![]() ![]() The initial commissioning of the beamline was carried out in May 2021. Shanghai Soft X-ray Free-Electron Laser (SXFEL) is the first X-ray free-electron laser facility in China. 3School of Physical Science and Technology, ShanghaiTech University, Shanghai, China.2Shanghai Synchrotron Radiation Facility, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai, China.1Center for Transformative Science, ShanghaiTech University, Shanghai, China.The efficiency of X-ray production is governed by major factors such as kVp, current, exposure time, atomic number of the anode material, and beam filtration 4.Yajun Tong 1 Jiadong Fan 1 Yonggan Nie 1 Zhi Guo 2 Zichen Gao 3 Xinye Yuan 3 Bo He 3 Jiahua Chen 2 Difei Zhang 3 Hui Luan 3 Jianhua Zhang 1 Donghao Lu 3 Minghan Xie 3 Peng Cheng 3 Chao Feng 2 Tao Liu 2 Haixiao Deng 2 Bo Liu 2 Zhi Liu 1,3 Huaidong Jiang 1,3* Most of the X-rays produced are of low energy because electron beams have higher chances of striking outer zones of the target atom that produces low energy photons than inner zones of the target atom that produces high energy photons 4. If the applied voltage is more than 70kVp, the Bremsstrahlung interactions. When the applied voltage is less than 70kVp, Bremsstrahlung interactions account for ~100% of the X-ray beam. Most of the X-ray beam consists of Bremsstrahlung interactions in the diagnostic range of 30 to 150 kVp. It follows that light particles such as electrons and positrons bombarding targets of high atomic number are more efficient producers of bremsstrahlung radiation than heavier particles such as alpha particles or neutrons (which can also cause X-rays to be produced through bremsstrahlung, though it's much more unlikely than with electrons). The intensity of bremsstrahlung radiation is proportional to the square of the atomic number of the target ( Z), the number of unit charges of the bombarding particle (z) and inversely with the mass of the bombarding particle (m): Z² z / m. The unfiltered bremsstrahlung spectrum demonstrates a ramp shape with the probability of photon production being inversely linear with KE. The 'peak' of the filtered spectrum typically occurs at approximately one-third of Emax so for a bremsstrahlung spectra with an Emax value of say 120 keV, the peak of the spectrum would be at approximately 40 keV. Bremsstrahlung can have any energy ranging from zero to the maximum KE of the bombarding electrons (i.e., 0 to Emax), depending on how much the electrons are influenced by the electric field, therefore forming a continuous spectrum. The 'lost' energy is emitted as X-ray photons, specifically bremsstrahlung radiation (bremsstrahlung is German for 'braking radiation'). The principle of the conservation of energy states that in producing the X-ray photon, the electron has lost some of its kinetic energy (KE):įinal KE of electron = initial KE of electron - energy of X-ray photon The course of these electrons would be deflected, and a portion or all of their kinetic energy would be lost. When bombarding electrons penetrate into the target, some electrons travel close to the nucleus due to the attraction of its positive charge and are subsequently influenced by its electric field. X-rays are produced by high-energy electrons bombarding a target, especially targets that have a high proton number ( Z).
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