Determination of the efficiency of high purity germanium and silicon diode detectors for improved assessment of emission spectra delivered by medical X-ray tubes
Résumé
X-ray sources are widely used in medicine: brachytherapy, radiodiagnosis, mammography and contact radiotherapy. Kerma in air is the primary quantity measured to determine the dose to the patient. Accurate air kerma assessment is obtained using correction factors calculated using the emission spectrum. The Laboratoire National Henri Becquerel launched an in-depth study of the spectral emission of its reference X-ray beams used in dosimetry.
Two semiconductor detectors are discussed here: a High-Purity germanium and a silicon PiN, both cooled and operated with dedicated electronics and software. In the low energy range (E < 50 keV), those spectrometers are complementary but require a careful calibration to deduce the emitted spectrum from the detected one. Indeed, both detectors were characterized in terms of spectral response and intrinsic efficiency using a tuneable monochromatic X-ray source (SOLEX at CEA Saclay) in the 5- to 20-keV energy range and various radionuclides.
The characterization methods and results, including the first measured spectra of medical X-ray tubes (high voltage < 50 kV), are presented in this work. This paper presents the first step of a broader project, aiming at assessing the emission spectrum independently of the detector choice.
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