This section provides overview, applications, and principles of x-ray tubes. Also, please take a look at the list of 4 x-ray tube manufacturers and their company rankings.
An X-ray tube is a type of X-ray generator.
X-rays are generated when thermal electrons moving at high speed from the cathode to the anode inside the X-ray tube are attracted to the metal nucleus of the anode and change direction.
There are two types of X-ray tubes: sealed tubes, in which the inside of the tube is always kept in a vacuum, and open tubes, in which a vacuum pump is installed outside the tube to create a high vacuum. Sealed tubes are further divided into rotating anode tubes with rotating anodes and fixed anode tubes without a rotating anode structure.
There are also microfocus and mini-focus types of X-ray tubes, depending on the focal spot size. These are X-ray tubes with focal lengths in the order of microns and millimeters, respectively.
X-rays are electromagnetic waves with shorter wavelengths than ultraviolet rays, and their high energy has a penetrating effect that allows them to pass through materials. Taking advantage of this penetrating effect, X-ray tubes are used as X-ray generators in a variety of fields.
In the medical field, X-ray tubes are used for general radiography, mammography, CT examinations, and other testing applications, as well as for treatment applications such as X-ray therapy used in cancer treatment.
In the scientific and industrial fields, X-ray tubes are also used for analytical applications such as X-ray diffraction and fluorescent X-ray analysis, non-destructive testing, and inspection of materials such as thickness, etc. They are also used for baggage inspection at airports.
An X-ray tube consists of an enclosure, a cathode (filament), and an anode (target).
When a high voltage is applied between the cathode and anode after an electrical current has heated the cathode filament, heat electrons are emitted from the filament and travel at high speed to the anode target.
The thermal electrons are attracted to the nucleus of the anode material, such as tungsten, and rapidly change direction, releasing energy. At this time, 99% of the energy is converted to thermal energy, but the remaining 1% is emitted as X-rays. These X-rays are called bremsstrahlung X-rays and have a continuous spectrum.
Some thermal electrons collide with the target atom's electrons, which is rare. The collided electrons gain energy from the thermal electrons and are repelled, transitioning to the outer electron orbitals, but because of their instability, they quickly return to their original orbitals. The difference in the energy state of the electron orbital is emitted as X-rays. These X-rays are called characteristic X-rays and appear as a line spectrum.
Most X-rays produced by X-ray tubes are bremsstrahlung X-rays extracted through windows made of beryllium or other materials with low X-ray absorption in the tube enclosure.
*Including some distributors, etc.
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