X-ray detectors are used in many fields such as medicine, astronomy, security, and non-destructive testing. Research on X-ray detectors is also constantly developing. The film imaging system is the oldest X-ray imaging system and is still used in many backward hospitals. Although such a system has superior spatial resolution, this method is very inefficient, requires more human resources, and does not provide real-time imaging applications. In addition, conventional detectors such as detectors using photomultiplier tubes (PMT) and NaI scintillation crystals, and silicon-lithium drift detectors are not widely used due to their limitations. The former is bulky, the NaI scintillation crystal is deliquescent, the PMT needs stable high pressure to maintain the work, and the latter is limited by the low temperature cooling.
In recent years, with the development and maturity of silicon process technology, more and more researches on X-ray detectors based on silicon technology have been made and many achievements have been made. These results include photodetectors assembled with scintillation crystals and diodes, PIN diodes, and the like.
Structure and preparation of X-ray detector The X-ray detector developed consists of a scintillation crystal and an array of silicon photodiodes. The scintillation crystal converts the incident X-ray into visible light, the diode senses visible light, is converted into an electrical signal, and is read by the readout circuit.
Structure and working principle of array silicon photodiode with its own scanning circuit
The structure of the device is shown in the figure: it consists of five parts: shift register, transfer gate, photodiode, reset and output amplifier. In the figure, Vin and cp are the driving pulses of the device, Vdd, gnd, VD and VR are the working levels of the device, Q is the output verifying signal of the shift register, Vr is the reset pulse, and Vout is the signal output end.
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