OVERVIEW NEDA Introduction to the Simulations – Geometry The Simulations Conclusions 3.7% This work summarizes the introduction to the simulations of.

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)

NEDA

NEDA

7.4%

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%

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%

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%

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%

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%

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

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%

NEDA - Geometry

NEDA

In order to keep granularity for the detectors, the geometry

has been considered as flat for NEDA

37%

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%

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%

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%

NEDA - Simulations

Simulation #1:D = 510 mmS = 70 mm Θ = 32o (to cover whole array)# of Det. = 19Both BC501A and BC537En = 1 MeV ~ 10 MeV

51.9%

NEDA - SimulationsBC501A – Intrinsic Efficiency

0 2 4 6 8 10 12

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

20 keV70 keV

Neutron Energy

Intr

ins

ic E

ffic

ien

cy

Fold_ i / Fold_tot vs. Fold #

0 1 2 3 4 5 6 7 8 9

0.00E+00

1.00E-01

2.00E-01

3.00E-01

4.00E-01

5.00E-01

6.00E-01

7.00E-01

4 MeV

Fold #

Fo

ld_i

/ F

old

_to

tal

Fold_ i / Fold_tot vs. Neutron Energy

0 1 2 3 4 5 6 7 8 9 10

0.00E+00

1.00E-01

2.00E-01

3.00E-01

4.00E-01

5.00E-01

6.00E-01

7.00E-01

8.00E-01

Fold1/Fold_totalFold2/Fold_totalFold3/Fold_totalFold4/Fold_totalFold5/Fold_total

En (MeV)

Fo

ld_i

/ F

old

_To

tal

55.5%

NEDA - SimulationsBC537 – Intrinsic Efficiency

0 2 4 6 8 10 12

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.7020 keV70 keV

Neutron Energy

Intr

ins

ic E

ffic

ien

cy

Fold_ i / Fold_tot vs. Neutron EnergyFold_ i / Fold_tot vs. Fold #

0 1 2 3 4 5 6 7 8 9 10

0.00E+00

1.00E-01

2.00E-01

3.00E-01

4.00E-01

5.00E-01

6.00E-01

7.00E-01

Fold1/Fold_total

Fold2/Fold_total

E_n (MeV)

Fo

ld_i

/ F

old

_To

tal

0 1 2 3 4 5 6 7 8 9

0.00E+00

1.00E-01

2.00E-01

3.00E-01

4.00E-01

5.00E-01

6.00E-01

7.00E-01

4 MeV

Fold #

Fo

ld_i

/ F

old

_to

tal

59.3%

Intrinsic efficiency comparison for both scintillators:

NEDA - Simulations

63%

Simulation #3:In this simulation, distance D was increased to 100 cm.

D = 1000 mmS = 70 mm Θ = 17o (to cover whole array)# of Det. = 19Both BC501A and BC537En = 1 MeV & 8 MeV

NEDA - Simulations

66.7%

NEDA - Simulations

BC501A – Intrinsic Efficiency

Fold_ i / Fold_tot vs. Fold #

En

Threshold EnergyDistance20 keV 210 keV

1 MeV 73 % 70 %100 cm8 MeV 63 % 58 %

1 MeV 69 % 65 %51 cm 8 MeV 58 % 53 %

0 1 2 3 4 5 6 7 8 9

0.00E+00

1.00E-01

2.00E-01

3.00E-01

4.00E-01

5.00E-01

6.00E-01

7.00E-01

8.00E-01

1 MeV8 MeV

Fold #

Fo

ld_i

/ F

old

_to

tal

70.4%

The difference between the intrinsic efficiencies for 100cm and 51cm is due to geometrical factors.

NEDA - Simulations

BC537 – Intrinsic Efficiency

Fold_ i / Fold_tot vs. Fold #

En

Threshold EnergyDistance20 keV 210 keV

1 MeV 71 % 64 %100 cm8 MeV 63 % 58 %

1 MeV 66 % 59 %51 cm8 MeV 57 % 53 %

0 1 2 3 4 5 6 7 8 90.00E+00

1.00E-01

2.00E-01

3.00E-01

4.00E-01

5.00E-01

6.00E-01

7.00E-01

1 MeV8 MeV

Fold #

Fo

ld_i

/ F

old

_to

tal

74%

The difference between the intrinsic efficiencies for 100cm and 51cm is due to geometrical factors.

Simulation #6:In this simulation, D distance was held constant and S length was increased to 100 mm.

D = 100 cmS = 100 mm Θ = 24o (to cover whole array)# of Det. = 19Both BC501A and BC537En = 1 MeV & 8 MeV

NEDA - Simulations

77.8%

NEDA - Simulations

BC501A – Intrinsic Efficiency

Fold_ i / Fold_tot vs. Fold #

En

Threshold EnergySide

length20 keV 210 keV

1 MeV 72 % 69 % 100 mm8 MeV 62 % 57 %

1 MeV 71 % 64 %70 mm8 MeV 63 % 58 %

0 1 2 3 4 5 6 7 8 9

0.00E+00

1.00E-01

2.00E-01

3.00E-01

4.00E-01

5.00E-01

6.00E-01

7.00E-01

8.00E-01

1 MeV8 MeV

Fold #

Fo

ld_i

/ F

old

_to

tal

81.5%

NEDA - Simulations

BC537 – Intrinsic Efficiency

Fold_ i / Fold_tot vs. Fold #

En

Threshold EnergySide

length20 keV 210 keV

1 MeV 70 % 64 %100 mm8 MeV 61 % 56 %

1 MeV 71 % 64 %70 mm8 MeV 63 % 58 %

0 1 2 3 4 5 6 7 8 90.00E+00

1.00E-01

2.00E-01

3.00E-01

4.00E-01

5.00E-01

6.00E-01

7.00E-01

8.00E-01

1 MeV8 MeV

Fold #

Fo

ld_i

/ F

old

_to

tal

85.2%

NEDA - SimulationsBC501A – Side Length & Distance Dependency of Intrinsic Efficiency and X-talk

88.9%

NEDA - SimulationsBC537 – Side Length & Distance Dependency of Intrinsic Efficiency and X-talk

92.6%

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%

NEDA

Thank you for your attention.

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