X-ray Production yr1.pdf

X-ray Production X-rays are produced in an X-ray tube. In all X-ray tubes, the source of electrons is a heated filament made of tungsten wire, the cathode (negative charge) – Thermionic emission: discharge of electrons from heated filament....

X-ray Production X-rays are produced in an X-ray tube. In all X-ray tubes, the source of electrons is a heated filament made of tungsten wire, the cathode (negative charge) – Thermionic emission: discharge of electrons from heated filament. The area that is bombarded by the electrons is called the focal spot, and it is part of a metal body called the anode (positive charge). The high voltage in the tube accelerates the electrons from the cathode filament to the anode target, resulting in X-ray production. High speed electrons interact with the target nucleus in two ways: Bremsstrahlung Characteristic radiation Bremsstrahlung (braking radiation) occurs when electrons, are decelerated or slowed down as they interact with matter. Bremsstrahlung X-rays are generated by this abrupt deceleration of electrons, within the atomic structure of the target material. X-rays are produced from the conversion of kinetic energy of electrons into electromagnetic radiation when they are decelerated by interaction within a target material. Interaction with Atomic Nuclei: As these fast-moving electrons approach the atomic nuclei of the target atoms, they experience strong electrostatic forces from the positively charged nuclei, causing the electrons to slow down and change direction. This is the deceleration phase. o In other words, when electrons from the cathode enter the anode, some electrons are attracted to the positive charge of the nucleus within the tungsten atoms causing the electrons to slow down due to this attraction. Emission of X-rays: During this deceleration, energy is lost by the electrons in the form of electromagnetic radiation, primarily X-rays. The emitted X-rays have a broad spectrum of energies and are often referred to as "bremsstrahlung radiation." The energy of these X-rays depends on the initial energy of the incident electrons and the degree of their deceleration. Consequently, the resulting X-ray spectrum is continuous, meaning it covers a wide range of energies. 1  o In other words, the lost energy is released in the form of an x-ray photon – Bremsstrahlung radiation The x-ray energy depends on the interaction distance between the electron and the nucleus, and increases as the distance decreases. When the distance is zero, all the kinetic energy of the electron creates the maximum bremsstrahlung photon energy. (Kinetic energy loss converted to X-ray energy). Characteristic Radiation occurs when high-energy electrons interact with matter and it leads to the emission of X- rays with well-defined energies. These x-rays are produced when target K-shell electrons are ejected by the incident energetic electrons. The process of characteristic X-ray production can be explained as follows: Electron Interaction: In an X-ray tube, a beam of high-energy electrons is accelerated towards a target material. When these high-energy electrons approach the atoms of the target material, they interact with the electrons in the inner shells, K shells of the target atoms. Inner Shell Ionization: The high-energy electrons collide with the K shell electrons of the target atoms. During these collisions, some of the energy from the incident electrons is transferred to the K-shell electrons. As a result, K-shell electrons may be ejected, leaving behind vacancies in those shells. Cascade Effect: To fill these vacancies in the inner shells, outer-shell electrons drop down to lower energy levels. As they do so, they release energy in the form of X-ray photons. These X-ray photons have energies that are specific to the energy difference between the involved electron energy levels. Characteristic X-rays: The X-ray photons produced in this manner are called characteristic X-rays. They are characteristic of the target material because the energies of these X-rays are unique to each element. This results in X-ray spectra with distinct lines at specific energies, corresponding to the characteristic X-rays of the target material. 2 3