Functions Of Tube Head Components Flashcards
Define the cathode
Made up of tungsten filament and focussing cup
Negatively charged to repel electrons
Properties of the filament
Made of tungsten - high atomic number so many electrons
Very high melting point - can be safely heated
Properties and function of focussing cup
Shaped electrode surrounding filament
Poor heat conductor - repels electrons
Directs electrons towards target
Properties of anode
Formed of tungsten target
Positively charged to attract electrons
Copper base conducts heat to draw away from target
Lead lining function
Surrounds tube head
Absorbs majority of scatter
Directs some through window in base
Aluminium filter function
Situated a cross tube window
Removes low-energy x-rays
Function of light beam diaphragm
Collimation device
Controls size of emerging beam
Function and properties of glass envelope
Glass vacuum tube
Contains cathode and anode
Allows x-rays to travel in straight line
Function of copper stem
Draws heat away from target
Function of oil
Transfers heat away from anode
Function of cooling fins
Disperse heat
Define actual focal spot
Area of target struck by electrons
Define effective focal spot
Apparent area of beam origin
Much smaller than AFS due to angulation of target in relation to window
Define line focus principle
Aim to maximise AFS whilst minimising EFS through target angulation
Define penumbra effect
X-rays produced at different points of AFS travel at varying angles
Hit film at slightly different locations
Produces blurred margins
