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E-SiCure Collaboration Project: Silicon Carbide Material Studies and Detector Prototype Testing at the JSI TRIGA Reactor

In 2016, the NATO Science for Peace and Security research collaboration project “Engineering Silicon Carbide for Border and Port Security” – E-SiCure was launched, with the main objective to combine theoretical, experimental and applied research towards the development of radiation-hard SiC-based detectors of special nuclear materials (SNM), in order to enhance border and port security barriers. In the development, material modification processes are employed firstly to study and secondly to manipulate the most severe electrically active defects (which trap or annihilate free charge carriers), by specific ion implantation and defect engineering. This paper presents the experimental activities performed at the JSI TRIGA reactor in the framework of the E-SiCure project. To study neutron induced defects in SiC, n- type silicon carbide Schottky barrier diodes (SBDs) were fabricated onto nitrogen- doped epitaxial grown 4H-SiC single crystal layers approximately 25 µm thick, their lateral dimensions being 1 mm by 1 mm. Samples of Schottky diodes were irradiated bare and inside Cd thermal neutron filters with a wall thickness of 1 mm in the pneumatic tube (F24) irradiation location in the 250kW JSI TRIGA reactor in Ljubljana, Slovenia, the neutron fluences ranging from 1E8 n cm-2 to 1E15 n cm- 2. Neutron induced defects in the samples were studied using Deep-Level Transient Spectroscopy (DLTS) measurements. Prototype detectors were created, based on hexagonal (4H) SiC Schottky diodes with several active layer thicknesses, ranging from 25 µm to 170 µm, their lateral dimensions being 1 mm by 1 mm. To increase the neutron detection efficiency through the conversion of neutrons into heavy charged particles through (n, α) and (n, t) reactions, the use of capping layers containing 10B and 6Li was investigated through Monte Carlo particle transport calculations and realized on several prototype detectors using 10B4C material. Additionally 10B and 6LiF powders, deposited onto plastic film and placed over of the prototype detectors were tested. An experimental test of the prototype detectors was performed at the JSI using a 241Am alpha source and thermal and fission neutrons in the Dry Cell irradiation facility of the JSI TRIGA reactor at different reactor power levels. The experimental test successfully demonstrated the detection of alpha particles and thermal neutrons through heavy charged particles from nuclear reactions.

Silicon carbide ; Neutron detection ; Neutron converter ; JSI TRIGA reactor

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