Can you identify all X-ray tube parts and their functions if your life depended on it?
The X-ray tube is an essential part of an X-ray machine as it helps to produce and project the radiation energy that X-ray machines use to identify flaws and confirm material properties. However, the ability to define the individual parts of the X-ray tube is beneficial in so many ways including helping you know the functions of the X-ray tube components. Consequently, knowing the functions of these parts can be a lifesaver during the maintenance of the X-ray tube which is often done to prevent the breakdown of the X-ray tube and the X-ray machine.
So, if you are ready to know more then let’s dive in together.
I. X-ray Tube Anode (Target)
One of the most important parts of the X-ray tube is the Anode. The Anode acts as the complementary component to the cathode but functionally it attracts electrons from the cathode once the X-ray machine operator pushes the exposure button. However, the anode itself is positively charged and there is often a lot of heat generated during any X-ray machine operation.
This heat is responsible for using a high thermal resistant material like tungsten for manufacturing the Anode. Yet, the disc of the Anode rotates very fast to spread the heat generated across its entire surface thereby avoiding the concentration of the heat on a particular spot. But more importantly, the Anode acts as the target for the electrons coming from the cathode with an angle that helps the projection of the electron beams towards the detector.
In any case that the Anode’s rotation fails, then the impending damage will be huge. Despite the fact that tungsten can handle a tremendous amount of energy, even that will not be able to prevent the damage to the Anode if it does not rotate during an X-ray machine operation.
II. Cathode X-ray Tube (X-ray Tube Filament)
As a complementary component to the Anode, the Cathode has negative charges that it releases during operation, and it is directed towards the Anode for further projections. Primarily, you’ll find two other attached components with the Cathode, and these are the focusing cup and the filament.
These two attached elements are responsible for generating and channeling the electrons to the Anode as well as generating a lot of heat in the process. Fortunately, the Cathode is constructed with Molybdenum Nickel alloy, a material that has high heat resistance.
But here is the thing, the size of the X-ray beam generated and projected by the Cathode is dependent on the focal spot size set by the technologist operating the machine. But then, this focal spot size is selected based on the size of the tested sample.
For instance, a 50mm thick steel material will need more radiation for penetration than a 5mm thick steel material. Therefore, an operator is bound to set a higher value for the focal size when inspecting the 50mm thick material than the 5mm thick material.
III. Filament Holder
If the two most important parts of the X-ray tube are the cathode and anode, then it’s safe to say the filament holder falls in line as the next most important component of the X-ray tube. The reason is because the filament holder holds the filament which generates the X-ray energy in place making sure that it does not fall off during operation.
Depending on the size of the test sample the filament should generate enough radiation to penetrate the material and sometimes when the materials are so large the energy also becomes enormous. Nonetheless, the filament holder guarantees that there is no bridge between the filament and the power source ensuring that the right amount of energy gets to the filament.
IV. Guide Coil
For the electrical power to reach the stator and rotor the wires are passed through an insulating flexible coiled material known as the guide coil. The basic function of the Guide Coil is to enable the electrical connection to navigate the irregular shapes of the X-ray tube and to insulate other components that come in contact with these connecting elements.
V. Focus Coil
The focus coil is an accessory for the focusing cup and it assists in ensuring that the focus cup is able to accurately direct the electrons from the cathode to a predetermined point of the anode. While the predetermined point of the Anode also known as the focal point redirects the radiation to the test sample, a breakdown of the focus coil can reduce the efficiency of the focus cup from pointing the radiation to the focal point on the Anode.
VI. X-ray Tube Housing
Generally, X-ray tube components are categorized as either internal components or external components. However, the external component is usually the housing that keeps the internal components contained within the tube simply because the radiation produced travels in different directions within the X-ray tube. The X-ray tube housing is a metal container shielding the radiation produced within the x-ray tube from leaking out.
Additionally, the lead lining within the housing ensures that there is no possibility of any radiation exposure both to the operator as well as others around the machine. Most importantly, because of the high voltage required to produce the X-ray radiation the housing acts like an insulation wall to prevent the occurrence of an electric shock to the operator.
VII. X-ray Tube Glass Envelope
The glass envelope is an essential vacuum-filled part of the X-ray tube housing, and it contains the components necessary to produce the X-ray energy. Usually, these components consist of the anode, cathode, filament coils, focus cup, and focus coil. Also, the glass envelope is made with Pyrex glass which is suitable for withstanding the enormous heat generated in the radiation production process.
However, the production of the radiation generates immense heat that can cause the tungsten material used for anode to evaporate causing some deposits on the glass ware. Subsequently, these deposits begin to buildup and can become a hindrance to the production and appropriate projection of the radiation over time.
VIII. X-ray Tube Support
The X-ray tube support is simply the external accessories required to hold up the components of the X-ray tube as a unit without it falling apart during an operation. Some of these supports include the housing and all its accessories like screws, anchor plates, and metal strips. These elements ensure the rigidity and sturdiness of the X-ray tube.
However, regardless of how firm the X-ray tube support holds the X-ray tube in place, there is always a need to check these elements during periodic and routine maintenance activities to ensure they remain intact.
The rotor is a very key part of the X-ray tube in that it holds the anode disc in place before, during, and after any X-ray operation. The Anode disc can rotate at very speeds depending on the size of the sample under examination and the intensity of the radiation required. Therefore, the rotor ensures that during these high-speed operations the disc is well-supported, and it rotates according to the speed set.
The rotor and the Anode disc are rigidly connected through the Anode disc. However, while the Anode disc is made of molybdenum the rotor is made of copper since it does not receive any radiation to its body. The presence of a high-strength ball bearing in the rotor makes the rotation easy and smooth.
X. Induction Stator
While the Anode is complementary to the Cathode, the Rotor and Induction Stator seem to share this relationship also. The Induction Stator is an electric motor that serves as the enabler for the Rotor to rotate at sometimes very high speeds as it provides the electric power needed for this activity. Mostly, the stator uses an induction method which also uses a set of coils to induce a strong magnetic field to produce the electric energy needed for the rotation hence the name induction stator.
XI. Cooling Dielectric Oil
During the X-ray machine operations, the rotor and the Anode disc can rotate at up to 3,200 rpm speeds generating excessive heat in the process. Likewise, the heat is further intensified when the radiation from the filament hits the rotating Anode disc sometimes reaching extreme levels of heat. Dissipating this heat becomes very important to keep the machine working in optimum condition. Hence, cooling oil is provided to dissipate this heat. But that’s not all. The cooling oil also serves as an insulation medium to prevent electric shocks since both cathode and anode are electrically charged.
XII. Tube Window
Inside the glass envelope of the X-ray tube housing is an important opening that is not more than 5cm wide called the X-ray tube window. The importance of this tube window cannot be overemphasized as it remains the only opening through which any radiation generated can leave the glass envelope. It also makes sure that almost all the electron beam needed to reach the sample under inspection gets there.
However, a minute part of the radiation will not leave the glass envelope and will end up being absorbed by the glass housing and eventually reduce the efficiency of the glass tube. But the good news is that the glass material can be replaced to restore the glass envelope’s efficiency.
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What does all this mean? The benefits of knowing all the parts of the X-ray tube and their functions mentioned in this guide are numerous and includes the ability to troubleshoot a problem in the case of a breakdown in the X-ray machine. Sometimes the fault might be a minor one that pertains to the X-ray tube, and which can be fixed without the need to call an external technician who might be very expensive.
Also, if you are in the market for a new X-ray machine, you should be able to specify a suitable X-ray tube for the supplier based on your knowledge of the parts of the X-ray tube. In all, this guide has tried to educate you on the necessary basic knowledge of a major price-impacting part of an x-ray machine that any individual in the X-ray industry should understand.