Stationary Anode X-ray Tube (Part - 6)

Summary

The video script discusses the functioning and application of a stationary anode X-ray tube, commonly used in dental X-ray units. It explains the construction of the tube, which consists of a cathode and an anode within a vacuum-sealed glass bulb. The cathode, made of tungsten, emits electrons when heated by a low voltage supply. These electrons are focused into a straight line by a focusing cap towards the anode, also made of tungsten, which acts as the target. The anode is designed to be stationary, and the emitted radiation is released through a special part of the glass envelope called the tube window, made of beryllium. The video also touches on the importance of maintaining a high vacuum within the tube to prevent gas ionization and damage to the tube. The stationary anode X-ray tube is particularly useful in dental X-ray machines for diagnostic purposes, and the video hints at covering more on fluoroscopic systems in upcoming content.

Takeaways

• 📡 The script discusses the functioning and construction of a stationary anode X-ray tube, used in medical imaging and dental X-ray units.
• 🔌 The anode in the X-ray tube is made of tungsten, which is chosen for its properties and is placed inside a copper block for heat dissipation.
• 💡 The filament, also made of tungsten, is heated by a low voltage supply to generate electrons that are emitted towards the anode.
• 🚫 The focusing cup is used to focus the electron beam in a straight line towards the anode, and it also protects the tube from damage by the electrons.
• 🔋 A high voltage supply is applied between the cathode and anode to accelerate the electrons, which then strike the anode and produce X-rays.
• 🧲 The anode is continuously rotated to distribute the heat generated by the electron impact and to increase the life of the tube.
• 🚿 The inside of the X-ray tube is maintained at a high vacuum (around 10^-5 mmHg) to prevent interaction between the electrons and gas molecules.
• 📏 The dimensions of the tungsten filament are critical for its function, with a diameter of approximately 2 micrometers and a length of about 1 centimeter.
• ⚙️ The stationary anode X-ray tube is divided into two parts: the stationary anode and the rotating anode, with the stationary anode being fixed and the rotating anode continuously spinning.
• 🔥 The target material on the anode, which is where the electrons strike, is also made of tungsten due to its high melting point and ability to withstand high temperatures.
• 🌟 The emitted X-rays are mostly absorbed by the target and converted into heat, which is why efficient heat dissipation is crucial for the anode's longevity.

Q & A

What is the principle behind the working of a Coolidge tube?

The Coolidge tube operates on the principle of thermionic emission, where a heated filament (cathode) releases electrons that are then attracted to a positively charged target, known as the anode.

How is the anode in a stationary anode X-ray tube constructed?

The anode in a stationary anode X-ray tube is made of tungsten due to its high melting point and is usually designed in a rectangular or square shape with a thickness ranging from 2 to 3 mm and dimensions larger than the filament.

Why is the filament in the cathode assembly of an X-ray tube spiral-shaped?

The filament is spiral-shaped to increase the surface area for electron emission, which enhances the efficiency of the X-ray tube.

What is the purpose of the focusing cup in the cathode assembly?

The focusing cup helps to focus the emitted electrons into a straight line and towards the target in a controlled manner, improving the focus and quality of the X-ray beam.

How does the vacuum in the X-ray tube affect the electron flow?

The vacuum in the X-ray tube allows the electrons to flow from the cathode to the anode without colliding with gas molecules, which would otherwise cause ionization and reduce the efficiency of the X-ray production.

What is the role of the beryllium window in an X-ray tube?

The beryllium window serves as a special part of the glass envelope that allows the X-rays to exit the vacuum tube while maintaining the vacuum seal.

Why is the anode in a rotating anode X-ray tube designed to rotate continuously?

The anode is designed to rotate to distribute the heat generated by the electron impact evenly across the surface, which prevents overheating and extends the life of the anode.

What is the significance of the angle cut inside the anode?

The angle cut inside the anode, typically between 15 to 20 degrees, is designed to allow the emitted radiation to exit the tube at a focused angle, improving the directionality and quality of the X-ray beam.

How is the heat generated in the anode during X-ray production managed?

The heat is managed by using a material with a high melting point like tungsten for the anode and by rotating the anode in rotating anode X-ray tubes to distribute the heat evenly.

What is the difference between a stationary anode and a rotating anode X-ray tube in terms of usage?

Stationary anode X-ray tubes are typically used in low to medium workload environments, while rotating anode X-ray tubes are used in high workload environments due to their ability to dissipate heat more effectively.

In what medical equipment is the stationary anode X-ray tube commonly used?

The stationary anode X-ray tube is commonly used in dental X-ray units and portable X-ray units where the equipment is moved from one location to another.

How does the X-ray tube current (tube current) relate to the diagnostic purposes?

The X-ray tube current, measured in milliamperes, determines the intensity of the X-ray beam. In diagnostic procedures, the appropriate tube current is selected to produce an X-ray beam of suitable intensity for the specific diagnostic task.