New perspectives for undoped CaF2 scintillator as a threshold activation neutron detector

P Sibczyński ,Matthieu Hamel,Andrzej Dziedzic,Alessandro Iovene,Joanna Iwanowska-Hanke,Adrien Sari,Amélie Grabowski,M Moszyński ,F Carrel ,A Syntfeld-Każuch ,D Wolski ,Frédéric Lainé ,Ł Świderski ,Cristiano Lino Fontana ,C Tintori ,K Grodzicki ,F Pino

doi:10.1051/epjconf/201817007012

Abstract

In this paper we present the prompt photofission neutron detection performance of undoped CaF2 scintillator using Threshold Activation Detection (TAD). The study is carried out in the frame of C-BORD Horizon 2020 project, during which an efficient toolbox for high volume freight non-intrusive inspection (NII) is under development. Technologies for radiation monitoring are the part of the project. Particularly, detection of various radiological threats on country borders plays an important significant role in Homeland Security applications. Detection of illegal transfer of Special Nuclear Material (SNM) - 235U, 233U and 239Pu - is particular due to the potential use for production of nuclear weapon as well as radiological dispersal device (RDD) V known also as a “dirty bomb”. This technique relies on activation of 19F nuclei in the scintillator medium by fast neutrons and registration of high-energy β particles and γ-rays from the decay of reaction products. The radiation from SNM is detected after irradiation in order to avoid detector blinding. Despite the low 19F(n,α)16N or 19F(n,p)19O reaction cross-section, the method could be a good solution for detection of shielded nuclear material. Results obtained with the CaF2 detector were compared with the previous study done for BaF2 and 3He detector. These experimental results were obtained using 252Cf source and 9 MeV Varian Linatron M9 linear accelerator (LINAC). Finally, performance of the prompt neutron detection system based on CaF2 will be validated at Rotterdam Seaport during field trails in 2018.

Highlights

FOR several years detection of nuclear materials plays important role in Homeland Security and Border Monitoring
Fluorine based scintillation detectors were found to be good candidates for prompt photofission neutrons detection by means of threshold activation [1], [2], [3], [4]
The energy resolution plays secondary role in the Threshold Activation Detection (TAD) technique. This technique aims on detection of beta continuum with endpoint at 10.4 MeV and high energy delayed -rays emitted for variety of photofission products

Summary

INTRODUCTION

FOR several years detection of nuclear materials plays important role in Homeland Security and Border Monitoring. Prompt photofission neutrons can be registered by the 19F(n,α)16N threshold reaction in the scintillator medium using LINAC producing bremsstrahlung photons with endpoint at 9 MeV By this way, it is possible to detect characteristic β particles (energy endpoint at 4.3 MeV and 10.4 MeV) and -rays (6.1 MeV) emitted from the 19F(n,α)16N reaction product few seconds after irradiation. The energy resolution plays secondary role in the TAD technique This technique aims on detection of beta continuum with endpoint at 10.4 MeV and high energy delayed -rays emitted for variety of photofission products. We used an MCNP6 code for simulation of (n,α) reaction rate for the CaF2 and compared with the BaF2 of volume of Ø5” × 1”, studied in [6]

MCNP6 SIMULATIONS

MEASUREMENTS WITH A 252CF SOURCE AT NCBJ

ACTIVE MEASUREMENTS RESULTS AT SAPHIR

SUMMARY