Principles of X-Rays and the rotating-anode X-ray tube

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  • Created by: LZ95
  • Created on: 15-06-14 19:22
What are X rays?
Very high frequency electromagnetic waves produced when high-energy electrons lose energy as they collide with atoms.
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Why are the two electrodes in an evacuated glass tube?
So that there is no collision between electrons and air molecules, allowing the electrons to travel at high speeds
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Where are the electrons accelerated from and where are they accelerated to?
Cathode to Anode
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What happened when a fluorescent screen was placed a few metres from the tube?
It produced light when the tube was operating
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Why does the anode rotate in the rotating-anode X-ray tube?
So that electrons strike different areas of the target so local heating problems are reduced.
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How are electrons emitted from the Cathode?
Cathode is heated by a current and electrons emitted due to thermionic emission
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What happens when electrons reach the tungsten target?
They collide with target atoms
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What is 'bremsstrahlung'?
A continuous spectrum of X ray as a result of the slowing down of electrons
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What happens when high speed electrons have sufficient energy and collide with the electrons of target atoms?
Electrons of target atoms knocked out of their orbits and atoms are ionised
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Why are characteristic X rays emitted?
Other electrons in target atoms move down energy levels to fill the gap
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What does the max. potential energy of an X ray photon depend on?
P.d.
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What energy does an electrons gain when it is accelerated?
E= eV
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How much of the energy of an electron beam is converted to X-ray radiation and what is the rest transferred as?
1% and rest transferred as internal energy in the target
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Name 4 features which make tungsten a good target material
High thermal conductivity, high specific heat capacity, high melting point, high atomic number
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Why is it good in X ray production if the target material has a high atomic number?
Material has larger mass so this increases the probability that collisions result in X ray emission
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Why does the anode have a bevelled edge?
So that target can be wide without increasing the width of the X ray beam
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How can you change the intensity of X rays?
By changing the current supplied to the cathode
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Other cards in this set

Card 2

Front

Why are the two electrodes in an evacuated glass tube?

Back

So that there is no collision between electrons and air molecules, allowing the electrons to travel at high speeds

Card 3

Front

Where are the electrons accelerated from and where are they accelerated to?

Back

Preview of the front of card 3

Card 4

Front

What happened when a fluorescent screen was placed a few metres from the tube?

Back

Preview of the front of card 4

Card 5

Front

Why does the anode rotate in the rotating-anode X-ray tube?

Back

Preview of the front of card 5
View more cards

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