1. Nuclear Physics Institute Detection of relativistic neutrons by BaF2 scintillators Simulation on MCNPX Doctor V. Wagner Mitja Majerle Antonin Krasa Ondrej Svoboda Ludovic BATTISTA

2. SETUP view : py=0 view pz=3 5.9 cm 25 cm

3. Aluminium Separation

4. 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 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 OR

5. 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.

6. Determination of the amount of neutron passing through the detector without depositing energy σ = 2,95cm 25 cm σ = 77,8 %

7. 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

8. 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 0.0000 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 σ ≈ 30 % Setup view : py=0

9. Energy Deposition on Central Module SHAPE OBTAINED BY F8 TALLY IS ACCEPTED Shape of beam 400 MeV nps=5e5

10. 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

11. Fig. 5 : ε=f(E KIN,L THR ) 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 values of the electronic threshold L THR as a function of E KIN

12. Fig. 6 : ε=f(L THR,E KIN ) 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 E KIN as a function of L THR

13. Fig. 6 : ε=f(L THR,E KIN )

14. Exponential Regression Graph 20 : Exponential Regression of Fig. 6 for 23 different beams: Exponential Regression of Fig. 6 for 23 different beams

15. Fig. 4 : δ=f(E KIN ) Pulse height spectra measured with the BaF2 cluster detector for neutrons with kinetic energies E KIN =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 -->

16. BERTINI LCA J J J Fig 4 X 1,19 X 1,43 X 1,92 X 2,29

17. Fig 4 X 1,36 X 1,82 X 3,15 X 5,15 BERTINI LCA J J J X 3,15

18. Fig 4 Pulse Height Spectra using CEM2K model Beam 600 MeV CEM LCA 8J 1

19. 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). 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

20. Dealing with 2ndary particles BaF2 detector 3x bigger Neutron beam 800 MeV BaF2 detector Delimitation of free path

21. Dealing with 2ndary particles

22. Adding the polyethylene box Graph 15 : set up with polyethylene box. View py = 0 View pz = - 2.05

23. Graph 16 : pulse height spectra considering polyethylene box

24. 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

25. Fig 7 : 200 MeV (a) central module (b) the whole cluster

26. Fig 7 : 300 MeV (a) central module (b) the whole cluster

27. Fig 7 : 400 MeV (a) central module (b) the whole cluster

28. Fig 7 : 800 MeV (a) central module (b) the whole cluster

29. 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.

30. THANK YOU FOR YOUR ATTENTION