Neutron gamma discrimination in agata
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Neutron Gamma Discrimination in Agata. A.Ataç, A. Kaşkaş, S. Akkoyun, M. Şenyiğit, T. Hüyük, O.Kara and J. Nyberg. Possibility of discriminating neutrons and gammas by tracking Identify the neutron interaction points in Agata detectors Find a ‘pattern’ for neutron interactions.

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Neutron Gamma Discrimination in Agata

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Neutron gamma discrimination in agata

Neutron Gamma Discrimination in Agata

A.Ataç, A. Kaşkaş, S. Akkoyun, M. Şenyiğit,

T. Hüyük, O.Kara and J. Nyberg

Possibility of discriminating neutrons and gammas by tracking

Identify the neutron interaction points in Agata detectors

Find a ‘pattern’ for neutron interactions

NIM A, in print

Aim: Reducing the background in the γ – ray spectra

Agata as a neuton detector ?


Neutron gamma discrimination in agata

Cross-sections for the n + natGe reaction● elastic scattering natGe (n,n)● inelastic scattering natGe (n,n´γ)

Inelastic scattering

J. Ljungvall, J. Nyberg, NIM A546 (2005)553

J. Ljungvall, J. Nyberg, NIM A550 (2005)379


Method

Method

1) Simulations Geant4 with AGATA geometry

J. Allison et al. NIM A506(2003)250.

E. Farnea, D. Bazzacco LNL Anual Report 2003, p.158.

J. Ljungvall, J. Nyberg, NIM A546 (2005)553. Geant4 correction, pulse-height

defect (PHDEF)

2) Tracking MGT code, D. Bazzacco

----------------------------------------------------

First step:1 MeV neutrons on 74Ge (with and without PHDEF)

596 keV from the center of Agata

Methods:• small energy deposition produced by neutrons

• direction of the gammas

• Figure of Merit (FM) values

1208

596

0

74Ge

Second step:1 – 5 MeV neutrons on natGe

Mn = 6, Mγ = 10

Eth = 5 keV, trigger threshold = 50 keV

Number of neutrons

0

10

Neutron Energy (MeV)


Recoil energy inelastic scattering of 1 5 mev neutrons on natge

Recoil Energyinelastic scattering of 1- 5 MeV neutrons on natGe

no phdef

phdef

1 MeV

2 MeV

3 MeV

4 MeV

5 MeV

counts


Neutron gamma discrimination in agata

1 MeVneutrons on 74Ge, no phdef

n = 6

65 keV

Tracking –mgt

• clustering

• FM values

n = 5

n = 4

n = 3

n = 2

596 keV

n = 1


Method 1 energy of the first and second interaction points neutrons and gammas on 74ge

Method 1: Energy of the first and second interaction pointsNeutrons and gammas on 74Ge

1 MeV neutron

Efirst

n = 2 - 6

596 keV gamma

Esecond

n = 3 - 6

1 MeV neutron

counts

596 keV gamma

Energy (keV)


Method 2 g c

θgfrom the position of the interaction points

θc from Compton formula

Method 2:θg – θc

n > 2

1 MeV neutron

θg = θc

15

596 keV gamma

n > 2


Method 3 figure of merit fm

Method 3: Figure of Merit (FM)


Reduction in 1 mev neutrons on 74g e eth 5kev no phdef

Reduction in %1 MeV Neutrons on 74Ge, Eth = 5keV, no phdef

II

Gates I

GatesII


596 kev line with and without phdef 1 mev neutrons on 74g e eth 5kev

596 keV line with and without PHDEF1 MeV Neutrons on 74Ge, Eth = 5keV

596 keV

phdef

counts

nophdef

bump

Eγ (keV)


Gamma ray energy spectra after tracking mgt neutrons on 74ge phdef

Gamma-ray energy spectra after tracking (mgt)Neutrons on 74Ge, phdef

1204

608

5 MeV

596

596

596

608

0

74Ge

596

3 MeV

608

counts

596

2 MeV

608

596

1 MeV

Eγ (keV)


Gamma ray energy spectrum after tracking mgt flat distribution on 1 5 mev neutrons on nat ge phdef

Gamma-ray energy spectrum after tracking (mgt)Flat distribution on 1 –5 MeV neutrons on natGe, phdef

834 keV

counts

No gates

With gates

Gates I

Gates II

Eγ (keV)


Neutron gamma discrimination in agata

The neutron rejection methods were tested on a case where 6 neutrons with energies between 1 to 5 MeV were emitted in coincidence with a cascade of 10 rays.


Neutron gamma discrimination in agata

At Eγ = 1MeV, PTB is ratio is increased by a factor of 2.4

and the ε is reduced by a factor of 1.25 for gates II.

RPTB = PTB / PTB(after neutron rejection)

Rε = ε / ε (after neutron rejection)

Gates I

Gates II


Conclusion and future plans

Conclusion and Future Plans

We identified the γ-rays produced by neuton inelastic scattering on Ge isotopes by checking its direction, FM value and by the small energy it deposits in the detector.

The neutron rejection methods were also tested on a case where 6 neutrons with energies between 1 to 5 MeV were emitted in coincidence with a cascade of 10 rays. As a result, at a gamma-ray energy of 1 MeV, the suggested gate set increases the PTB value by a factor of 2.4, whereas the photopeak efficiency is reduced by a factor of 1.25.

•En > 5MeV isbeing studied. For Giant Resonance studies

• An experiment with AGATA detectors by using a 252Cfsource and BaF2 detector for TOF selection of neutrons.

 Menekşe’s talk


Number of interaction points in ge after tracking

Number of interaction points in Ge after tracking

n'

596 keV gamma

n

596 keV gamma

Counts

596 keV gamma

1 MeV neutron

Number of interaction points


Gamma ray energy spectrum after tracking mgt flat distribution on 1 5 mev neutrons on nat ge phdef1

Gamma-ray energy spectrum after tracking (mgt)Flat distribution on 1 –5 MeV neutrons on natGe, phdef

Number of neutrons

0

10

Neutron energy (MeV)

596 keV, 74Ge

834 keV, 72Ge

counts

1039 keV, 70Ge

608 keV, 74Ge

Eγ (keV)


Hittites 1650 1200 bc

Hittites 1650 - 1200 BC

Anakara U: A.Ataç, A. Kaşkaş, S. Akkoyun, M. Şenyiğit, T. Hüyük, O.Kara

Uppsala U: J. Nyberg

Ceremonial Standard


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