How often have you heard about X-ray tube filament without an idea what it means?
X-ray tubes can be described as the engine of the X-ray machine since the x-ray radiation comes from this device. However, the X-ray tube consists of other internal components which it uses to generate the X-ray radiation. Perhaps the most important of these components is the filament, as it combines with other internal components of the X-ray tube to produce the required electron beam. Understanding the filament’s function has a lot of benefits, especially in setting parameters like amperage and voltage is supplied to the filament during X-ray machine operation.
So, if you’d like to know more about the filament, then let’s dive in together.
I. What is the Filament of an X-ray Tube?
Generally, the filament is an integral part of the cathode. It is responsible for emitting the electrons beams from the circuit to hit the anode target’s focal spot. The filament is essentially a coil of wires, and it is a regulated source of electrons to produce X-ray beams created by heating the filament. Also, the filament is located inside a nickel cup-shaped formation used to focus the electron beams on the anode.
II. What is a Filament Circuit?
Within the main X-ray, machine circuit is a sub-circuit known as the filament circuit, which is responsible for supplying a low current for heating the filament to release electrons. The electrons are released using thermionic emission inside the X-ray tube. However, this circuit is divided by a stepdown transformer into two parts and is activated by the operator using the amperage selector on the generator. Furthermore, the current selector regulates the amperage of the filament circuit, which is responsible for regulating the heat generated while the X-ray machine is in operation.
III. What is Filament Current in an X-ray Tube?
The electric current responsible for exciting the filament to produce electrons is called the filament current. Usually, the heat generated when this current passes through the filament gets to a level that frees some of the electrons from the electrostatic forces keeping them in the filament. Naturally, the amount of current flowing in the filament is often proportional to the free electrons in the filament. It is generally related but not the same as the amperage controlled by the X-ray machine operator.
IV. What Material is the X-ray Tube Filament Constructed?
Due to the high heat energy produced during the X-ray machine operation, it is essential that the X-ray tube components, including the filament, be made from materials that can withstand this heat. Consequently, the filament is manufactured using tungsten material since tungsten has a high thermal resistance which makes it a suitable filament material. However, there is usually a cooling system provided within the X-ray tube to reduce the effect of the heat. Nonetheless, the tungsten material may start melting when the cooling system is inadequate for consistent heat, which can shorten the lifespan of the filament and even the X-ray tube.
V. Where is the Filament in an X-ray Tube?
Though the filament is one of the X-ray tube components, it is explicitly located within a structured component called the focusing cup. The focusing cup ensures that when the electrons are released by thermionic emission from the filament, they are well-directed at the focal spot of the anode. Without the focusing cup in place, there is the possibility of increased electron scatter, which makes the projection of the electrons ineffective and may cause an overheating of the filament, leading to the evaporation of the tungsten material.
VI. How to Maximize the Life of the X-ray Tube Filament?
The process of generating electrons is a necessary part of every X-ray machine operation, and with it comes heat generation from the filament. When heated to around 2,000 degrees Celsius, tungsten is an abundant emitter of electrons. However, a filament is bound to wear with continuous use if not properly maintained.
One good preventive maintenance practice to maximize the life of your X-ray tube filament is by using low voltages to power the filament as much as possible. The continuous high voltage delivery to the filament continuously contributes to the thinning of the filament and eventually causes a shorter lifespan.
Another good practice to maximize the filament’s life is using the manufacturer’s chart. Often, X-ray tube manufacturers provide charts and graphs to show the optimum combination of parameters like amperage, exposure time, boot time, and voltage requirements. Following the combinations of these parameters can help you elongate the life of your X-ray tube filament.
Likewise, ensuring the optimal function of the cooling system can help maximize the life of your X-ray tube filament. If the cooling system experiences a breakdown, it can cause heat.
In conclusion, while the X-ray tube filament is an essential element of the X-ray machine, understanding its working can have numerous benefits. Aside from being the producer of electrons for the X-ray machine, it also ensures that the required radiation for accurate inspection of the test sample is generated. It is placed in a nickel focus cup that ensures the electrons get to the focal spot of the anode. However, care and maintenance good practices need to be engaged to ensure you maximize the lifespan of the X-ray tube filament.
Now that you have this information, the ball is in your court. What’s your next move?