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Questions and Answers
What is the primary function of the cathode in an X-ray tube?
What is the purpose of the tungsten filament coils in the cathode?
Why is tungsten used for the filament coils?
What is the function of the focusing cap?
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What is a benefit of using biased focusing caps?
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What is the result of accelerating electrons towards the anode?
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What is the typical material used to make focusing caps?
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What is the primary mechanism by which the anode copes with heat?
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What is the purpose of angling the anode in an X-ray tube?
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What can be adjusted to change the size of the focal spot?
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What is the primary method of heat removal from the anode?
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What is the primary material used to make the anode?
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What can be adjusted to balance image quality needs with heat production at the anode?
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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.
