M
eV-1
)
MCNPXsimulation
experimentalresults
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,/ 1E8: 0 1e-6 80i 800
Shape of beam 400 MeV nps=5e4 -->
BERTINILCA J J J
Fig 4 Pulse Height Spectra with coefficents
0.00
0.01
0.10
0.00 200.00 400.00 600.00 800.00
L [MeV]
Co
un
ts
Ekin=200 MeV
Ekin=300 MeV
Ekin=400 MeV
Ekin=600 MeV
Ekin=800 MeV
X1,19 X1,43 X1,92
X2,29
Pulse Height Spectra with Bigger Coefficients
0.00
0.00
0.01
0.10
1.00
0 100 200 300 400 500 600 700
L [MeV]
Co
un
ts
Ekin=200 MeV
Ekin=300 MeV
Ekin=400 MeV
Ekin= 600 MeV
Ekin= 80 MeV
Fig 4
X1,36X1,82
X3,15
X5,15
BERTINILCA J J J
X3,15
Fig 4
Pulse Height Spectra using CEM2K model
Beam 600 MeV
CEMLCA 8J 1
manual extensionCoincidence counting of capture multiplicities and moments requires analog capture: CUT:N 2J0 0. Calculations must be totally analog, with no variance reduction. Fission multiplicity also isrequired: PHYS:N J 100 3J –1. An FT8 CAP tally in an input file automatically will set analogcapture, fission multiplicity, and exit with error messages if variance reduction is used. Thecapture multiplicities and moments are stored in 80 cosine bins, which are printed out with theF8 tally. A much more readable table of capture multiplicities and moments is given in PrintTable 118. The captures and moments can be compared with Print Table 117, which has thespontaneous-fission source and induced-fission summaries of fission neutrons and moments(Section 3.3.3).
Pulse Height Spectra using PHYS:N J 100 3J -1
beam 600 MeV
Fig 4
In output file : warning. f8 tally unreliable since neutron transport nonanalog
Dealing with 2ndary particles
BaF2 detector 3x bigger
Neutron beam 800 MeV
Neutron beam 800 MeV
BaF2 detector Delimitation
of free path
Dealing with 2ndary particles
Pulse height spectra for BaF2 cylinder with beam 800 MeV
0.00
0.01
0.10
1.00
0 200 400 600 800 1000
energy bins [MeV]
effic
ienc
y
Pulse height spectra for BaF2 cylinder 3x bigger with beam 800 MeV
0.00
0.01
0.10
1.00
0 200 400 600 800 1000
energy bins [MeV]
Effic
ienc
y
Adding the polyethylene box
Graph 15 : set up with polyethylene box.
View py = 0 View pz = - 2.05
pulse height spectrum simulated in BaF2 detector with polyethylene box infront, for
beam 600 MeV
0.0001
0.001
0.01
0.1
0 200 400 600 800 1000
Energy bins [MeV]
Co
un
ts
Graph 16 : pulse height spectra considering polyethylene box
pulse height spectrum simulated in BaF2 detector with polyethylene box infront, for
beam 800 MeV
0.0001
0.001
0.01
0.1
0 200 400 600 800 1000
Energy bins [MeV]
cou
nts
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
(a) central module (b) the whole cluster
Fig 7 : 300 MeV
(a) central module (b) the whole cluster
Fig 7 : 400 MeV
(a) central module (b) the whole cluster
Fig 7 : 800 MeV
(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