The working principle of an X-ray irradiation instrument is based on the generation, propagation, and interaction of X-rays with matter. Its core scientific mechanism covers three major links: radiation source generation, energy regulation, and precise dose control.
Radiation source generation: The X-ray irradiator accelerates electrons with high voltage to collide with metal targets such as tungsten or molybdenum. The inner layer electrons of the target material atoms are excited to a high energy level and then transition back to a low energy level, releasing energy in the form of X-rays. This process produces continuous spectrum X-rays, whose energy range depends on the acceleration voltage and the characteristics of the target material. For example, when the electron energy reaches the level of gigaelectronvolts, hard X-rays with wavelengths less than 0.1 nanometers can be radiated.
Energy regulation mechanism: The interaction between X-rays and matter mainly achieves energy deposition through photoelectric effect, Compton scattering, and electron pair effect. In the photoelectric effect, the energy of incident photons is absorbed by matter and electrons are released; Compton scattering leads to an increase in photon wavelength and a decrease in energy, while electrons gain kinetic energy. By adjusting the tube voltage (which determines photon energy and penetration capability) and tube current (which affects photon dose and imaging signal-to-noise ratio), the output characteristics of X-rays can be precisely controlled. For example, increasing the time product of tube current when reducing tube voltage can reduce radiation dose while ensuring imaging quality.
Accurate dose control: Dose control is the key to ensuring the safety of experiments and the reliability of results. It is achieved through multiple mechanisms: using automatic exposure control (AEC) to monitor the dose of penetrating radiation in real time, and automatically terminating the exposure when the preset threshold is reached; Using collimator beam limiting technology to accurately cover the target area with the irradiation field, avoiding ineffective radiation; By absorbing low-energy X-rays through a filtering plate, the effective dose distribution is optimized. In addition, the dose calibration process uses standard measurement tools such as finger ionization chambers and dosimeters to measure the dosimetric parameters of the equipment under specified conditions (such as SSD=100cm, field 10cm × 10cm), and adjust the equipment indication values to be consistent with the standard values to ensure the accuracy of dose output.