Production and Properites

Question 1

Atomic no and atomic mass no

Answer 1

Atomic no Z = protons in nucleus
Atomic mass no A = protons and nucleus
Z electrons in orbit around nucleus (determines chemical properties)
Atom electrically neutral

Question 2

Electron shells

Answer 2

Each shell has fixed energy for particular element - dependent on Z

K2 L8 M18 N..

Question 3

Excitation

Answer 3

Normally atom electrically neutral. When E jumps from low energy to high energy shell. (Inner to outer)

Question 4

Binding energy

Answer 4

Negative E attracted to positive nucleus
Work needed to overcome attraction remove electron - binding energy
Greatest for K she’ll as closest to nucleus

Question 5

Ionisation

Answer 5

X-ray photon removes E from atom to give a positive ion.

Ion pair - positive ion and electron

Question 6

What are X-rays?

Answer 6

Wave packets of energy
Each packet = photon. Quantum of energy.
X-ray beam has millions of photons
Form of EM radiation

Question 7

X-ray properties

Answer 7

Invisible and weightless
Travel in straight lines
Travel at the speed of light
Range of wavelengths 0.01-0.05nm
Different wavelengths/frequencies give diff properties (40-150V)
In free space- obey inverse square law

Question 8

Production of X-rays

Answer 8

Produce lots of E
Accelerate to high energy
Smash them into target
Must be in vacuum - otherwise gas/air in way

Question 9

X-ray process production

Answer 9

Electrons produced by filament heating, thermionic emission (CATHODE/mA) Tube current (flow between anode and cathode) fixed 7-10mA. Controlled by heat.

Electrons accelerated to anode by high potential difference (KV)
Variable 60-70kV, higher kV lower dose to patient.

Rapid deceleration by electrons by target, interaction of electrons with targets. (ANODE)

Question 10

Heat producing collisions

Answer 10

E bombard tungsten target - suddenly brought to rest
Each incoming E can have many heat producing collisions
Energy lost by E - xrays (1%) heat (99%) wasteful, dissipated by copper block and oils.

Question 11

Tungsten

Answer 11

High melting point, last a long time

High atomic number, lots of atomic E for filament to interact with, lots of Xrays produced.

Question 12

X-ray set variables

Answer 12

kV- QUALITY OF X-RAY BEAM
Determines penetrating power of photons
Affects film contrast

mA and time - QUANTITY OF PHOTONS
Affects degree of blackening of film (optical density)

Question 13

What happens in Bremsstrahlung radiation?

Answer 13

E penetrates outer shells and passes close to nucleus
E is slowed down and loses energy in the form of Xrays
Low E P are not useful and discarded in filtration.
If E stopped max potential energy produced as high energy photons

Question 14

In continuous spectrum…?

Answer 14

E slowed down and deflected to various degrees
Produces complete range/continuous spectrum of X-ray photon energies

Lower kV = lower emax = less Xrays produced

Question 15

Characteristic radiation

Answer 15

E collides with inner shell tungsten E displacing to outer shell/from atom
Large energy loss = X-ray production

Question 16

Characteristic radiation binding energy

Answer 16

Only K shells are of diagnostic importance
Bombarding high speed E needs at least 69.5kV to displace K shell E to produce characteristic line on spectrum.
Energy to incoming E directly related to kV across X-ray tube

Question 17

Binding energy process

Answer 17

After ionisation tungsten E rearrange themselves to return atom to neutral state
Involves E jumping from one energy level to another
Jump results in X-ray photon with a specific energy

Question 18

X-ray producing collision

Answer 18

M to K K beta radiation
L to K K alpha radiation

Only X-ray photons of specific energies emitted following repositioning of orbiting electrons

These energy emissions are CHARACTERISTIC of tungsten

Question 19

Combined spectra

Answer 19

X-ray equipment operating above 69.5kV of the final total spectrum will be addition of continuous and characteristic spectra

Question 20

Atom structure

Answer 20

Nucleus in centre (protons and neutrons)
Electrons orbit nucleus

P positive mass =1amu
N neutral 1amu
E negative 1/1840amu

Amu = 1/12th mass 12C atom