Transcript tube interactions - El Camino College

Review of Science, Math
Review of X-Tube Construction
1
Self Quiz
Convert 1/7 into a decimal.
Convert .11 into a fraction
Multiply:
Solve for x:
Solve for x:
4
7
x 
3
8
5x2=45
2
5

32
x
2
What is an atom?
smallest particle of an element
What are the parts of an atom?
nucleus-protons, neutrons
electrons
What is Atomic Number?
What is the electrostatic law of attraction?
un-like charges attract,
like charges repel
3
4
BOHR model
of the atom
Electrons orbit
around a nucleus
(center)
5
6
Remember
this for
later…
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8
9
v
a
c
u
u
m
v
a
c
u
u
m
Tube
Housing
Glass
Envelope
Cathode
Anode
10
Review of X-ray Tube
Stators
Rotors
mA current
High voltage current
Focal track
11
A source of electrons
a means to accelerate
them
A force to stop them
quickly
12
What Energy radiating thru matter
is it?
Referred to as a photon, packet
of energy, bundle of energy
Travels at the speed of light
13
A
A
14
What the heck are those squiggly lines????
15
1.
Spectrum


2.
Continuous range of energy
Although there are precise ranges defined, they
often overlap
3 most important to Radiologic technology:



Visible light
X-radiation
Radiofrequency
16
Ionizing Radiation
Has same properties as all EM
radiation, has properties unique
to ionizing radiation, has
wavelength and frequency
unique to ionizing radiation
17
Inversely proportional
18
Distance
19

Wavelength is the difference between:


Crest to Crest
Valley to Valley
20

Frequency is the number of wavelengths
passing a point of observation per second
21
22
23
1.
Wavelength & frequency are inversely
proportional


As Wavelength increases frequency decreases
As wavelength decreases frequency increases
2.
Frequency and wavelength are closely
associated with the relative energy of
electromagnetic radiation.
3.
More energetic radiations have shorter
wavelengths and higher frequency.
24
1.
Have no mass or physical form
2.
Travel in a linear path (until interaction
occurs)
3.
Dual nature: wave vs. particle
4.
Unaffected by


electric or magnetic fields
gravity
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26
Heat
Brems
Characteristic
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

Heat = 99%
X-ray = 1%

Bremsstrahlung
(Brems) = 80%

Characteristic =
20%
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29
True or False
1. X-ray production begins as the electrons stream
begins toward the anode.
2. The energy production in the x-ray tube is 90%
heat, 80% brems, 20% characteristic.
3. Heat results from a mild ionization.
4. As wavelength increases, the frequency also
increases.
5. The smallest packet of electromagnetic energy is
called a photon.
6. Thoughtful challenge question: What is the
most frequent ionizing tube interaction?
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

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
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33
HEAT
8 p+ + 8e- = neutral atom
e
1. Projectile
electrons
from
cathode
2. Pass by the
electrons in
the target
3. Causing the
electrons to
vibrate
(excitation)
e
4. Excitation
produces
small
amounts of
heat
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35




Diagnostic radiation production happens in the
x-ray tube
Two kinds of diagnostic radiation production:
characteristic and bremsstrahlung
Incoming electron
Interacts with:


inner shell electron = characteristic radiation
nuclear force field = bremsstrahlung radiation
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37
38
brems animation
39
The closer the
Electron passes
To the nucleus,
The more energetic
The resulting x-ray
Photon.
40
The incoming electron passes near enough to the nucleus
to be affected by the law of electrostatic attraction. The
electron starts to slow down and veer toward the nucleus
but never hits the nucleus or another electron. The
slowing down motion changes the direction of the
incoming electron and release some of the energy of that
electron. The form of energy released is x-ray radiation.
Brem radiation 2
http://youtu.be/q-cTw1x7TzA
41



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 outershell e- fills an inner-shell void
42
animation of characteristic
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44
It is called
characteristic
because it is
characteristic of
the target element
in the energy of
the photon
produced

45
characteristic radiation -1
characteristic radiation-2
46
http://www.coursewareobjects.com/objec
ts/mrophysics_v1/mod08/0808a.htm
47
1.
Electron hits inner
shell e in orbit –
knocked out &
creates a hole
2.
Other E’s want to
jump in
3.
Energy released
as PHOTONS
48
49
Radiation Interaction in the Tube
50
What do we know so far about x-rays?
51
What is This?
52
What is This?
53
What is This?
54