Neutron Gamma Discrimination in Agata
description
Transcript of Neutron Gamma Discrimination in Agata
Neutron Gamma Discrimination in AgataAyAyşşe Atae Ataçç
Possibility of discriminating neutrons and gammas by trackingPossibility of discriminating neutrons and gammas by tracking
Identify the neutron interaction points in Agata detectorsIdentify the neutron interaction points in Agata detectors
Find a ‘pattern’ for neutron interactionsFind a ‘pattern’ for neutron interactions
AimAim: Reducing the background in the : Reducing the background in the γ – ray spectraγ – ray spectra
Agata as a neuton detectorAgata as a neuton detector ? ?
Cross-sections for the n + natGe reaction ● elastic scattering natGe (n,n) ● inelastic scattering natGe (n,n´γ)
J. Ljungvall, J. Nyberg, NIM A550 (2005)379
J. Ljungvall, J. Nyberg, NIM A546 (2005)553
Inelastic scatteringInelastic scattering
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
----------------------------------------------------1208
596
074Ge
00 1010N
um
ber
of
Nu
mb
er o
f n
eutr
ons
neu
tron
s
First step: 1 MeV neutrons on 74Ge (with and without PHDEF)
596 keV from the center of Agata
Criteria: • small energy deposition produced by neutrons
• direction of the gammas
Neutron Energy (MeV)Neutron Energy (MeV)
Second step: 1 – 5 MeV neutrons on natGe
EEth th = 5 keV= 5 keV
Mn, MMn, Mγ = 1γ = 1
Number of interaction points in Ge after tracking
596 keV gamma596 keV gamma
1 MeV neutron1 MeV neutron
596 keV gamma
nn
nn''
596 keV gamma
Cou
nts
Number of interaction points
Recoil Energyelastic scattering of 1- 5 MeV neutrons on Ge isotopes
JENDLJENDL
Ge recoil energy Ge recoil energy Erec (keV)Erec (keV)
cou
nts
cou
nts
1 MeV
2 MeV
3 MeV
4 MeV
5 MeV
Recoil Energyinelastic scattering of 1- 5 MeV neutrons on natGe
1 MeV
cou
nts
2 MeV
3 MeV
4 MeV
5 MeV
no phdef phdef
Gamma-ray spectra after tracking (mgt)1 MeV neutrons on 74Ge, no phdef
00
596596
12081208
74Ge74Ge
596 596
n = 6n = 6
n = 5n = 5
n = 4n = 4
n = 3n = 3
n = 2n = 2
n = 1n = 1
n = number of interaction points n = number of interaction points
596596
bumpbump
596 keV596 keVn = 1
n = 2
n = 3
n = 4
n = 5
n = 680 keV
1 MeV neutrons on 74Ge, no phdef
Criteria 1: Energy of the first and second interaction pointsNeutrons and gammas on 74Ge
1 MeV neutron1 MeV neutron
596 keV gamma596 keV gamma
1 MeV neutron1 MeV neutron
596 keV gamma596 keV gamma
Energy (keV)Energy (keV)
cou
nts
cou
nts
EfirstEfirst
n = 2 - 6n = 2 - 6
EsecondEsecond
n = 3 - 6n = 3 - 6
Criteria 2: θg – θc
1515
596 keV gamma596 keV gamma
1 MeV 1 MeV neutronneutron
n > 2n > 2
n > 2n > 2
θg = θc
θg from the position of the interaction points
θc from Compton formula
θg - θc
n>1n>1
n = 2n = 2
n = 3n = 3
n = 4n = 4
n = 5n = 5
n = 6n = 6
Reduction in %1 MeV Neutrons on 74Ge, Eth = 5keV, no phdef
596keV
bumpbump
EEγ (keV)γ (keV)
cou
nts
cou
nts
23883557θg – θc or efirst or esec.
15752650θg – θc or efirst
662538efirst
11632341 θg - θc
596 keV gamma
bumppeak
596 keV
total
No conditionsNo conditions
With conditionsWith conditions
596 keV line with and without PHDEF 1 MeV Neutrons on 74Ge, Eth = 5keV
596 keV596 keV
bumpbump
phdefphdef
EEγ (keV)γ (keV)
cou
nts
cou
nts
nophdefnophdef
Reduction in % 1 MeV Neutrons on 74GePHDEF, Eth = 5keV
596keV
EEγ (keV)γ (keV)
cou
nts
cou
nts
123328θg – θc or efirst or esec.
113126θg – θc or efirst
165efirst
113126θg - θc
596 keV gamma
peak + bump
596 keV
total
No conditionsNo conditions
With conditionsWith conditions
Gamma-ray energy spectra after tracking (mgt)Neutrons on 74Ge, phdef
5 MeV
596
Eγ (keV)
cou
nts
3 MeV
2 MeV
1 MeV
596
596
596
608
608
608
1204
596
074Ge
596596
608608
Gamma-ray energy spectrum after tracking (mgt)Flat distribution on 1 –5 MeV neutrons on natGe, phdef
00 1010 Neutron energy (MeV)Neutron energy (MeV)
Nu
mb
er o
f N
um
ber
of
neu
tron
sn
eutr
ons
596 keV, 74Ge596 keV, 74Ge
608 keV, 74Ge608 keV, 74Ge
834 keV, 72Ge834 keV, 72Ge
EEγ (keV)γ (keV)
cou
nts
cou
nts
1039 keV, 70Ge1039 keV, 70Ge
Gamma-ray energy spectrum after tracking (mgt)Flat distribution on 1 –5 MeV neutrons on natGe, phdef
14692838θg – θc or efirst or esec.
11562534θg – θc or efirst
137-10efirst
10512432θg - θc
1 MeV gamma
bumppeak
834 keV
total
834 keV834 keV
EEγ (keV)γ (keV)
coun
tscou
ntsNo conditionsNo conditions
With conditionsWith conditions
We identified the γ-rays produced by neuton inelastic scattering on Ge isotopes by checking its direction and by the small energy it deposits in the detector.
For En = 1-5 MeV, if the recoil energy is included in a cluster during tracking, we can eliminate 69% of the background with a loss of 14 % in good γ-rays from the target place.
• We may improve the results by doing the selection during the tracking!
• Mn > 1 should be studied.
• An experiment with AGATA detectors by using a 252Cf
source, BaF2 and plastic detectors for TOF of the neutrons.
Conclusion and Future Plans
Hittites 1650 - 1200 BCCeremonial StandardCeremonial Standard
AAnakara nakara U: A.Ataç, A. Kaşkaş, S. U: A.Ataç, A. Kaşkaş, S. Akkoyun, M. Şenyiğit, T. Hüyük, Akkoyun, M. Şenyiğit, T. Hüyük,
O.Kara O.Kara
UUppsala ppsala U: J. Nyberg U: J. Nyberg