2. OVERVIEW NEDA Introduction to the Simulations – Geometry The Simulations Conclusions 3.7% This work summarizes the introduction to the simulations of a new generation neutron detector which has been started to develop and will be used for SPIRAL2 Project (GANIL-France)

3. NEDA 7.4%

4. NEDA: Motivation We need better intrinsic efficiency and cross-talk for neutron detectors We want to change old analogical electronics with new digital ones. 11.1%

5. NEDA NEDA is an acronym for NEutron Detector Array It’s a new generation neutron detector array and it’s being developed for SPIRAL2 Project. A former project named Neutron Wall* has been taken into account while designing NEDA * J. Ljungvall, M. Palacz, J. Nyberg, Monte Carlo simulations of the Neutron Wall detector system, Nuclear Instruments and Methods in Physics Research A 528 (2004) 741–762 14.8%

6. Neutron Wall In Neutron Wall, single detector has been physically segmented into three parts One side length of a single detector is 140 mm The depth of a single detector is 159.12 mm 18.5%

7. Neutron Wall The detectors have 2.5 mm thickness of Aluminum encapsulation. NWall consists of two types of hexagonal detectors and a pentagon detector at the center. NWall has 55% intrinsic efficiency (1 MeV neutron, 23 keV threshold energy) and 7% cross-talk probability, as mentioned by J. Ljungvall et al., NIM A528(2004)741 22.2%

8. NEDA - Geometry As a mimic to Neutron Wall, the hexagonal geometry has been considered for the NEDA detectors. A simple starting geometry for the construction of a single detector of NEDA 26%

9. NEDA - Geometry Unlike Neutron Wall, the single detector has been divided into 3 hexagonal segments in NEDA 140 mm side length for one detector has been kept in NEDA, and 159.12 mm depth length as well Only one type of detectors has been considered for NEDA 29.6% We try to mimic the Neutron Wall with a simple flat geometry

10. NEDA - Geometry The whole system has been designed as triple clusters with hexagon shapes. Each cell has 2.5 mm thickness of aluminum encapsulation and total 159.12 mm of depth. 33.3%

11. NEDA - Geometry NEDA In order to keep granularity for the detectors, the geometry has been considered as flat for NEDA 37%

12. NEDA - Simulations Geant4 Simulation Kit has been used for the NEDA simulations. The simulations were performed with NArray which is a modified code of the AGATA and written by E. Farnea (LNL) 40.7%

13. NEDA - Simulations Cross-Talk and intrinsic efficiency were investigated We used the following ratio in order to express (and measure) X-talk: Intrinsic efficiency was calculated by using the following ratio: Fold i is the number of detectors fired by one neutron If there is no X-talk between the detectors then this ratio must be “1”! 44.4%

14. NEDA - Simulations The Simulations were performed with: Two kinds of scintillators – BC501A and BC537 Varied side length -> S = 70 mm, 80 mm, 90 mm, 100 mm Two different source-to-detector distance -> D = 510 mm, 1000 mm Varied theta angle of conical beam according to D and S parameters 100 000 neutrons were shot 48%

15. NEDA - Simulations Simulation #1: D = 510 mm S = 70 mm Θ = 32 o (to cover whole array) # of Det. = 19 Both BC501A and BC537 E n = 1 MeV ~ 10 MeV 51.9%

16. NEDA - Simulations BC501A – Intrinsic Efficiency Fold_ i / Fold_tot vs. Fold # Fold_ i / Fold_tot vs. Neutron Energy 55.5%

17. NEDA - Simulations BC537 – Intrinsic Efficiency Fold_ i / Fold_tot vs. Neutron EnergyFold_ i / Fold_tot vs. Fold # 59.3%

18. Intrinsic efficiency comparison for both scintillators: NEDA - Simulations 63%

19. Simulation #3: In this simulation, distance D was increased to 100 cm. D = 1000 mm S = 70 mm Θ = 17 o (to cover whole array) # of Det. = 19 Both BC501A and BC537 E n = 1 MeV & 8 MeV NEDA - Simulations 66.7%

20. NEDA - Simulations BC501A – Intrinsic Efficiency Fold_ i / Fold_tot vs. Fold # EnEn Threshold Energy Distance 20 keV210 keV 1 MeV73 %70 % 100 cm 8 MeV63 %58 % 1 MeV69 %65 % 51 cm 8 MeV58 %53 % 70.4% The difference between the intrinsic efficiencies for 100cm and 51cm is due to geometrical factors.

21. NEDA - Simulations BC537 – Intrinsic Efficiency Fold_ i / Fold_tot vs. Fold # EnEn Threshold Energy Distance 20 keV210 keV 1 MeV71 %64 % 100 cm 8 MeV63 %58 % 1 MeV66 %59 % 51 cm 8 MeV57 %53 % 74% The difference between the intrinsic efficiencies for 100cm and 51cm is due to geometrical factors.

22. Simulation #6: In this simulation, D distance was held constant and S length was increased to 100 mm. D = 100 cm S = 100 mm Θ = 24 o (to cover whole array) # of Det. = 19 Both BC501A and BC537 E n = 1 MeV & 8 MeV NEDA - Simulations 77.8%

23. NEDA - Simulations BC501A – Intrinsic Efficiency Fold_ i / Fold_tot vs. Fold # EnEn Threshold Energy Side length 20 keV210 keV 1 MeV72 %69 % 100 mm 8 MeV62 %57 % 1 MeV71 %64 % 70 mm 8 MeV63 %58 % 81.5%

24. NEDA - Simulations BC537 – Intrinsic Efficiency Fold_ i / Fold_tot vs. Fold # EnEn Threshold Energy Side length 20 keV210 keV 1 MeV70 %64 % 100 mm 8 MeV61 %56 % 1 MeV71 %64 % 70 mm 8 MeV63 %58 % 85.2%

25. NEDA - Simulations BC501A – Side Length & Distance Dependency of Intrinsic Efficiency and X- talk 88.9%

26. NEDA - Simulations BC537 – Side Length & Distance Dependency of Intrinsic Efficiency and X- talk 92.6%

27. Conclusions & Open Questions With a simple and versatile geometry, intrinsic efficiency and X-talk do not dramatically change for: Both scintillators Source-to-detector distant (D) Only positive change was observed as we increase the side length of the detectors (X-talk is better) One should perform the simulations with another code? Optimization of the geometry, flat or spherical or … ? Flat -> versatility, economical advantage, … Which scintillator should we use? 96.3%

28. NEDA Thank you for your attention. 100%