Thermionic-Emission Modeling and DN-PSO Based Parameter Identification of X-Ray Tube

The X-ray tube is a crucial and costly component of X-ray machines. It generates tube current through filament heating and a high-voltage electric field, both of which are related to the X-ray dose rate. However, changing conditions within the tube can lead to deviations and overshoots in tube current control, which in turn affects the X-ray dose rate. Manual calibration of the tube is occasionally necessary to adjust the mathematical relationship pre-stored in the microcontroller, but this process can reduce the lifespan of the X-ray tube. To address this issue, this paper presents a thermionic-emission model for the X-ray tube current. A heat transfer model for the tungsten cathode has been developed, and the unknown parameters in the tube current model are identified using a dynamic neighborhood particle swarm optimization (DN-PSO) algorithm. The proposed tube current model is utilized to enhance the control of filament current. Experiments were conducted using a 1 kW/100 kV C-arm X-ray generator equipped with an XD56 tube. The results indicate that the proposed identification method significantly improves the accuracy of the derived model in comparison to the actual tube current. The improvements in filament current control have led to a reduction in tube current overshoot, a shorter tube current establishment time, and fewer instances of tube current dropping below a specified threshold.