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RTEC A - WEEK 3 GENERAL SCIENCE REVIEW

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RTEC A - WEEK 3 GENERAL SCIENCE REVIEW & X-RAY PRODUCTION IN THE TUBE Objectives General Science review Atomic interactions in the tube Atomic Models BOHR model of ... – PowerPoint PPT presentation

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Title: RTEC A - WEEK 3 GENERAL SCIENCE REVIEW


1
RTEC A - WEEK 3GENERAL SCIENCE REVIEWX-RAY
PRODUCTION IN THE TUBE
2
Objectives
  • General Science review
  • Atomic interactions in the tube

3
Atomic Models
  • BOHR model of the atom.
  • Electrons orbit around a nucleus (center)

4
ATOM
5
Differences in Binding Energy
6
K L M Shells
7
Electrostatic Laws
  • Repulsion/attraction
  • Like charges repel
  • Unlike charges attract
  • Inverse square relationship
  • Electrostatic force is very strong when objects
    are close together
  • It decreases rapidly as objects separate

8
How X-rays are created
  • TO PRODUCE X-RAYS
  • YOU NEED
  • A SOURCE OF ELECTRONS
  • A FORCE TO MOVE THEM QUICKLY
  • SOMETHING TO STOP THEM SUDDENLY

9
How X-rays are created
  • Power is sent to x-ray tube via cables
  • mA (milliamperage) is sent to filament on cathode
    side.
  • Filament heats up electrons boil off
  • Negative charge

10
How X-rays are created
  • Positive voltage (kVp) is applied to ANODE
  • Negative electrons attracted across the tube to
    the positive ANODE.
  • Electrons slam into anode suddenly stopped.
  • X-RAY PHOTONS ARE CREATED

11
Electromagnetic Energy Spectrum
  • Spectrum
  • Continuous range of energy
  • Although there are precise ranges defined, they
    often overlap
  • 3 most important to Radiologic technology
  • Visible light
  • X-radiation
  • Radiofrequency

12
Electromagnetic Radiation
  • Photon is the smallest quantity of any type of EM
    radiation
  • It is a small bundle of energy traveling at the
    speed of light
  • Only visible light is naturally apparent to us
  • May be described as wavelike fluctuations of
    electric and magnetic fields.

13
Electromagnetic Radiation
  • These bundles of electric and magnetic fields
    travel at the same velocity
  • Travel at the speed of light
  • 3 x 108 m/s or 186,400 miles per sec
  • The Photons of EM radiation differ only in
    frequency and wavelength

14
General Characteristics of EMSX-ray photons
  • Have no mass or physical form
  • Travel in a linear path (until interaction
    occurs)
  • Dual nature wave vs. particle
  • Unaffected by
  • electric or magnetic fields
  • gravity

15
Wavelength and Frequency
  • Wavelength is the difference between
  • Crest to Crest
  • Valley to Valley
  • Frequency is the number of wavelengths passing a
    point of observation per second
  • Wavelength frequency are inversely proportional
  • As Wavelength increases frequency decreases
  • As wavelength decreases frequency increases

16
Wavelength and Frequency
  • Frequency and wavelength are closely associated
    with the relative energy of electromagnetic
    radiations.
  • More energetic radiations have shorter
    wavelengths and higher frequency.

17
Wavelength
18
Frequency
19
The shorter the wavelength the higher the
frequency
20
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21
The Electromagnetic Spectrum
  • X-rays have wavelengths much shorter than visible
    light, but longer than high energy gamma rays.

22
What is Ionization?
23
When an electron is added or removed from the
atom- it is ionized
24
Kinetic energy
  • Energy of motion
  • The electrons KINETIC energy is converted to
    electromagnetic or PHOTON energy

25
X-ray production begins at the atomic level
Energy (photons) are released when the electron
collides with another electron,or passes close
to the nucleus of the atom the change in energy
of the shells produces photons
26
X-ray Production in the TUBE
27
INTERACTIONS IN THE TUBE
  • BREMS (Bremsstrahlung)
  • CHARACTERISTIC
  • HEAT

28
Tube Interactions
  • Heat 99
  • X-ray 1
  • Bremsstrahlung
  • (Brems) 80
  • Characteristic 20

29
Bremsstrahlung Radiation
  • Heat Characteristic produces EM energy by e-
    interacting with tungsten atoms e- of the target
    material
  • Bremsstrahlung is produced by e- passing by
    closely with the nucleus of a target tungsten
    atom the change in direction of the electron
    releases a photon of energy

30
Heat
  • Most kinetic energy of projectile e- is converted
    into heat 99
  • Projectile e- interact with the outer-shell e- of
    the target atoms but do not transfer enough
    energy to the outer-shell e- to ionize

31
Heat
32
  1. Projectile electrons from cathode
  2. Pass by the electrons in the target
  3. Causing the electrons to vibrate (excitation)
  4. Excitation produces small amounts of heat

HEAT
e
e
33
Heat is an excitation rather than an ionization
34
Bremsstrahlung
  • German
  • word meaning
  • slowed-down
  • or braking
  • radiation

35
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36
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37
Bremsstrahlung Radiation
38
X-ray Photons BREMS
38
39
Energy (photons) are released when the e passes
close to the nucleus, then changes direction
40
BREMS RADIATION
  • Electron
  • Passes by nucleus
  • Changes direction
  • Energy released as a PHOTON

41
Brems Radiation Animation
  • http//www.coursewareobjects.com/objects/mrophysic
    s_v1/mod08/0816a.htm

42
Characteristic Radiation
  • Projectile e- with high enough energy to totally
    remove an inner-shell electron of the tungsten
    target
  • All tube interactions result in a loss of kinetic
    energy from the projectile e-
  • Characteristic x-rays are produced when
    outer-shell e- fills an inner-shell void

43
Characteristic Radiation (Tube)
44
CHARACTERISTIC (in tube)
  • Electron hits inner shell e in orbit knocked
    out creates a hole
  • Other Es want to jump in
  • Energy released as PHOTONS

45
  • It is called
  • characteristic
  • because it is
  • characteristic of
  • the target element
  • in the energy of
  • the photon
  • produced

46
Characteristic Radiation Animation
  • http//www.coursewareobjects.com/objects/mrophysic
    s_v1/mod08/0808a.htm

47
Tungsten Atom
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