X-射线教学课件电子教案全套课件.pptx

Chapter 16 X-rays X-rays were discovered late in the nineteenth century by the German physicist Wilhelm Roentgen. Roentgen was studying low-pressure discharges in a gas and noticed that the anode of his discharge tube was the source of energetic and penetrating radiation. The penetrating properties of x-rays are of great practical important and have been utilized by medical profession almost since the year of their discovery.X-ray are produced when high-velocity electrons strike a solid target. (usually metal) Chapter 16 X-raysξ16-1 The generate of x-rays1.Device for generating X-ray1. the condition for generating X-ray are:(1). High-velocity electrons beam (2). the metal target The metal target resist the motion of the electrons and transfer their kinetic energy to the X-rays energy. X-rays are high-frequency electromagnetic wave whose possess the wavelength between some 0.05—100?. An electron discharge through a low-pressure gas makes relatively small energies available for excitation. The outmost atomic electron is excited and the resulting spectrum mainly in the visible and infrared region. A mode of excitation that can eject electrons from inner levels result in x-rays emission. Let us briefly describe the usual method of exciting inner shell electrons. And then interpret The situation in term of quantum energy levels. Chapter 16 X-raysThe numbers of the emitted x ray photons and the total energy is approximately proportional to the square of the atomic number of the target material. High voltage applied to the tube V: 100-102kvcurrent across the tube i:102-103mA 2. X ray generatorA typical X-ray tube is illustrated in figure below. A beam of electrons emitted from a hot cathode in a vacuum is accelerated by high-voltage and strike a metal target anode. Fig 16-1Am102kvcathodeanode Chapter 16 X-raysThe impact energy of the beam of electrons eject some electrons from the inner shells of the atoms in the target, enabling