X-Ray Production

Question 1

How efficient is the process of X-Ray production?

Answer 1

Inefficient process - 99% heat 1% photons

Question 2

Where does the heat from X-Ray production come from?

Answer 2

Kinetic energy being given off

Question 3

Why is there heat produced from x-ray production?

Answer 3

The incident e- interacts with the entire atom rather than undergoing other processes such as bremsstrahlung which causes it to lose kinetic energy which is irradiated as infared

Question 4

What is the process of producing incident e-‘s through heating up the filament called?

Answer 4

Thermoionic emission

Question 5

Describe the process of thermoionic emission

Answer 5

-Current flows through filament & heats filament up
-Atoms vibrate & release e- from outermost orbital shell with low binding energy
-E- tightly packed to reduce penumbra at anode

Question 6

What temperatures does thermoionic emission occur at?

Answer 6

2000>

Question 7

How would you increase the flow of current?

Answer 7

-reducing diameter of wire to inc resistance
-force a large current through the filament so it heats up more rapidly

Question 8

What is the space charge?

Answer 8

E-‘s that were dislodged through the vibration of atoms which sits outside the filament

Question 9

What happens to the space charge?

Answer 9

A potential difference is applied so that e- accelerate towards anode

Question 10

What how does kV and mAs relate to the space charge?

Answer 10

kV dictates the potential difference that the space charge experience

mAs dictates the number of incident e-‘s within the space charge

Question 11

Units for tube current

Answer 11

Milliamps

Question 12

Units for filament current

Answer 12

Amps

Question 13

What is tube current?

Answer 13

Directly relates to mAs - the number of e- moving from the filament to the anode

Question 14

What are the two processes that can happen to generate x-ray production?

Answer 14

Bremsstrahlung (continuous radiation)
Characteristic

Question 15

What must the kV be for bremsstrahlung to occur?

Answer 15

Below 70kV

Question 16

What is bremsstrahlung?

Answer 16

The release of electromagnetic radiation (EMR) when e- are slowed down

Question 17

Describe the bremsstrahlung process

Answer 17

-incident e- doesn’t attract with e- of tungsten target so slowed down
-so loses kinetic energy & changes direction by electrostatic attraction to nucleus,
-then releases energy as x-ray photon
-Distance from nucleus dictates how much it has slowed down

Question 18

What is characteristic radiation?

Answer 18

An interaction between incident electron and orbital electron

Question 19

What is characteristic radiation?

Answer 19

An interaction between incident electron and orbital electron

Question 20

Describe the process of characteristic radiation

Answer 20

-Incident e- gives energy to orbital electron
-Energy will be equal to or slightly higher than the binding energy
Orbital E- gets ejected and is known as a photoelectron
Cascade event occurs
Gap in the shells so the e- further away will fill in the shell
Closer to the nucleus has a higher binding energy and needs less potential energy to stay in orbit
Further away e- give up PE they don’t need to stay in orbit as x-ray photon