What Is an X-Ray Generator?
An X-ray generator is a device that generates X-rays, a type of radiation. X-rays were discovered by Dr. Wilhelm Convert Roentgen in 1895. It was the great discovery of the century because of its property of penetrating matter, and X-rays astonished people of that time.
Today, X-ray generators are used in a wide variety of locations, taking advantage of their penetrating properties for industrial applications such as medical and industrial machinery, as well as for physical and chemical research purposes. It can be said that this technology is widely known, especially since it is used in medical applications as X-rays.
Uses of X-Ray Generators
X-ray generators are widely used for medical purposes. X-ray examination, which everyone has heard of, is another technology that uses X-rays.
When the human body is irradiated with X-rays, low-density areas such as the skin and lungs are penetrated by the X-rays, while high-density areas such as bones and teeth are not penetrated and are absorbed.
The X-ray beam is also used in industrial applications to check products, as it can be used to check the inside of products without destroying them. This technology is also used in familiar places such as baggage screening at airports.
Principle of X-Ray Generators
An X-ray generator, also called an X-ray tube, consists of a target, which serves as the anode, and a filament, which serves as the cathode, inside a vacuum.
When a high voltage (tens to hundreds of thousands of volts) is applied between the electrodes, hot electrons are ejected from the cathode filament and travel at high speed to the anode target. X-rays are generated when they hit the target.
When electrons strike the target and enter the atom, most of their energy is converted to heat. Some of the electrons collide with electrons in the atom, forming an unstable state (an excited state). When an atom enters an excited state, it releases energy to return to a stable state. X-rays are produced as energy during the transition from the excited state to the stable state. There are two main types of X-rays produced.
1. Characteristic X-Rays
Characteristic X-rays are X-rays that are emitted when excited electrons transition to the stable state. Since X-rays equal to the energy difference between electron orbitals are generated, they have strong energy at a single wavelength. Since the energy between electron orbitals is unique for each element, the element-specific X-rays are also generated. This property is used in X-ray fluorescence (XRF) to analyze the composition of materials.
2. Continuous X-Rays
X-rays are produced when thermal electrons collide with a target and rapidly decelerate. The X-rays are also called bremsstrahlung X-rays because they are produced during the braking process. The wavelength of the X-rays produced depends on where on the target they strike, so they are compound wavelengths. They are used in fluoroscopy and other applications. The majority of the X-rays emitted are continuous X-rays.
Other Information on X-ray Generators
1. Tubes of X-Ray Generators
The tube of an X-ray generator is a vacuum tube, mainly made of glass, with a positive electrode (anode) and a negative electrode (cathode) inside the tube. The tube bulb has a filament (converging electrode) at the cathode and a target at the anode.
When a high voltage is applied to both electrodes using a high-voltage transformer or other high-voltage power supply, thermal electrons are emitted from the filament to the target. Tungsten is used for the filament, and tungsten or molybdenum is used for the target.
There are two types of tubes: fixed-anode X-ray tubes, which do not have a rotating anode structure, and rotating-anode X-ray tubes, which have a rotating anode structure. In the rotating type, an umbrella-shaped target is rotated at high speed to prevent local overheating of the target surface. This increases the tube current and thus the X-ray intensity.
Rotating anode X-ray tubes sometimes emit abnormal noise due to misalignment of the axis of rotation or distortion of the bearings after years of use. If the X-ray tube walls are made of glass, continued use of the tube in such a condition may cause the anode to melt or the anode axis to bend, destroying the tube itself.
2. Notification of Use Regarding X-Ray Generators
The following actions are required when installing an X-ray generator for industrial use.
- Central government agencies: Notification to the National Personnel Authority within 30 days of installation
- Public institutions: Notification to the Personnel Affairs Commission of each prefecture at least 30 days before the planned installation
- Private companies: Notify the Labor Standards Inspection Office within 30 days before installation
It is also important to carefully check the local government’s notification rules for X-ray equipment, as notification to the local government may also be required when changing the location of the equipment or when disposing of the equipment. Equipment with a 1 cm dose equivalent rate of external radiation exceeding 20 μSv/h must be installed in a radiation equipment room. On the other hand, equipment that is shielded below 20 μSv/h does not need to be installed in a radiation equipment room.
In addition, when using an X-ray generator, an X-ray work supervisor must be appointed for each controlled area from among those who have obtained an X-ray work supervisor license in principle. However, if the irradiation area is not irradiated unless it is separated from the