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