Title: RTEC A - WEEK 3 GENERAL SCIENCE REVIEW
1RTEC A - WEEK 3GENERAL SCIENCE REVIEWX-RAY
PRODUCTION IN THE TUBE
2Objectives
- General Science review
- Atomic interactions in the tube
3Atomic Models
- BOHR model of the atom.
- Electrons orbit around a nucleus (center)
4ATOM
5Differences in Binding Energy
6K L M Shells
7Electrostatic 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
8How 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
9How 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
10How 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
11Electromagnetic 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
12Electromagnetic 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.
13Electromagnetic 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
14General 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
15Wavelength 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
16Wavelength and Frequency
- Frequency and wavelength are closely associated
with the relative energy of electromagnetic
radiations. - More energetic radiations have shorter
wavelengths and higher frequency.
17Wavelength
18Frequency
19The shorter the wavelength the higher the
frequency
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21The Electromagnetic Spectrum
- X-rays have wavelengths much shorter than visible
light, but longer than high energy gamma rays.
22What is Ionization?
23When an electron is added or removed from the
atom- it is ionized
24Kinetic energy
- Energy of motion
- The electrons KINETIC energy is converted to
electromagnetic or PHOTON energy
25X-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
26X-ray Production in the TUBE
27INTERACTIONS IN THE TUBE
- BREMS (Bremsstrahlung)
- CHARACTERISTIC
- HEAT
28Tube Interactions
- Heat 99
- X-ray 1
- Bremsstrahlung
- (Brems) 80
- Characteristic 20
29Bremsstrahlung 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
30Heat
- 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
31Heat
32- Projectile electrons from cathode
- Pass by the electrons in the target
- Causing the electrons to vibrate (excitation)
- Excitation produces small amounts of heat
HEAT
e
e
33Heat is an excitation rather than an ionization
34Bremsstrahlung
- German
- word meaning
- slowed-down
- or braking
- radiation
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37Bremsstrahlung Radiation
38X-ray Photons BREMS
38
39Energy (photons) are released when the e passes
close to the nucleus, then changes direction
40BREMS 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
42Characteristic 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
43Characteristic Radiation (Tube)
44CHARACTERISTIC (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
46Characteristic Radiation Animation
- http//www.coursewareobjects.com/objects/mrophysic
s_v1/mod08/0808a.htm
47Tungsten Atom