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.

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The effect of 8.2 MeV electron and the 6.5 MeV proton irradiation on the electrical characteristics of n-type Ni/4H-SiC-based Fast Neutron Detectors (FNDs) is investigated with the help of a commercial device simulator, i.e., TCAD. As a consequence of irradiation, deep-levels are generated in the band-gap of the semiconductor material. These deep-levels cause significant changes in the electrical response of the semiconductor device. The current-voltage (I-V) and capacitance-voltage (C-V) characteristics have been simulated to predict the device performance subjected to the high fluence of electron and proton. Critical device parameters such as the ideality factor, barrier height, doping concentration, series-resistance, etc., are also estimated. The carrier removal rate of 0.74 cm −1 and 5.53 cm −1 for electron and proton irradiation, respectively, is found in SiC-based devices which is lower compared to Si-based devices. The study evinces the radiation hardness of SiC-based devices and ensures its applicability in the harsh environment as often encountered in Nuclear Power Plants. K: Detector modelling and simulations II (electric fields, charge transport, multiplication and induction, pulse formation, electron emission, etc); Neutron detectors (cold, thermal, fast neutrons); Radiation damage to detector materials (solid state); Radiation-hard detectors 1Corresponding author.

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