Detection of 14 MeV neutrons in high temperature environment up to 500⁰C using 4H-SiC based diode detector

In reactor technology and industrial applications detection of fast and thermal neutrons plays a crucial role in getting relevant information about the reactor environment and neutron yield. The inevitable elevated temperatures make neutron yield measurements problematic. Out of the currently available semiconductors 4H-SiC seems to be the most suitable neutron detector material under extreme conditions due to its high heat and radiation resistance, large band-gap and lower cost of production than in case of competing diamond detectors. In the case of 4H-SiC power devices, the theoretical maximum operating temperature that can be
reached is ~1000 ºC. In practice this limit is determined by the thermal tolerance of the various materials used to form the detector and by the current flow through the junction [1]. In addition to the temperature dependent leakage current, under irradiation the diode current is elevated by the charge carriers generated by incident particles to the sensitive region of the diode. The two components collectively elevate the junction temperature higher than the ambient temperature. This process, beyond a critical junction temperature, leads to thermal runaway effect [2]. ... mehrTherefore, in the case of detectors for high temperature measurements it is extremely important to develop an appropriate diode geometry and to use materials with high thermal resistance.
In the framework of the European I-Smart project, after several years of developments more optimal
diode geometries were developed by the Aix-Marseille University, University of Insa Lyon, and University of Oslo, and have been tested under different radiation fields [3]. Led by Karlsruhe Institute of Technology and SCK-CEN measurements were performed in pure Maxwellian thermal neutron field in the BR1 at SCK-CEN, Mol in Belgium and with 14 MeV fast neutrons supplied by a deuteriumtritium neutron generator at Neutron Laboratory of the Technical University of Dresden in Germany from room temperatures up to several hundred degrees Celsius. In the present work we will discuss the measurements on elevated temperatures with 14 MeV fast neutrons. Based on the results of the diode measurements, detector geometries appear to play a crucial role for high temperature measurements over 400 ºC. The Karlsruhe Institute of Technology is a leading institution of the international fusion neutronics community with a long-standing expertise in the field of neutronics and nuclear data for fusion
technology applications. Nuclear design analysis are being performed on a regular basis in the frame of the European Fusion Technology Program for ITER, fusion demonstration reactors and power plants. Experimental set-ups using SiC detectors are under construction to simulate operation in the harsh environmental conditions found in the tritium breeding blanket, such as high radiation flux and elevated temperatures up to 500-550 ºC, which is planned to be the location of neutron flux characterization measurements in fusion reactors.