Dosimetric characterization of a Silicon Carbide p-n junction detector in kilovoltage x-ray beams with varying field sizes

Abstract This work assesses the relative dosimetric performance of a custom 4H-SiC p-n junction detector in intermediate-energy kilovoltage X-ray beams for preclinical applications. Percentage depth dose (PDD) curves and relative field output factors were measured in water at a source-to-surface distance of 50 cm for three beam energies (160, 250 and 320 kVp) and three square field sizes (2×2, 5×5 and 10×10 cm 2 ). The SiC detector (10 μm epitaxial active layer, 2×2 mm 2 sensitive area) was benchmarked against a PTW 60019 microDiamond and a PTW 34045 Advanced Markus parallel-plate ionization chamber. For all energies and field sizes, the SiC PDDs reproduced the expected monotonic attenuation of filtered kV beams and were found in agreement with those of the microDiamond and the chamber to within a few percent beyond the first millimetres. No field-size-dependent nonlinearity, saturation or anomalous depth-dose features were observed indicating uniform charge collection across its sensitive area under all tested beam conditions. Once combined with previously reported absolute-dose and reproducibility studies on the same detector, these results support a compact, water-immersible SiC p-n junction as a robust candidate for relative dosimetry and beam commissioning in 160–320 kVp varying-field X-ray beams, on par with a state-of-the-art synthetic diamond detector and superior to a reference ionization chamber in the most demanding configurations.