2.5 X-ray and Its Physical Characteristics
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(1) Penetrating Capability
The X-rays have the short wavelength, high-energy and no charged properties.
When matter is radiated by the X-rays, only a small fraction of energy is
absorbed by the matter while most of the energy is passed through the atomic
gaps of the matter. And thus, the X-rays usually show so strong penetration
capability that they can easily pass through a book with several thousand pages
thick, plank or hard rubber with several centimeters and aluminum plate with
less than 20 mm. The penetrating capabilities of the X-rays are related with their
wavelengths and the densities of various matters. A plumbum plate only with
1.5 mm thickness can almost obstruct all X-rays to pass through. Moreover,
X-rays can also not pass through the dense atmosphere.
(2) Ionizing Radiation
The X-ray photons carry enough energy to ionize atoms and disrupt molecular
bonds. Under the irradiation of the X-rays, the electrons outside the atomic
nuclei for matter will escape from the atomic orbits to bring up ionizing. By
measuring the ionizing charges, the radiation dose of X-rays can be determined.
This is a basic principle of detecting the X-rays. The ionizing radiations of Xrays can induce gas to conduct electricity, matter to happen chemical reaction
and organism to bring up biological effect.
(3) Fluorescent Effects
The wavelengths of X-rays are shorter than those of visible lights and usually
are invisible. However, if some chemical compounds, such as phosphorus,
barium platinocyanide, cadmium zinc sulfide and calcium tungstate, are radiated by the X-rays, the fluorescents, like visible lights or ultraviolet rays, will
occur in these materials. The strengths of the fluorescents are proportional to
the radiation dose of X-rays. This is a basic principle of X-ray fluoroscope
imaging.
(4) Thermal Effects
When a solid material has absorbed the energy of X-rays, most of the energy
is transformed into the thermal energy resulting in the temperature rise. The
amount of temperature rise is dependent on the energy of the X-ray photons.
(5) Interference, Diffraction and Reflection Effects
The X-rays have much shorter wavelengths than visible light, which makes it
possible to probe material structures much smaller than can be seen using a
normal microscope. The property is used in X-ray microscopy to acquire highresolution images, and also in X-ray crystallography to determine the positions
of atoms in crystals. In these applications, the interference, diffraction and
reflection effects of X-rays can be shown sufficiently.
2.6 Mechanism of X-ray Detection
In essence, the interactions between X-ray photons and materials are an absorption
process. High-energy photons interact with material atoms to lose all their energy,
59
(1) Penetrating Capability
The X-rays have the short wavelength, high-energy and no charged properties.
When matter is radiated by the X-rays, only a small fraction of energy is
absorbed by the matter while most of the energy is passed through the atomic
gaps of the matter. And thus, the X-rays usually show so strong penetration
capability that they can easily pass through a book with several thousand pages
thick, plank or hard rubber with several centimeters and aluminum plate with
less than 20 mm. The penetrating capabilities of the X-rays are related with their
wavelengths and the densities of various matters. A plumbum plate only with
1.5 mm thickness can almost obstruct all X-rays to pass through. Moreover,
X-rays can also not pass through the dense atmosphere.
(2) Ionizing Radiation
The X-ray photons carry enough energy to ionize atoms and disrupt molecular
bonds. Under the irradiation of the X-rays, the electrons outside the atomic
nuclei for matter will escape from the atomic orbits to bring up ionizing. By
measuring the ionizing charges, the radiation dose of X-rays can be determined.
This is a basic principle of detecting the X-rays. The ionizing radiations of Xrays can induce gas to conduct electricity, matter to happen chemical reaction
and organism to bring up biological effect.
(3) Fluorescent Effects
The wavelengths of X-rays are shorter than those of visible lights and usually
are invisible. However, if some chemical compounds, such as phosphorus,
barium platinocyanide, cadmium zinc sulfide and calcium tungstate, are radiated by the X-rays, the fluorescents, like visible lights or ultraviolet rays, will
occur in these materials. The strengths of the fluorescents are proportional to
the radiation dose of X-rays. This is a basic principle of X-ray fluoroscope
imaging.
(4) Thermal Effects
When a solid material has absorbed the energy of X-rays, most of the energy
is transformed into the thermal energy resulting in the temperature rise. The
amount of temperature rise is dependent on the energy of the X-ray photons.
(5) Interference, Diffraction and Reflection Effects
The X-rays have much shorter wavelengths than visible light, which makes it
possible to probe material structures much smaller than can be seen using a
normal microscope. The property is used in X-ray microscopy to acquire highresolution images, and also in X-ray crystallography to determine the positions
of atoms in crystals. In these applications, the interference, diffraction and
reflection effects of X-rays can be shown sufficiently.
2.6 Mechanism of X-ray Detection
In essence, the interactions between X-ray photons and materials are an absorption
process. High-energy photons interact with material atoms to lose all their energy,