Graded-gap AlxGa1−xAs high-energy X-ray radiation dosimeter

The detectors for high-energy X-ray dosimetry based on graded-gap AlxGa1−xAs structures were developed. Two types of graded-gap AlxGa1−xAs structures characterized by different operating mechanisms (the first type, an internal optical response, and the second one, a charge collection by an internal graded-gap field) were investigated as high-energy X-ray radiation detectors. The linear response on absorbed dose and dose rate for both 6 and 15 MV photon beams was obtained. The angular dependence of the detector response was negligible for a wide range (±90°) of incidence angle of radiation beam. Good agreement of relative depth dose distribution measured by the first type of detector and ionization chamber in PMMA phantom is obtained in the vicinity of the absorbed dose maximum. The radiation field profile measurements show a better spatial resolution of the graded-gap AlxGa1−xAs detector in comparison with the spatial resolution of the small-volume ionization chamber. The experimental results of this study demonstrate suitability of the graded-gap AlxGa1−xAs detector for relative dosimetry of high-energy X-ray beams, especially for a high spatial resolution measurement.