X-ray Flashcards
glass tube
It is sealed and evacuated. It allows electrons to travel unimpeded
rotating anode
Rotation of the anode spreads out the heated area on the target It is made of metal (tugsten or molybdenum) and emits X-rays when hit by (energetic) electrons
filament [or cathode]
It is the heat source necessary for the release of electrons from surface of cathode by thermionic emission
lead housing
It prevents X-rays from escaping in unwanted directions
Explain why the anode is rotated
The anode is rotated so that the heat produced is spread over a greater volume/area/section This allows more energetic X-rays to be produced [or allows X-rays to be generated for longer] without risk of melting the anode.
Explain why the anode has a bevelled edge.
The bevelled edge gives larger target area for the electrons
but a smaller source area from which the X-rays are produced. This gives a sharper image beam of X-rays and produces a sharper image.
Define for a material, the linear attenuation coefficient
The linear attenuation coefficient, is the fraction of X-rays removed per unit thickness of the material.
Define for a material, the half-value thickness.
The thickness of the material which will reduce the intensity to half its original level for a specified energy of the X-rays
State the purpose of the fluorescent screen,
It converts X rays to visible photons
state the purpose of photocathode
It converts photons to emission of electrons
State the purpose the anodes,
They increases the kinetic energy of electrons travelling from cathode to anode and they also focus the rays of electrons to produce a faithful image
state the purpose he fluorescent screen
It converts (increased) electron energy into light photons
Give one example of a medical application for which an image intensifier might be used. Explain why the use of an image intensifier is required.
It might be used for a dynamic process - such as fluid flow It cuts the radiation dose whilst still providing good image [or allows multiple or continuous use of X rays]
State two methods which can be used to increase the intensity of the X-ray beam produced by the tube.
Method 1: increasing the potential difference (voltage) across the tube
Method 2: increasing the tube current or increasing the filament temperature
For each method of increasing intensity, state the effect on the maximum X-ray photon energy.
(Method 1: increasing the potential difference (voltage) across the tube)
Method 1: will increase the maximum photon energy
(Method 2: increasing the tube current or increasing the filament temperature )
Method 2: will not change the maximum photon energy