The X-Ray Tube Flashcards
what is accelerated across the vacuum x-ray tube?
electrons
what is the cathode filament made of?
Tungsten
what is the process of heating the Tungsten called?
thermionic emission
why are the electrons attracted to the anode?
the electrons are negatively charged, the anode is positively charged
what is used to help direct the electrons to the anode
a focussing cup
what controls the tube current
the filament current
above what kVp does the tube reach saturation?
above 40kVp
what are the two different focal spot sizes?
the broad and the fine focus spots
what is the focal spot
where the electrons hit the anode and x-rays are produced
why does the anode rotate
larger target area for the electron beam
less damage to anode surface
better heat dissipation
higher tube currents can be used
what are the requirements of the anode material
high atomic number
high thermal conductivity
high melting point
how much energy produced in the tube is heat energy?
98%
what effect does a smaller focal spot size have on spatial resolution
smaller focal spot, better spatial resolution
how does angling the anode affect the focal spot size
we can angle the anode to reduce the focal spot size
what is a small target angle associated with
smaller effective focal spot size
