Production of X-rays Flashcards
What temperature is the filament within the X-ray tube heated too?
> 2200° C
What’s a ‘space charge’?
A cloud of electrons hanging around the filament
What does a bigger the space charge allow?
More electrons are available to transit across the x-ray tube and potentially produce x-rays
What 4 ways does electrons and the target (anode) interact?
- Excitation
- Ionisation
- Bremsstrahlung
- Characteristic Radiation
Describe Excitation
The incoming electron collides with an electron
A small amount of energy is transferred to the electron in the shell
The electron moves to a higher energy level then drops back into the same shell releasing energy as heat
Describe Ionisation
An incoming (incident) electron collides with an outer shell electron
The outer shell electron is given sufficient energy to break away from the atom as a secondary electron
If it has sufficient energy, the secondary electron may go on to produce further excitation / ionisations
The incident electron only gives up small amount of energy
Describe Bremsstrahlung
The incoming (incident) electron passes close to nucleus and the attractive force of nucleus decelerates the electron
The electron loses energy (i.e. it brakes) - the closer to the nucleus the electron passes the greater the deceleration and the greater the energy loss
If the electron is brought to a rest, maximum energy is released
When the electron ‘brakes’ the continuous spectrum of x-rays are produced
Describe Characteristic Radiation
The incoming (incident) electron knocks an inner shell electron from its shell
An electron in a higher shell drops down to fill the gap
As the electron drops down to fill the gap, a photon of
characteristic radiation is then emitted
The energy of the photon of Characteristic Radiation is
equal to the difference in shell binding energies
What is the relationship between Bremsstrahlung and atomic number?
Bremsstrahlung ∞ Z of target material
What is the relationship between Bremsstrahlung and atomic kVp?
Bremsstrahlung ∞ kVp²
What is the relationship between Bremsstrahlung and mA?
Bremsstrahlung ∞ mA
What is Charateristic radiation equal too?
Difference in shell binding energies of target material
What does the ‘quality’ of a beam refer too?
The penertrating ability of the beam
