|
内容記述 |
Purpose: Real-time and high-sensitivity dosimetry in diagnostic radiology demands compact detectors that operate at low bias voltage, exhibit minimal energy dependence, and ensure stable charge collection. This study evaluates a heteroepitaxial diamond ionization chamber (HED-IC) fabricated on a 4 × 4 × 0.5 mm³ substrate for its performance under diagnostic X-ray conditions.Methods: The HED-IC, equipped with Ti/Au electrodes, was operated at bias voltages of −0 to −500 V and irradiated with diagnostic X-rays (effective energy: 25–45 keV). Dose linearity, sensitivity, energy dependence, and charge-collection stability were measured. The volumetric sensitivity was compared with that of a standard air-ionization chamber. Monte Carlo simulations using PHITS were performed to estimate the expected enhancement in energy-absorption density within diamond.Results: The HED-IC exhibited excellent dose linearity (R² > 0.997) even at bias voltages as low as −50 V. At −50 V to −100 V, its sensitivity was comparable to or higher than that of a standard air-ionization chamber despite a 1/830 smaller active volume. The volumetric sensitivity enhancement (4.5 × 10³–8.5 × 10³) was of the same order as the PHITS-calculated values (5 × 10³–6 × 10³), indicating consistent experimental and theoretical trends. The energy dependence across 25–45 keV remained within ±10 % without energy-compensation filters. After pre-irradiation (priming), the detector demonstrated negligible leakage current and reproducible charge-collection characteristics.Conclusions: The HED-IC provides a unique combination of high sensitivity, low-voltage operation, and minimal energy dependence, fulfilling key requirements for diagnostic X-ray dosimetry. Its scalability and cost-effectiveness enabled by heteroepitaxial diamond growth make it a promising candidate for compact, tissue-equivalent, real-time dosimetry and quality assurance in diagnostic radiology. |
