1. Neutron Detector Simulations for Fast Neutrons with GEANT4
Brian Roeder
LPC Caen
1/15/2019

2. Motivation Want to design a “next generation” neutron detector array.
Array to detect neutrons over a large energy range (1 MeV < En< 150 MeV) with good energy and angular resolution.
Would like the capability to detect multiple neutron events for breakup experiments and -multiple N decays.
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3. Development Issues Response of detector modules
Detection efficiency (materials)
-N discrimination
Minimization of “Cross – Talk”
Geometry of array setup
Development of offline cross talk rejection
Optimization of detector array for different types of experiments
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4. Monte Carlo Sims. With GEANT4
GEANT4 has the following advantages:
Built-in, 3D Visualization of detector and events!
Tracking of all particles before and after detection (important for Cross Talk simulation).
Realistic design of detectors with all materials; easy to change materials without rewriting whole simulation.
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5. Overview of Sim. Validation
Create a simulation in GEANT4 of an existing detector module with measured detection efficiency – DEMON
Test neutron scattering models provided by GEANT4 vs. DEMON efficiency and other simulations (e.g. MENATE).
If necessary, modify existing scattering models in GEANT4 to obtain a more realistic simulation…
DEMON – I. Tilquin et al. NIM A365, (1995), Pg. 446
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MENATE – P. Désesquelles et al., NIM A307 (1991) 366

6. The MARGOT simulation
Tube of BC-501A liquid scintillator with DEMON module dimensions
Can measure energy deposited, position of neutron hit, and time of flight
Currently converts energy loss of ions by hand into electron-equivalent (MeVee) energy using [Cec79] equations.
Tracks all particles produced in neutron interactions.
Can produce different neutron beams
Detection Threshold set at 0.5 MeVee.
R.A. Cecil et al., NIM 161 (1979) Pg. 439
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7. Standard GEANT4 neutron elastic scattering
LEElastic scattering model
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Points – Cyril Varignon – these – LPC Caen (1999)

8. Improvement with JENDL data set
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9. Addition of Standard Inelastic Model
Corrects for drop in efficiency after 20 MeV.
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10. Evaluation Over-estimates efficiency between 2 and 5 MeV.
Under-estimates efficiency after 25 MeV.
Does not produce heavy-ion residuals, gammas from (n,n’) events. Seems to randomly produce d,t,, etc.
Would like a more-realistic simulation with the “KNOWN” organic scintillator reactions!
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11. Inelastic Neutron Scattering for En>4 MeV
Mostly inelastic scattering, transfer, and breakup reactions on 12C.
The GOOD: 12C(n,p)12B and 12C(n,)9Be
The BAD: 12C(n,3)n’ and 12C(n,np)11B
The UGLY: 12C(n,n’ ) and 12C(n,2n)11C
Cross sections for these reactions are known, have been used in other simulations – e.g. MENATE.
A. Del Guerra – NIM 135 (1976) Pg. 337
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M. Labiche – these – LPC Caen (1999)

12. GEANT4 NeutronHP model
Includes inelastic reactions specifically with reference to total cross sections.
Data and parameterizations available from thermal energies to 20 MeV with the G4NDL.
With a few “modifications”, can be extended to 100 MeV by adding cross section data from MENATE  LEFastNeutron Model
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13. Comparison MENATE vs. GEANT4 LEFastNeutron
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14. Results of LEFastNeutron model
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15. What about the 1 to 4 MeV efficiency?
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16. Results
Have developed a Monte Carlo simulation in GEANT4 for BC-501A scintillator.
Reasonable agreement between simulation and measured efficiency
More realistic representation of inelastic reactions with LEFastNeutron model
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17. Future Work
Test how GEANT4 simulates angular distributions of scattered neutrons
Study “Cross-Talk” for different neutron energies.
Develop setup of future array and test cross section rejection schemes.
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18. Special Thanks Marc Labiche for initial help with GEANT4.
Franck Delaunay for providing the MENATE calculations presented.
Other collaborators : Nigel Orr, Miguel Marqués, Benoit Laurent, writers of GEANT4.
We acknowledge the financial support of the European Community under the FP6 "Research Infrastructure Action-Structuring the European Research Area" EURISOL DS Project contract no RIDS. The EC is not liable for the use that can be made of the information contained herein.
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19. FIN
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20. Discussion
Is there some other way to improve result at low energy other than conic beam spot or adjustment of cross sections?
Is it proper to leave out alpha reactions to improve simulation of efficiency?
Suggestions from meeting participants on how this simulation can be improved.
1/15/2019