Lecture 3 Flashcards
bremsstrahlung radiation
incoming charged particle slows down as it interacts with the nucleus. Collisional energy loss is through heat and radiative energy loss forms the Xray
what is the intensity of the bremsstahlung determined by
target z. radiative energy loss/ total energy loss= EkZ/820000. Where EK is the kinetic energy
what happens with higher z
more efficient material- like tungsten or mollubenium or rhodium
what is a characteristic x-ray production
it is discrete energy levels
what is an electron cascade
fills the vacancy of the inner shells of electrons
when does emission of characteristic Xray happen
only happens when the incoming electron has kinetic energy that exceeds the binding energy of an orbital electron. They can also come from electron transitions as holes fill but for image formation purposes, the K characteristic X-rays because the others have energies too low for imaging
what is the electron source
cathode
what is the target
anode
what is the device to energize the electron to gain kinetic energy
generator
what are the components of an X-ray tube
cathode, anode, gnerator, envelope, rotator/stator, housing
cathode assembly
filament current heats a wire and thermionic emission of electrons. The filament current is 10mV and current goes up to 7000
what is a tungsten filament
helical wire coil, 5-20mmlong with 2-5 mm width
what do the electrons accelerate towards
anode
what does the focus cup do
it compresses the electron stream
what is dual focus
a second shorter filament is present and it can be selected during the exam
why is there not a point focal spot
it is impossible plus tube current limits
what is the max tube current dependent on
kV
what is the max focal spot size dependent on
KV and mA
why is tungsten good for X-ray tubes
relatively high bremmastralung output and high melting point alloyed with things to make it even higher