1: X-ray Generation

Question 1

1901, first Nobel prize in physics

Answer 1

Röntgen with discovery of x-ray

Question 2

x-ray generation three components

Answer 2

1) thermal emission
2) electron acceleration
3) x-ray generation in target

Question 3

thermal emission takes place in

Answer 3

cathode

Question 4

x-ray generation takes place in

Answer 4

anode

Question 5

medical imaging kV range

Answer 5

30-140 kV

Question 6

thermal emission: #electrons depend on 2 things

Answer 6

Fermi Energy level
Temperature

Question 7

richardson dushman eqn

Answer 7

explains how much electron goes out of cathode
J = A0 T^2 exp( -W / k T)
current density = Richardson const * temp^2 * exp( work function / boltzman const Temp)

Question 8

<acceleration in the vacuum depends on 2 things

Answer 8

acceleration voltage
temperature

Question 9

explain three different regimes in the electron beam current plot

Answer 9

beginning: leakage current
linear part: increases linearly with acc voltage
saturation part: almost flat, higher temp, higher saturation current level

Question 10

x-ray generation in target: 2 principles

Answer 10

bremsstrahlung: continuous spectrum
characteristic emission of x-ray: material specific property

Question 11

bremsstrahlung

Answer 11

electron beam gets closer to nucleus, bends and changes the direction, emits continuous x-rays

closer to nucleus, higher the energy of x-ray

Question 12

max energy of emitted x-ray in bremsstrahlung is equal to

Answer 12

kinetic energy of the incoming electron

Question 13

how to estimate the min wavelength, max energy pf the emitted brensstrahlubg

Answer 13

Ephoton=Ekinetic,electron
hc = eU
lambda,min = hc/eU
h:planck const
c: light velocity
e: elementary charge
U: acceleration voltage

Question 14

bremsstrahlung spectrum shape
energy vs relative output

Answer 14

filtered: like a hill, low energy part absorbed by the window material AND also self absorption in metal target
unfiltered: linear decreasing line

Question 15

bremsstrahlung spectrum shape for different acc voltage

Answer 15

photons increases as kV increases
peak shifts to right, peak #electrons emitted at higher energy level

Question 16

difference between x-ray and gamma ray

Answer 16

1) produced ,n the electronic processes
2) produced in the nuclei

Question 17

who proved x-rays are lights and got nobel prize in 1914

Answer 17

max von laue

Question 18

characteristic x-ray emission physical process

Answer 18

incoming electron collides and releases an inner shell electron

another electron from higher shell transitions to lower one and releases energy by geenrating a characteristic x-ray photon

Question 19

characteristic x-ray law

Answer 19

moseley law

Question 20

moseley law: wavelength depends on

Answer 20

rydberg const
atomic number in periodic table
shielding constant
main quantum numbers of shells

Question 21

why tungsten target material

Answer 21

high melting point, gives lots of electron before it melts

Question 22

other target materials

Answer 22

iron —– x-ray diffraction
cupper —– x-ray diffraction
molybdenum —– mammography
rhodium —– mammography
tungsten —– radiography / CT

Question 23

why rotating anodes?

Answer 23

for more power
distribution of heat is more even,

Question 24

equipment provides more precise focal spot for high resolution

Answer 24

microfocus transmission tubes

Question 25

liquid metal jet sources main idea

Answer 25

replace solid target so it’s already melted
get more power
not yet used for medical imaging

Question 26

performance parameter for x-ray sources

Answer 26

brilliance

Question 27

brilliance equals

Answer 27

photons /( time * source area * solid angle * bandwidth)

Question 28

synchrotron radiation main idea

Answer 28

use magnetic field to bend electrons and generate x-ray

Question 29

synchrotron provides ___ brilliance through ____

Answer 29

synchrotron provides high brilliance through lorentz contraction