The radiation detection properties of semiconductor detectors made of 4H silicon carbide were evaluated. Both Schottky and p-n junction devices were tested. Exposure to alpha particles from a 238Pu source led to robust signals from the detectors. The resolution of the Schottky S i c detector was 5.8% (FWHM) at an energy of 294 keV, while that of the p-n junction was 6.6% (EWHM) at 260 keV.No effect of temperature in the range of 22 to 89 "C was observed on the characteristics of the Pu alpha-induced signal from the S i c detector. In addition, testing in a gamma field of 10,000 rad-Si h" showed that the alpha-induced signal was separable from the gamma signal. 238

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Fast neutron response measurements are reported for radiation detectors based on large-volume SiC p-i-n diodes. Multiple reaction peaks are observed for 14-MeV neutron reactions with the silicon and carbon nuclides in the SiC detector. A high degree of linearity is observed for the 28 Si(n i ) reaction set of six energy levels in the product 25 Mg nucleus, and pulse height defect differences between the observed 12 C(n 0 ) 28 Si(n ) energy responses are discussed. Energy spectrometry applications in fission and fusion neutron fields are also discussed.

SiC detectors with active volume dimensions sufficient to stop alpha particles have been manufactured and tested. A linear energy response and excellent energy resolution have been obtained for various alpha emitters in the 3.18-MeV to 8.38-MeV energy range. Evaluation of the contributing factors to the SiC detector energy resolution indicates that the measured values for the full width at half maximum (FWHM) are limited by energy straggling of the alpha particles as they pass through the metallic contact layers that comprise the entrance window to the detector. Even with this component included in the measured FWHM, the measured values are comparable to those achievable with silicon alpha spectrometers. The possibility that the energy resolution that can be achieved with SiC may surpass that of silicon can not be excluded. SiC alpha spectrometers are expected to be useful in many nuclear applications where the ability to operate in high-temperature and high-radiation environments is required. Such applications include monitoring of alpha particles, neutrons, and low-energy gamma rays and X-rays in actinide waste-tank environments as well as neutron and gamma-ray monitoring of spent nuclear fuel assemblies.

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