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

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. 1/15/2019

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 1/15/2019

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. 1/15/2019

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 1/15/2019 MENATE – P. Désesquelles et al., NIM A307 (1991) 366

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 1/15/2019

Standard GEANT4 neutron elastic scattering LEElastic scattering model 1/15/2019 Points – Cyril Varignon – these – LPC Caen (1999)

Improvement with JENDL data set 1/15/2019

Addition of Standard Inelastic Model Corrects for drop in efficiency after 20 MeV. 1/15/2019

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! 1/15/2019

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 1/15/2019 M. Labiche – these – LPC Caen (1999)

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 1/15/2019

Comparison MENATE vs. GEANT4 LEFastNeutron 1/15/2019

Results of LEFastNeutron model 1/15/2019

What about the 1 to 4 MeV efficiency? 1/15/2019

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 1/15/2019

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. 1/15/2019

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 515768 RIDS. The EC is not liable for the use that can be made of the information contained herein. 1/15/2019

FIN 1/15/2019

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