Neutron Detector Simulations for Fast Neutrons with GEANT

Neutron Detector Simulations for Fast Neutrons with GEANT 4 Brian Roeder LPC Caen 10/20/2021 1

Motivation Want to design a “next generation” neutron detector array. Array to detect neutrons over a large energy range (1 Me. V < En< 150 Me. V) with good energy and angular resolution. Would like the capability to detect multiple neutron events for breakup experiments and -multiple N decays. 10/20/2021 2

Development Issues Response of detector modules Detection efficiency (materials) l -N discrimination l Minimization of “Cross – Talk” Geometry of array setup l Development of offline cross talk rejection l Optimization of detector array for different types of experiments 10/20/2021 3

Monte Carlo Sims. With GEANT 4 has the following advantages: Built-in, 3 D Visualization of detector and events! l Tracking of all particles before and after detection (important for Cross Talk simulation). l Realistic design of detectors with all materials; easy to change materials without rewriting whole simulation. l 10/20/2021 4

Overview of Sim. Validation Create a simulation in GEANT 4 of an existing detector module with measured detection efficiency – DEMON Test neutron scattering models provided by GEANT 4 vs. DEMON efficiency and other simulations (e. g. MENATE). If necessary, modify existing scattering models in GEANT 4 to obtain a more realistic simulation… DEMON – I. Tilquin et al. NIM A 365, (1995), Pg. 446 10/20/2021 MENATE – P. Désesquelles et al. , NIM A 307 (1991) 366 5

The MARGOT simulation Tube of BC-501 A 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 (Me. Vee) energy using [Cec 79] equations. Tracks all particles produced in neutron interactions. Can produce different neutron beams Detection Threshold set at 0. 5 Me. Vee. 10/20/2021 R. A. Cecil et al. , NIM 161 (1979) Pg. 439 6

Standard GEANT 4 neutron elastic scattering LEElastic scattering model 10/20/2021 Points – Cyril Varignon – these – LPC Caen (1999) 7

Improvement with JENDL data set 10/20/2021 8

Addition of Standard Inelastic Model Corrects for drop in efficiency after 20 Me. V. 10/20/2021 9

Evaluation Over-estimates efficiency between 2 and 5 Me. V. Under-estimates efficiency after 25 Me. V. 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! 10/20/2021 10

Inelastic Neutron Scattering for En>4 Me. V Mostly inelastic scattering, transfer, and breakup reactions on 12 C. The GOOD: 12 C(n, p)12 B and 12 C(n, )9 Be l The BAD: 12 C(n, 3 )n’ and 12 C(n, np)11 B l The UGLY: 12 C(n, n’ ) and 12 C(n, 2 n)11 C l Cross sections for these reactions are known, have been used in other simulations – e. g. MENATE. A. Del Guerra – NIM 135 (1976) Pg. 337 10/20/2021 M. Labiche – these – LPC Caen (1999) 11

GEANT 4 Neutron. HP model Includes inelastic reactions specifically with reference to total cross sections. Data and parameterizations available from thermal energies to 20 Me. V with the G 4 NDL. With a few “modifications”, can be extended to 100 Me. V by adding cross section data from MENATE LEFast. Neutron Model 10/20/2021 12

Comparison MENATE vs. GEANT 4 LEFast. Neutron 10/20/2021 13

Results of LEFast. Neutron model 10/20/2021 14

What about the 1 to 4 Me. V efficiency? 10/20/2021 15

Results Have developed a Monte Carlo simulation in GEANT 4 for BC-501 A scintillator. Reasonable agreement between simulation and measured efficiency More realistic representation of inelastic reactions with LEFast. Neutron model 10/20/2021 16

Future Work Test how GEANT 4 simulates angular distributions of scattered neutrons Study “Cross-Talk” for different neutron energies. Develop setup of future array and test cross section rejection schemes. 10/20/2021 17

Special Thanks Marc Labiche for initial help with GEANT 4. Franck Delaunay for providing the MENATE calculations presented. Other collaborators : Nigel Orr, Miguel Marqués, Benoit Laurent, writers of GEANT 4. We acknowledge the financial support of the European Community under the FP 6 "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. 10/20/2021 18

FIN 10/20/2021 19

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. 10/20/2021 20