Hard X-ray and γ-ray spectroscopy at high temperatures using a COTS SiC photodiode

Abstract A commercial-off-the-shelf (COTS) silicon carbide (4H-SiC) UV photodiode was electrically characterized and investigated as a low-cost spectroscopic photon counting detector of X-rays and γ -rays. The detector was coupled to a custom-built low-noise charge-sensitive preamplifier, and illuminated by 55Fe and 109Cd radioisotope X-ray sources and an 241Am radioisotope γ -ray source, thus providing photon energies from 5.9 keV to 59.5 keV. The detector and preamplifier were operated uncooled at temperatures between 20 °C and 100 °C. The energy resolution (full width at half maximum, FWHM) of the spectrometer was found to be 1.66 keV ± 0.15 keV at 5.9 keV and 22.16 keV, and 1.83 keV ± 0.15 keV at 59.5 keV when operated at 20 °C. At a temperature of 100 °C, the FWHM were 2.69 ± 0.25 keV, 2.65 keV ± 0.25 keV, and 3.30 keV  ±  0.30 keV, at the same energies. Shaping time noise analysis found dielectric noise to be the dominant noise source, except when long amplifier shaping times were used at high temperatures when white parallel noise dominated. Noise associated with incomplete charge collection was found to be negligible at energies up to 22.16 keV and at temperatures ≤ 60 °C; but incomplete charge collection noise could not be discounted when the spectrometer was operated at higher temperature (80 °C) and at higher energy (59.5 keV). Although the detector was thin (and thus inefficient at high photon energies) the low cost and commercial availability of the SiC device make it an attractive prospect for use in cost-sensitive applications such as university-led CubeSat missions.