Design and Response Testing of Boron-Diffused Silicon Carbide Neutron Detectors for Dosimetry and Monitoring Applications

Abstract

A high-sensitivity boron-diffused silicon carbide (4H-SiC) p-n diode has been designed and fabricated using vapor-phase epitaxy. Boron-10 (10B) is diffused into nitrogen-doped n− SiC, forming the p+ layer, and thermal neutrons are detected through the ionization produced in the detector by 10B(n,α)7Li reactions. These detectors have been tested with thermalized neutrons from an isotopic californium-252 (252Cf) source and have been shown to provide a robust pulse-height spectrum, which is easily separable from the anticipated gamma-ray response. The detectors are expected to be useful for neutron and gamma-ray fluence rate measurements in high gamma-ray fields for extended times at temperatures up to 700°C.

Design Considerations for Boron-Diffused and Implanted 4H-SiC Epitaxial Neutron Detectors for Dosimetry and Monitoring Applications

“…Furthermore, SiC radiation detectors are extremely radiation tolerant, and have been shown to be operational after gamma-ray doses up to 22.7 MGy ( 137 Cs) [9] and fast-neutron (E >1MeV) fluences up to 1.7 x 10 17 cm -2 [10]. SiC detectors are particularly well suited to spent fuel monitoring applications as reported at previous symposia in this series [11][12][13].…”

“…Like all neutron detectors, SiC detectors rely on detection of neutron-induced reaction products in the form of energetic ions, which can produce detectable ionization when they interact with the detector. SiC detectors based on boron neutron-convertor layers that have been implanted into the detector [14] or diffused into the detector [11] have been reported previously in this symposium series. In both cases, neutron-induced 10 B(n,α) 7 Li reaction products enter the active volume of the detector and produce ionization and detectable charge pulses.…”

“…In the case of boron-diffused detectors [11], boron (a p-type dopant) is diffused into ntype 4H-SiC to produce a p-n junction as depicted in Fig. 1.…”

SiC detectors: A review on the use of silicon carbide as radiation detection material

“…A converter layer is required to detect thermal neutrons, and the sensitivity of the detector is largely determined by its properties. The coverter can be applied as a thin layer in front of the SiC sensor, or it can be directly incorporated using diffusion [112] or ion implantation [113]. This layer must be rich in isotopes with large cross-sections for thermal neutrons, such as 6 Li, 10 B, or 235 U.…”

Performance and Applications of Silicon Carbide Neutron Detectors in Harsh Nuclear Environments

“…For thermalneutron detection, the 10 B(n,α) 7 Li and 6 Li(n,α) 3 H reactions have proven useful [4,11], because solid-state compounds of boron and lithium are readily available and can be configured to allow the energetic charged-particle reaction products to enter the detector active volume [4][5][6]12]. In practice, the thermalneutron convertor material can be in the form of a thin layer juxtaposed near the active volume or can be incorporated into the detector by ion implantation [13] or diffusion [14].…”