tailieunhanh - Advances in Measurement Systems Part 4

Tham khảo tài liệu 'advances in measurement systems part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 116 Advances in Measurement Systems concerning the energy dependencies of the Mass Attenuation Coefficient . The resulting spectrum contains a higher energy content making the beam more penetrating harder . Figure provides example plots of spectral content of Tungsten target radiation attenuated by a glass window aperture for differing applied tube potentials. Fig. - Graphical representations of the spectral content of the radiation emitted from a Tungsten target X-Ray tube with a glass aperture window showing the Characteristic and Bremsstrahlung radiation spectrum for 80kV and 40kV tube potentials. The key feature of this spectrum is the significant attenuation by the aperture window of the lower energy region as noted by the diminished region of Bremsstrahlung radiation below 20kV . It is important to note that the lower tube potential 40kV does not provide an electron beam with sufficient kinetic energy to dislodge the target material s K shell electrons indicated by the lack of K Series recombinational spectral lines . Controlled Variability of Tube Generator Emissions - By varying the applied tube potential and beam current the radiated tube generator spectral content and intensity can be adjusted to meet the needs of the measurement application. Figures and show the reactions of the Bremsstrahlung radiation spectra to changes in the tube potential and beam current respectively. Beam Hardening - This term traditionally describes the process of increasing the average energy of the emitted spectrum. This causes the resulting beam to have a greater penetrating capability. Beam hardening can be achieved through the used of selected pre-absorbers whose spectral attenuation characteristics suppress lower energy regions compare Figures and . This beam hardening effect can also be formed by increasing the applied tube potential. As shown in Figure increasing the tube voltage causes the emitted spectrum s peak intensity to shift to higher