Towards radiation hard converter material for SiC-based fast neutron detectors

Abstract

In the present work, Geant4 Monte-Carlo simulations have been carried out to study the neutron detection efficiency of the various neutron to other charge particle (recoil proton) converter materials. The converter material is placed over Silicon Carbide (SiC) in Fast Neutron detectors (FNDs) to achieve higher neutron detection efficiency as compared to bare SiC FNDs. Hydrogenous converter material such as High-Density Polyethylene (HDPE) is preferred over other converter materials due to the virtue of its high elastic scattering reaction cross-section for fast neutron detection at room temperature. Upon interaction with fast neutrons, hydrogenous converter material generates recoil protons which liberate e-hole pairs in the active region of SiC detector to provide a detector signal. The neutron detection efficiency offered by HDPE converter is compared with several other hydrogenous materials viz., 1) Lithium Hydride (LiH), 2) Perylene, 3) PTCDA. It is found that, HDPE, though providing highest efficiency among various studied materials, cannot withstand high temperature and harsh radiation environment. On the other hand, perylene and PTCDA can sustain harsh environments, but yields low efficiency. The analysis carried out reveals that LiH is a better material for neutron to other charge particle conversion with competent efficiency and desired radiation hardness. Further, the thickness of LiH has also been optimized for various mono-energetic neutron beams and Am-Be neutron source generating a neutron fluence of 10 9 neutrons/cm 2 . The optimized thickness of LiH converter for fast neutron detection is found to be ∼ 500 µm. However, the estimated efficiency for fast neutron detection is only 0.1%, which is deemed to be inadequate for reliable detection of neutrons. A sensitivity study has also been done investigating the gamma background effect on the neutron detection efficiency for various energy threshold of Low-Level Discriminator (LLD). The detection efficiency of a stacked structure concept has been explored by juxtaposing several converter-detector layers to improve the efficiency of LiH-SiC-based FNDs. It is observed that approximately tenfold efficiency improvement has been 1Corresponding author.

Effect of electron and proton irradiation on the electrical characteristics of the SiC-based fast neutron detectors

“…Monte-Carlo methods were employed due to the random nature of particle transport and interaction with the matter. The study revealed the optimum thickness of ∼ 500 µm for LiH converter layer for Am-Be neutron source [11].…”

“…Fast neutrons have relatively high cross-section for elastic scattering reaction with the low Z or hydrogenous materials. Therefore, a layer of hydrogenous material such as HDPE, LiH, etc., have been used over SiC to detect the fast neutrons [10,11]. The thickness of the converter and the detector efficiency are two important design parameters.…”

Simulation of the charge collection characteristics of the 4H-SiC PIN fast neutron detector with TCAD

“…Wide band SiC radiation detectors have potential applications in extreme radiation environments such as neutron energy spectrum monitoring in reactor radiation fields and space exploration. [7][8][9] Many studies have simulated 4H-SiC fast neutron detectors using Geant4 software and TCAD software, [10][11][12][13] but few have coupled Geant4 software and TCAD software to perform simulations. Therefore, this paper coupled Geant4 and TCAD software to simulate the 4H-SiC PIN fast neutron detector to provide an important parameter basis for the optimal configuration of detector conditions and its readout electronics design.…”

Silicon carbide diodes for neutron detection

“…Another advantage of hydrogenous fast neutron converters consists on the large recoil penetration depth of H + into the semiconductor layer. Hydrogenous converter materials such as polyethylene show high conversion performance when compared to other materials [30]. Unfortunately, they usually cannot withstand high temperatures and/or harsh radiation environments.…”