Monte Carlo simulation of liquid scintillation neutron detectors: BC501 vs. BC537
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Monte Carlo simulation of liquid scintillation neutron detectors:
BC501 vs. BC537
J.L. [email protected]
Instituto de Física Corpuscular
C.S.I.C - Univ. Valencia
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BC537 as low neutron sensitivity -ray detector
State of the art detectors for (n,) measurements using the Pulse Height Weighting Technique at time-of-flight facilities
C6D6 detectors at n_TOF-CERN
(n,n)
(n,)
1keV 1MeV
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BC501 BC537
En=2.5MeV
En=4.3MeV
From S. Williams (TRIUMF) : (@ Warsaw, Oct 2007)DESCANT: DEuterated SCintillator Array for Neutron Tagging
Motivation:
102.5cm
!?
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BC501/NE213 liquid scintillators
Mono-energetic neutron response
C1H1.212
= 0.874g/cm3
n (@425nm) = 1.53 = 3.2 (32.3, 270) ns
5cm5cm
NIMA476 (02) 132
255cm
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Neutron scattering
s-wave (l=0) elastic scattering:
A
n
min
There is a minimum neutron energy (maximum recoil energy) after the collision, A dependent:
Isotropic in CMS:
Energy-momentum conservation:
1-: H (1.0), D(0.89), C(0.28), Fe(0.069), Pb(0.019)
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ELASTIC SCATTERING ANGULAR DISTRIBUTION
1H 2H
12C 208Pb
CM system
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Angular distribution in the LAB reference frame
1H
2H
En = 1MeV
En = 5.5MeV
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Monte Carlo simulations of liquid scintillation neutron detectors
• General purpose codes: GEANT3, Geant4,… and specific codes: NRESP, SCINFUL, …
• Requires nuclear reaction data (missing information on 12C(n,n3), …)
• Requires material response (light production, …)
ENDF/B-VII.0
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Luminescence in organic materials
Several time components
The non-radiative transfer mechanism between excited centers induces an energy-loss dependent light production …
dxdE
kB
dxdE
S
dx
dL
1… and a varying time distribution
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p, , 12C in NE213: Dekempeneer et al. NIM A256 (1987) 489 d in NE230: Croft et al. NIM A316 (1992) 324
Simulations with GEANT3/GCALOR
Light production curves:
(In reality there is some dependence on chemical composition, fabrication, age, …)
EELELL (assumed same and 12C light curves in BC501 & BC537)
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(10x10cm)
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“ENERGY CALIBRATION”
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Neutron interaction time
t=5ns:C6D6: 98.3%BC501: 95.6%
CONCLUSION: !?
C6D6 =12.2%BC501=17.7%(Eth=100keVee)
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Does the use of C6D6 diminishes the cross-talk?
Simulation: • cluster of 7 hexagonal detectors• diameter: 15 cm• length: 5 cm and 15 cm• maximal illumination of central detector• source at 1 m• neutron energies: 1 MeV and 5 MeV
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En15cm15c
mMULT 1 MULT 2 MULT 3 M2/M1
1 MeVBC501 76.4% 15.5% 0.5% 20.3%
C6D6 69.3% 12.5% 0.24% 18.1%
5 MeVBC501 49.5% 22.3% 2.3% 45.2%
C6D6 45.3% 18.6% 2.4% 41.1%
En = 1 MeV En = 5 MeV
Eth=100keV
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En 5cm15cm MULT 1 MULT 2 MULT 3 M2/M1
1 MeVBC501 61.5% 5.1% 0.1% 8.28%
C6D6 44.1% 3.9% 0.04% 8.87%
5 MeVBC501 31.8% 3.6% 0.2% 11.35%
C6D6 27.1% 2.9% 0.15% 10.55%
En = 1 MeV En = 5 MeV
Eth=100keV
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En
15cm15cm
BC501 C6D6
1 MeV 2.8% 5.6%
5 MeV 6.3% 10.4%
Ratio of counts scattered to outer detectors respect to central detector in the energy window [Emax/2,Emax]
En
5cm15cm
BC501 C6D6
1 MeV 1.4% 2.5%
5 MeV 2.6% 3.5%
En = 1 MeV En = 5 MeV15cm15cm
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Conclusion:The use of deuterated scintillators does not seem to represent an advantage with respect to hydrogenated scintillators in order to reduce the inter-module neutron scattering
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