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X-Ray Tube Cathode and Focusing Caps Quiz

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X-Ray Tube Cathode and Focusing Caps Quiz

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Questions and Answers

What is the primary function of the cathode in an X-ray tube?

To focus electrons onto the anode

To accelerate electrons towards the anode

To produce X-rays

To generate electrons through thermionic emission (correct)

What is the purpose of the tungsten filament coils in the cathode?

To accelerate electrons towards the anode

To generate heat for thermionic emission (correct)

To produce X-rays

To focus electrons onto the anode

Why is tungsten used for the filament coils?

Because it has a low atomic number

Because it is cheap and abundant

Because it can be machined into thin coils with high surface area, high melting point, and is a good thermionic emitter (correct)

Because it has a low melting point

What is the function of the focusing cap?

To focus electrons onto a smaller area on the anode Signup and view all the answers

What is a benefit of using biased focusing caps?

They allow for independent control over the focus of electrons Signup and view all the answers

What is the result of accelerating electrons towards the anode?

The production of X-rays Signup and view all the answers

What is the typical material used to make focusing caps?

Molybdenum or nickel Signup and view all the answers

What is the primary mechanism by which the anode copes with heat?

Radiation and uranium addition to prevent surface cracking Signup and view all the answers

What is the purpose of angling the anode in an X-ray tube?

To improve x-ray beam geometry Signup and view all the answers

What can be adjusted to change the size of the focal spot?

Anode angle Signup and view all the answers

What is the primary method of heat removal from the anode?

Radiation Signup and view all the answers

What is the primary material used to make the anode?

Tungsten Signup and view all the answers

What can be adjusted to balance image quality needs with heat production at the anode?

Tube potential and filament current Signup and view all the answers

Study Notes

The cathode is the negative electrode in an X-ray tube responsible for producing electrons through thermionic emission.
Electrons produced at the cathode are accelerated towards the anode when a voltage is applied across the tube, leading to the generation of x-rays.
The cathode contains tungsten filament coils that are machined into the face of the cathode, allowing for the production of electrons on its surface through thermionic emission.
Thermionic emission works by running a current through the tungsten filament coils, generating heat that excites valence electrons to the surface, making them available for acceleration.
Tungsten is used for the filament coils due to its ability to be machined into thin coils with high surface area, high melting point, and being a good thermionic emitter with a high atomic number.
The focusing cap, usually made of molybdenum or nickel, helps focus electrons onto a smaller area on the anode to create a more defined focal spot for better image quality.
Focusing caps can be unbiased or biased, with biased caps allowing for independent control over the focus of electrons without needing to release more electrons.

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Description

Test your knowledge on the cathode and focusing caps in X-ray tubes, including their functions and materials. Learn about thermionic emission, tungsten filament coils, and the purpose of focusing caps in electron acceleration. Explore the differences between biased and unbiased focusing caps for controlling electron focus.