Research on the β-ray Radiation Effects and Detection Methods of CMOS Active Pixel Sensors

his paper conducts research on -ray detection methods based on complementary metal-oxy-semiconductor (CMOS) active pixel sensors (APS), analyzes the mechanism and characteristics of -radiation response and damage, discusses the nonlinear influence characteristics of annealing effect on sensor damage, and proposes a gain optimization method based on double-threshold constraints and develops a noise suppression technique utilizing temporal differences. Additionally, it establishes a -ray detection model correlating visual imaging with radiation absorption dose. Through 63Ni radioactive source irradiation experiments and Geant4 Monte Carlo simulations, the characteristics of -ray radiation response events of CMOS APS at different gains, the average pixel values of dark images at different integration times, energy deposition, damage modes and room-temperature annealing effects are studied. The experimental results show that the -radiation response event is characterized by the near-saturation of the pixel value of a single pixel and affects the sharp increase of the pixel values of a very small number of surrounding pixels. The optimal gain for -ray measurement was obtained as 43dB through the double-threshold constraint gain optimization method. When it is lower than 43dB, the sensor does not amplify the charge signal generated by -rays sufficiently, and the effective signal intensity is weak. When the gain is higher than 43dB, the response signal is distorted due to charge overflow. With the increase of irradiation time, the damage of CMOS APS keeps intensifying. The room-temperature annealing effect leads to a nonlinear change in its damage trend. During the annealing process, the reduction in the number of dark signals is partly due to the sensor's self-recovery to the pedestal noise level, and partly because of the intermittent failure of the pixels, temporarily losing the charge collection ability, manifested as a pixel value of 0. The temporal difference filtering method can well remove noise and effectively retain response events. Its retention rate reaches 99.75%, the signal-to-noise ratio has increased by 5.17 times compared with that before noise reduction. When the sensor is in the low-integration time region below 5.625ms, the matching degree between the calculated energy deposition and the simulated energy deposition is relatively high. However, in the high-integration time region above 5.625ms, the charge saturation effect occurs in the sensor pixels, the error increases significantly. The gray value - dose detection model based on piecewise exponential attenuation correction can achieve the quantification of the absorbed dose of -rays.