Detectors 215
Detectors 215 : Particle Detectors: (4.27) X-Ray Detector: X-ray detectors are devices used to measure the flux, spatial distribution, spectrum or other properties of X-rays. They vary in shape and function depending on their purpose. Some common principles used to detect X-rays include the ionization of gas, the conversion to visible light in a scintillator and the production ofelectron-hole pairs in a semiconductor detector. Imaging detectors such as those used for radiography were originally based on photographic plates and laterphotographic film but are now mostly replaced by various digital detector types such as image plates or flat panel detectors. For radiation protection direct exposure hazard is often evaluated using ionization chambers, while dosimeters are used to measure the radiation dose a person has been exposed to. X-ray spectra can be measured either by energy dispersive or wavelength dispersive spectrometers. X-ray detectors can be either photon counting or integrating. Photon-counting detectors measure each individual x-ray photon separately, while integrating detectors measure the total amount of energy deposited in the active region of the detector. Photon-counting detectors are normally more sensitive since they do not suffer from thermal and readout noise in the same way. An other advantage is that they can be set to count only photons in a certain energy range, or even messure the energy of each absorbed photon. Integrating detectors are normally simpler and can handle much higher photon fluxes
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