Nuclear Physics Institute

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

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

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 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

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

7. 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 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 BaF2 Cylinder view : pz=3 σ ≈ 30 % Set up view : py=0

8. 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 0.0000 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 Setup view : py=0 σ≈30 %

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

10. Problem of Normalization ? 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 F8 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 F1 F8 tally DOES take into account particle passing through without depositing energy

11. Fig. 5 : ε=f(EKIN,LTHR) Neutron efficiency of the BaF2 cluster detector for various values of the electronic threshold LTHR as a function of 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

12. Fig. 6 : ε=f(LTHR,EKIN) Neutron efficiency of the BaF2 cluster detector for various incident neutron kinetic energies EKINas a function of LTHR 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

13. Fig. 6 : ε=f(LTHR,EKIN)

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

15. 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 -->

16. Fig 4 X2,29 X1,92 X1,43 X1,19 BERTINI LCA J J J

17. Fig 4 X5,15 X3,15 X3,15 X1,82 X1,36 BERTINI LCA J J J

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

19. 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 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).

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

21. Dealing with 2ndary particles

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

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